......

 

REPRODUCTION, MILK PRODUCTION.
AND CULUNG IN DAIRY COWS
INSEMJNATED AT FIRST ESTRUS AFTER
40 OR 60 DAYS POSTPARTUM

Thesis for the Degree of M. S.
MICHIGAN STATE UNIVERSITY
DMD. SEA-Y HARRISON
E975

-.—_‘.

.4.

 

 

 

 

 

 

 

 

m

w
a
N
{D
(.0
O
_|
o
\l
a)
N
a)
a

”Ana-b r ‘- v. «.

"' .O‘ .

:-_“‘.],_.'. .:.nf-¢r
kw 4...: a 3.2. .1..«,] ,‘j
'3 L‘.
A ‘
WJM.V-ia=vsfl o7<nw¢~.'rsuvmv .

 

 

 

  

‘3' mam avg Y =
. "ME 8: WW
'- ‘I‘ HOOK BINDERY INC.

'5‘ 23mm BlNDERS‘ .
' "' '. veepulculu‘nn

    
  

 

   
   

 

 

 

ABSTRACT

REPRODUCTION, MILK PRODUCTION, AND CULLING IN DAIRY
COWS INSEMINATED AT FIRST ESTRUS AFTER
40 OR 60 DAYS POSTPARTUM

BY

David Seay Harrison

Cows in twelve c00perating dairy herds in south
central Michigan were assigned to be bred at either first
estrus after 40 days (Treatment I) or 60 days (Treatment II)
postpartum. Cows clinically abnormal at parturition were
assigned to be bred when diagnosed as normal by the herd
veterinarian (Treatment III). Thirteen percent of the cows
calving were assigned to Treatment III with retained
placenta and uterine infection accounting for 68 percent
of those assignments. Fewer cows in Treatment I were
culled then in Treatments II and III. Low production was
the greatest cause for culling in all groups. Sterility
and inferitility was the second major cause.

Interestrual intervals and intervals between-
inseminations averaged 31 days for all cows, an indication
that 50 percent of the expected estrous periods were not
observed. Interval to first estrus was 58 days, and was not
affected by treatments.

Cows assigned to Treatment I averaged 73 days to

first insemination which was shorter than the 82 and 83

David Seay Harrison

days for Treatments II and III, respectively. In eleven
herds cows assigned to Treatment I had shorter intervals
to first insemination than those assigned to Treatment II.
All cows averaged 84 days to first insemination in 1972
which was the pretreatment control period. Treatment and
herds within herd size significantly affected interval to
first insemination as determined by least squares analysis.

Interval to conception was 99 days for cows in
Treatment I which was less than 112 days for cows in
Treatment III, but not different than 105 days for cows in
Treatment II. These correspond to 12.5 to 13 month calving
intervals. Only one herd achieved a twelve month calving
interval, but ten herds had calving intervals shorter or
similar to those for 1972. Therefore, breeding some cows
early reduced overall days Open. Interval to conception
was affected by interval to first insemination and interval
from first insemination to conception and their inter-
actions with other reproductive measurements as determined
by least squares analysis.

Intervals from first insemination to conception and
inseminations per conception for cows were similar between
treatments and years indicating no detrimental effects of
early breeding. Least squares analysis revealed that
interval to first insemination, interval to conception, and
the interactions of 150 day milk yield with interval to
first estrus and interval to conception significantly

affected the interval from first insemination to conception.

David Seay Harrison

Inseminations per conception were affected by housing type,
interval to conception, and 150 day milk yield's inter-
actions with interval to first insemination, interval from
first insemination to conception, and interval to conception.
Conception rate for all inseminations was 55 percent or
above, and was not affected by treatments.

When the data were grouped by 20 day intervals to
first insemination, ignoring treatments, a significant
effect was noted for all intervals studied. As the interval
to first insemination increased, there was an associated
increase in interval to first estrus, and interval to con-
ception, but a decrease in interval from first insemination
to conception and inseminations per conception. However,
cows first inseminated less than 40 days postpartum had
more days open than cows first inseminated from 40-60 days
postpartum, indicating that breeding before 40 days was
undesirable.

No effects on milk yield per day for the first 180
days of lactation were observed for treatments or intervals
to conception. Lactation curves for the first 180 days of
lactation were not affected by treatments or intervals to
conception. Least squares analysis of 150 day milk yields
revealed significant treatment, and herds within herd size
effects.

Season affected none of parameters measured. Age
at calving affected only 150 day milk production. Herd

variation existed for all parameters measured. At the end

David Seay Harrison

of the study, eleven of the c00perating dairymen planned to
continue breeding some cows early, an indication that their
participation in the study convinced them of the benefits

of early breeding.

REPRODUCTION, MILK PRODUCTION, AND CULLING IN DAIRY
COWS INSEMINATED AT FIRST ESTRUS AFTER

40 OR 60 DAYS POSTPARTUM

BY

David Seay Harrison

A THESIS

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

MASTER OF SCIENCE
Department of Dairy Science

1975

ACKNOWLEDGMENTS

The author wishes to acknowledge the guidance and
assistance of Dr. Jack H. Britt, his major professor, in
preparation of this manuscript, and in the author's overall
graduate program.

Graduate guidance committee members Drs. Roger W.
Mellenberger, Clinton E. Meadows, and Stephen B. Harsh are
thanked for their suggestions and comments regarding this
thesis.

Roger R. Neitzel is thanked for his statistical
advice and computer programming of the statistical analyses
for the field data collected.

