_v——< A-

 

FACTORS INFLUENCING THE FERTILITY OF
NATURALLY AND ARTIFICIALLY
MATED SWINE

Thesls for the Degree of DH. D.
MICHIGAN STATE UfiIVERSITE’
Anthony Borton

1964

 

THESIS

This is to certify that the

thesis entitled

FACTORS INFLUENCING THE FERTILITY OF
NATURALLY AND ARTIFICIALLY
MA‘I‘ED SWINE

presented by

Anthony Borton

has been accepted towards fulfillment
of the requirements for

Ph. 0 D 0 degree in Animal HUSbandry

     

Major professor

Date May 25, 196+

0-169

   
     

  

LIBRARY

Michigan State ..
University '

ABSTRACT

FACTORS INFLUENCING THE FERTILITY OF
NATURALLY AND ARTIFICIALLY MATED SWINE.

by Anthony Borton

The problems of boar semen collection, extension, handling and
preservation require particular attention since many of the techniques
developed for artificial insemination of other species are not applicable.
Additional difficulties are encountered with the insemination of the
sow and accurate estrus detection. Therefore, the artificial insemination
of swine has developed slowly in the United States and conception rates
have generally been low. This study was concerned with fertility of
artificially inseminated swine and with boar semen preservation and
handling techniques. Comparisons were made in the fertility of naturally
and artificially mated swine.

A series of laboratory experiments on the preservation of boar semen
did not indicate any improved storage methods. Although satisfactory
spermatozoa motility was maintained, the pregnancy rate of boar semen
stored 5 to 10 days was 9.1%. The fertility of stored boar semen was
not closely related to Spermatozoa motility.

The methods of semen collection and extension and artificial in-
semination techniques were described. The standard insemination dose
was 5 x 109 spermatozoa diluted to a 50 ml. volume with an egg yolk-sodium
bicarbonate-glucose extender. The diluted semen was deposited in the
female tract with a plastic dairy inseminating catheter connected by a

piece of tubing to a 50 ml. plastic syringe.

Anthony Borton

A swine artificial insemination field trial comprised of 65k
matings was conducted at Southern Michigan State Prison. Complete
breeding and farrowing information was available on #38 predominately
gilt inseminations. A farrowing rate of 32.0% was obtained with an
average litter size of 7.0 pigs. A significantly higher (P<70.0l)
farrowing rate was obtained with two services during estrus (hh.5%)
than with one service (21.3%). There was also a highly significant
(P< 0.01) difference in the farrowing rates obtained from the three
boars used in the study. The least square estimate of the difference
between the high and the low boars was 19%. Three inseminators also
obtained significantly (P<{0.05) different conception rates. The storage
age of semen, up to 30 hours, did not significantly influence swine
fertility. The progressive and total motility of boar spermatozoa was
not closely associated with subsequent farrowing rates. The backflow of
semen from the female tract following service did not indicate an im-
proper insemination technique since those sows exhibiting backflow had a
significantly (P< 0.01) higher farrowing rate than those that had no
backflow. None of the factors studied had a significant influence on
litter size.

Artificial insemination was compared with natural breeding in 37%
matings on the Michigan State University swine farm. A farrowing rate of
6h.5% and an average litter size of 10.0 pigs obtained on 25h natural
matings was compared to a 50.0% farrowing rate and a 9.3 average litter

size on 120 artificial inseminations. These differences were not signi-

Anthony Borton
ficant when analyzed by the method of least squares. The boar was the
only factor examined that had a highly significant (E’<CLCHJ influence on
farrowing rate in this study. The differences in farrowing rates between
sows or gilts and one or two services during estrus were not significant.
Since the farrowing rate increased with twice serviced females in the A.I.
group but decreased with twice bred females in the natural group, there
was a significant interaction (P( 0.05) between type of mating and number
of services. A similar interaction (P<f0.05) was also observed for litter
size. Differences in litter size by breeding seasons were highly
significant (P(0.0l). The litter size was significantly (P< 0.01) larger

(1.96 pigs) for sows than for gilts.

FACTORS INFLUENCING THE FERTILITY OF

NATURALLY AND ARTIFICIALLY MATED SWINE

by

Anthony Borton

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Animal Husbandry

196A

ACKNOWLEDGMENTS

The author greatly appreciates the encouragement and direction of
Dr. J. E. Nellor as a major professor. Without his guidance and generous
provision of facilities this research would not have been possible.

With equal appreciation thanks are extended to Dr. W. T. Magee who
assisted the author in many ways including advice on the statistical
analysis and programming of the electronic computers.

The writer is also indebted to Dr. D. E. Ullrey, who critically
reviewed this manuscript and made helpful suggestions and to Dr. J.
Meites who served on the guidance committee.

Sincere graditude is expressed to Dr. R. H. Nelson, the Michigan
State Department of Animal Husbandry and Southern Michigan State Prison
for financial assistance and the facilities for this research.

Thanks go as well to the staff of the Endocrine Unit and particular—
ly to Arthur Jaworski and Terry Gardner for their many hours of hard
work in the boar stud and with the breeding trials.

The excellent typing and long hours spent carefully preparing this
manuscript by Marie Stehlik is gratefully appreciated.

Finally the author is especially indebted to his wife, Ann, for her

sacrifices that made this graduate program possible.

ii

TABLE OF CONTENTS

I. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . I
II. REVIEW OF LITERATURE . . . . . . . . . . . . . . . . . . . . . . A
The Semen of the Boar . . . . . . . . . . . . . . . . . . . . . h
Physiology of Breeding the Sow . . . . . . . . . . . . . . . . 23
Artificial Insemination of Swine . . . . . . . . . . . . . . . 29

III. EXPERIMENTAL PROCEDURE . . . . . . . . . . . . . . . . . . . . 51
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Boar Semen Preservation . . . . . . . . . . . . . . . . . . . . 56
Field Trials . . . . . . . . . . . . . . . . . . . . . . . . . 58

IV. RESUDTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Boar Semen Preservation . . . . . . . . . . . . . . . . . . . . 61
Southern Michigan State Prison Field Trial . . . . . . . . . . 62
Michigan State University Swine Farm Trial . . . . . . . . . . 73

V. DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Boar Semen Preservation Trials . . . . . . . . . . . . . . . . 82
Swine A.I. Field Trials . . . . . . . . . . . . . . . . . . . . 8A

VI. SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . 96
VII. BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . lOO

VIII. APPENDIX . . . . . . . . . . . . . . . . . . . . . . . . . . 115

iii

Table

l.

10.

ll.

12.

13.

11+.

15.

16.

Progressive motility and total motility of boar

LIST OF TABLES

spermatozoa after storage .

The fertility of boar Spermatozoa stored for 5 to 11 days -

Farrowing rate and average litter size of artificially

inseminated swine .

The influence of number of services during estrus on the

fertility of artificially inseminated swine .

The influence of different inseminators on fertility of

artificially inseminated SWine .

The influence of different boars on fertility of artificially

inseminated swine-

The influence of storage age of semen on fertility of

artificially inseminated swine .

The influence of semen backflow on fertility of artificially

inseminated swine .

The influence of the number of spermatozoa inseminated on

fertility of artificially inseminated swine .

The influence of progressive motility of spermatozoa on

fertility of artificially inseminated swine .

The influence of total spermatozoa motility on fertility of

artificially inseminated swine .

The influence of semen arrival temperature on fertility of

artificially inseminated swine .

A comparison of fertility of artificially inseminated gilts

and sows . . . . .

Analysis of variance of factors influencing farrowing rate
of artificially inseminated swine.

Analysis of variance of factors influencing litter size of

artificially inseminated swine .

A comparison between natural and artificial matings in the

M.S.U. swine herd .

iv

0

61
62

63

6h

65

65

66

67.

68

69

69

TO

71

T2

73

7h

Table

17.

18.

19.

20.

21.

22.

23.

2h.

25.

26.

LIST OF TABLES (Continued)

Page
The influence of different boars on fertility of
naturally bred swine . . . . . . . . . . . . . . . . . . . . 75
The influence of different boars on fertility of artificially
inseminated Swine ' 0 0 0 ° 0 0 0 0 0 O O 0 o O o o o o o o 75
The influence of breeding period on fertility of naturally
and artificially mated swine. . . . . . . . . . . . . . . . .76

Analysis of variance of factors influencing farrowing rate
in naturally and artificially mated swine , , , , , , , , , 77

Farrowing rates by type of mating and number of services
dur ing eswus O O O O O O O O O O O O O O O O O O O O O O O 78

Analysis of variance of factors influencing litter size of
naturally and artificially mated Swine . . . . . . . . . , , 78

Litter size by type of mating and number of services
during eStruS O O 0 O O O 0 0 O O O O O O O O O O O O O O 0 T9

The influence of backflow at insemination on fertility of
artificially inseminated swine. . . . . . , , , , , , , , , 79

Analysis of variance of factors influencing farrowing rate
in artificially inseminated swine . . . . . . , , , , , , ,, 80

Analysis of variance of factors influencing litter size in
artificially inseminated swine . . . . . . . . . . . . . . . 80

LIST OF APPENDIX
Table

A Breeding Information on Gilts Inseminated with Stored
Semen . . . . . . . . . . . . . . . . . . . . . .

vi

I. INTRODUCTION

The enthusiastic acceptance of artificial insemination
revolutionized dairy cattle breeding in this country. From a modest
beginning in 1938, the artificial breeding industry has grown to
include over A0% of the dairy cattle and 5% of the beef cattle
annually. The economic and safety advantages, as well as the pos-
sibilities for health and genetic improvement have contributed to
this popularity. Artificial insemination techniques have been adapted
for routine use with poultry, goats and dogs and to a limited extent
for horses, sheep and swine.

The expansion of artificial insemination of swine has been slow
since most of the cattle techniques are not applicable to swine
artificial breeding. In addition, in the United States research and
field trials have been plagued by discouraging conception rates.
Accurate heat detection and reduced fertility following semen storage
have presented additional problems. Nevertheless, producer interest
has remained high as it offers distinct advantages to present management
practices. Swine artificial insemination is suited to programs of
disease free pigs, feeder pig production and carcass improvement.

In 1959 Michigan State University initiated its investigations in
swine artificial insemination (A.I.). Initial semen collections were made
on the University swine farm using an artificial vagina and a teaser
sow. Insemination was accomplished with plastic squeeze bottles and
dairy inseminating catheters. In the fall a boar stud was established
in conjunction with the Endocrine Research Unit, a cooperative laboratory

-1-

-2-
between the Departments of Animal Husbandry and Physiology.

The boar stud was organized by N. L. First and since its in-
ception has been under the direction of J. E. Nellor, Director of
the Endocrine Research Unit. Initially 5 boars were housed and trained
for semen collection in a converted draft horse barn. In the fall of
1959 an experimental field trial on the fertility of artificially in-
seminated estrous-controlled gilts was conducted under the direction of
N. L. First, J. A. Hoefer and J. E. Nellor. An orally active progesterone
was fed for 15 days and the gilts artificially inseminated when they ex-
hibited standing estrus following the last hormone feeding. A farrowing
rate of 5A% was obtained on the 39 gilts synchronized for estrus and
serviced artificially.

Additional studies were conducted to examine A.I. techniques in
swine on the University Farm. Within a year the boar stud was expanded
to include 8 boars, and over 100 University sows and gilts had been in-
seminated. E. C. Miller, A. Borton and J. E. Nellor conducted a series of
studies on estrous synchronization and artificial insemination at the
Endocrine Research Unit which, in the fall of 1960, culminated in a field
trial. One hundred and fifty two gilts, on 11 cooperating central Michi-
gan farms, were put on treatment and inseminated during the controlled
estrus by artificial insemination. No consistent response was observed,
as results varied from herd to herd.

The artificial insemination program continued to expand and on
March 10, 1962 new facilities for the Endocrine Research Unit, including

a seperate Artificial Insemination Research Boar Stud, were completed.

The present facility, managed by A. Jaworski, was the first one constructed
specifically as a research center for swine A.I., and afforded the possibility
of expanded research programs and field trials.

To date at Michigan State University nearly #0 boars have been
trained and semen has been collected in excess of 2,000 times. More
than 1,500 females have been inseminated either in the campus herd or
in the field. The work presented in this report was initiated to: (I)
examine methods of handling and preserving boar semen and (2) to investi-”
gate factors influencing fertility of artificially inseminated swine.
In order to attain these objectives a number of storage techniques were
examined, and field trials were conducted at the Michigan State Univer-
sity swine farm, the Southern Michigan State Prison farm and the Ionia

Reformatory farm.

II. REVIEW OF LITERATURE

The Semen of the Boar

 

Collection procedure

The development of artificial insemination in any species requires
a simple and efficient method of obtaining semen from the male. Many
methods of semen collection from a boar have been attempted. Walton
(1933) described early methods where semen was withdrawn from the
vagina of a mated sow by suction or with a sponge. Coronel and
MasankayaArenas (195A) collected semen as it dripped from the external
genitals of a sow during mating. Recently Mihailov (1963) described a
new method of obtaining boar semen by inserting a removable tampon into
the uterine cervix of the sow and collecting the ejaculate as it runs
out of the vagina. The problem of contamination in any of these methods
is obvious.

Hammond (1957) noted that, whereas in the ram and bull coitus is
quick and the ejaculation mechanism is temperature sensitive, coitus
in the boar is a prolonged affair and ejaculation is stimulated by
pressure. Numerous artificial vaginas have been designed for collecting
semen from the boar. Ito et_gl. (l9h8a) observed that the average boar
ejaculation lasted 6 minutes 36 seconds (range 2 min. to 23 min. 35 sec.)
and collection equipment must make use of pressure stimulation throughout
this period. Various types of artificial vaginas have been described
(Glover, 1955; Polge, 1956b; Turkheimer 2:0. 21-, 1958 ,- Aamdal, 1960) all
of which make use of internal pressure to initiate ejaculation. Many

are fitted with rubber bulbs to control pressure levels and provide

-h-

-5-
pulsating pressure, while others make use of hand pressure or a spiral
wire into which the boar's penis locks.
Hancock and Hovell (1959) reported the collection of semen by hand
using a rubber glove. The "artificial vagina" is made by forming an
Opening in the hand with the encircling thumb and index finger. Ejaculation
is evoked by applying pressure to the spiral end of the boar's penis.
Although this method is attributed to Niwa (1958), a modification of this
principle was used earlier by McKenzie et 21. (1938) where a rubber tube was
placed around the penis instead of the rubber glove. Dziuk (1963) and other
workers in this country have been using the "glove" method for several years.
Collection by electrical stimulation was reported by Vera Cruz
(1959), and Arhiporec (1961) developed an apparatus which fractionates
the semen at collection. Some mention should also be made of Beseth's
(1962) findings which indicate a sensitivity of boar spermatozoa to
certain artificial vagina rubber liners.
Boars can be collected off a "teaser" sow as described by McKenzie
et 31. (1938) or they can be readily trained to mount a "dummy" (Rodolfo,
193kb, Hancock, 1959c). Descriptions and illustrations of various types
of "dummies" are cited by Glover (1955), Niwa et_al. (1959a), Rowson
(1959), and Aamdal (1960).
The question of boar nutrition and management under a program at
a boar stud has been investigated by Hanson (1951), Nikulina and
Ermakova (1962) and Stevermer e£_gl. (1961). In general, they observed

that exercise, direct sunlight and pasture were not essential for the

-6-
production of fertile semen. When boars were raised in confinement
there was no appreciable difference in libido or semen characteristics.
In addition, widely varying planes of nutrition can be tolerated by
boars without detrimental effects on spermatozoa. Dziuk (1962) related
that enforced exercise over an obstacle course was required of boars
at studs in France.

Ejaculate characteristics of the boar.

 

Volume, spermatozoa concentration and fractions.

The boar's ejaculate is unique among the domestic animals. The
composition of the semen and its manner of ejaculation were thoroughly
described by MCKenzie et‘el. (1938). More recent reports (Ito EE.§l-:
191+8a; Niwa, 1958; Hancock, 1959c; Self, 1959; Gerrits e1 21-: 1962)
generally agree with this earlier work. The boar ejaculate, characterized
by a large volume (average 250 m1.), contains four distinct fractions:
presperm, sperm rich, post sperm and plug. The plug averages about 20% of
the total ejaculate but can range from 5% to nearly 50%.

Spermatozoa concentration is in the neighborhood of 150 to 250 x 106 per

6

milliliter in the entire ejaculate but averages 600 x 10 in the sperm rich
fraction. Self (1959) reported that by collecting only the sperm rich
fraction, 60% of the total ejaculate~volume could be discarded with only a
loss of 20% of the sperm numbers. Niwa (1958) observed that most of the
sperm cells are ejaculated in the first half of a collection, 82% appearing

in the first two minutes. The sperm rich fraction was "ejaculated undulating-

ly", appearing as waves. The majority of the ejaculates contained only one

wave, but instances of four waves and irregular waves were also reported.

Frequency of ejaculation

Wallace (19h9) noted that when normal boars were regularly collected
over an extended period of time there were considerable variations in
both semen volume and spermatozoa concentration. Similar variations
have been reported by McKenzie et el. (1938), Ito et g1. (l9h8c) and Niwa
(1958). They also observed that frequency of ejaculation was an important
factor affecting not only semen volume and concentration but also sperm
morphology and duration of motility.

A boar should not be used more than once every two weeks according
to Rodolfo (193ha). Niwa (1958) stated that, with a collection interval
of three days, you can expect about 70-80% of the normal spermatozoa
output and an interval of 5 to 6 days avoids any effect on the semen
volume and sperm concentration. He also stated that a vigorous boar can
be used daily but twice daily collection is over use of a boar.
Pitkjanen (1962) observed that a boar avoided the dummy after two days
on a twice daily collection schedule. On a once daily collection the
volume remained constant but sperm concentration fell after a week. At
the end of five weeks of daily collection libido was diminished. A
once a week collection schedule resulted in no variation in sperm
number of semen volume. Gerrits et a1. (1962) noticed similar results on a
daily collection schedule with the exception that there was a significant
reduction in semen volume, and occasionally the ejaculate was devoid of
spermatozoa. A h8 hour collection interval resulted in the greatest total
sperm production. By examining reserves of epididymal spermatozoa in the
boar, Singh (1962) estimated that the average daily production of sperm-

atozoa was 13.9 x 109. On the basis of these findings he concluded that a

-8-
3 to A day interval between collections was necessary for optimal semen
concentrations.