Appreciation is expressed to Dr. Charles A.
Lassiter, Chairman, Department of Dairy Science, for the
financial assistance provided that made the author's
graduate studies and work possible.

The twelve c00perating dairymen who completed the
study are also gratefully acknowledged. Without their
c00peration, the study would have been impossible to

complete.

ii

A special thanks is given to the graduate students,
staff, and friends who helped in so many ways.

And, last of all, to Mom and Dad and the rest of
my family for everything they have done and provided for

me.

iii

TABLE

OF

CONTENTS

Page

LIST OF TABLES . . . . . . . . . . . . vi

LIST OF FIGURES. . . . . . . . . . . . ix

INTRODUCTION. . . . . . . . . . . . . .

REVIEW OF LITERATURE . . . . . . . . . . . 3
Interval to First Ovulation and Estrus . . . . 5
Detection of Estrus. . . . . . . . . . . 6
Interval to First Insemination . . . . . . . 7
Fertility at First Insemination. . . . . . . 8
Inseminations per Conception. . . . . . . . 9
Interval from First Insemination to Conception. . 10
Calving Interval. . . . . . . . . . . . ll
Cows with Postpartum Disorders . . . . . . . 11
Season . . . . . . . . . . . . . . . 12
Level of Milk Production . . . . . . . . . l4
Herd Size . . . . . . . . . . . . . . 15
Nutrition . . . . . . . . . . . . . 16

MATERIALS AND METHODS. . . . . . . . . . . 18
Herd Selection . . . . . . . . . . . . 18
Pretreatment Data . . . . . . . . . . . 18
Treatment Groups and Procedures. . . . . . . 20
Analysis by Interval to First Insemination . . . 22
Lactation Curves by Interval to Conception . . . 23
Least Squares Analysis. . . . . . . . . . 23

RESULTS . . . . . . . . . . . . . . . 26
Treatment III Assignments. . . . . . . . 28
Interval to First Estrus . . . . . . . . . 29
Interval to First Insemination . . . . . . ,. 33
Estrus and Insemination Intervals . . . . . . 40
Interval to Conception. . . . . . . . . . 42
Interval from First Insemination to Conception. . 48

iv

Percent Conception at Various Inseminations
Percent Pregnant
Inseminations per Conception
Milk Production
Cull Reasons and Frequencies

DISCUSSION.
SUMMARY. .
APPENDICES
Appendix

A.

B.

C.

D.

BIBLIOGRAPHY

Tables.

Weekly Report Form for Field Study

Sample Computer Printout for Assigned
Minimum Insemination Dates, and Actual
Insemination Dates

Sample of Questionnaire Sent to Cooperating
Dairymen, and Their Responses to Questions

Page
49
57
58
59
68
74

83

87

88

89
92

128

Table

1.

10.

11.

LIST OF TABLES

Number of cows calving or assigned, percent
pregnant, percent abnormal, and percent
culled by herds during 1972 and 1973-74 . .

Reasons and frequencies for assignments to
Treatment III (cows abnormal at calving). .

Reproductive performance for cows assigned to
Treatment I, II, and III during 1973-74 . .

Reproductive performance for cows first
inseminated at various 20 day postpartum
intervals . . . . . . . . . . . .

Percent of cows in Treatments I, II, and III
first inseminated at various 20 day post-
partum intervals. . . . . . . . . .

Days between estrus and inseminations for
cows in Treatments I, II, and III . . . .

Percent conception at the first through fourth
inseminations for all cows and cows in
Treatments I, II, and III. . . . . . .

Percent conception at first insemination for
normal (Treatments I and II) and abnormal
(Treatment III) cows bred at various 20 day
postpartum intervals . . . . . . . .

Percent conception at the first through fourth
inseminations for cows first bred at various
20 day postpartum intervals . . . . . .

Summary of data for 1972 and 1973-74 for herds
participating in the early breeding project.

Average milk yield per day during the first

180 days of lactation for cows in Treatments
I, II, and III . . . . . . . . . .

vi

Page

27

29

30

32

39

41

54

55

56

60

68

Table

12.

13.

Average milk yield per day during the first 180
days of lactation for cows that conceived
during various 20 days postpartum intervals .

Cull reasons and frequencies for all cows
during 1972, and for all treatments and cows
during 1973-74. 0 o o o o o o o o 0

Age at calving, lactation number, and herd milk
yields for cows in herds participating in the
early breeding project . . . . . . . .

Description of variables used in the least
squares multiple regression analyses . . .

Interval to first estrus for cows in Treatments
I, II, and III within herds--l973-74 . . .

Least squares analysis of variance for interval
to first estrus . . . . . . . . . .

Least squares adjusted means for interval to
first estrus . . . . . . . . . . .

Days to first insemination for cows within
herds by years and treatments. . . . . .

Least squares analysis of variance for interval
to first insemination . . . . . . . .

Least squares adjusted means for interval to
first insemination . . . . . . . . .

Days between estrus and inseminations for all
cows by herds . . . . . . . . . . .

Days from first estrus to first insemination
for cows in Treatments I, II, and III within
herds. O O O O O O O O O O O C 0

Days to conception for cows within herds by
years and treatments. . . . . . . . .

Least squares analysis of variance for interval
to conception . . . . . . . . . . .

Least squares adjusted means for interval to
conception . . . . . . . . . . . .

Days from first insemination to conception for
cows within herds by years and treatments. .

vii

Page

69

73

104

105

107

108

109

110

111

112

113

114

115

116

117

118

Table

0-15.

D-20.

D-21.