Radford (1961c) observed that variations in boar ejaculates depended
far more on the type of artificial vagina used than on the frequency
of collection. Although the variation in volume with collection interval
was not significant in boars over two years old, there was a significant
(P<70.01) increase in the sperm concentration as collection interval
increased. He recommended a four day interval for immature boars and
a two to three times a week collection for mature boars. On this
schedule he estimated that the average mature boar could produce semen
annually for 1,000 to 1,500 inseminations and the immature boar semen
for 550 to 600 inseminations.

McKenzie §£.§l° (1938) reported an increase in abnormal spermatozoa
with increased frequency of collection and considerable variations
between boars. Gerrits et 31. (1962) confirmed this finding. Niwa
(1958) and Gerrits et el. (1962) estimated the average percentage of
abnormal sperm in healthy boars to be between 5 and 10%. MCKenzie et el.
(1938), Niwa (1958), Hancock (1957b) and Hancock (1959c) described the types
of abnormal sperm found in boar semen. The highest proportion of the
abnormal spermatozoa were either immature with protoplasmic drops or
coiled-tail spermatozoa.

McKenzie gt g1. (1938) reported that the duration of sperm motility

increased as the interval between collections increased. The average
duration of motility of samples collected at 12 hour intervals from 5

normal boars was 2.5 days while the duration of motility increased to

-9-
8.5 days in samples from a 72 hour collection interval. Pitkjanen
(1962) also noted that spermatozoa from samples collected once or twice
weekly survived longer than in samples collected more frequently.

Age of boar.

A major factor affecting the composition of the ejaculate is the
age of the boar. Turkheimer gt _a_l_. (1958), Bane (1959), Niwa 343 2.1:
(1959b) and Radford (1961c) observed that in young boars the semen was
of a poorer quality than in mature boars. Initial ejaculates were
often contaminated with urine, low in volume and sperm concentration,
and contained a large number of immature or abnormal spermatozoa. How-
ever, with increasing age, a successive improvement in semen quality
occurred. Turkheimer et_§1. (1958) obtained first ejaculations from
young boars at 120 to 133 days of age and by 3b to A6 weeks semen output
per ejaculate had reached a high level. Niwa et el. (1959b) also noted
the appearance of spermatozoa first at four months and after six months
spermatogenesis was described as vigorous.

Season of the year.

The season of the year also influences the composition of the
ejaculate. Okauchi and Hirakata (1962) reported that semen volume was
lowest during the seasons of maximum and minimum environmental tempera-
ture, although this did not have a significant influence on the numbers
of spermatozoa. Stevermer et_§1, (1961) agreed that volume increased
during the moderate fall months but they also noted that total sperm-
atozoa numbers were highest in the summer. (June through August).

During the summer a decrease in viability and the percentage of live

-10-
spermatozoa was observed by Okauchi and Hirakata (1962), Mizuho
et el. (1963b) and Corteel (1963). At the French boar stud in Poitou
Corteel (1963) noted that the rejection rate of ejaculates due to dead
or a high percentage of abnormal Spermatozoa was five times greater
from August to November than it was for the remainder of the year.
Chemical composition of boar semen.

The first major investigation into the chemical properties of
boar semen was undertaken by McKenzie et_el. (1938). They analyzed
boar semen for chlorides, glucose, urea, creatinine, solids and total
organic nitrogen. It wasn't until Mann's (195A) studies on the bio-
chemistry of semen that complete semen analyses were reported. His
book presents an excellent review of the chemical composition of the
boar's ejaculate. Additional information can be found in the works of
Glover and Mann (l95u), Glover (1955), Niwa (1958), Polge (1959), Self
(1959),Bia1y and Self (1959), Aalbers 23.21- (1961), and Hartree (1962).
They substantiate Mann's report that the boar seminal plasma has an
unusually low content of fructose and sorbitol and a remarkably high
content of citric acid, ergothioneine and inositol as compared to other
animals.

Recent emphasis on the biochemistry of boar semen revolves around
the work of Graham.(l963) in Minnesota. Analysis of the carbohydrate
components of semen indicated that fructose, glucose and sorbitol are
metabolized, while mannitol and glycerol serve as intermediates. The
amino acids of boar semen were also isolated and identified. Glutamic

and aspartic acid concentrations were as high as 60 mg. %. The total

-11-

nitrogen content of boar semen ranged from #00 to 800 mg. % of which 1h

to 28% was non-protein nitrogen. The Minnesota researchers are also
studying the phospholipid content of boar semen. Graham and Mann, as well
as others, emphasize the marked variability in composition of boar semen.
Extreme variation exists between boars as well as a large and signifi-
cant variation between ejaculates from the same boar. It is interest-

ing that many of the factors which affect ejaculate volume and concen-
tration are also reported to affect its chemical composition.

Boar Semen Storage

 

Temperature

The boar ejaculate has already been described as differing from
that of the bull and ram by virture of its large volume and comparitively
low sperm concentration. In addition, researchers have found that boar
spermatozoa are unique in their behavior in’yitrg. Niwa et.§1. (1959a)
reported that 150 t0 200 C was the optimal temperature for maintaining
motility in the whole ejaculate. The sperm survival at these relatively
high temperatures was remarkably longer than that observed with bull and
ram spermatozoa. Boar semen storage at the "usual" temperatures (around
50 C) resulted in spermatozoa death. By contrast, the sperm rich
fraction of boar semen is similar to other species in that sperm survival
at high temperatures is relatively-short and motility can be maintained
at temperatures of 30 to 100 C. Polge (1959) suggested that some factors
in the boar seminal plasma were responsible for the high temperature
survival, and that bull and ram spermatozoa stored in boar seminal fluids

had increased survival at 200 C.

-12-

Aalbers et el. (1961) noted several other unique features of the
boar ejaculate. Whereas bull and ram spermatozoa maintain their
motility equally well under aerobic and anaerobic conditions, boar
spermatozoa are comparatively ineffective anaerobes. Under aerobic
conditions the R.Q. of the boar spermatozoa equals that of the ram and
bull and boar spermatozoa were able to oxidize lactic acid (the main
product of anaerobic fructolysis) as well as other substrates. How—
ever, it was reported that boar spermatozoa were incapable of oxidizing
sorbitol. Aalbers et 21- (1961) also noted that oxygen uptake of the
boar ejaculate was not entirely by the spermatozoa, but was in part by
the seminal plasma itself. In fact, even with a declining motility the
oxygen consumption increased upon storage lg 32:39.

Anabiosis

Another peculiarity of boar spermatozoa concerns their behavior
during storage, wherein they quickly lose their motility and settle out.
This property of boar semen has been referred to by the early Russian
and Japanese workers (Ito et a1.,19h8c) as anabiosis. Sperm cells that
have undergone anabiosis can be re-activated by warming to 370 C and
shaking in the presence of air. As demonstrated by Polge (1956b) and
Niwa (1958) reactivation may require 2 or 3 hours following a period of
storage. This peculiarity of boar semen must be considered in any study
in which motility estimates are made of stored samples.

Mizuho et 21. (1960) observed a close relationship between metab-
olism and anabiosis. When boar semen was stored at low temperatures

anabiosis occurred earlier than when semen was stored at higher

-13-
temperatures. In an attempt to control this sedimentation or anabiosis,
Wettke _e_t_ _a__l__. (1962b) examined the influence of adding gelatin to
various storage diluents. In all diluters studied gelatin was effective
in reducing or preventing sedimentation, but sperm motility was also
reduced compared to gelatin free controls. Mizuho e; 21. (1960) also
mentioned that anabiosis was prevented and metabolism maintained, even
at low temperatures, by shaking. This may have a practical implication
for transported semen, since the shaking in transit could cause a loss
in energy and viability through maintenance of high metabolic levels.
Prokopcev (1963) also noted that agitation was harmful to stored semen.
Samples that had been agitated had an increased pH.
Diluters and extenders.

With these behavior peculiarities in mind, research was undertaken
to formulate diluters and storage procedures specifically for boar
spermatozoa. The ideal diluter should serve to preserve spermatozoa,
extend the volume, prevent temperature shock and provide a buffer system
without any loss in fertility. The early Russian diluters, as described
by Walton (1933) and Rodin and Lipatov (1936), contained gluCose and
small amounts of sodium sulphate or sodium potassium tartrate and peptone.
Ito et_g1. (l9h8c) preserved undiluted semen at 200 C for 5 days but
vigorous motility was retained for only about two days. They also noted
that Kreb's phosphate, Ringer's solution and physiological saline did not
harm the sperm cell and could be used to increase volume. The advent
of sperm diluents containing egg yolk by Lardy and Phillips (1939), or

milk and milk products (Thacker and Almquist, 1951) resulted in con-

-1h-
siderable investigation into their use for boar spermatozoa. While Polge
(1959) indicated that boar spermatozoa would not survive at 50 C in the
typical yolk-citrate medium used for bulls, both milk and egg yolk have
become important components of recent boar semen extenders. Jakobsen and
Mann (1960), while working on biochemical methods of appraising semen
quality, noted that the action of a milk diluent was not so much to
provide an additional nutrient substrate as it was to provide a protective
or life preserving effect. They ascribed similiar actions for egg yolk
and other colloidal substances. These diluter components acted not to
increase the initial rate of metabolism but rather to maintain it over a
period of time. On the other hand, Mizuho et_el. (1963a) reported that
both egg yolk and milk not only preserved good sperm motility but also
caused an acceleration of respiration and glycolysis.

A large scale study of over 200 extenders was conducted at Cornell
(Young et e1.,1957) where various combinations of sodium citrate, sodium
phosphate, sodium bicarbonate, glucose, glycine, glycerol, inositol and
egg yolk were examined. They observed the best survival in a diluter
of 20% egg yolk, .33% citrate, .33% glycine and 1% glucose stored in
sealed vials at 150 C. The addition of .75% sodium bicarbonate and 1.25%
inositol also gave satisfactory results. They reported 20% egg yolk
superior to 50%. Dzuik (1958a) examined over #00 semen samples in 26
diluters. From a motility basis he observed the most satisfactory
diluters contained glucose or glycine and egg yolk or milk. Optimum

motility was attained when semen was stored at 70 C in a diluter of 3 gm.

glucose, 0.15 gm. sodium bicarbonate, 30 ml. (30%) egg yolk and 70 m1.

-15-
distilled water plus penicillin and streptomycin. Niwa (1958), Hess
et_el. (1960a) and Feredean et_§l, (1962) also obtained best results with
egg yolk diluters.

Irwin (1959) compared glycine and citrate in egg yolk and milk at
different temperatures and obtained the most satisfactory results with
a combination of egg yolk and milk at 50 C. Pasztor and Toth (1962)
compared six milk diluents; heated skimmilk with 2% egg yolk gave the
best sperm survival. Paredis (1959) also reported that skimmilk powder
with some egg yolk made a more satisfactory diluter than egg yolk alone.

Subin (1962) tested diluents containing egg yolk, citrate, glucose,
bicarbonate, or milk stored at three temperatures; the greatest
motility was maintained at 150 to 200 C when the extender contained
bicarbonate, citrate or milk. No advantage was obtained by adding egg
yolk or glucose to milk. All diluents were unsatisfactory at storage
temperatures of 00 C.) Whole milk or skimmilk as extenders have been
popular with other workers. Although Dzuik (1958a) obtained optimum
motility with a yolk extender he also received good motility results
with a skimmilk-glucose-distilled water extender. Niwa et_gl. (1959e)
reported satisfactory results with a milk powder diluent. Self (1959),
Bialy and Self (1959) and Stratman (1961), maintained sperm motility for
the longest period at 90 C storage with a heated homogenized whole milk
extender. Several heated skimmilk-glycine-egg yolk diluters were also
examined and found to be superior to the egg yolk-glucose-bicarbonate
diluter.

Mizuho et_§1. (1963a) depressed sperm respiration and glycolysis

-16-

with the addition of sugars to milk and egg yolk extenders. Pasztor
and T6th (1962) indicated that the addition of glucose did not increase
spermatozoal survival. Radford (196ld) augmented semen with fructose
and increased survival, although it was not sufficiently improved to
be considered a good storage technique. Numerous other ingredients have
been utilized. For example, Arhiporec (1962) benefited motility with small
amounts of ascorbic or salicylic acid while Prokopcev (1963) utilized
boric acid.

Sodium citrate is a common ingredient of bull diluents. Noll
(1919), Young et _a__1_. (1957), Hammond (1957), Dzuik (1958a), Gotink
(1959) and Polge (1959) however, reported that citrate appeared to be
toxic to boar spermatozoa. Aamdal and Hogset (1957) and Bane (1959),
in contrast, obtained satisfactory conception rates with an egg yolk-
sodium citrate diluter. This anomaly was explained in part by Niwa et el.
(1959d), who indicated that sodium citrate was harmful to semen unless
it was mixed with egg yolk at a rate not to exceed A to 1. Another
common ingredient of bull extenders, for freezing, is glycerol but
Young e_t_ g_l_. (1957), Polge (1959) and Graham (1963) observed that
glycerol decreased boar sperm motility.

The inclusion of antibacterial agents in semen extenders is a
common practice. Yoshida et_el. (1951) examined various agents for
bacterial control in boar semen stored at 200 C. The addition of
streptomycin, sodium sulphamerazine, sodium sulphadiazine, homosulphamine
or boric acid increased the duration of boar spermatozoa survival. The

sulpha compounds were more effective when combined than when used alone.

-17-

Mizuho EE.EI° (1963a) noted that streptomycin and penicillin in com-
bination were suitable, but chlortetracycline adversely affected sperm-
atozoa at concentrations compatible with antibacterial efficiency.
Coronel and MasankayeArenas (195h) tested the effect of antibiotics in
eleven different diluters and concluded that variations in viability of
boar spermatozoa were as much due to quality of individual samples as to
the different types and proportions of antibiotics. However, anti-
bacterial agents are widely used in swine semen diluters and have been
demonstrated by Polge and Rowson (1956) to improve fertility. The most
popular antibiotic combination at present is streptomycin and penicillin.

Spermatozoa survival in storage was the highest when the seminal
fluids were removed (Stratman 1961). Removal of the accessory fluids by
centrifugation was discussed by Bialy and Self (1959) and Self (1959).
Centrifuging significantly lowered the motility of stored spermatozoa
compared to non-centrifuged controls after two days storage. Dott and
Walton (1960), working with ram semen, commented that resuspension of
the sperm cells was difficult after centrifuging semen. Manipulation of
spermatozoa resulted in increased agglutination or clumping of motile
spermatozoa. This phenomenon is a common problem and its occurrance has
been recorded by Bialy and Self (1959) and Aalbers et 21- (1961).

Although Noll (19h9) reported no difference in sperm survival under
anaerobic or aerobic conditions, Young et 31. (1957) obtained a signi-
ficantly better survival of semen stored in sealed ampullas as opposed
to corked tubes. Even though sperm activity was reduced in a CO2

atmosphere no increase in survival was obtained by Polge (1959) with

-18-

storage in either a C02 or nitrogen atmosphere at 200 C. Arhipovec
(1961), Ben Joseph and DuMesnil du Buisson (1962), DuMesnil du Buisson
and Dauzier (1959) and Foley (1962) have experimented with the effect
of C02 saturated diluters or C02 atmosphere on boar sperm survival, the
French workers reporting excellent results.

Investigations into the effect of osmotic pressure on the preserva-
tion of boar spermatozoa have been conducted by Stevermer et_e1. (1962,
196A). Using a skimmilk diluter, osmotic pressure was controlled by
adding mesoinositol or D-fructose. Motility was highest between freezing
point depressions of -.A20 and -.5h8O C. Fertility, based on only
limited breedings, was significantly (P<(.05) greater at a freezing

point depression of -.5360 C compared to -.1+20O C and -.1+80O C.

They concluded that osmotic pressure may be a more important factor in
maintaining motility and fertility than is generally recognized.
Numerous ranges of temperatures have been investigated for the
storage of boar sperm. It appears that 5 to 120 C is most satisfactory
for fractionated ejaculates and 15 to 200 C for whole ejaculates. The
rate of cooling of the sperm cell is of equal importance. The phenomenon
of "temperature shock" long recognized to occur in the semen of other
species has not been critically studied in boar spermatozoa. Since the
volume of the ejaculate is large it is not as obviously susceptible to
environmental temperature variations. Lasley and Bogart (l9hh) examined
the influence of cold Shock on boar spermatozoa and observed that
epididymal spermatozoa had a higher resistance than did ejaculated

spermatozoa. However, investigation revealed that the secretions of the

-19-
accessory glands did not in themselves greatly influence the resistance
of the boar spermatozoa. Further, they observed that the fluids of the
epididymis did not increase the resistance of ejaculated spermatozoa
but an egg yolk-phosphate buffer did provide temperature shock protection
for both epididymal and ejaculated spermatozoa.

-Diluted boar semen suffered less damage from slow cooling than from
quick cooling (Willems, 1959). Slow cooled spermatozoa maintained a
60% motility at A days while quick cooled spermatozoa had a rapid loss
in motility after 2h hours. Feredean et.e1. (1962) reported that the
optimum cooling time for boar spermatozoa to refrigerated temperatures
was 10 to 12 hours. Dzuik (1958) suggested a rate of less than 50 C per
hour. Mizuho et 31. (1963a) observed temperature shock to be more marked
in rapidly cooled samples.

The role of semen dilution and its interrelationship with spermatozoa
resistance to cold shock has been the subject of conflicting reports.
Choong and Wales (1962) reported that diluted suspensions of bull
spermatozoa were more susceptible to cold shock than more concentrated
samples. However, Lasley and Bogart (19Ah) indicated that the degree
of dilution had no influence upon the resistance of boar spermatozoa
to cold shock.

A deleterious effect of dilution on the boar sperm cell was sug-
gested by Kvasnitsky (1959). Ito et 31. (19A8c) and Niwa (1958) re-
commended that dilution not exceed 1:6 and preferably less for semen
extended with physiological saline at the time of insemination. Rodin

and Lipatov (1936) noted that a h fold extension gave satisfactory results.

-20-
Boar spermatozoa did not survive as well in higher dilutions of 1:20
as they did in lower dilutions of 1:2 or 1:5 (Polge 1959). On the other
hand, Dziuk (1958) indicated that 1:1 dilutions had lower motility on
storage than 1:2, lzh or 1:8 dilutions. Mizuho et el. (1963a) reported
that with rapid addition of diluter the depression of motility and metab-
olism were proportional to the extent of dilution. The degree of dilution
shock varied according to the temperature at which dilution took place
and little damage was done to sperm cells in a 1:10 dilution if the
dilution was made gradually. Holt (1959) observed that a dilution of
more than 1:10 could be used without a loss of fertility.