Page

Least squares analysis of variance for interval
from first insemination to conception . . . ll9

Least squares adjusted means for interval from
first insemination to conception. . . . . 120

Percent conception at the first through fourth
insemination for cows within herds-~1972 . . 121

Percent conception at the first through fourth
insemination for cows within herds--l973-74 . 122

Inseminations per conception for cows within
herds by years and treatments. . . . . . 123

Least squares analysis of variance for insemi—
nations per conception . . . . . . . . 124

Least squares adjusted means for inseminations
per conception. . . . . . . . . . . 125

Least squares analysis of variance for 150 day
milk yield . . . . . . . . . . . . 126

Least squares adjusted means for 150 day milk
yield. . . . . . . . . . . . . . 127

viii

LIST OF FIGURES

Figure

1. Least squares regression of interval to first
insemination on interval to first estrus . .

2. Least squares regression of interval to first
insemination on number of estrus periods
before initial insemination . . . . . .

3. Least squares regression of interval to con-
ception on interval to first insemiantion. .

4. Least squares regression of interval to con-
ception on interval from first insemination
to conception . . . . . . . . . . .

5. Least squares regression of interval from first
insemination to conception on interval to
conception . . . . . . . . . . . .

6. Least squares regression of interval from first
insemination to conception on interval to
first insemination . . . . . . . . .

7. 180 day lactation curves for cows in Treatments
I, II, and III. 0 O O O O O O O O O

8. 180 day lactation curves for cows that conceived
during various 20 day postpartum intervals I.

9. 180 day lactation curves for cows that conceived
during various 20 day postpartum intervals

II. 0 O I O O O O O O O O O O O

10. Least squares regression of 150 day milk yield
on age at calving. . . . . . . . . .

ix

Page

36

38

45

47

51

53

63

67

71

INTRODUCTION

In today's highly competitive agriculture, every
effort must be made to achieve the maximal and/or most
efficient production from every farm enterprise. While
the dairy industry is the most efficient producer of animal
protein, there is at least one achievable, desirable
characteristic of a dairy enterprise that is seldom
realized. A twelve month calving interval for dairy cows
is considered best for highest milk yield per day of
production and most calves per lifetime. However, the
average dairy herd calving interval in Michigan is 13
months. It appears that one of the causes (if not the main
cause) for long calving intervals is the failure of dairy-
men to begin breeding their cows soon enough after
parturition. In Michigan, the average interval from
calving to first insemination for dairy cows is 94 days,
but a cow must conceive again within 85 days to maintain
12 month calving intervals. While the recommended
interval to first postpartum breeding is 60 days, various
studies have concluded that, for normal cows, 40 days is
an acceptable period to wait for postpartum breeding

without resulting in increased reproductive problems.

Therefore, it was decided to compare in selected
Michigan dairy herds the reproductive performance of cows
that were bred either at first estrus after 40 or 60 days

postpartum.

REVIEW OF LITERATURE

A dairy cow should have a twelve month or less
calving interval to maximize milk and calves produced per
lifetime (Speicher and Meadows, 1967; Louca and Legates,
1968). Cows that maintain twelve month calving intervals
produce less milk in 305 day lactations than cows with
longer calving intervals, but they yield more milk per day
of calving interval and productive life because they
produce at a higher level of milk production for a greater
percentage of time (Olds and Seath, 1965). C00per (1966)
estimated that milk per day of calving interval would be
0.4 kg higher for each month calving interval is shortened
to eleven months. Louca and Legates (1968) observed a
decline of 3.6 kg of milk for each additional day Open for
second and third lactation cows. They also observed an
increase of 1.16 kg of milk for each additional day open
up to 120 days for first lactation cows. They attributed
the difference to higher persistencies in first lactation
cows. For optimal milk production they suggested the
calving interval should be as short as possible for second

and later lactation cows, and thirteen months for cows in

first lactation. Data from the Milk Marketing Board
(1968-69) indicated that optimal milk production actually
occurred with a 350 day calving interval.

Speicher and Meadows (1967) reported that over a
five year production span cows with twelve month calving
intervals produced one more calf (4.9 vs 3.8) than cows
that had fourteen month calving intervals.

Decreased possible incomes of 5.50-1.00 per day of
calving interval over twelve months are generally quoted
(Speicher and Meadows, 1967; Louca and Legates, 1968; Olds,
1969). Britt (1975) adjusted prices used by Speicher and
Meadows to 1974 prices and found a possible loss in
potential income of $1.00-2.00 a day. Hafs gt_al. (1973)
estimated a total yearly loss of over $500 million to the
nation's dairymen due to sterility and infertility of
dairy cows, and postulated that one-half of this loss
could be avoided by prOper management.

Several variables are involved in the actual
achievement of a calving interval. Intervals from
parturition to first ovulation, estrus, insemination, and
conception are important factors. Ovulation is of primary
importance, and is usually preceded by estrus. The dairy-
man (or bull) has to detect the cow in estrus for insemi-
nation to occur. PrOperly timed artificial or natural
breeding with subsequent fertilization and normal gestation

will result in a newborn calf in about 280 days.