In summary, a number of diluters, temperatures and techniques for
the storage of boar spermatozoa have been examined but no completely
satisfactory method has been developed. Diluting fluids containing
either milk or egg yolk have been satisfactory for the maintenance of
motility for about 7 to 10 days at refrigerator temperatures. The
longest duration of motility noted in this review was 19 days at 120 C.
(Irwin, 1959). It was observed by Aalbers et_§1. (1961) that a large
proportion of boar spermatozoa could be regarded as motile during
storage, but only a very small portion could be regarded as progressive-
ly motile. Critical motility estimates are further hampered by agglutin-
ation of spermatozoa, anabiosis and the accompanying necessary reactiva-
tion process. El Sheikh and Casida (195A) suggested that with rabbit
spermatozoa motility lg £1339 and fertility may not be similar physiol-
ogical phenomena. Hammond (1957) noted that many researchers have

observed that fertility was lost even though motility was retained.

-21-

Self (1959) observed that the percentage of motile spermatozoa was not
significantly correlated with the percentage of fertilized ova obtained
with the same sample. While there was a highly significant association
(r = 0.89, P('0.01) between percent fertilized ova and the type of
motility in fresh semen this relationship did not exist in stored semen.
The data of Stevermer et_g1. (196A) indicated that motility of stored
spermatozoa was not a reliable indicator of fertility. It is apparent
that significant contributions to boar semen storage methods must be
accompanied by fertility information.
Freezing boar spermatozoa.

To date attempts at storage of boar semen by freezing have not
been successful. Many (Roy, 1955; Hess et al., 1960b; Hoffman, 1959;
Bane, 1959; Niwa et al., 1962; Dukelow and Graham, 1962; Settergren, 1958;
Polge, 1959) have obtained some motile spermatozoa after thawing frozen
semen but only two investigations have reported any conceptions re-
sulting from the use of frozen boar semen. Hess e: 21. (1957) artificially
inseminated 25 gilts with boar semen which had been stored at «950 C for
l to 19 days. The gilts were slaughtered 20 to 60 days following A.I.
Seven of the gilts had an average of 9.A embryos. Hoffman (1959) in-

seminated 11 sows with semen frozen at -790 C and one sow farrowed a

litter of nine pigs. This was the only record found of a litter produced
with frozen boar semen.

Although there have been few successes with frozen boar semen some
important contributions have been made. The N8rdiska Veterinarmotet

Report (1958) along with Settergren (1958) established that boar semen

-22-
froze better in small rather than large containers. The largest
volume they successfully froze was 15 ml. in long narrow tubes, but
Hess e: 21. (1960b) reportedly utilized 50 m1. heat resistant bottles.
Polge (1959) and Hoffman (1959) observed sperm survival best when the
seminal plasma was removed before freezing; however, Niwa et_§1. (1962)
determined that the seminal secretions did not have adverse effects.

Clycerol has been an essential ingredient in bull and ram freezing
diluters, but the glycerol levels necessary for best cell recovery
from freezing caused a decrease in motility of the boar spermatozoa
(Young ep_g;. 1957, Polge 1959 and Graham 1963). Even though it appears
that glycerol is more toxic to boar spermatozoa than to bull or ram
spermatozoa, it was an ingredient in all the freezing attempts where
satisfactory motility was observed following thawing. Recent work
by Niwa e: g1. (1962), Dukelow and Graham (1962) and Graham (1963) in-
dicated that short equilibration times of h to 6 hours with 5 to 7%
levels of glycerol were the most satisfactory for maximum recovery of
spermatozoa motility.

Dukelow and Graham (1962) reported the most critical temperature
for freezing boar semen was between -80 C and -380 C. Freezing rates of
10 to 30 C per minute were recommended. Niwa et_gl. (1962) proposed a
differential freezing rate of $0 C per minute to -100 C, 50 C per
minute to -300 C and 50 to 100 C per minute down to -790 C. The
maximum motility following freezing was 60% reported by Niwa ep.al.
(1962).

Skimmilk, whole milk, egg yolk, glucose, glycine and sow's milk

-23-
have been tried as components of frozen boar semen extenders. The
problem of freezing boar semen with successful preservation of its
fertilizing ability, however has not been resolved.

Physiology of Breeding the Sow

 

Natural matihg

 

The natural mating of a boar and a sow is a prolonged event.
The boar will spend considerable time pushing and nudging the sow prior
to mounting. If the sow is in estrus she will stand quietly and accept
the overtures of the boar. Although Milovanov and Sokolovskaya (19h6)
and Burger (1952) believed the boar's penis penetrated the cervix and
ejaculation occurred into the uterus, more recent work by Smith and
Nalbandov (1958) indicated that the penis penetrates only midway into
the vaginal portion of the cervix. In contradiction to Burger they
reported the cervix of the sow did not relax but rather constricted at
estrus. Utilizing a system of radiographs they also observed that the
penis only penetrates the cervix to the depth of a few centimeters,
where the annular rings seem to grip it, bringing about ejaculation.
These findings concur with earlier reports by McKenzie ep 521- (1938),
Anderson (l9u5), Hammond (1957) and Polge (1956a) that semen was de-
posited in the vaginal portion of the cervix. The large volume of the
ejaculate evidently forces semen into the uterus and the gel plug serves
to reduce its flowback. McKenzie et_§1. (1938), Anderson (l9h5) and
Burger (1952) observed that although the plug will effectively seal the
cervix following a natural mating it is not indespensible for successful

conception.

-2h-
Artificial insemination procedures.
Catheters

The insemination catheters developed for artificial insemination of
swine have been designed with the anatomy of the cervix in mind. Most
commonly used in this country are the plastic dairy insemination
catheters, which many workers modify by corkscrewing the end to fit into
the annular rings of the cervix. Almquist (1959) summarized the in-
seminating equipment used in other countries, including catheters made
of glass, rubber, ebonite and plastic. Aamdal and Hogset (1957)
developed an insemination tube that had an inflatable balloon near the
tip that was designed to seal the cervix and thereby force semen into
the uterus. Melrose and O‘Hagan (1962) compared this Norwegian catheter
to other varieties and in general found no significant difference in
conception rates due to type of catheter. However, they did find the
Norwegian catheter superior to the Japanese hard rubber catheter
described by Niwa e: 2;. (1959c).

Site of semen deposition in artificial insemination.

The actual extent to which the insemination catheter penetrates is
the subject of some controversy, although it is generally agreed that
the site of deposition depends on the age of the pig and the type catheter
used. Smith and Nalbandov (1958) examined the size of the cervical
opening and expressed doubt if even the smallest of their probes
entered the uterine portion of the cervix, much less the uterus itself.
Melrose and O'Hagan (1962) examined the passage of catheters at different

stages of the estrous cycle and found the deepest penetration occurred

-25-

when animals were not in estrus. Japanese researchers (Ito ephel.,
l9h8b) place the site of insemination as the second prominence of the
cervix uteri. This it appears that artificial insemination at estrus
deposits the semen in approximately the same place as in natural mating,
and penetration of the uterus by the pipette does not occur.

Holt (1959) and Hancock (1959a) however, reported fertility dif-
ferences based on intrauterine and intracervical inseminations.
Fertility was higher when semen was reportedly deposited in the uterus
than when placed in the cervical canal (Hancock,l959a); conception was
not obtained with vaginal inseminations. On the other hand, Holt (1959)
observed no difference in conception of intrauterine as compared to
intracervical insemination but convencing proof of the extent of pene-
tration of the catheter was not presented. Paredis (1961a) found no
relation between the depth of insemination and conception rate.

Semen injectors.

Because of the relatively large volumes involved, several methods
of placing the semen into the female tract have been developed.

Almquist (1959) describes the use of syringes, gravity flow bottles, in-
fusion pumps and plastic squeeze bottles as "injectors". Gusev (1962)
describes a disposable plastic bag, the content of which is emptied into
the insemination tube by squeeze pressure. Holt (1959) observed that
the conception rate was slightly higher with insemination by gravity
flow instead of pressure, but the highest conception occurred when a
combination of the two methods was employed. DeMesnil du Buisson

(1961) reported inseminating 10,000 sows in the field by means of flow

-26-
by gravity. The time required for 250 ml. was A to 7 minutes, the speed
being dependent on uterine contractions on the part of the sow.

Stimulation at mating,

 

Hammond (1957) and Polge and Rowson (1956) suggested that considerable
stimulation of the female cervix occurs at natural mating and may be
involved in a subsequent oxytocin release, which in turn could influence
uterine muscle contractions. Artificial insemination therefore may be
deficient in stimulating one of the physiological mechanisms involved
in sperm transport. It would appear also that gilts and sows should
be handled quietly prior and during insemination since adrenalin re-
lease has been shown to counteract the action of oxytocin (Polge and
Rowson, 1956).

Pitkjanen (1955) suggested that the act of mating may influence the
time and number of eggs shed. Examination of sows slaughtered following
estrus indicated that 88% of those mated had shed eggs compared with uni
for those not mated. When sows were mated to a vasectomized boar 28.5%
more ovulated than with the unmated control.

gfierm transport.

 

It is generally accepted that the horns of the uterus are filled
with semen soon after mating. Spermatozoa reach the utero-tubular
junction within 10 minutes (Mann et_§1., 1956) but the passage into the
oviducts may be somewhat slower. Pikjanen and subin (1961) detected no
spermatozoa in the oviducts 1% hours after insemination although some
spermatozoa had reached the mid-portion 2 hours after A.I. Ito et_g1.

(l9hh) determined that semen reached the Fallopian tubes 5 hour after

-27-
mating. They also observed, as did DuMesnil du Buisson and Dauzier
(1955b), that the rate of transport of spermatozoa was affected by the
stage of estrus, being more rapid toward ovulation.

The large volume of a boar's ejaculate may be necessary to fill the
greater length of the sow's uterine horns, (Hammond, 1957). In addition
the sow possesses less uterine fluid at the time of estrus than does
the cow and ewe. DuMesnil du Buisson and Dauzier (1955a), Mann et_§1.
(1956) and Lovell (1958) noticed that the large volume of the boar
ejaculate was quickly absorbed, the bulk disappearing within 5 to 8
hours. Seminal secretions and a large percentage of spermatozoa
disappeared from the tract during this time. Spermatozoa disappearance
was least and survival greatest at the utero-tubular junction. The rate
of disappearance did not appear affected by phase of estrus. Ito et_el.
(19HA) ascertained that spermatozoa viability in the sow's tract could
last h2§ hours and maintain fertilizing ability for 25 to 30 hours.
Pitkjanen and Subin (1961) estimated that 80% of the spermatozoa in the
oviducts were motile after 6 hours and some progressively motile sperm-
atozoa were present in the horns after A8 hours. McKenzie et 31. (1935)
recovered viable spermatozoa from the Fallopian tubes 5 hours after mating.

Optimum time to service.

 

Since the viability of the ova and spermatozoa in the female tract
is limited,it is important that service, either natural or artificial,
are in proper relationship to the time of ovulation. Hancock and
Hovell (1962) observed that fertilization failure was the greatest

single cause of low conception when inseminations were made too early

-28-

or late in the estrous period. This was interpreted as a failure of the
spermatozoa to reach the ova rather than a loss of fertilizing ability,
since spermatozoa were not found in the zona pellucida of the ova.
Mating late during estrus also increased the frequency of polyspermic
fertilization in swine (Hancock, 1959b) and might represent a source of
embryonic mortality in A.I. swine.

Ito e£_e1. (19AM) studied normal estrus in swine and reported
the optimal time of service was 10 to 25.5 hours after the onset of
estrus. A Wisconsin field trial involving several hundred sows (Self,
1961) indicated that sows inseminated within 12 hours after the onset of
estrus had a significantly (P<0.01) higher farrowing rate than sows
serviced over 2h hours after the start of estrus. This relationship
did not apply to gilts where no significant difference in conception
rate due to time of insemination was evident. Bane (1959) and Madden
(1959a) also obtained highest fertility with sows inseminated in the
first 2h hours of estrus. 0n the other hand, Rodin and Lipatov (1936),
Stratman (1961) and Hancock and Hovell (1962) obtained a higher fertility
by breeding on the second day of estrus in sows. Madden (1959b) could
not determine a pattern in fertility of gilts bred 1 to 60 hours after
the onset of estrus. Radford (1961b) reported a higher farrowing rate
for gilts bred on the third day of estrus as compared to the second day,
irrespective of whether they stood to be served.

Madden (1959b) determined the first post weaning estrus was more
fertile than subsequent ones, but with a limited number of sows Self

(1961) reported the conception rate highest when sows were bred on

-29-
the second day of the second post lactation estrus.

Sow behavior at breedigg.

 

Behavior at the time of service may influence conception.
Radford (1961b) obtained a higher farrowing rate from sows that stood
firm when serviced compared to those that moved. Madden (1959b)
acquired a 7% difference in farrowing rates in favor of sows that
stood during service. No relationship was noted between swelling or
reddening of the vulva and conception. Holt (1959) also utilized the
swelling of the vulva as a guide to stage of estrus but found it un-
reliable. A 63.8% farrowing rate was obtained when sows were "very
quiet" at breeding but only a 3h.l% rate when they were "agitated"
(DuMesnil du Buisson, 1961). Self (1962) also reported a significantly
higher rate for sows and gilts in standing estrus.

Artificial Insemination of Swine

 

Artificial insemination has not developed as rapidly with swine as
it has with some other species, primarily because of some of the problems
already cited. The first relatively large scale use of artificial
insemination was with horses around the turn of the century. Professor
Elie Ivanov of the Russian State Stud, the father of modern A.I., was
named director of the Russian Central Experimental Breeding Station in
1919 and he instigated research on preservation of semen and insemination
techniques in all Species. An excellent history of these early years of
artificial insemination was presented by Walton (1933). The Russians'
first published report on swine artificial breeding was presented by

Milovanov (193A). McKenzie, Lasley and Phillips (1939) were the first

-30-
to report successful artificial insemination of swine in this country.
From this beginning swine A.I. is now under investigation in many
countries and in commercial operation in several.

Methods of calculating fertiligy.

 

Conception rates for swine cannot be accurately calculated on a
non-return basis. Swine are not usually maintained under intensive
surveilance by the farmer and consequently estrus detection is not very
accurate. An artificial insemination trial of over 1,000 sows was
reported by Holt (1956) where the non-return rate was calculated as 71%.
At farrowing, however, only 1h% had litters. Polge and Rowson (1956)
decided that 30-60 day non-return figures bore little relation to
farrowing, figures being 65% for the former and 2h% for the latter.
Instances of gilts and sows failing to Show estrus after breeding and then
proving to be non pregnant are common (Hancock and Hovell, 1961;

Melrose and O'Hagan, 1959; Polge and Rowson, 1956). The major reason

for infertility of sows has been attributed to embryonic death (Warnick
et 31., 19h9). The conception rate is always lower if calculated from
fetuses present at 25 days than if calculated from sow's with cleaved

ova at 3 days (Self, 1959; Stratman and Self, 1960). Considerable
fertility research has been reported on the basis of 3 day slaughter
data. Self (1959) and Dziuk (1960), however, emphasize the errors in-
herent in this system where fragmented ova may be mistaken for fertilized
ova. First 23 21. (1963) indicated that 3 day slaughter data may still
have validity if the spontaneous cleavage rate is determined for the

population under investigation.

-31-

Although several methods have been used to calculate swine
fertility, the most desirable is farrowing rate based on first service,
along with average litter size (Almquist, 1959; Rowson, 1962). A report
on swine artificial insemination in the European countries by Beattie
et a1. (1961) emphasized that farrowing rate may be misleading as a
criterion of A.I. success if some of the sows were rejected by the
inseminator at the time of service for not showing sufficient indications
of estrus. To illustrate, they calculate that a 70% farrowing rate
with a 15% rejection rate means that only 58.5% of the females presented
to the inseminator became pregnant.

Several workers have compared the conception rates from first
services with repeat breedings. Holt (1959) detected no difference in
farrowing rates of first inseminated compared to reinseminated sows.
Similarly, Madden (1959a) experienced no difference between first
inseminations and repeat inseminations in the first 1,000 females
serviced in a field study; however, later results indicated a slight but
nonsignificant increase in favor of the first insemination. Self (1961)
and Jacobsen (1959) observed a slight but nonsignificant increased
farrowing rate in first serviced sows over reserviced sows. Whereas
Self noted no difference in farrowing rates of first serviced and rebred
gilts, Jacobsen (1959) observed that the reserviced gilts had a signifi-
cantly (P( 0.05) higher farrowing rate.

Natural mating compared to artificial insemination.

 

Several workers (Stratman, 1961; Stratman and Self, 1962; Subin,

1962; Niwa, 1958) have reported no appreciable difference in conception

-32-

rates or litter sizes between sows bred naturally and those mated
artificially. Others (Lovell, 1958; Paredis, 1961) observed that con—
ception rates on artificially mated sows generally ran 10 to 12% under
naturally bred sows. Hancock (1957a) ascertained that 91% of the ova
from 15 naturally bred sows were cleaved whereas in four groups of sows
serviced artificially the percent of cleaved ova ranged from 21.7% to
h7.8%. An 86% farrowing rate with a 10.9 average litter size was re-
ported by Madden (1959a) when 915 sows were mated naturally but when the
same sows were serviced artificially during the next breeding season only
h5% farrowed with an average litter Size of 10.A. Paredis (1961)
detected slightly higher litter sizes for natural mating than for A.I.
(i.e. 0.6 pigs), but this difference was not statistically significant.
Niwa (1958) observed that litter size as a result of A.I. does not

differ markedly from that of natural mating. Paredis (1962) used the
same A boars to breed 365 pigs, naturally and artificially, and ob-
tained a A8% conception rate on the artificially inseminated females

and a 3A% rate on those naturally bred, these conception rates were below
the local district averages.

Factors affecting fertility in artificially inseminated swine.

 

Diluters and extenders.