Interval to First Ovulation and Estrus

 

Silent and non-standing estrus are common in the
early postpartum period. Morrow 32 a1. (1966) found the
average interval from parturition to first silent or
standing estrus to be fifteen days for normal cows. They
reported a 79 percent incidence of silent estrus at first
ovulation. Saiduddin 33 31. (1968) monitored 213 first
postpartum ovulations of cows by weekly palpations and
found that 46.5 percent of the cows ovulated without
estrous activity, and of the 53.5 percent that ovulated
with estrous activity 32.5 percent was of the non-standing
type. Whitmore 32 El. (1974) compared two breeding inter-
vals (bred at first estrus, and bred at first estrus after
74 days postpartum),2 genetic levels of milk production
(high and low), and 2 levels of nutrition (average and
150% average), and found that interval to first ovulation
for all cows was approximately 30 days. They also found
that interval to first estrus averaged 35 to 42 days among
groups, and noted significantly shorter intervals for
average nutrition, and low production groups compared with
high nutrition, and high production groups. Thatcher and
Wilcox (1972) reported an average interval to first estrus
of 43 days for 577 cows in 1,398 postpartum intervals.
They also reported that as the number of estrous periods
before 60 days increased, inseminations required per
conception declined. This effect appeared to be mostly

due to the number of estrous periods prior to 30 days

postpartum. A summary of six studies on interval to first
ovulation, and 17 studies on interval to first estrus for
dairy cows found average ranges of 20—45 days and 30-72
days postpartum, respectively (Wisconsin Research Bulletin
270, 1968). Pelissier (1972) reported that 42 percent of
the cows in a California study had not been detected in
estrus by 60 days postpartum, and that 12.5 percent had not

been detected in estrus by 90 days postpartum.

Detection of Estrus

 

Failure of a cow to be detected in estrus can
generally be attributed to physiological or managerial
causes. Physiological causes include pyometra, ovarian
follicular cysts, metritis, etc. (Pelissier, 1972). Silent
and short estrous periods also occur, eSpecially in the
first few weeks postpartum (Morrow et al., 1966; Whitmore
gt 31., 1974). However, Zemjanis (1969) proposed that
90 percent of anestrous cases are due to failure in
observation of estrus (i.e., management). Hall 23 31.
(1959) reported that 20 percent of the expected estrous
periods were missed when cows were observed for estrus
twice daily, but only 10 percent were missed when cows
were observed four times daily. Hurnik EE.Sl° (1974) used
a videorecorder and continuously monitored two groups of
twelve Holstein cows for estrous behavior during a nine
week period. They found that 75 percent of mounting

activity occurred at night and they were able to detect

94 percent of the cows at their first estrus (second
ovulation), and 100 percent at second estrus (third

ovulation).

Interval to First Insemination

 

The interval from parturition to first insemination
is one of the most important factors in determining calving
interval length (Bozworth 33 31., 1972; Pelissier, 1972).
Hafs 33 31. (1973), and others, recommended breeding at
first estrus after 60 days. This is the current recommenda-
tion of most bull studs, universities, and dairymen. It is
commonly believed that cows bred before 60 days postpartum
have a greater incidence of abortions and infertility as
reported by Hofstad (1941) in a study of five cows.
Trimberger (1954) found that cows first bred at less than
50 days were Open longer than cows first bred at 50-90 days
due to repeat breeders, but he did not find an increased
incidence of abortions, retained placenta, or uterine
infections among the early bred cows. VanDemark and
Salisbury (1950) recommended not to breed cows before
60-80 days postpartum, and considered the 101-120 day
postpartum period as the time of maximum fertility because
cows first bred at that period required fewer inseminations
per conception and had higher percent conception at first
insemination. Olds and C00per (1970) and Whitmore 33 31.
(1974) studied large numbers of cows and determined that

there is not an increased occurrence of abortion,

infertility, and delayed returns for cows bred before 60
days.

Pelissier (1972) found that 33 percent of the cows
in 24 commercial California dairy herds had not received a
first insemination by 90 days postpartum, the time they
should have conceived to maintain 12 month calving inter-
vals. Britt (1975) reported an average interval to first
insemination of 94 days for cows on Michigan Dairy Herd

Improvement Association (DHIA) test.

Fertility at First Insemination

 

Fertility at first insemination is lower in cows
bred before 60 days postpartum than in cows bred after 60
days. Britt (1975) summarized data from seven studies on
early postpartum breeding, and used unweighted means to
calculate 20 day postpartum interval fertility levels.
He concluded that fertility was lowest during the first
20 days postpartum, and increased to 60 days postpartum
where it stabilized at about 60 percent. He further con-
cluded that a 10 percent rise in fertility occurred from
50 to 60 days postpartum. Olds and Cooper (1970) and
Whitmore 3£_31. (1974) found that by third insemination
fertility was just as high in early bred cows as in later
bred cows. A cow should conceive by 85-90 days postpartum
to maintain a 12 month calving interval. Beginning
breeding at 40 days would give one more chance for con-

ception before 90 days. Olds and C00per (1970) concluded

that "to advise against breeding at less than 60 days is
to remove the most effective means available to a dairyman

for shortening calving intervals.“

Inseminations per Conception

 

Several investigators have found that as interval
to first insemination increases, number of inseminations
required per conception decreases, at least up to 100 days
postpartum. Olds and COOper (1970) found a decrease from
1.83 inseminations per conception for cows first bred at
l-20 days postpartum to 1.37 inseminations per conception
for cows bred first at 91-100 days after calving. VanDemark
and Salisbury (1950) found 2.86 and 1.88 inseminations per
conception for similar periods. Whitmore 33 31. (1974)
compared animals bred at first estrus (i=39 days) with
those bred at first estrus after 74 days and found that 2.2
and 1.6 inseminations per conception were required for each
group, respectively. The Milk Marketing Board Annual Report
(1968-69) used interval to first insemination and probability
of conceiving at that and succeeding inseminations as
variables and calculated 2.0 inseminations per conception
for cows first bred at 11-31 days postpartum, and 1.46
inseminations per conception for cows first bred at 95-115
days postpartum. Studies involving over 12,000 cows in
Israel averaged 1.73 inseminations per conception for cows
first bred at an average of 48 days (bred at less than 60
days) postpartum, and 1.55 for cows first bred at an

average of 81 days (bred after 60 days; Hasherut A. I.