The components of swine semen extenders and their ability to
maintain motility has already been reviewed but some workers have
compared the fertility obtained with different diluents. Jokinen (1961)
compared a sodium citrate—glucose-egg yolk extender with one of powdered

nrilkeegg yolk and obtained no difference in conception rate between

-33-
diluters. An experiment comparing skimmilk-egg yolk, sodium citrate-egg
yolk and glucose-egg yolk (Paredis,1959) indicated little difference in
farrowing rate between the three diluters. There was a slight improve-
ment in favor of the milk-egg yolk diluter, however. Using the Split
ejaculate technique a slight but nonsignificant advantage in favor of
homogenized milk extender with 10% fat as compared to the egg yolk-
citrate extender was obtained by Jakobsen (1959), and similar results
comparing the same diluters were reported by Hansen EL.§I° (1960). With
a 0.2% sodium bicarbonate-glucose-egg yolk extender Gotink (1959)
obtained conception rates of over 75% in gilts. He found this buffer
gave better results than skimmilk, glycine or glucose buffers.

Corteel (1963) examined the effect of CO2 on farrowing rate using
a split ejaculate technique. This resulted in a 39.05% farrowing rate

with a 8.35 pig average with the IVT extender plus C02 gas and a 51.07%

farrowing rate with a 9.51 pig average with the IVT alone. Subsequently
a modified IVT without C02 gave a farrowing rate of 56.6% on 1373 first
inseminations. Finally, Polge and Rowson (1956) showed that the
addition of antibiotics resulted in a definite improvement in fertility
and litter size of both 6 hour and 2A hour old semen that was diluted
With a 2% glycine-egg yolk extender.
Motility.

The ineffectiveness of motility as a critical means of evaluating
semen is recognized, but several workers have related semen motility to
fertility. Selection of an ejaculate on the basis of initial motility

is likely to increase the conception rate according to Paredis (1961),

-3h_
who indicated that intensity of motility was related to pregnancy rate,
particularly in the extreme cases. Paredis and Vandeplassche (1962)
obtained a significantly (P<’0.05) higher conception rate when initial
motility was greater than 75% than when it was below 75%. Higher
incidences of pregnancy at 21 day slaughter were acheived by Hess et el.
(1960a) when semen motility was in the 80-90% motility range prior to in-
semination. Niwa EE.EI° (1959a) and Ito et 21. (l9h8b) recommend that
motility be at least 70% before an ejaculate is used for artificial
insemination.

Stratman et_§1. (1958) detected no significant association between
the percentage of motile spermatozoa ani the percentage of fertilized
ova at 3 days. When stored semen of h7% motility was compared to fresh
semen of 95% motility, the conception rates were approximately the same.
They concluded that motility was a satisfactory indicator of fertilizing
capacity of fresh semen but was not of stored semen. 0n the contrary,
the type of motility of stored semen was found to be closely related
to fertility by Missouri workers. (Lasley and Day, 1960).

Volume and spermatozoa concentration.

The relationship between volume of semen inseminated and fertility
achieved in swine may be extremely important. Hammond (1957) suggested
that the large volume of the boar's ejaculate may be necessary to
provide fluid to fill the greater length of the sow's uterine horn.
Rodin and Lipatov (1936) inseminated 1, 5, 25, 50 and 100 m1. of fresh
semen and recommended the larger volumes for the highest fertility.

wiéflgens e: g1. (1951) detected little difference in the fertility

-35_

(cleaved ova at 3 days) of sows inseminated with either 50 ml. or
250 ml. volumes. Self (1959) and Stratman (1961) reported no
difference in conceptions with 50 ml. or 100 m1. of undiluted fresh
semen. A 50 ml. volume produced a higher rate of embryo survival
(P('0.01) and conception rate (P<'0.05) than did 10 ml. or 20 ml. with
varying spermatozoa concentrations (Stratman and Self, 1960). It was
suggested that spermatozoa number did not affect litter size as much as
did the volume inseminated.

Hancock and Hovell (1961) compared 20 and 120 m1. volumes and
found no evidence that sperm transport was improved with the larger
volume. This was estimated by the number of spermatozoa in the zona
pellucida of recovered ova. Coronel (1953) reported that the semen
volume was not related to litter size, but his data were limited and not
analyzed statistically. He reported conceptions with as little as 10 to
12 m1. of semen. First g _a_1. (1960), with 19 inseminations in each
group, obtained a A2% farrowing rate using 35 ml. and 68% rate with 70 ml.
Pitkjanen (1955) indicated that the fertilization rate was 5b% greater
with 200 m1. as compared to 100 m1. but unfortunately the number of
breedings involved was not mentioned. Rothe (1960) found 100 m1. better
than 50 m1. and Polge (1959) reported that conception results were lower
With 25 ml. or 50 m1. than with 100 ml.

The role of semen volume in sperm transport is not thoroughly-
understood and the effect of sperm dilution ip'yiyg has been studied.
In this process a small concentrated amount of semen is first inseminated

and this is followed with a large volume of diluter. Rodin and Lipatov

-36-
(1936) reported inferior results from attempts to dilute lg YIYQ'
Kvasnickii and Konjuhova (1960) obtained a conception rate of 91.6%
when 20 ml. of undiluted semen was-placed in the neck of the uterus and
followed by 100 m1. of pure diluent and then 150 to 200 m1. of filtered
air. Melrose and O‘Hagan (1959) described a system where first 125 m1.
of diluted semen was inseminated followed by 100 ml. of extender con-
taining 25% freeze-dried gel. Although controls were not available for
comparison their conception rate was not appreciably different from
that of other workers. Hancock and Hovell (1961) inseminated one group
of swine with 20 m1. of semen and a second group with 20 m1. of semen
followed by 100 ml. of pure diluent. The first treatment resulted in a
significantly (P<70.05) higher fertilization rate and there was no
evidence from the number of spermatozoa in the zona pellucida of re-
covered ova that sperm transport was enhanced by the larger volume.

The relationship between sperm concentration and insemination
volume was examined by Polge (1959) who observed a 16% farrowing rate
with a 7.7 pig average at a low concentration and volume (.5 to 1 billion
spermatozoa in 25 m1.). At the highest concentration and volume studied
(10 to 20 billion spermatozoa in 100 ml.) the farrowing rate was 7W%
With a 10.5 pig average. Paredis and Vandeplassche (1962) indicated
that the number of spermatozoa retained in the female tract after in—
semination had a highly significant (P<’0.01) effect on conception rate.
The increased conception that occurred was more pronounced in sows than
in gilts. They also noted that litter size was significantly (P<’0.05)

smaJJer when spermatozoa numbers were less than 2 billion. Self (1959)

-37-

and Stratman and Self (1960) reported no difference in conception rates
or embryo survival between sperm concentrations of 2.5, 5 and 10 billion.
In a later study Stratman and Self (1961) observed no significant
difference in conception rates when 1.25 and 2.5 billion Spermatozoa
were inseminated. Dauzier and DuMesnil du Buisson (1959) reported that
conception rates were reduced when less than 6 billion spermatozoa were
inseminated. Paredis (1961) indicated that farrowing rate and litter
size increased with increasing spermatozoa concentration up to 7 billion.
0n the other hand, Radford (1961b) observed that spermatozoa concentrations
of 1 to 30 billion had no effect on farrowing rates or litter size.
Plisko (1961) noted no difference in conception when from 0.5 to 10
billion spermatozoa were inseminated but he did find conception rates
were lower when 0.3 billion spermatozoa were inseminated. Wiggens (1951),
with small numbers of sows, realized no decrease in conception rate
when as few as 0.2 billion spermatozoa were inseminated. Hancock and
Hovell (1961) published results that indicate that in a 20 ml. volume 1
and 10 billion spermatozoa resulted in a significantly higher (P( 0.01)
conception rate than 0.1 billion. It appears, therefore, that the optimum
number of spermatozoa per insemination is somewhere between 1 and 7 billion.

The injection of oxytocin or its addition to boar semen had little
influence on fertility of gilts inseminated with low spermatozoa numbers
and reduced semen volume (Stratman ep.el., 1959; Self, 1959; Stratman,
1961). On the other hand, Milovanov and Sergeev (1961) and Sergeev
(1963) indicated that litter size and conception rates were improved 8%

to 20% over controls when oxytocin was added to the boar semen.

-38-
Semen backflow following insemination.

Those familiar with insemination of swine recognize that some back-
flow of semen may occur following service. Lasley and Day (1960) re-
ported that difficulty was encountered in making the semen remain in the
reproductive tract of the gilt following insemination. Ohio workers
(Hess et_gl., 1960a) suggested that improper insemination technique could
be detected by the backflow of diluted semen from the vagina. Polge and
Rowson (1956) and Melrose and O'Hagan (1959) attempted to replace the
natural plug and minimize runback by completing the artificial mating
with the insemination of freeze-dried gel. They concluded that the
presence of freeze-dried gel in a diluent does not appreciably affect
conception rate. Polge (1956a) had previously suggested the use of a
sterile cotton plug to control flowback but Dziuk (1958), Madden (1959),
Radford (1961b) and Paredis (1961) reported that there was no relationship
between the volume of semen lost during insemination and conception rate
or litter size. A farrowing rate of 18% with no backflow was observed
by Holt (1956), with some backflow it was 20% and with considerable
backflow the rate was 27%. This difference diminished as overall con-
ception improved but the farrowing rate for those with backflow remained
higher than those with no backflow (Holt, 1959).
lpzyippg storage age of semen.

The effect of storage of semen on fertility is subject to some
conflicting reports. Stratman Si.§l° (1958) and Madden (1959b) reported
no decrease in conception rate when semen was stored for 12 hours.

.Akatov ep_g1. (1962) perceived no drOp in either conception rate or

-39-

litter Size with semen stored up to 2h hours. On the other hand,
numerous workers (Paredis and Vandeplassche, 1962; Dauzier and DuMesnil
du Buisson, 1958; Aamdal, 1959; Niwa, 1958; Feredean and Slavescu, 1961)
observed a progressive, nonsignificant decline in conception when semen
age increased from less than 2 hours to more than 2h hours. In no in-
stance was the reduction more than 10%. However, Paredis (1962) ob-
served a significant (P<’0.05) decrease in conception rate after A hours
and a significant (P< 0.05) reduction in litter size after 2 hours storage.
Litter size was the highest with fresh semen. Jacobsen (1959) obtained
a significant decrease (P’<CLCfl) in farrowing percentage and litter size
in sows and gilts when semen age increased from 2 up to 12 hours.

There is more conclusive evidence that a decrease in fertility
occurs when semen is stored longer than 2A hours. Holt (1959) observed
that the conception rate for semen stored over 2h hours was half of that
for fresh semen. DuMesnil du Buisson (1961) reported on over h,000 in—
seminations using semen less than 6 days old stored at 150 C under C02,
and rediluted just before use. The overall conception rate was 51.3%
and the conception rate for 33 sows bred with A, 5 or 6 day semen was
25.h%. A progressive drop in conception rate was noted on each additional
day of storage. Conception rates of 53.h and 51.2%, respectively, were
obtained with fresh and 2h hour old semen, the difference being non-
significant. Litter size was reported to be normal for the breeds used.

Other researchers (Ito 3: al., l9h8b; Hess ep_§l,, 1960a; Polge, 1959;
Lasley and Day, 1960; Aamdal and Hogset, 1957) reported drastic decreases

in farrowing rates and litter size following storage. Ito ep_al. (19h8b)

-ho-
also noted a slight decrease in the percentage of males at birth follow-
ing ip YATES storage of semen. Polge (1959) obtained a 72% conception
rate with fresh diluted semen which dropped each succeeding day until
after A days the conception rate was 13%. During the same period the
litter size dropped from 10.7 to 7.3 pigs. The drop in fertility was
greater than one would expect from motility estimations made prior to
insemination. Saturation with C02 failed to improve the pregnancy rate
obtained from stored semen.

The effect of boar semen storage on embryonic mortality in A.I.
gilts was investigated by comparing cleaved eggs at 3 day slaughter to
fetuses at 25 days (Dziuk and Henshaw, 1958; Dziuk, 1958b). Conception
rates were reduced after 72 hours of storage and embryonic mortality
was also higher than for semen stored either 5 hour or 2A hours. No
significant differences were found in conception rates (3 day slaughter)
with semen stored either 6 hours or 5A hours (First 2: e1., 1963).
However, significantly (P< 0.01) more ova were fertilized with 6 hour
(61.0%) than with 5A hour semen (39.3%). The percentages of pregnancies
and corpora lutea that were represented by 25 day embryos was greater
for the 6 hour than for the 5A hour stored semen. They also observed
that ip.yippg Sperm age affected the number of spermatozoa in the zona
pellucida of cleaved ova. Pitkjanen and Subin (1961) reported similar
results when comparing fresh with semen stored 2A hours. Fewer sperm-
atozoa of semen stored 72 hours were found in the oviducts, the percent
sperm motility was less and the percentage of phagocytized spermatozoa

Was greater.

-h1-

How long stored boar semen retains its fertilizing capacity is
uncertain. Coronel and Masankay-Arenas (195A) reported a sow that
farrowed 7 pigs with semen stored 5 days. DuMesnil du Buisson (1961)
obtained fifteen pregnancies with semen stored A, 5 and 6 days, while
Niwa ep_e1. (1959a) reported successful conceptions with 7 day old semen.
Sows compared to gilts.

A 1961 report on artificial insemination of swine in European
countries (Beattie ep‘el., 1961) noted that in general the conception
rate for gilts is lower than for sows. Jakobsen (1959) indicated a
significantly (P< 0.01) higher farrowing percentage for 382 first
service sows than for 260 first service gilts. With over 200 females
in both groups Self (1961) also observed a significantly (P< 0.025)
higher farrowing rate for sows than for gilts (A6.l% to 35.A%). Other
workers (Madden, 1959a; Paredis, 1962; Hess ep.el., 1960a; Larsson, 1960;
Gotink, 1959; Holt, 1959; Bane, 1959, Feredean and Slauescu, 1961)
reported conception rates to be 2 to 17% higher for sows than for gilts.
Number of services in estrous period.

An early A.I. experiment at Missouri (McKenzie ep_§1., 1939)
achieved a 21% conception rate for gilts inseminated one time and a 53%
rate for those inseminated two times during estrus. Weaver and Bogart
(19A3) cited J. F. Lasley's Missouri thesis work where gilts bred twice
in the same estrus showed greater conception rates and farrowed more
pigs than gilts bred once. Over a two year period Alexandrowicz (1955)
also observed that double mating of sows increased the average litter

size from 9.5 to 10.23 pigs. According to Dziuk and Henshaw (1958)

-h2-
a single insemination resulted in a A0% conception rate and a 50% rate
was obtained with insemination on two consecutive days. On the other
hand, Holt (1956) and Akatov ep.§1. (1962) observed no increase in con-
ception rates from double matings. The latter, however, did observe
a 2.2 increase in the average litter size when sows were serviced twice.
Inseminator differences.

An inseminator influence on fertility has been observed in dairy
cattle (Dunn, 1961; Dombroske, 196A) and the same appears to occur in
swine A.I. Two college veterinarians in a Norwegian Swine A.I. trial
had a higher conception rate (70.2%) than 30 practicing veterinarians
(57.9%). (Aamdal and Hogset, 1957). Madden (1959a), in a field trial of
about 500 sows and A00 gilts, observed considerable variation in farrow-
ing rates between technicians. For sows the rate ranged from 36% to 57%.
One inseminator consistently produced a higher fertility. Since a sow
rejection policy was in force it was concluded that this improvement'
represented a greater ability of this inseminator to detect estrus.
Paredis (1961b) likewise observed differences of 28% to A9% in conception
rates obtained by inseminators. A Wisconsin field trial (Self, 1961),
with dairy technicians doing the breeding, resulted in inseminator con-
ception rates which ranged from 71.A% to 1A.3%. It was concluded that
the technician is perhaps the most important single factor in the success
of swine A.I. Madden (1960) estimated that conception rate improved-
from A0% to 70% when two swine technicians replaced 2A dairy inseminators.
Boar differences.

Aamdal (1959) and Paredis (1962) observed highly significant

-h3-
(P< 0.01) differences in conception rates between boars used f0r
artificial insemination. The latter also noted highly significant
(P< 0.01) differences in litter size between boars. Hancock and 'Hov'ell
(1961) also noted a significant (P(’0.05) difference in fertility of two
boars as judged by percent cleaved ova. Similar findings were indicated
by Radford (1961a) and Madden (1959a). Bane (1959) reported that the
fertility of stored semen differed with boars and First EL 2l° (1963)
detected a significant (P<f0.05) interaction between sperm age and boars.
Earlier Wisconsin studies (Stratman and Self, 1961) indicated that
conception rates between 7 boars did not differ appreciably. However,
in a field trial with 11 boars (Self, 1961), a considerable range in
conception rates between boars was observed, the spread being greater in
gilt breedings than in sows. The ranking of the boars on the basis of
conception rate in sows was almost in reverse order to their ranking in
gilts.
Swine Artificial Insemination in Practice.
Experimental results compared to field results.

The preceeding literature review points out that considerable in-
vestigation into artificial insemination of swine has been conducted
throughout the world. One striking characteristic of this research has
been the differences in the results obtained in closely supervised ex-
periments and those obtained in the field. DuMesnil du Buisson (1961),
Campbell (1962) and Polge (1956a) reported conception rates in field
trials to be as much as 20 to 30% below experimental results. In general,

the lower rates were attributed to difficulty in accurately detecting

-hh-
estrus.

This is not to imply that swine artificial insemination has not
been successful in the field. On the contrary, satisfactory conception
rates with large numbers of breedings were reported by Scandanavian,
Japanese, French, Dutch, and Russian workers. This success was always
accompanied by patience, diligence and persistence on the part of those
working with the swine (Rowson, 1959). For example, in Asia where the
manpower per sow is high, A.I. conception rates approached those obtain-
ed naturally. Similiarly, in closely supervised experments throughout
the world the conception rates from artificial insemination have often
approached natural breeding.

Artificial insemination in Asia.

The countries where the largest number of swine are artificially
inseminated each year are probably Japan and Russia. Unfortunately
little is known of its actual extent in Russia, but in Japan, research
in swine A.I. started in 1938 and by 1960 approximately 20% of the
national pig herd was artificially inseminated (Niwa, 1958; Beattie
.EE.E$-: 1961). A farrowing rate of 68.2% was reported for 51,687 first
inseminations in 1960. Some 500 breeding centers handle the inseminating,
each center servicing small areas and on the average servicing only about
100 pigs annually. The artificial breeding of swine in Japan is an
intensive, closely supervised program.

The Japanese A.I. techniques are also utilized in Formosa, Okinawa,
and the Philippines. A successful experimental airlift of boar semen

from Japan to Formosa was undertaken in 195A (Niwa e3 e1., 1959a). The

-h5-
Philippines have had researchers working with swine for a period of
years (Rodolfo, 193Aa, 193Ab; Noll, 19A9; Coronel and MasankayeArenas,
195A) but no large scale program has been developed. The latter workers
have reported on the insemination of 271 sows resulting in a 2A.A%
conception rate. Carpenter (1962) indicated that a swine A.I. program
was initiated in Thailand in February, 1961 and that approximately 500
sows were bred.

The present staus of artificial insemination on the Chinese
mainland is difficult to ascertain. Felix Green, one of the few
Westerners to recently tour China, states in his book, Chipa (1961)
that swine are being bred by artificial insemination and this method
is preferred to natural breeding by the managers of the communes. The
government has undertaken a large scale drive to double China's pig
population but the role of A.I. in this drive was not defined.
Artificial insemination in Europe and the United Kingdom.

A number of European countries have been conducting research and
field trials on artificial insemination of swine. It is difficult to
ascertain the extent of swine A.I. in some countries since figures are
reported only for particular experiments, rather than national averages.
Some initial information on the extent of swine A.I. was presented at a
colloquium in Paris in 1959. The first service farrowing results, as
reported by researchers, were as follows:

Norway - 50%, A Centers; 6-7,000 annually (Aamdal, 1959)

Sweden - 59% on 637 sows; h8% on 260 gilts (Bane, 1959)

Belgium - 51% on 39A sows (Paredis, 1959)

-h6-

Denmark - 5A% on 382 sows; 3A% on 260 gilts (Jakobsen, 1959)

England - A2% on 1,993 sows and gilts (Madden, 1959a)

Additional reports were made on research in England (Melrose ‘
and O'Hagan, 1959; Polge, 1959), France (DuMesnil du Buisson and Dauzier,
1959), Japan (Niwa e: 31., 1959a) and the United States (Self, 1959).

More recently, at the Ath International Conference of Animal
Reproduction, Beattie, Field and Melrose (1961) were able to compile a
report on the status of swine A.I. in a number of countries. They

reported the following:

 

Country Worker . No. of Conception -Remarks
inseminations rate

England Madden 652 71.5% strict selection

England Melrose and O'Hagan -- 58% 12% rejection

France DuMesnil du Buisson -- 5A.9% no selection

Holland Smidt A,A67 60.3% 12 to 15% rejection

Belgium Paredis 6,000 A3% no selection

 

The 71.5% and 58% reported by English workers was considerably
higher than earlier results in their country. Madden (1959a) had pre-
viously reported a A2% conception rate when no sow rejection was em—
ployed at the time of breeding. Holt (1956) only obtained a 1A% farrow-
ing rate on 1,11A matings; however, he later (Holt, 1959) improved this
to 2A.A% on 5AA first services. The work of many other researchers
already cited, such as Polge, Radford, Hancock and Mann, has added

immeasurably to our present knowledge of swine A.I.

 

L4

-h7-

The 5A.9% obtained in France was an improvement over the 36% on
over 1,000 sows earlier reported by the same workers (Dauzier and Du
Mesnil du Buisson, 1958). DuMesnil du Buisson (1961) also reported a
51.3% farrowing rate on A,338 inseminations made with semen stored up
to six days. At the Roville Experiment Station a 56.6% conception rate
was obtained on 1,373 first services in 1962. (Corteel, 1963). This
was a considerable improvement over the previous year when the rate had
been 36.2% on 3,606 first inseminations. Recently Dzuik (1962) also
reported that four centers in France obtained a 70% conception rate on
11,000 sows and gilts bred artificially.

Dzuik (1962) also updated information on A.I. results in Holland
indicating a 60 to 70% farrowing rate from 20 breeding centers in 11
Provinces. The technicians were following a program of rejecting animals
not considered to be in a good standing estrus. It was anticipated that
60,000 inseminations would be made in 1962.

Artificial breedings of swine were performed for the first time in
Finland in 1960 (Jokinen, 1961). A 60% pregnancy rate was reported for
the 120 sows inseminated. Larsson (1960) gave notice of swine-A.I.
in 5 centers in Sweden in 1959. A conception rate of 77.6% was Obtained
on 911 sow first services and 73.3% on 205 gilt first services.

There have been several recent accounts of swine artificial inn
semination expanding to other countries. ~Cerne (1960) reported on the
first successful attempts to inseminate pigs in Yugoslavia. Campbell
(1962) described results in Jamaica. Ben Joseph and DuMesnil du Buisson

(1961) collaborated in the successful insemination of pigs in Israel

-48-
with semen flown from France. Air transportation also has been used
successfully to impregnate sows in Ceylon with semen from Britain
(Jeganathan and Fernando, 1961). In December, 1956 the United States
Department of Agriculture (1957) participated in an experiment in which
swine semen imported from Norway to Beltsville, Maryland resulted in a
A6% farrowing rate in the 2A sows bred.
Artificial insemination in the United States. ‘

In this country there has been considerable interest in swine
artificial insemination but the development has been slow since the
original investigations of the Missouri station (McKenzie et_§l., 1935,
1938, 1939; Lasley, l9A0; Lasley and Bogart, 19AA). Research on the
problems coincident with swine.A.I. has been subject to study by the
agriculture experiment stations in New York (Young ep_el., 1957; Turk-
heimer egg _a_1_., 1958), Illinois (Dzuik, 1958a, 1958b, 1960, 1963 ; Smith
and Nalbandov, 1958), Wisconsin (Bialy and Self, 1959; First e: al., 1963;
Self, 1959,1960, 1962; Stevermer gt 5.31., 1961, 1962; Stratman g; _a__1_.,
1958, 1959, 1960,1962; Stratman, 1961), Ohio (Hess at. _g_1_., 1957, 1960;
Wilson _ep _ap, 1963), Iowa (Iovell, 1958 ; Self, 1960, 1962), Minnesota
(Gerrits _ejg _a_l_., 1962,- Graham, 1963; Niwa 33 9.1., 1962) and Michigan
(First EE.EI°: 1960) but disappointing results have prompted few large
scale field studies.

Eastern Iowa Breeders at Cedar Rapids and Iowa Breeders at Des
Moines supported early swine field studies (Self, 1961). In 1959 and
1960 four bull stud cooperatives in Wisconsin (Badger Breeders Coop;

East Central Coop; Southern Breeders Coop and Tri-State Breeders Coop)

-h9-

financed one of the largest swine A.I. field trials to be undertaken
in this country. Using the facilities and personnel of the Badgers '
Breeders Coop, A85 inseminations were performed on 162 farms in 6
northeastern Wisconsin counties by 30 dairy technicians. A total
farrowing rate of A1% (first and second services) was obtained on sows
with an average litter of 10.6 pigs and 35.A% on gilts averaging 9.0
pigs per litter. The first service rates were A7.2% for sows and
35.3% for gilts. Farrowing rates were compared by technicians, boars,
time of insemination and condition of estrus as already reported.

As a result of this preliminary study an exploratory commercial
swine insemination program was initiated by Tri-State Breeders Coop,
Westby, Wisconsin. Beginning in April of 1963 they developed a Swine
Division that supplies semen from four breeds to a three county area.
Charging $5 for first service and $2 for repeats, the two fulltime
swine technicians averaged 85 inseminations a month for the first year.
They reported conception rates of 7A.3% on a A0-60 day non-return basis
and farrowing rates of 72.5% on the first 273 sows and gilts. (Tri-State
Breeder Coop, 196A). On March 1, 196A the second commercial swine stud
was to Hegin operation under the direction of Badger Breeders Coop. A
swine A.I. program in 10 townships in Door County, Wisconsin was planned,
with a $5.00 service fee for insemination to one of A Hampshire boars
(First, 196A).

Another large scale swine A.I. field study was conducted in central
Ohio from January 1, 1961 to July 15, 1962 (Wilson e: g1., 1963; Wilson,

196A). A 20.8% conception rate was obtained on 1,079 first inseminations

-50-
by 32 technicians on A53 farms. The greatest variation in fertility was
between inseminators and between boars. As in previous field studies

the major problem was accurate estrus detection on the farm.

III. EXPERIMENTAL PROCEDURE
General

Boars and facilities. ‘

 

The boars used for these artificial insemination studies were of
the Yorkshire, Hampshire, Duroc and Chester White breeds. They were
selected on the basis of performance testing, as well as on their
individual merit, with the exception of several Yorkshires which were
part of a University inbred swine project.

The boars were housed in a 22' x 85' barn constructed specifically
as a boar stud. The barn contains boar pens, feed room, heated
collection room and a semen processing laboratory. The boar section
of the barn is open to the east and contains twelve 5' x 16' pens with
concrete floors and wood partitions. Bedding was placed in the back
of the pens with feed and automatic waterers available in the front.

The boars were maintained on a high fiber, 17% protein nutritionally'
balanced swine ration. No exercise was provided for the boars and they
remained in their pens except for the time when semen was collected. A
careful program of boar hygiene was followed, including careful attention
to foot trimming, detusking and internal and external parasite control.
No visitors were allowed to enter the barn without special sanitary
precautions.

A six foot alleyway in front of the pens led to a 12‘ x 1A'
collection room housing the "dummy" sow. In cold weather the collection
room was heated to 500 to 600 F. to prevent any extreme temperature shock
to semen.

-51-

-52-

Boar training.

 

Over a five year period 39 boars were placed in the stud and only
2 boars could not be trained to mount the dummy. One was a young boar
that also experienced difficulty in naturally serving gilts. The second
boar was a mature boar that would mate naturally but would not accept
the dummy. He was eliminated because of distrust and meanness toward
the herdsman. A third boar trained easily to the dummy as a yearling
but after a period of use refused to mount the dummy. This boar was
later found to also refuse natural matings.

Thus 37 boars were successfully trained to mount the dummy, which
was a burlap and canvas covered piece of 10 inch metal pipe fitted with
adjustable legs and boar foot braces. The training and collection of
boars took place in the collection room, which was used only for this
purpose. Originally, boars were collected off of "teaser" gilts in the
collection area prior to collection off the dummy. However, since moving
to the new facilities, 12 young boars and 2 mature boars have been trained
to the dummy without the presence of "teaser" gilts. It is essential
that the person handling the boars have patience, work quietly and gain
their confidence. Once the boar entered the room and mounted the dummy
the collection procedure was initiated.

Collection procedure.

 

Two collection procedures were followed. The first utilized an
artificial vagina made from a piece of rubber hose 2% x 7" (radiator hose)
to which a rubber squeeze bulb was attached. A rubber liner was placed

through the hose, folded back and attached at both ends. Warm water

-53- “
(520 C.) was placed in the space between the artificial vagina and the
rubber liner. The squeeze bulb could provide either steady or pulsating
pressure to the interior of the vagina. A 12" rubber cone was fitted
to one end of the artificial vagina.

As the boar obtained an erection and mounted the dummy the operator
placed the end of the artificial vagina over the penis and the boar
began his thrusting motions. As the penis passed through the warm ‘
vagina and into the rubber cone pressure stimulation was applied with
the squeeze bulb. When the boar's penis was well extended through the
artificial vagina and into the cone the operator grasped the rubber
cone, locking his hand on the spiral tip of the boar's penis.' The thrust-
ing motions ceased and the boar became tranquil as ejaculation proceeded.
The semen was collected in fractions as it flowed from the end of the
rubber cone. The presperm, post sperm and gel fractions were collected
in a 1000 ml. plastic beaker and the sperm rich portion directly'into a
250 m1. plastic beaker that was suspended in a A0O C. plastic water
jacket. The plastic vessels were preferred because there was less
breakage and they were found to be poor conductors of extreme environ-
mental temperature variations.

A second method of collection was used on many boars. After the
boar mounted the dummy the operator grasped the tip of the penis
directly with his plastic gloved hand. With practice the tip of the
penis could be locked between the thumb and the index finger and the
ejaculate's flow easily directed into the beakers in fractions as above.

The advantage of this method was that it required less preparation and

-5h-
was more sanitary since throwaway plastic gloves were used.

Semen handling;

 

Immediately upon collection the Sperm rich fraction was transferred
to the heated (700 F.) processing room adjacent to the collection room.

The semen was then filtered through two layers of cheese cloth (to
remove any gel) into a graduated cylinder where the volume was recorded.
The semen was then transferred to a 500 ml. plastic bottle suspended by
means of a styrofoam float in a large thermostatically controlled water
bath (380 C.).

Concentration determinations were made by removing a small semen
sample with a hemocytometer pipet, diluting it in the standard manner
with 3% acetic acid solution, and counting sperm cells in a hemocyto-
meter counting chamber. Two concentrations determinations were made on
each sample; the average was used to calculate dilution rate.

Final semen dilution was performed by adding the desired amount of
prewarmed extender to the semen as it remained in the water bath. Since
both the semen and extender were in the bath prior to dilution, tempera-
ture shock was minimized.

Motility was estimated by counting the percentage of total and
progressive motility in the freshly diluted sample. Several drops Of
stock extender (without egg yolk) were placed on a microscope slide on
a warming plate (380 C.). A small amount of diluted semen was added
to the Slide which was then quickly coverslipped and observed under a
phase contrast microscope. Estimations of percentage motility were then

made. While this procedure was subjective and Open to some estimation

-55-

error, it was felt to be an adequate method of identifying unsatisfactory

samples. Very few samples had to be rejected because Of low motility.

Subsequent to motility estimates the diluted semen sample was re-

moved from the water bath, identified, capped and placed at room tempera-

ture (200 C.) to begin the initial cooling process. After 10 to 20

minutes the diluted sample was transferred to either a refrigerator (50
so

to O C.) or styrofoam shipping cartons containing ice cans. The cooling

rate of semen in the refrigerator did not exceed 100 C. an hour. Semen

shipped in styrofoam boxes cooled at a slightly slower rate.

Insemination procedure.

 

The insemination procedure used was basically the same in all the
fertility studies. The standard dose was 5 x 109 spermatozoa in a 50 m1.
volume. Plastic dairy inseminating catheters (6mm x lcc x 16") were used
with the tips modified to facilitate entry into the cervix. A short
piece of polyethylene tubing connected the catheter to a 50 ml. plastic
syringe, which served as the semen injector. In most instances the semen
was inseminated at refrigerator temperature.

Diluter.

The diluter of choice in the field trials and campus breedings was
the standard egg yolk-sodium bicarbonate-glucose extender also found to
be the most satisfactory by Dzuik (1958).

Stock Solution:

1000 ml. distilled water

30 gm. glucose

1.5 gm. sodium bicarbonate

 

-56-

1,000,000 units penicillin

1 gm. dehydrostreptomycin

The stock was prepared and stored in a glass stoppered bottle at
50 C. Just prior to use the final extender was prepared. This consisted
of 70% of stock solution and 30% of egg yolk (by volume).

Plastic containers, glassware and rubber tubing were washed with
a laboratory soap (Sparkleen) and rinsed in ethyl alcohol and then
distilled water.

Boar Semen Preservation

 

Motility studies of stored boar semen.

 

A series of investigations were conducted on boar semen storage and
its influence on spermatozoa motility. A number of diluters and preser-
vation procedures were examined and the motility determined after various
storage periods, up through 21 days. Since boar spermatozoa undergo
anabiosis upon cold temperature storage (80 C.) it became necessary to
develop standard reactivation procedures. The following procedure was
adopted. The polyethylene bottles containing the stored semen samples
were slowly inverted until the anabiosis layer was again in suspension.
Pipets were used to withdraw 10 ml. aliquots which were placed into
test tubes. These unstoppered test tubes were vigorously agitated on a
mechanical shaker for 1% to 2 hours at room temperature (250 C.). The
test tubes were suspended in a thermostatically controlled 370 C. water
bath and motility determinations were performed.

The estimation of motility, while highly satisfactory for general

semen evaluation, was not critical enough to detect small motility

-57-
differences between stored boar semen samples. Therefore, a method of
motility determination was developed wherein the number of motile sperm-
atozoa could be more accurately counted. The procedure used a standard
hemocytometer pipet and counting chamber. The reactivated semen sample
was drawn into a clean hemocytometer pipet, as in a concentration deter-
mination, and a prewarmed physiological solution (saline or stock boar
extender without egg yolk) was used to complete the dilution. The
diluted sample was placed onto a warm hemocytometer slide and the
number of progressively motile, motile and dead spermatozoa, within the
microscope grid, counted. A total of at least 100 spermatozoa were
counted for each sample and the progressive and total motility calculated.
This procedure, provided a grid against which spermatozoa could be
counted, prevented coverslip pressure directly upon the sample and
allowed a direct motility count rather than an estimation.

Fertility_trials with stored boar semen.

 

The value of motility as an indication of fertility of stored boar
spermatozoa is questionable, so a number of inseminations were under-
taken tO test fertility of semen stored 5 to 10 days.

The animals used for these trials were gilts from the Southern
Michigan State Prison (S.M.S.P.) and Michigan State University (M.S.U.)
swine herds. They were maintained on pasture lots at M.S.U. during this
study and were examined for estrus twice daily with a vasectomized boar.
The gilts were slaughtered 25 to 50 days post breeding and their repro-
ductive tracts examined for pregnancy and/or gross anatomical abnormal-

ities.

-58-

Semen samples were collected daily and subjected to storage treat-
ments suggested by earlier motility studies. Samples were stored in
sealed, 100 ml. or 250 m1. polyethylene bottles at 80 C. Motility
determinations were made on the stored samples prior to insemination
at estrus.

Field Trials

 

Animals and procedures at the Southern Michigan State Prison.

The field trial held at Southern Michigan State Prison (S.M.S.P.)
consisted of 65A inseminations made from November 5, 1962 to OctOber
30, 1963. The majority of these breedings were performed on gilts,
only A7 of them being sows. The entire breeding program at the S.M.S.P.
farm was converted to artificial insemination. The gilts used in this
trial were selected by the herdsman as the regular replacement females
for the Hampshire herd.

The gilts were placed in pastures in groups of approximately 25
and were self fed a balanced ration containing 16% protein. Estrus de-
tection was carried out by trustee inmates each morning from 9 to 10:30 a.m.
These workers varied in their dependability, thoroughness and experience.
Boars were not used to verify estrus and those gilts determined to be in
estrus were assigned to holding pens to await insemination.