10

Annual Report, 1971—72). From 1969 to 1972 the percentage
of cows first bred before 60 days in the Israeli study has
changed from 24 to 60 percent, practical evidence that

early breeding is an acceptable management practice.

Interval from First Insemination to Conception

 

Olds 33 31. (1966) reported that 60 percent of the
variation in length of calving interval was due to variation
in the period from first insemination to conception. They
considered returns to insemination of 26 days or longer as
delayed returned, and attributed 29 percent of the variance
in delayed returns to difference among herds. Olds (1969)
reported that 45 percent of all returns are delayed returns,
and that 16.7 percent of all returns occurred more than
60 days post-breeding. He estimated that 20 percent of
delayed returns could be prevented by better management.
Hall 33 31. (1959) reported that 69 percent of the cycles
they observed were in the normal 16-24 day range.

Pelissier (1970) estimated that one in six estrous periods
was missed after first estrus was recorded. Olds (1969)
summarized three studies on one cause of delayed returns,
embryonic death, and concluded that 28.5 percent of
delayed returns are due to embryonic death. Lassiter and
Seath (1955) attributed a 5-6 percent loss of pregnancy

to abortion, another cause of delayed returns. Another
seeming cause of delayed returns, post-conception estrus,
occurred in 14 percent of the cows observed by Hall 33 31.

(1959).

11

Calving Interval

 

While a twelve month calving interval is the goal
of dairymen, it frequently is not achieved. Pelissier
(1972) reported an average calving interval of 13.5 months
for cows in the United States enrolled in the DHIA programs.
Others have reported average calving intervals of about
thirteen months (Legates, 1954; Everett 33_31., 1966;

Norman and Thoele, 1967; Miller 33 31., 1967; Olds and
COOper, 1970). Studies in Michigan reported by Britt

(1975) showed that the average calving interval for Holstein
cows enrolled in DHIA was also about thirteen months.

Spike (1973) studied Michigan herds on DHIA from 1953-1970

and found the average calving interval to be 395:77 days.

Cows with Postpartum Disorders

 

Admittedly not all cows have returned to a clini-
cally normal reproductive state by forty days postpartum.
Cows that had dystocia, twins, and uterine infections at
parturition, or retained placenta, metritis and other
reproductive problems afterwards were considered abnormal
by Morrow 33 31. (1966). They found that abnormal cows
had a significantly longer interval to first estrus,
interval to conception, and required more inseminations
per conception than normal cows (cows without reproductive
problems), and recommended an interval to first insemination
for abnormal cows of 75-90 days postpartum. Ayalon 33 31.

(1971) and Hasherut A.I. Annual Report (1971-72) studied

12

herds in Israel and recommended an interval to first
insemination of 61-75 days for abnormal cows. All of
these investigators stressed that abnormal cows be treated

for their reproductive problems.

Season

Several investigators have studied the effect of
season, light, and temperature upon reproductive perfor-
mance. Gwazdauskas 33 31. (1975) reported an extensive
study of variables associated with seasonal effects. They
used twenty-one climatological measurements for least
squares analysis of reproductive fertility. They analyzed
5,062 services that occurred within an eleven year period
in the Florida Agricultural Experiment Station dairy herd.
The five most important measures were: (1) maximum temper-
ature day after insemination, (2) rainfall day of insemi-
nation, (3) minimum temperature day of insemination,
(4) solar radiation day of insemination, and (5) minimum
temperature day after insemination. They also observed
higher conception rates (40.1 vs 33.7%) in cool months
(November through May) than hot months (June through
October).

Records that covered a twenty year period at the
Purdue University herd were analyzed by Erb (1940). He
found considerable seasonal variation in percent conception
per month, the highest being May (74.3%) and the lowest in

August (58.2%). Hall 33 31. (1959) found that duration of

13

estrus was significantly shorter in April and May than in
September and December, but they did not attribute this
difference to a seasonal pattern. Stott (1961) analyzed
data that covered a ten year period in Arizona, and found

a significant difference in fertility among months. The
biggest decline occurred from June to July with a subsequent
similar rise in September to October, and another decline in
early winter. In a North Carolina study, Britt and Ulberg
(1970) found the lowest percentage of a herd conceived in
July and August, and the highest percent conceived in March
and April.

Carman (1955) studied two herds for a ten year
period and found that cows that calved in March took
significantly longer to come into estrus than cows that
calved in September. He found no difference in time to
first insemination and inseminations per conception, however.
In a California study that covered a ten year period and
included over 10,000 records, Armstrong (1964) found no
significant difference among months for breeding efficiency,
interval to first estrus, interval from first insemination
to conception, and days open. Morrow 33 31. (1966) reported
a nonsignificant influence of season on interval to first
estrus, but did find a significantly higher incidence of
cystic corpora lutea in August to January than February to
July, and more ovarian follicular cysts in November to
January. In an Israeli study, Ayalon 33 31. (1971)

reported a nonsignificant effect of season on fertility at

14

different first insemination intervals. Spike (1973) noted
that cows that calved in the winter and spring had longer
calving intervals than cows that calved in the summer and
fall. He attributed part of this difference to dairymen
who attempted to have cows at peak lactation during the

base price period.