The semen was collected at the Endocrine Research Unit's A.I.
Stud three mornings a week. The diluted semen was shipped by bus in
sealed 500 ml. plastic bottles, packed with ice cans in styrofoam ship—
ping containers. The semen reached the prison within A hours and was

used for insemination approximately 6 hours, 2A hours, 30 hours or over

-59-
A8 hours after collection. Upon arrival the diluted semen was unpacked,
the temperature recorded and then placed in a refrigerator at 100 C.

Insemination was performed by three men who were employees of the
Prison; they had previously been trained in A.I. techniques at the
M.S.U. Boar Stud. Gilts in estrus were driven into a specially designed
breeding crate where they were inseminated and ear tagged. Some gilts
were reserviced 2A hours later. All of the animals presented to the
inseminators were artificially inseminated and no rejection system was
employed.

The bred gilts were placed in large pastures during gestation and
were transferred to the farrowing barn as parturition approached.

These pastures were checked for recyling gilts, but apparently the
inmates did not perform this task effectively.

The major problem in the S.MAS.P. trial was the identification of
gilts in the program. Since the Prison had no previous identification
system the gilts were ear tagged with large (2% x 1 5/8"), colored,
butyl rubber tags. These tags were easy to read at a distance and seemed
ideal in this situation where different men were working with the hogs.
Unfortunately the tags were easily pulled out and identification was
lost on one third of the females inseminated. Thus, complete informa-
tion was obtained on only A38 breedings.

Animals and procedures at the Michigan State University swine farm.

The University swine breeding program consists of three week

breeding periods, six times a year. The present study included 10

breeding periods from March 1962 to October 1963 during which the

-60-

fertility resulting from natural and artificial matings could be com-
pared. During this period 17A gilts and 200 sows were serviced; 25A by
natural service and 120 by artificial insemination.

The animals used constituted all the gilts and sows serviced in
the University Yorkshire, Hampshire and crossbred herds during the
period Of this study. All were handled in the same manner, irrespective
Of breeding method. There were 25 boars used during this period, 19
naturally and 6 artificially. Management and nutrition was approxi-
mately the same for both groups of boars.

The females were housed in outside lots, approximately 10 to 20 to
a group, and were regularly checked for estrus once daily with a boar.
Females bred naturally were hand mated to selected boars. Females mated
artificially were serviced in the lots if they stood quietly. Occasion-
ally a sow or gilt would not stand for insemination and these were
placed in a specially constructed breeding crate for the insemination.
Both ear notches and ear tags were available as a means of female

identification.

IV. RESULTS

Boar Semen Preservation

 

Motility of stored boar semen.

 

The influence of various treatments on the progressive and total
motility of stored boar spermatozoa was examined. A number of treatments,
including changes in storage temperatures, diluents and atmospheric
environment, maintained satisfactory sperm motility for periods of 5

to 1A days. The average progressive and total motilities of samples

stored at 80 C. in the standard egg yolk-glucose-sodium bicarbonate

diluter are presented in table 1. The term "pooled" samples refers to

samples in which the semen from several boars was combined prior to

dilution and storage. The "centrifuged" samples had the spermatozoa

removed from their seminal plasma by centrifugation for 20 minutes at

1020 x G prior to resuspension and storage in the standard diluent.
TABLE 1

Progressive motility (PM) and total motility (TM) of boar spermatozoa
after storgge.

 

 

NO. Best
Treatment samples 1 da. 5 da. 7 da. 10 da. 7 da.
PM TM PM TM FM TM PM TM PM TM
Standard
diluter 112 72.7 86.8 25.5 65.3 20.1 5u.3 23.3 A7.5 61 8A
Centri- 63 69.1 79.3 A1.1 76.2 25.A 58.1 1A.A A8.3 67 83
fuged
Pooled A0 71.2 8u.8 A1.2 62.2 23,2 61.7 20.5 38.2 73 85

 

Fertilipy of stored boar semen.

 

Fertility tests of boar semen stored 5 to 11 days were conducted with
55 samples. Estrus was not Observed in 5 of the 51 gilts used but the

-61-

-62-

remaining A6 were inseminated a total of 55 times, 9 of them being re-
serviced when they returned to estrus. (A complete record of these insemi-
nations appears in Appendix Table A). A number of the inseminations were
performed with "pooled" and "centrifuged" samples. Several other treat-
ments were also tested with 2A inseminations but no pregnancies resulted.
A summary of the fertility results with stored boar spermatozoa is
presented in table 2.

TABLE 2

The fertilitypof boar epermatozoa stored for_5 to 11 days.

 

 

Treatment No. bred No. preg. Preg. rate Av. no. of fetuses
Pooled 15 21 13 . 3% 6.0
Centrifuged 16 32 18.8% 6.3

Other 2A 0 0 0

Total 55 5 9.1% 6.2

 

lBoth samples stored 7 days.
Samples stored 5, 6 and 7 days.

Southern Michigan State Prison (S.M.S.P.) Field Trial

 

Overall results.

 

The field trial at S.M.S.P. was inaugerated to establish the
effectiveness Of swine artificial insemination under field conditions,
and to provide large numbers of gilt inseminations to effectively test
experimental semen samples. The first objective was effectively accom-
plished, however, due to poor farrowing results insufficient numbers of
gilts were available to test a variety of experimental semen samples.

In the year from November, 1962 to October, 1963 a total of 65A insemi-

-63-
nations were performed. As already mentioned, considerable difficulty
was encountered in identification of these gilts; thus complete infor-
mation was available on only A38 of these breedings. The results of
first and repeat breedings are summarized in table 3.
TABLE 3

Farrowingprate and average litter size of artificially inseminated swine.

 

 

Breeding. No. bred Farr. rate Litter Size
First 276 3A.8% 6.8
First repeat 115 27.0% 6.6
Second repeat 35 25.7% 8.5
Third or more repeat 12 33:3% 10.3
Total of all breedings A38 32.0% 7.0

 

These data were also summarized and examined to determine the
influence of the number of breedings during estrus, inseminators, boars,
storage age of semen, runback at breeding, number of spermatozoa in-
seminated, progressive motility, total motility and arrival temperature.
Those animals serviced three or more times and any with missing data
were not used in subsequent analyses, thus complete information is
presented on A22 artificial inseminations.

The influence of number of services during an estrous period on A.I.

 

fertility;

 

At the beginning of this trial approximately one half of the gilts
were inseminated once and the other half were inseminated twice during

estrus, the repeat services occurring 12 to 2A hours following the

-6h-
initial breeding. This policy was continued until February 1963 when
non-return rates indicated a much higher conception resulted from the
double inseminations. Therefore the data on the number of services in
a heat period were summarized for only the first A months and is presented
in table A.
TABLE A

The influence of number of services during estrus on the fertility of
artificially inseminated swine.

 

NO. of services No. bred Farr. rate** Litter size
Once 61 21. 3% 6.9
Twice 92 AA. 5% 6. 3

 

1
**’X = 8.6, significant at P< 0.01.

 

Influence of inseminator on fertility with swine A.I.

Three men performed the inseminations. In the instances when the
pigs were serviced twice, different inseminators often performed each
breeding; this situation is referred to as "combined" in table 5. The
results by inseminator include females inseminated either once or twice

by the same technician.

-65-
TABLE 5

The influence Of different inseminators on fertility of artificially
inseminated swine.

 

Inseminator No. bred Farr. rate** Litter size
A 73 30.1% 6.9
B 1A5 28.3% 7.0
c 55 52.7% 7.3
Combined 1A9 28.2% 6.8

 

z
)6an =12.A8, significant at P<0.01.

 

Influence of different boars on fertility with swine A.I.
Three purebred Hampshire boars were used throughout the study. The
farrowing rates and litter sizes, by boar are presented in table 6.
TABLE 6

The influence of different boars on fertility of artificially inseminated
swine.

 

Boar NO. bredl Farr. rate** Litter size
5-6 192 21.A% 6.A
11-11 108 36.1% 7.6
12-10 120 A1.7% 6.9

 

1
** 'X = 16.11, significant at P (0.01.
Data on 2 gilts excluded as they were serviced by a fourth boar.

#

_lpfluence of age on the fertility of stored boar semen.
The diluted semen was used either on the day Of collection (6 hours),

On the following morning (2A hours) or on the following afternoon

-66-

(30 hours). These three periods represented the stored age of the
majority of the semen, but occasionally older semen samples were used
(A8 hour or Older). In gilts serviced two times, calculations were
based on the semen age at the time of the first insemination. No signifi-
cant difference was found in the farrowing rate due to semen storage age.
(Table 7).

TABLE 7

The influence of storage age of semen on fertility Of artificially
inseminated swine.

 

 

Stored semen age, NO. bred Farr. rate Litter size
6 hours 306 32.0% 7.1
2A hours 58 30.5% 5.6
30 hours AA 30.0% 7.5
118 hours +(a) 11+ 7.1% 2.0

 

(a) 5A hour old semen was the oldest semen utilized that resulted in
conception in this study.

 

Influence of semen backflow followipgginsemination on A.I. fertility.
The inseminators were asked to make estimations Of the amount of
semen that flowed back out of the vagina following artificial breeding.
While this was a purely subjective measurement it seems a cause for
concern among both COOperating farmers and researchers. Therefore the
relationship of backflow to farrowing rate and litter size was examined
in the present study. Since many of the females were inseminated twice
and exhibited different amounts of backflow at each breeding, only those

were included that either (1) were inseminated once or (2) exhibited the

-67-
same backflow at both services. The conception rate was significantly
higher (P(0.0l) when some backflow occurred after insemination as in-
dicated in table 8.
TABLE 8

The influence of semen backflow on fertility of artificially inseminated
swine.

 

Estimate of backflow NO. bred Farr. rate** Litter size
None 67 10.1% 7.0
Slight 39 2+3 . 6% 7 .1.
Medium 65 10.0% 6.9
Large 52 38. 5% 6.1

 

** Y= 55.59, Significant at P<0.0l.

 

Influence of number of spermatozoa inseminated on A.I. fertility.

The concentration and volume inseminated were generally held at
5 X lOQ‘Spermatozoa in a 50 ml. volume. However, on several occasions
there was an abundance of semen at collection, so the concentration
remained intentionally higher than 5 x 109. Also on a few occasions
semen was extended to less than 5 billion spermatozoa per insemination
sample. The volume of diluted semen inseminated was maintained at 50 ml.
regardless of sperm concentration. A summary, by concentration, appears
in table 9. The differences found were not significant but there were

relatively few observations at concentrations other than 5 x 109.

-68—
TABLE 9

The influence of the number of spermatozoa inseminated on fertility of
artificiallyginseminated swine.

 

 

Spermatozoa

concentration No. bred Farr. rate Litter size
A.0 - A.9 x 109 21 A2.9% 6.7

5.0 - 5.9 x 109 276 32.2% 7.1
6.0 — 6.9 x 109 57 2A.6% 7.2
7.0 - 7.9 x 109 30 26.7% 5.5

8.0 - 8.9 x 109 21 ' 9.5% 7.5
over 9.0 x 109 17 35.3% 6.7

 

Influence Of progressive motility on semen fertility.

Progressive motility and total motility of Spermatozoa are often
used as estimates of semen quality. This relationship to fertility was
examined in the S.M.S.P. trial. The motility estimates were made at the
time of dilution of the semen and not at the time of insemination.

The data in table 10 suggest a decline in the farrowing rate at the
lower progressive motility levels. These differences were nonsignificant

by chi-square analysis.

-69-

TABLE 10

The influence of progressive motility of spermatozoa on fertility in
artificially inseminated swine.

 

Progressive motilipyl NO. bred Farr. rate Litter size
20-29% 13 15.A% 5.0
30-39% 27 25.9% 6.7
A0-A9% 89 32.6% 8.3
50-59% 61 A2.6% 7.8
60-69% 112 30.u% 5.7
70-79% 7A 32.h% 7.3
80-89% A6 35.8% 5.8

 

iMotility estimates made at time of semen dilution.

Influence of total motility on semen fertility.

 

When the percent total motility was related to farrowing rate they
appeared to increase together. (Table 11).
TABLE 11

The influence of total spermatozoa motility on fertility of artificially
inseminated swine.

 

 

Total motilityl No. bred Farr. rate* Litter size
60-69% 36 13.9% 5.1
70—79% A8 29.2% 8.8
80-89% 209 37.3% 7.6
90-99% 129 31.0% 6.3

 

3
* X = 9.25, significant at P<0.05.

 

lMotility estimates made at time of semen dilution.

-70-

Influence of arrival temperature of semen fertility.

 

The temperature of the diluted semen sample was measured on arrival
at the Prison. The arrival temperature varied considerably so the
influence of arrival temperature on the subsequent fertilizing capacity
of the semen was examined. Since the collection, dilution, transportah
tion and pickup of semen were on a rigid schedule the arrival tempera-
ture shOuld in effect be a measurement of semen cooling rate. This
summary is presented in table 12.

TABLE 12

The influence of semen arrival temperature on fertility of artificially
inseminated swine.

 

 

Arrival temp. No. bredl Farr. rate Litter size

8° C. 19 A2.1% 6.9

9° C. 31 A5.2% 7.5
100 c. 55 25.5% 7.3
11° C. 3A 1A.7% A.8
12° C. 18 38.9% 7.A
13° 0. A5 A2.2% 8.9
1A0 C. 52 32.7% 5.8
15-160 C. A0 37.5% 6.A
170 0. 1A 21.A% 7.0
18-190 C. 1A 28.6% 6.3
20-210 c. 29 20.7% 6.7

 

1Some data missing due to failure to record semen arrival temperature.

 

Comparison of fertility of artificially inseminated gilts and sows.

 

-71-

The majority Of the matings were to gilts although a few first
litter sows were included. The distinction between sow and gilts is
referred to as female reproductive age in table 13.

TABLE 13

A comparison of fertility of artificially inseminated gilts and sows.

 

Female reproductive age No. bred Farr. rate Litter size
Gilt 391 30.11% 6.8
Sow A7 AA.7% 8.0

 

At this point a more sophisticated statistical analysis was made
Of the more salient factors influencing fertility in the S.M.S.P. swine
A.I. trial. A least squares method of statistical analysis was employed
because Of the unequal subclass numbers. The analysis Of variance was
set up to include the effects due to number of services during estrus,
inseminators, boars and semen storage age. Although differences due to
semen age were not significant in the initial chi-square analysis this
effect was included in order that it could be analyzed more critically.

The influence of semen backflow was not included since insufficient
meaningful observations were available on the entire population. The
number of spermatozoa inseminated, the motility and the arrival temper-
ature were not included as components of the final analysis since prior
examination had indicated they exerted little influence on A.I. fertility.

The information was punched onto IBM cards and the necessary least

square computations were performed on a C.D.C. 3600 electronic computer.

-72-
The direct effect of these factors on the variance in farrowing rate is
presented in the analysis of variance. (Table 1A).
TABLE 1A

Analysis of variance of factors influencing farrowing rate of artificially
inseminated swine.

 

 

Source df Sum of squares Mean square F

Direct effect of number ( )

Of services 2 a 2.50 1.25 6.19**
Direct effect of

inseminator 3 1.66 .55 2.7A*
Direct effect of boar 2 2.77 1.29 6.36**
Direct effect of semen age 3 .63 .21 1.0A
Error All 83.10 .202

* P<0.05
**P<Ofil

(a) l. bred once ) until February 1963-
2. bred twice )

3. all breedings after February 1963.

This analysis indicates a highly significant (P<0.0l) effect on
farrowing rate due to number of services during estrus and on the boar
used. A significant (P(0.05) effect was also indicated due to different
inseminators. No significant influence was ascribed to the stored age
of the semen at time Of insemination.

A particular treatment effect was estimated by using the method of
least square which were adjusted for other factors influencing farrowing
rate. The least square estimate for two inseminations during estrus was
22% higher than for one. The farrowing rates for inseminator C was 16%
above A and 20% above B. The farrowing rate of boar 5~6 was 19% below

boar 12-10 and 1h% below that of boar 11-11.

-73-
The influence of these same factors on litter size Of the 136
farrowings was analyzed in a similar manner and is presented in table 15.
TABLE 15

Analysis of variance of factors influencing litter size of artificially
inseminated swine.

 

Source df Sum of squares Mean square F
Direct effect of number 2 26.07 13.0A 1.81
of services
Direct effect of inseminator 3 2.16 .72 .10
Direct effect of boar 2 35.03 17.51 2.AA
Direct effect Of semen age 3 22.95 7.65 1.06
Error 125 898.9A 7.19

 

None of the factors examined in the S.M.S.P. study had a significant
effect on litter size in the females which did farrow.

Michigan State University Swine Farm Trial

 

A compgrison between natural and artificial mating at M.S.U.

The breeding program at the University swine farm afforded an
opportunity to compare natural and artificial mating under identical
management practices within the same swine herd. Farrowing rates and
litter sizes were available on 37A females serviced from March 1962 to
October 1963.

Comparisons between type of mating (natural vs. artificial), female
reproductive age (sows vs. gilts) and number of services during estrus

(once vs. twice) are summarized in table 16.

-7h-
TABLE 16

A comparison between natural and artificial matings in the MSU swine herd.

 

Type of breeding NATURAL BREEDING ARTIFICIAL INSEMINATION
No. Farr. Litter No. Farr. Litter
bred rate size bred rate size

Gilts bred once A9 73.5% 9.2 13 38.5% 7.A

Gilts bred twice 71 57.7% 8.5 A1 56.1% 8.A

Total gilts 120 6A.2% 8.8 5A 51.9% 8.2

Sows bred once 27 77.8% 11.8 35 A2.9% 9.7

Sows bred twice 107 61.7% 10.7 31 5A.8% 10.8

Total sows 13h 6A.9% 11.0 . 66 A8.5% 10.3

Total breedings 25A 6A.5%* 10.0 120 50.0%* 9.3

 

a.
* I = 6.81., significant at P<0.01.

 

Influence of boars on fertility in naturally and artificially mated swine.
An examination of the data by boars is presented in tables 17 and 18.
A significant difference (P<'0.05) in farrowing rate was observed between

boars used both naturally and artificially.

-75-
TABLE 17

The influence of different boars on fertility of naturally bred swine.

 

Boar no. No. bred Farr. rate* Litter size
1 53 ‘ 66.0% 9.8
2 13 53.8% 8.3
3 20 100% 11.3
A A3 58.1% 10.2
6 2A 75.0% 9.7
7 1A 57.1% 9-5
16 A8 72.9% 9.1
Others (1) 39 h1.0% 10.6

 

(1 Combination of 12 boars that had less than 10 breedings.
* "= 1A.65y_significant at P;0.05.