Level of Milk Production

 

Milk production levels have also been investigated
as to their effect on reproduction. Marion and Gier (1968)
found an effect of milk production on interval from
parturition to first ovulation and estrus. They reported
intervals of 13.1, 14.0, and 15.5 days to first ovulation
for cows that produced less than 22, 22-30, and over 30 kg
milk per day, respectively, and reported 28.4, 33.1, and
36.9 days to first estrus for the three groups. Carman
(1955) found that interval from parturition to conception
increased as production increased, however, he found that
days to first insemination had no relation to milk
production level. Cows that produced over 7270 kg had a
higher number of ovulations without standing estrus, longer
calving intervals, and more inseminations per conception
than cows that produced less in a study reported by Morrow
33 31. (1966). Boyd 33 31. (1954) found no difference in
inseminations per conception by production levels among
519 cows. Large herds in Israel were studied by Ayalon

33 31. (1971) and they found no difference in conception

15

rate at first insemination for average and high production
herds. However, they reported that culling for infertility
among normal cows was significantly higher in high pro-
duction herds, while culling for infertility among abnormal
cows was significantly higher in average production herds.
Cows in a University of Wisconsin herd during 1965-71 were
divided into groups for high or low genetic ability for
milk production (Whitmore 33 31., 1974). They reported
significantly shorter intervals to first ovulation, and
estrus for low genetic ability cows, as well as less
incidence of retained placenta. Fertility at first
insemination, and the incidence of metritis, dystocia,
abortions and infertility were not significantly different
between groups. Spike (1973) noted that Michigan herds
that averaged over 6364 kg of milk had longer calving
intervals (401 vs 392 days) than did herds that produced

less.

Herd Size

 

Herd size also apparently has an associated effect
on herd reproduction. Spike (1973) reported that small
(less than 25 cows) and large (greater than 100 cows)
Holstein herds in Michigan had approximately one week
longer calving intervals (400 vs 393 days) than did herds
of 26-99 cows. Olds and Deaton (1968) reported that herd
fertility declined .08 percent for each increase of one

cow in herd size in a study of 505 herds that ranged in

16

size from 20 to 111 cows. Ayalon 33 31. (1971) compared
reproductive efficiency in large and small herds (average
herd sizes of 197 and 10.5 cows), and reported that small
herds had a significantly higher conception rate at first
insemination, but that there was no difference in percent
of cows culled for infertility between groups. These

results may not be a true indication of herd size effects
because these herds had much different management systems

and herd milk production levels.

Nutrition

 

The exact relationships between nutrition and
reproduction have not been clearly defined (Boyd, 1970).
However, puberty is delayed in underfed heifers (Reid
33 31., 1957), and anestrus may result in underfed cows
(Hignett, 1960). Deficiencies in certain minerals, most
notably phosphorus, may also affect reproduction as shown
by Salisbury and VanDemark (1961).

Lamb 33 31. (1965) found that cows fed alfalfa hay
only, and cows fed alfalfa hay plus .45 kg grain for each
1.6 kg milk produced had similar intervals to first estrus
and insemination, interval to conception, number of estrous
periods before insemination, and inseminations per con-
ception. Two levels of grain feeding did not affect
interval to first estrus, interval to conception, and
inseminations per conception in cows observed by Fuquay

33 31. (1966).

17

Whitmore 33 31. (1974) fed two levels (average and
150% of average) of 16 percent concentrate and found that
average level cows had significantly shorter intervals to
first ovulation and estrus, less incidence of retained
placenta, and acute metritis, but he did not find a differ-
ence in fertility at first insemination or inseminations
per conception. These results may be confounded because
they found significant interaction between milk production
levels and nutrition levels.

Boyd (1970) concluded that "in general, if nutrition
requirements for milk production and general health of the
cow are met, then the cow's nutritive requirements for

reproduction should be adequate."

MATERIALS AND METHODS

Herd Selection

 

A representative sample of Southern Michigan
Holstein herds on DHIA was needed for the study. Agri-
cultural Extension Agents in counties within a fifty mile
radius of Michigan State University were sent an explanation
of the experimental objectives and were asked to submit
names of cooperative dairymen who might be interested in
participating. These dairymen and their herd veterinarians
were sent letters that explained the study, and those that
indicated an interest in participating were visited by
extension and research staff to further explain the experi-
mental procedures. Fifteen farms started the study with
herd sizes that ranged from 35 to 150 cows. All herds but
one had a regular herd health program that included post-
partum examinations, pregnancy diagnosis, and treatment of

reproductive problems.

Pretreatment Data

 

Data from a pretreatment period were needed to
determine the dairymen's usual reproductive management
practices. Therefore, participating farms were visited

and reproductive and milk information for all cows that

18

l9

calved in 1972 were obtained from herd and DHIA records.

Age at calving, calving month, lactation number, and cull
reasons for cows sold were determined. Interval from
parturition to first insemination, interval from parturition
to conception, interval from first insemination to con-
ception, inseminations per conception, and percent con-
ception at the first through fourth inseminations were
calculated from the data obtained. Cows that were open
longer than 250 days, and those that failed to calve in

1972 were excluded from the calculations. If available,

305 day milk yield for that lactation was recorded (any
lactation over 250 days was projected to a 305 day record
using factors given by McDaniel 33_31., 1965). Pregnancies
that occurred during 1972 were confirmed by rectal palpation
or by actual parturition.

Analysis of variance was used to partition main
effects and interactions and variances were tested by the
f-test (Fisher's variance ratio). The standard t-test,
Dunnett's t, or Scheffe's interval were used to test
differences among means. In means involving percentages,
significance was determined by Chi Square test. The
analysis of variance, f-tests, and correlations were
calculated by a statistical program package of Michigan
State University's CDC 6500 computer system. Tests of

differences among means were done by hand calculation.

20

Treatment Grogps and Procedures

 

Herds were started on the study with cows that
calved in August-September 1973, and concluded with cows
that calved in August-September 1974. Cows that calved
during this period were assigned within the first month
postpartum to one of three treatment groups. All cows which
calved without clinical complications were randomly assigned
to be bred at first estrus after forty days (Treatment I),
or sixty days (Treatment II). These times were chosen
because forty days is as early as acceptable fertility
occurs (Britt, 1975) and sixty days is the usual period
that dairymen wait before the initial postpartum insemina-
tion. Cows that delivered twins or had a difficult
parturition, and cows that had retained placenta, metritis,
or pyrometra during the first two weeks postpartum were
assigned to an abnormal group (Treatment III) and were to
be bred when the dairyman and herd veterinarian considered
them ready for breeding.

Report forms (Appendix A) for recording calving,
estrus, and insemination dates were exchanged bi-weekly
with each dairyman. Treatment assignments were made from
information received on the reports. Space was also
provided on the forms for results of veterinarian visits,
any problems that occurred, and culling reasons and dates.
Cows were listed by both a control number and a barn name
or number to prevent duplication of a barn name or number

for different cows during the study. From data provided

21

in these reports, interval from parturition to first estrus,
interval from parturition to first insemination, inter-
estrual intervals, intervals between inseminations, R
inseminations per conception, days open to conception, and
days open between first insemination and conception were
calculated. Also calving month, abnormal assignment
reasons and frequencies, and cull reasons, frequencies, and
dates were determined. Information was monitored bi-weekly
to determine the study's progress and the dairyman's
adherence to the assigned breeding dates.

A computer program was written to calculate and
print the minimum date for first insemination, and to
print the first three insemination dates. Additional
space for other insemination dates were provided. These
printouts (Appendix B) were updated every four weeks, a
copy sent to the dairyman and a c0py kept for our records.
An updated report listed assigned minimum insemination
dates for cows that had calved recently, as well as recent
insemination dates for cows already assigned. Neither.
calving date nor treatment group was listed on the printouta
since it was felt these might bias the dairyman's decision
as to whether to inseminate a cow at first estrus after the,
minimum breeding date. Cows were listed either by numerical
or alphabetical order depending on the method of identifi-
cation used in the herd. Each printout listed all cows
still in the herd that had calved since the study began.

When a cow was determined to be pregnant, PREG was written

22

next to the conception date on the computer printout.
Pregnancies were determined by rectal palpation in herds
that had herd health programs, and by non-return to estrus
in herds without herd health programs.

Four visits were made to the farms during the study
to answer questions and discuss the progress of the experi-
ment. A final visit was made to most farms to check for
accuracy in the information. In addition to visits, a
questionnaire (Appendix C) was sent to the dairymen that
completed the study to determine management practices,
changes in the dairy operation that occurred within the
year, and their reaction to the experiment.

DHIA records were used to obtain days in milk,
daily milk yield, and milk yield to date for each cow until
the first test date past 150 days postpartum. These-data
were used to determine the lactation curves for the first
180 days of lactation for cows'in the three treatment groups.
In addition, 150 day milk yield for each cow, and average
daily yield per cow for each group and overall was deter-
mined. Age at calving was also obtained from DHIA records.

Statistical analysis techniques were similar to

those used for the 1972 data.

Analysis by Interval to First Insemination

 

Cows were also grouped, ignoring treatments, by
twenty day intervals to first insemination. Data from only

pregnant cows were used. The range used was from less

23

than forty days to greater than 120 days open. The para-
meters calculated and analyzed for these groups were the
same as those used for the treatment groups. Analysis was

similar to previously mentioned methods.

Lactation Curves by Interval to Conception

 

Lactation curves for the first 180 days of lactation
were calculated from DHIA records, and were plotted by
twenty day interval to conception periods from twenty to
180 days. All the individual milk weights during successive
five day periods, beginning eight to thirteen days post-
partum, were averaged to make single points on the lactation
curve. This provided for thirty-five 5-day periods for
each treatment, interval to conception period, and overall
180 day lactation curve. The cubic regression equations
for these 180 day lactation curves were tested to determine
if differences existed among interval to conception periods,
and treatments. The method used to test for differences
between equations was an extension of a technique to test
for differences between two linear regressions (Gill, 1975).

Average daily yield was also determined for each group.

Least Squares Analysis

 

Interval to first estrus, interval to first insemi-
nation, interval to conception, interval from first
insemination to conception, inseminations per conception,
and 150 day milk yield were analyzed by least squares

techniques on the CDC 6500 computer. For purposes of

- 24

analysis, herd size, housing, treatments, and season of
calving were classified into groups. Herd size was deter-
mined to be either small (less than 50 cows), medium

(50-70 cows), medium-large (71-90 cows), or large (more

than 90 cows) depending principally on the herd size during
the year. Housing was considered either as free stall or
stanchion. Three treatments have been described previously.
Season of calving was divided into quarter periods beginning
with January through March. Age at calving, the number of
times detected in estrus before initial insemination, the
previously mentioned intervals, inseminations per conception,
and 150 day milk yield were used as variables where appro-

priate. The general equation used is as follows:

= u + T1 + Sj + H + Z + TS. + TH. + TZ +

Yijklm k 1 lj 1k 11

SH. + 82. + HZ

3k 31 k1 + TSHi.