TABLE 18

The influence of different boars on fertility of artificially inseminated
swine.

 

Boar no. No. bred Farr. rate* Litter size
11 2A 29.2% 8.9
13 25 52.0% 8.3
19 35 A8.6% 10.3
20 22 50.0% 8.5
Other (1) 1A 78.6% 10.5

 

(1)ICombination Of 2 boars that had less than 10 breedings.
* 'X’= 10.1; significant at P<0.05.

The influence of breeding season on fertility of naturally and artificially

 

mated swine.

 

-76-

The breeding program at MSU is based upon six farrowings a year.
Therefore, the breeding schedule consists of 6 three week breeding
periods. A summary of the 10 breeding periods occurring during this
study are presented in table 19.

TABLE 19

The influence of breeding period on fertility Of naturally and
artificially mated swine.

 

 

Natural breeding Artificial insemination
No. Farr. Litter NO. Farr. Litter

Breeding period bred rate size bred rate Size
March 21 to April 10, 1962 37 6A.9% 9.8 -- -- --

May 21 to June 10, 1962 3A 76.5% 11.2 -— -- --

July 21 to Aug. 10, 1962 29 79.3% 10.5 13 73.8% 9.0
Sept. 20 to Oct. 11, 1962 22 68.2% 7.7 5 0 0

Nov. 20 to Dec. 12, 1962 25 A8.0% 7.5 26 65.h% 8.A
Jan. 18 to Feb. 13, 1963 2A 79.2% 10.5 19 60.5% 9.3
March 20 to April 10, 1963 15 66.7% 9.1 26 50.0% 88.8
May 21 to June 10, 1963 30 60.0% 10.6 11 5A.5% 11.8
July 21 to Aug. 10, 1963 18 22.2% 11.0 12 50.0% 10.2
Sept. 23 to Oct. 1A, 1963 20 65.0% 10.1 8 37.5% 10.7

 

As in the previous trial the roughness of the chi-square analysis
with unequal subclass numbers suggested the need for a more complete
statistical analysis. Therefore, these data were also subjected to
least squares analyses with a C.D.C. 3600 electronic computer. Table 20

contains the analysis of variance of factors affecting farrowing rate.

-77-
TABLE 20

Analysis of variance of factors influencing farrowing rate in naturally
and artificially mated swine.

 

 

 

Mean
Source df Sum of squares square F

Direct effect of type of mating l .70 .70 3.18
Direct effect of reproductive age 1 .1A .1A .6A
Direct effect of no. of services 1 .06 .06 .27
Direct effect Of boars/type of

mating 11 6.21 .56 2.55**
No. of services x type of mating

interaction 1 .93 .93 A.23*
Direct effect of breeding seasons 9 2.88 .32 1.A5
Error vfifi 3A9 76.78 .22

* P< 0.05
** PC 0.01

 

The boar used was the only factor examined that had a highly
significant effect (P< 0.01) on farrowing rate. The chi-square analysis
had indicated a significant effect due to type Of mating, but the
difference in farrowing rates of naturally (6A.5%) and artificially
(50.0%) mated swine was nonsignificant by the analysis of variance. When
these data were adjusted for all factors besides type of mating the
least square estimate of the difference was 12%.

The analysis of variance also indicated a significant interaction
(P( 0.05) between the number of services during estrus and the type of
mating. The least squares estimate of this interaction is presented

in table 21.

-78-
TABLE 21
Farrowing_rates by pype of matinggand number of services during estrus.

T e of mating

 

 

 

 

 

 

Natural Artificial Average
1 x 69% A3% 56%

No. of services 2 x 59% 61% 69%
Av. 6A% 52%

 

An analysis of the factors influencing litter size of those that
farrowed is presented in table 22.

TABLE 22.

Analysis of variance of factors influencing litter size of naturally and
artificially mated swine.

 

 

 

Source df Sum of squares Mean square F
Direct effect of type of mating 1 A.06 A.06 .A2
Direct effect of reproductive age 1 118.01 118.01 12.15**
Direct effect of no. of services 1 16.13 16.13 1.66
Direct effect of boars/type of

mating ll llA.OA 10.37 1.07
No. of services x type of mating

int. 1 53-75 53-75 5-53*
Direct effect Of breeding season 9 218.37 2A.26 2.50**
Error 199 1,932.52 9.71

* P<?O.O5

** P(0.0l

 

The reproductive age and the breeding season both had highly signifi-

cant (P< 0.01) effects on litter size. The least squares estimate in-

-79-
dicated that sows averaged 1.96 more pigs per litter than gilts when
the data was adjusted for the effects of all other factors.

The interaction between the number of services during estrus and the
type of mating also was significant (P< 0.05) and the least squares
estimate of this interaction is presented in table 23.

TABLE 23
Litter size by type of mating and number of services during estrus.

T e of matin

 

Natural Artificial Average

 

 

l x 9.85 7.89 8.87
No. of services 2 x 9.17 10.29 4y9.73
Av. 9.51 9.09

 

 

 

 

 

The MSU results on swine A.I. were analyzed independently of the
natural breedings in order that they could be compared with the S.M.S.P.
swine A.I. results. Backflow was recorded on 109 of the artificial
breedings and the farrowing rates and litter sizes were compared. These
differences, as presented in table 2A were not significant.

TABLE 2A

The influence Of backflow at insemination on fertility of artificially
inseminated swine.

No. bred Farr. rate Litter size
No backflow 61 5h.1% 9.A2

Some backflow A8 A5.8% 9.18

 

-80-

Table 25 includes the least squares analysis of factors influencing
farrowing rate in M.S.U. artificially inseminated swine. None of the
factors examined significantly influenced farrowing rates.

TABLE 25

Analysis of variance of factors influencing farrowing rate in artificially
inseminated swine.

 

 

Mean
Source df Sum of squares pguare F
Direct effect of reproductive age 1 .16 .16 .67
Direct effect of number of services 1 .06 .06 .25
Direct effect of boars A 1.89 .A7 1.96
Direct effect of seasons 7 1.67 .2A 1.00
Error 106 25.A8 .2A

 

The data was also examined for factors influencing litter size
(Table 26).

TABLE 26

Analysis of variance of factors influencing litter size in artificially
inseminated swine.

 

 

Mean
Sources df Sum of squares square F
Direct effect of reproductive age 1 A9.A9 A9.A9 A.90*
Direct effect of no. of services 1 1.57 1.57 .15
Direct effect of boars A 111.26 27.82 2.75*
Direct effect of season 7 1A1.28 20.18 2.00
Error A6 A6A.87 10.11

 

* P<0.05
The reproductive age (sow or gilt) and the boar used were the only

factors that significantly influenced litter Size in the artificially

~81-

inseminated swine on the M.S.U. farm. The least square estimate of

difference in litter size due to reproductive age indicated that at

M.S.U. artificially inseminated sows averaged 2.1 more pigs per litter

than gilts.

V. DISCUSSION

Boar Semen Preservation Trials

 

The inability of boar spermatozoa to maintain fertility after
periods of storage is one of the major problems confronting swine
artificial insemination. A "shotgun" approach to the problem of storage
was undertaken and a number of treatments were found that maintained
motility for extended periods. In fact, dilution with the standard
extender and refrigeration at 80 C. in sealed polyethylene bottles for
10 days maintained 50% to 60% total motility consistently.

An unsatisfactory relationship between motility and fertility of
stored boar spermatozoa was noted by Stratman gt §l° (1958) and
Stevermer gt a1. (196A). It seemed advisable, therefore, to conduct
fertility trials with boar semen stored at least 5 days. Primarily two
treatments prior to storage were examined: (1) separation of sperm-
atozoa from their seminal fluids by centrifugation and (2) pooling the
ejaculates of two boars.

Stratman (1961) observed that spermatozoa survival in storage was
best when they were removed from their seminal fluids. At M.S.U. this
was attempted by centrifugation or by separation after anabiosis using
a separatory funnel. No pregnancies were obtained from h breedings with
semen treated in the latter manner but a 18.7% rate was obtained on 16
breedings with 5 to 7 day old centrifuged semen. Bialy and Self (1959)
and Self (1959) reported that removal of accessory fluids by centri-
fugation significantly lowered the motility of boar spermatozoa after

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--83-
two days storage but no fertility tests were conducted. In the present
study motility was not adversely affected in the centrifuged sample as
compared to the control.

The use of pooled ejaculates has increased the fertilizing capacity
of semen in cattle (Hess 23.9l-: 195%), sheep (Hamraev, 1958) and rabbits
(Beatty, 1960). Individual ejaculates were compared with pooled
ejaculates in swine by First 23': 21. (1960) but 61+ gilt breedings
indicated no difference in farrowing rates due to pooling. In the
present study a 13.3% pregnancy percentage was obtained from 15 in-
seminations with pooled semen samples that had been stored 5 to 10
days.

A total of 55 inseminations with boar semen stored 5 to 11 days
resulted in a 9.1% pregnancy rate when all experimental treatments were
combined (Table 2). The average number of fetuses 25 to 50 days post
breeding was 6.2. DuMesnil du Buisson (1961) obtained a h5.h% con-
ception rate from 33 inseminations with semen stored h, 5 or 6 days at
150 C. under a C02 atmosphere. This compared to a 53.h% rate for fresh
semen in the same study. However other workers have indicated that
fertility generally decreases drastically after the first day of
storage. Conception rate was reduced one half by storing boar spermatozoa
over 2h hours (Holt, 1959). Aamdal and Hogset (1957) observed farrowing
rates of 79.2% for fresh semen, 60.9% for 1 day, 36.5% for 2 day, 16.1%
for 3 day and 5.6% for A day old boar semen. Polge (1959) obtained
farrowing rates of 72%, A2%, 28%, 17% and 13% for semen stored for the

same periods. The pregnancy rates obtained in the present semen

-8h-
preservation trials were no better then those obtained in these previous
studies.
Swine A.I. Field Trials
The farrowing results from artificial insemination of swine at
S.M.S.P. were disappointing, but still provided considerable information
on some of the factors that influence fertility following A.I. The first
service farrowing rate (3h.8%), although comparable to the 20.8% rate in
an Ohio trial (Wilson gt al., 1963, Wilson 196A) and the 35.3% reported
on first service gilts in Wisconsin (Self, 1961), was considered in-
sufficient for widespread practical acceptance. 0n the other hand,
the comparison between natural and artificial breedings on the M.S.U.
swine farm indicated that under similiar conditions the conception rate
for natural mating (6A.5%) was not significantly different from the con-
ception rate for artificial mating (50.0%). Subin (1962) and Stratman
(1961) noted that conception rate of artificially mated sows did not
differ appreciably from sows bred naturally. Lovell (1958) obtained a
63% conception rate on to sows serviced artificially while 75% of the
naturally bred control sows conceived.. A similar comparison by Paredis
(1961b) also indicated that conception rates for artificially inseminated
swine are generally lower than those bred naturally. Madden (1959a)
obtained an 86% farrowing on sows bred naturally but when the same sows
were serviced artificially in the next breeding season only h5% farrowed.
The differences in litter sizes (0.5 pig) were not significant and in-
dicated that litter size is little affected by the type of mating. In

the present study an 0.7 pig difference in favor of natural mating was

-85-
observed in the M.S.U. herd. This was not significant and approached
the nonsignificant 0.6 pig difference observed by Paredis (1961b).

A slight decrease in the farrowing rate of repeat breedings was
noted in the S.M.S.P. study (table 3). This difference was not
significantly below that for first services. This characteristic between
first and repeat services has been observed previously by other re-
searchers. Madden (1959a) noted little difference in conception rates
for repeat inseminations- A 2A.A% conception rate for first services
and a 2h.0% for repeat services was recorded by Holt (1959). Similarly,
Self (1961) found the rates for second services comparable to first
services in both sows and gilts. Jacobsen (1959) obtained a 3h.2%
farrowing rate on first service gilts which was significantly below
(P< 0.05) the 16.5% rate for repeat breedings. It appears that when the
farrowing rates are low, as they have been in swine artificial insemi-
nation, there is little selection for fertility in the first breedings.
Therefore the S.MmS.P. data for first and repeat inseminations were
combined in further statistical analyses.

Two services during estrus significantly (P< 0.01) increased con-
ception rate in swine artificially inseminated at S.M.S.P. This did not
occur in the M,S.U. trial. However, there was a significant interaction
(P<’0.05) between the number of services and the type of mating. The
least squares estimates of farrowing rates, as presented in table 21,
suggest that the number of matings did not greatly influence farrowing
rate in the combined data because of this interaction. Surprisingly, at

M.S.U. the use of two matings decreased the conception rate 10% in

-86-
naturally mated sows and gilts. 0n the other hand, the sows and gilts
artificially inseminated twice during estrus had an 18% higher farrowing
rate than those inseminated only once. Therefore, both the S.M.S.P. and
M.S.U. studies indicate that A.I. farrowing rates are improved with two
inseminations. The trend towards increased conception with double
artificial services of swine was noted 25 years ago by McKenzie gt 2l°
(1939), when they obtained a 52.9% conception rate with double in-
seminations and a 20.7% rate with single inseminations. Weaver and
Bogart (19h3) also reported an 18% increased conception with double
inseminations. A 10% improvement in conception was indicated by Dziuk
and Henshaw (1958) when swine were inseminated twice during estrus.

At M.S.U. concurrent with the decreased conception of swine mated
naturally twice during estrus was a decrease in the average litter size.
Litter size was also subject of a significant interaction (P<:0.05) be-
tween number of services and type of mating (Table 23).

Alexandrowicz (1955) observed that litter size was increased by double
matings. At MJS.U. the A.I. swine that were serviced twice averaged
2.h more pigs than those inseminated once. The doubly mated gilts at
S.M.S.P. averaged 0.6 less pigs per litter so no consistent trend was
evident. There is little reason to assume that two matings are more
satisfactory than one breeding at the optional time of estrus. However,
optimal time for service is difficult to ascertain when utilizing A.I.
Madden (1959b) has stated that the greatest improvement in fertility

in swine A.I. was due more to critical assessment of the optimum-

service time than ahy improvement in technique. The personnel and

-87-
methods employed at M.S.U. undoubtedly resulted in more accurate detection
of estrus. Therefore, the differences in the two trials could be a re-
flection of the accuracy of detection of estrus.

The estrus detection at S.M.S.P. was not above criticism. It was
conducted by inmates utilizing Visual and manual pressure techniques
without the assistance of a boar. These men often lacked an interest
and desire to do their job well. In the Literature Review the im-
portance of accurate estrus detection and correct timing of the breeding
was repeatedly emphasized. No rejection of females for poor estrus was
practiced by the S.M.S.P. inseminators. Another reason to question the
accuracy of S.M.S.P. estrus detection was the high number of gilts
(8.3% of total) that were reserviced or slaughtered for presumably
returning to estrus and later found to be pregnant from earlier matings.
In the M.S.U. trial pregnant gilts were not observed to recycle.

The different inseminator's influence on fertility led Self (1961)
to conclude that perhaps the technician is the most important single
factor in the success of swine A.I. Certainly the results from S.M.S.P.
demonstrate a considerable range in the conception rates obtained by
the three inseminators (28.3% to 52.7%) (Table 5), a difference
significant at the 5% level. Similar ranges in the conception rates
of inseminators were noted by Aamdal and Hogset (1957) where college
personnel had a 70.2% rate as compared to 57.9% for 30 practicing
veterinarians. Madden (1959b) also examined the inseminator influence on
swine fertility. One technician was consistently higher than the others.

This was attributed to his greater ability to assess the optimal stage of

-88-
estrus for A.I. Wilson et a1. (1963) explained inseminator differences
on the basis of experience. Since the conception rates did not appear
to be markedly different after the inseminator had made 10 or more
inseminations.

Statistical analysis revealed no significant inseminator effect
on litter size but there was a trend for the best technician to have
the highest litter size and the poorest the lowest. Madden (1959b) also
noted that the best inseminators tended to have the largest litters but
the difference was not significant. 0f coincident interest was the
attitude of the S.M.S.P. inseminators toward the swine A.I. project.
Technician C, with the highest conception rate, had enthusiastically
welcomed the trial and was partly responsible for its initiation as a
research project. In addition this man was the swine herdsman and
enjoyed working with swine. The other two technicians, although not
swine men, accepted the assignment as part of their job; however, as the
trial progressed it became apparent that inseminator B was discouraged
and impatient with the A.I. program. No inseminator comparison was
possible at M.S.U. because one highly qualified technician did the
breedings.

The one factor in each study that Consistently had the greatest
influence on farrowing rates was the boar used. At S.M.S.P., where 3
boars were used, the range in farrowing rate was 2l.h% to h1.7% while at
M.S.U. the range on 6 boars was 29.2% to 78.6%. In the naturally mated
swine the boar's range in farrowing rate was Al% to 100%. These

differences in farrowing rates by boars were significant at the 1% level.

-89-

There were significant (P< 0.05) boar differences in litter size in the
A.I. swine at M.S.U. Paredis (1962) reported highly significant
(P( 0.01) differences in conception rates and litter size by different
boars used for A.I.

Aamdal (1959) observed a statistically significant difference in
conception rate between 16 boars used in over 6,500 inseminations.
The conception rates by boars ranged from 37.5% to 60.8%. A range in
farrowing rates by individual boars was also noted by Madden (1959a) but
the differences were not significant. The difference in conception rate
between high and low boars was greater in gilt than sow breedings, but
the ranking of the boars on the basis of conception rate in sows was
almost in the reverse order to their rank in gilts (Self, 1961).

Numerous reports on the effects of semen storage on farrowing
rates and litter size are cited in the Review of Literature. The
development of satisfactory storage methods for boar semen is the major
problem limiting the expansion of swine A.I. A progressive nonsignificant
decline in conception when semen age increased up to 2A hours was report-
ed by Paredis and Vandeplassche (1962). A similar situation was noted
by Aamdal (1959). The same observation was made in the present S.M.S.P.
field trial where the farrowing rate of semen stored 6 hours (32.0%) was
not significantly greater than that of semen stored 2A hours (30.5%) or
30 hours (30%). Litter size was also apparently unaffected by semen.
storage. The highest average litter sizes (7.5 pigs) occurred in gilts
bred with 30 hour semen. Since only a limited number of breedings (1A)

were made with semen stored A8 hours or longer it is not possible to

-90-
formulate conclusions for storage periods longer than 30 hours. However,
as already noted a marked decrease in fertility of semen stored longer
then one day has been reported. With semen stored only 10 hours Jacobsen
(1959) indicated that decreased farrowing rates and litter sizes with
increasing semen age were significant. In his study semen stored 2
hours provided a 63.0% farrowing rate and an average of 11.3 pigs while
semen 8 to 10 hours old resulted in a A8% farrowing rate and an 8.8 pig
litter average. Conception did not result when 5 sows were inseminated
with 12 hour semen. Madden (1959a), however, determined no evidence of a
decrease in fertility with increasing semen age up to 10 hours. In the
current S.M.S.P. trial semen was stored for 30 hours without a significant
decrease in fertilizing capacity.

Semen backflow may occur following the artificial insemination of
swine. Lasley and Day (1960) reported difficulty in making the semen
remain in the female tract, and Hess gt El' (1960a) suggested that back-
flow indicated improper insemination technique. Dzuik and Henshaw (1958),
Madden (1959a) Radford (1961b) and Paredis (1961b) reported no relation-
ship between backflow and fertility. This apparently occurred in the
present trial with the M.S.U. swine herd, but the S.M.S.P. trial in-
dicated conception was significantly higher (P( 0.01) when semen back-
flow occurred. Hammond (1957) and Polge and Rowson (1956) suggested
that uterine contractions play an important role in sperm transport. It
appears that semen backflow reflects muscular activity of the female
reproductive tract. If this is correct backflow may be an accurate in-

dication of proper uterine receptivity. 0n the other hand, backflow

-91-
could also result if the infusion of semen is too rapid, since con-
siderable backflow occurs when large volumes of cold semen are in-
seminated too quickly. The quiet, deliberate insemination procedures
utilized could explain why backflow was not related to increased fertility
in the M.S.U. herd. Some difficulty was encountered in training the
S.M.S.P. technicians to slow the speed of semen insemination. 0f the
swine inseminated at M.S.U. only AA% exhibited backflow as compared to
8A% for those inseminated at the S.M.S.P. In each study backflow occasion—

ally occurred even when the gilts were handled quietly and inseminated

 

slowly. The relationship of semen backflow to fertility in these studies
demonstrates that backflow does not indicate ineffective insemination
technique. It is also true that backflow is sometimes observed following
natural mating.

The complex relationship between the volume and spermatozoa con-
centration of the insemination dose has been discussed. The present
trials were not designed to study this relationship. The concentration

(5 billion) and volume (50 ml.) selected were within those levels re-

 

commended by other workers. (Stratman and Self, 1960; First, gt El°
1960; Paredis, 1961b).

The most satisfactory test of boar semen quality is fertility.

However, numberous studies have utilized spermatozoa motility as the end
point in spermatozoa evaluation. The S.M.S.P. study indicated that pro-
gressive motility estimates made at the time of semen collection had
little relationship to fertility except at the lower motilities. The

lowest farrowing rate and litter size were obtained from the semen

-92-
samples with the lowest progressive motility, and the lowest total
motility. Thus while motility estimates may not be closely related to
fertility at higher motility levels it appears that poor motility reflects
inferior spermatozoa. This is in support of earlier observations by“!
Paredis and Vandeplassche (1962), Hess _e_t_ _a_l_. (1960a), Ito _a_t _a__1_. (19A8b)
and Niwa 23 al. (1959a) where higher conception rates were obtained when
the initial motility exceeded 70%. There is some evidence which indicates
that motility may be a particularly poor measure of fertility of stored
boar spermatoza (Stratman 23 al., 1958; Self, 1959; Stevermer gt 21.,
196A). This belief was also supported by previous, unpublished work at
M.S.U.

A study of the cooling rate of boar spermatozoa (arrival tempera-
ture) was not intentionally designed into the S.M.S.P. study but the
differences that did develop in shipment did not significantly influence
the subsequent fertility of artificially inseminated swine. However,
the arrival temperatures were within the range of those commonly accepted
for storage of boar spermatoza (80 C. to 200 C.). Fertility apparently
decreased when semen was received at the higher temperatures (170 C. to
210 C) but the results were inconsistent and no definite trend was I

apparent. For example the highest farrowing rate (A5.2%) occurred from

 

the 90 C. samples and the lowest (1A.7%) from the 110 C. samples.

The study at M.S.U. afforded the opportunity to compare the fer-
tility between sows and gilts. Generally, the farrowing rates are re-
ported to be higher for sows than for gilts (Jacobsen, 1959; Self, 1961).

No difference was observed in the present trial. The conception rate for

-93-
17A gilts was 60.3% as compared to 59.5% for 200 sows. The type of breed-
ing (A.I. or natural) did not change this relationship between gilts and
sows. A limited number of sow breedings at S.M.S.P. (10% of the total
breedings) indicated a 30.A% farrowing rate for gilts and AA.7% for sows.
In the M.S.U. study the average litter size was increased by more than 2
pigs in sows compared to gilts regardless of type of mating. This in-
crease in average litter size of sows as compared to gilts was highly
significant (P < 0.01) .

The breeding season did not significantly effect farrowing rate and
no particular trend was observed. The two highest farrowing rates for
naturallyrbred sows occurred in July-August 1962 (79.3%) and January-
February 1963 (79.2%). The lowest farrowing rate was in JulynAugust
1963 (22.2%). There was a highly significant difference (P<'0.01) in
litter size by seasons in the combined M.S.U. data but this difference
did not exist when the A.I. results were analyzed alone. In several
breeding periods the A.I. farrowing rate was superior to the rate for
naturally bred swine.

The behavior pattern of swine during insemination may be important.
DuMesnil du Buisson (1961) obtained a 63.8% farrowing rate when sows
were "very quiet" at the time of insemination and 3A.l% when they were
"agitated". At the S.M.S.P. the procedure of driving the gilts into the
.breeding crate often had them in an agitated condition. The gilts were
subjected to eartagging immediately prior to their first insemination,
undoubtedly a stressful exposure. Patient handling of swine at breeding

was recommended by Polge and Rowson (1956). Since it is recognized that

—9A-
adrenalin will antagonize the normal activity of the female genital
tract during breeding.

Gilts that failed to conceive after three inseminations were
autopsied at the S.M.S.P. slaughtering plant and their reproductive
tracts were examined. The incidence of anatomical abnormalities in the
reproductive tracts of these gilts was not unusually high. Only 20.8%
of the "non breeders" slaughtered exhibited reproductive abnormalities
on gross examination and this represented less than 2% of all the gilts
utilized in this trial.

Non return rates when utilized as a measure of swine fertility, are
not satisfactory. The non return rate calculated for first breedings
at S.M.S.P. was 51.7% while the farrowing rate for the same group was
3A.2%. The same situation has been reported by Holt (1956) where a 71%
non return rate represented a 1A% farrowing rate in artificially in-
seminated swine.

In the S.M.S.P. trial a total of 61 litters, averaging 7.1 pigs,
were farrowed to gilts that lost their ear tags subsequent to service.
These unidentified farrowings approximated 29.A% of the total matings
to animals that lost their tags after insemination. This approaches the
32% rate obtained in the tagged gilts and suggests that the loss of ear
tags was random with respect to the various parameters of the trial.

A limited field trial was also conducted at the Ionia Reformatory
farm in Ionia, Michigan in May 1963. Only 7 gilts and 13 sows were
inseminated but this represented the entire spring breeding on the

Reformatory farm. The sows and gilts were checked daily by an inmate

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with a boar. Sows were inseminated on their first post weaning estrus
and the gilts were serviced whenever they exhibited estrus during the
three week breeding period. A breeding crate was used for the in-
seminations. The techniques used were similar to those used in other
trials. The semen was provided from the Endocrine Research Unit Boar
Stud and the insemination was performed by the dairy cattle herdsman
and his assistant. The farrowing rates on first breeding for the 13
sows was 61.5% with an 8.25 pig average. Identification was lost on all
of the gilts, but 2 farrowed an average of A.5 pigs for a 28.6%
farrowing rate. Although relatively few animals were inseminated,
trends paralleled the S.M.S.P. trial in respect to the influence of
number of services, inseminator, flowback and different boars on

farrowing rates.

VI. SUMMARY AND CONCLUSIONS

Research on artificial insemination of swine was intiated at
Michigan State University in 1959. A boar stud was organized and swine
insemination techniques were investigated.

A series of boar semen preservation studies indicated that
spermatozoa motility could be satisfactorily maintained with a variety
of treatments for storage periods of 5 to 10 days. Fertility trials
provided 55 inseminations with semen stored 5 to 11 days. The pregnancy
rate at 25 to 50 day post breeding slaughter was 9.1% with an average
of 6.2 fetuses per pregnancy.

Two experimental field trials were conducted to study the factors
which affect fertility in swine artificial insemination. One trial,
undertaken at the Southern Michigan State Prison farm, afforded complete
information on A38 inseminations. The second trial, conducted on the
Michigan State University swine farm, consisted of 120 artificial matings
with 25A natural breedings for comparison. The overall conception rate
on 276 first inseminations at S.M.S.P. was 3A.8% with a 6.8 pig average
litter size. The conception rate on 120 first inseminations at M.S.U.
was 50.0% with a 9.3 pig average.

The farrowing rate for the naturally bred swine at M.S.U. was 6A.5%
while the rate for the artificially inseminated swine was 50.0%. This
difference did not prove to be statistically significant when analyzed
by the method of least squares. The average litter size for naturally
bred swine was 0.7 of a pig higher than for those artificially“inseminated,
but this difference was not significant.

The conception rates obtained from first and repeat inseminations

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-97-
at S.M.S.P. were not statistically different; however the number of
inseminations during estrus significantly influenced farrowing rate.
When gilts were serviced twice during estrus the farrowing rate was
AA.5% as compared to 21.3% for gilts serviced once. This difference was
highly significant (P(0.01). An increase in farrowing rates of swine
inseminated twice during estrus was also apparent in the M.S.U. trial but
the differences were not significant. There was a significant inter-
action (P( 0.05) between type of mating and number of services with the
naturally bred swine having an increased farrowing rate in favor of the
singly bred gilts and sows.

The age of semen up to 30 hours had no influence on fertility in
the S.M.S.P. study, but the inseminator and the backflow of semen at
insemination markedly influenced farrowing rates. Semen stored 6 hours,
2A hours, 30 hours and a few samples stored over A8 hours did not
significantly influence litter sizes or farrowing rates. When three
inseminators were compared their differences in farrowing rates were
significant (P( 0.05). An estimate of semen backflow during and after
insemination was related to farrowing rate, the farrowing rate being
significantly (P< 0.01) higher when some backflow occurred. No such
relationship was observed in the M.S.U. studies.

The greatest factor to influence fertility at S.M.S.P. and M.S.U.
was the differences between boars. A highly significant (P< 0.01) boar
effect on farrowing rate was observed in both studies. At M.S.U. this
difference was significant for boars used either naturally or arti-

ficially.

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Sows did not have a significantly higher farrowing rate than gilts
following natural or the artificial matings at the University. The
average litter size of sows, however, was significantly (P<f0.01) larger
than gilts. The majority of the breedings at S.M.S.P. were with gilts.
However, the few sows that were artificially inseminated had higher
farrowing rates and larger litters than gilts. These differences were
not significant.

The season of breeding did not significantly influence farrowing
rate in the M.S.U. breedings although the breeding season influence on
litter size was highly significant (P< 0.01).

Motility estimates, at the time of collection and dilution of the
semen, were not closely related to fertility. However, the lower
progressively motile samples resulted in the lowest fertility and
samples with less than 70% total motility were significantly (P<0.05)
lower in fertility than samples above 70% total motility.

Successful artificial insemination of swine is not a simple process
and many factors are involved in achieving adequate fertility rates. The
follOWing conclusions were drawn from the data:

Farrowing rates of artificially inseminated swine approach those
of naturally mated swine when A.I. is closely supervised. Litter size is
not appreciably different following artificial insemination as compared
to natural mating.

Boars used for artificial insemination may differ in their con-
ception rates. A similiar variation in fertility also occurs in boars

used naturally.

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Artificial insemination technicians vary considerably in their
abilities. This is indicated by marked differences in farrowing rates
and average litter sizes of swine they inseminate.

Boar spermatozoa can be stored at refrigerator temperatures

(50 C. to 80 C.) for at least 30 hours without greatly reducing fer-
tility.

Two breedings during estrus increases the farrowing rate in
artificially inseminated swine. Artificially inseminated sows tend to
have higher farrowing percentages than artificially inseminated gilts but
these differences are not always significant. Artificially inseminated
sows have larger litters then do similiarly mated gilts.

The backflow of semen at the time of artificial insemination does
not necessarily indicate ineffective insemination technique. In some
instances improved farrowing rates are associated with the occurrance of
some insemination backflow.

The progressive and total motility of boar spermatozoa upon
collection can be used to determine inferior semen samples. Progressive
motility should be above A0% and total motility above 70% for the most
satisfactory fertility results. At these higher percentages, however,
increased motility is not closely related to increased fertility of a
semen sample.

These data indicate that artificial insemination of swine is
practical but further investigation is needed to improve conception rates.
The problems of extension and storage of boar semen require further
attention as do factors relating to the detection of estrus in swine and

inproved techniques of insemination.

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' ' ”an

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‘Aaafil

North Central Regional Committee on Artificial Insemination of Swine.
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North Central Regional Committee on Artificial Insemination of Swine.

1963. (NOR-26)

 

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-115-

APPENDIX TABLE A

Breeding_Information on Gilt§_Inseminated

With Stored Semen

 

Gilt Age of
no. Date bred Treatments semen P.M. T.M. Condition at slaughter
5 5-1-62 Seperated 7 da. A9% 76% Cystic,
by funnel
6 5-3-62 Other buffer 7 da. 5% 75% Normal, non preg.
1 5-3-62 C02 atmosphere 7 da. 39% 6A% Normal, non preg.
7 5-3-62 002 atmosphere 7 da. 39% 6A% Normal, non preg.
8 5-A-62 Other buffer 8 da. 23% A2% Normal, non preg.
10 5-8-62 Pooled 5 da. 22% 39% Normal, non preg.
25 5-8-62 Pooled 5 da. 22% 39% Normal, non preg.
11 5-10-62 Standard
diluter 7 da. 20% 35% Normal, non preg.
23 5-10-62 Centrifuged 7 da. 10% AO% Normal, non preg.
12 5-11-62 Standard
diluter 7 da. 12% 50% Normal, non preg.
l3 5-12-62 Standard
diluter 7 da. 15% A0% Normal, non preg.
2A 5-12-62 Centrifuged 8 da. 13% 7A% Cystic
9 5-12—62 CO2 atmosphere 7 da. 20% 51% Cystic
3 5-15-62 Other sugar 7 da. 2A% 76% Normal, non preg.
16 5-18-62 Standard
diluter 7 da. A0% 90% Normal, non preg.
2 5-18-62 Pooled 7 da. 10% 85% Pregnant, 5 pigs
15 5-18-62 Pooled 7 da. 10% 85% Normal, non preg.
30 5-18-62 CO2 atmosphere 7 da. 38% 67% Normal, non preg.
6* 5-22—62 Standard
diluter 11 da. 3% 18% Normal, non preg.
18 5-22—62 Other buffer 8 da. 10% 60% Normal, non preg.
17 5-22-62 Centrifuged 8 da. A5% 60% Normal, non preg.
26 5-22-62 Seperated 8 da. 35% 70% Normal, non preg.
8* 5-22-62 C02 atmosphere 11 da. AA% 78% Normal, non preg.
l9 5—23—62 Standard
diluter 9 da. 0% 75% Normal, non preg.
1* 5-23-62 Seperated by
funnel 5 da. A5% 75% Normal, non preg.
20 5-25-62 Centrifuged 5 da. 35% 50% Normal, non preg.
7* 5—25-62 Centrifuged 5 da. 35% 50% Pregnant, 3 pigs
21 5-25-62 Seperated by
funnel 5 da. A0% 65% Normal, non preg.
3* 5-28-62 Other buffer 5 da. 50% 92% Normal, non preg.
10* 5-28-62 Other buffer 5 da. 50% 92% Normal, non preg.
1A 5-29-62 Standard
diluter 8 da. A0% 70% Normal, non preg.
12* 5~29-62 Other buffer 5 da. 25% 65% Normal, non preg.

-116-

APPENDIX TABLE A (CONTINUED)

Breeding Information on Gilts Inseminated With Stored Semen

 

 

Gilt Age of
no. Date bred Treatments semen PSM. T.M. Condition at slaughter
22 5-29-62 Other buffer 5 da. 25% 65% Normal, non preg.
29 5-31-62 Centrifuged 7 da. 18% 52% Normal, non preg.
A 6—2A—62 Pooled 8 da. 12% A3% Normal, non preg.
10A 7-11-62 Centrifuged 7 da. 12% 50% Pregnant, 8 pigs
108 7-10-62 Centrifuged 6 da. 25% A5% Pregnant, 8 pigs
110 7-19-62 Centrifuged 8 da. 2% 19% Normal, non preg.
107 7-19-62 Centrifuged 8 da. 2% 19% Normal, non preg.
103 7-2Au62 Centrifuged 8 da. 15% 37% Normal, non preg.
102 7-2A-62 Centrifuged 8 da. 15% 37% Normal, non preg.
101 7-25—62 Centrifuged 5 da. 18% 50% Immature
113 7-28-62 Centrifuged 8 da. 10% A0% Cystic
106 7-29-62 Centrifuged 5 da. 25% 55% Normal, non preg.
111 7-31-62 Centrifuged 7 da. 20% 35% Normal, non preg.
121-7 7-2A-62 Pooled 8 da. 1A% 56% Normal, non preg.
122-A 7-25-62 Pooled 8 da. 12% A6% Normal, non preg.
18~8 7-26-62 Pooled 8 da. 25% AO% Normal, non preg.
1A~8 7-28-62 Pooled 7 da. 18% 52% Normal, non preg.
16-9 7-29-62 Pooled 7 da. 20% 35% Pregnant, 7 pigs
17-2 8—9-62 Pooled 9 da. 52% 83% Normal, non preg.
A5-8 8-1A-62 Pooled 9 da. 30% 70% Normal, non preg.
16—3 8-1A-62 Pooled 9 da. 30% 70% Normal, non preg.
18~8* 8u15-62 Pooled 10 da. 33% 76% Normal, non preg.
122—A*8-16-62 Pooled 9 da. 20% 55% Normal, non preg.

 

* Gilts reserviced.