3k + TSZi.

31 + bixi + e.

ijklm

The description of variable symbols are given in Appendix
Table 2, parts 1 and 3.

The above model failed to account for herd variation.
Therefore, an equation was develOped that included a herd
within herd size variable, but excluded the housing variable.

That equation is given below:

= u + Ti + Sj + Z + R + TS.. TZ. + 82 +

Yijlmn 1 n1 1] 1k jk

TSZ.. + b.X. + e
11

ijk ijlmn

25

Variable symbols are described in Appendix Table 2, parts
2 and 3. For each parameter, the equation that resulted
in the highest multiple correlation coefficient was used.
The actual model used for each parameter of interest is

given in the results section for that parameter.

RESULTS

Twelve of the fifteen initial herds completed the
field study. A total of 976 cows were assigned during the
study period August 1973 to September 1974. Of those, 420
cows were assigned to Treatment I (43.0%), 422 to Treat-
ment II (43.2%), and 134 to Treatment III (13.7%). Data
from cows that conceived in less than 250 days were used
for most of the analyses. This included 304, 298, and 83
cows, reSpectively, for the three treatment groups. The
remaining cows were open more than 250 days (15 cows),
culled non-pregnant (181 cows), or inseminated but not
confirmed pregnant when culled or at the end of the study
(98 cows), and were therefore considered as open. Of 837
cows that calved in these 12 herds during 1972 (pre-
treatment control period), 30 cows were open longer than
250 days and were excluded from the analyses for that
period. Of the remaining cows, 591 conceived in less than
250 days, and 213 were culled as non-pregnant.

Herd sizes during 1972 as determined by the number
of cows calving within the year are given in Table 1. The
four largest herds accounted for 48 percent of the total

cows calving in 1972, and for 45 percent of the total cows

26

27

.omcmflmmm Ho ocH>Hmo m3oo mo unmouwm m mam

.HHH ucmfiummua ou Umcmflmmm unmoummp

.ucmcmmum
commoflmcoo no pomocmmwp mum3 umcu cums mom Umcmwmmm m3oo mo unmoumm 8 mac

.Uwcmflmmm m3oo mo HmQEszn

.mcH>Hmo mzoo mo HmnESZM

 

 

 

 

 

 

mm mm «.ma as Hem nmm .m>¢
Hmuoe

om mm o.oa mm om mm NH
mm mm v.0N v0 MOH mm Ha
mm mm v.va mm mad Hma OH
av m m.va no vm mm m
av vm o.v mm . OHH mm m
mm mm S.HH eh moa mm b
Hm mm N.hH Hm mm mv m
om NN H.m on FM mm m
an hm 0.0m Nb OHH mm v
mm mm o.m Nb om Hm m
ma om m.va mm mm mm N
am mm m.m mm mm an a

vulmnma tha whimsma whimnma Q¢hlmnma Mmhma

momaaso unmouom UHmEHocnd oucmcmwum msoo mo Honesz pumm

unmoumm unmoumm

 

.vhnmwma pcm whoa mcflwso women an Umaaso unmoumm
paw .HmEuocnm unmoumm .ucmcmwum unwoumm .wmcmflmmm Ho mafl>amo m3oo mo Hmnfidzll.a magma

28

assigned in 1973-74. Seventy-one percent of the cows were
housed in free stalls, 21 percent in stanchions, and 6 per-
cent in loose housing. Other characteristics of the dairy
farms are given in tables in Appendix C. These data were
prepared from responses to the questionnaire sent to each
c00perating dairyman. There were significant differences
among herds for age at calving and lactation number (p <
.01); herd means ranged from 40-58 months, and 2.0-3.0
lactations respectively (overall means were 48 months and
2.0 lactations; Appendix Table 1).

Average age for cows assigned during 1973-74 was
47 months. A simple correlation of .95 between age at
calving and lactation number was calculated which agrees

with that reported by Everett 33 31. (1966).

Treatment III Assignments

 

Retained placenta and uterine infection, defined
as infection within the first two weeks postpartum,
accounted for 68 percent of the assignments to Treatment III
(Table 2). Dystocia, twinning, abortion, and combinations
of the abnormalities at parturition accounted for the
remainder of the cows assigned to Treatment III (abnormal
group). Percent of abnormal cows assigned per herd is shown
in Table l. Herd means ranged from 2 to 30 percent. Herd
four had a high incidence of uterine infections within two
weeks postpartum which accounted for 72 percent of the cows

assigned to Treatment III in that herd. Herd 11 had a high

29

Table 2.-—Reasons and frequencies for assignments to
Treatment III (cows abnormal at calving).a

Percent of
Total Abnormal Percent of
Reason Assignments Total Assignments

 

 

Twins 5 0.6
Retained placenta 28 3.9
Uterine infectionb 40 5.4
Abortion 7 1.1
Dystocia 10 1.3
CombinationC 10 1.4
Total 100 13.7
aN = 134.
b

Defined as diagnosed uterine infection within two
weeks postpartum -

CCombination of two or more preceding conditions.

occurrence of retained placenta which accounted for 76 per-

cent of the cows assigned to Treatment III in that herd.

Interval to First Estrus

 

The average interval to first estrus for all cows
was 58 days (Table 3), and was not different among treat—
ments. The number of cows having an observed estrus after
partuition was 881 or 92 percent of cows assigned. The
other cows were culled before observed and/or recorded in
estrus. Within herds, treatment means were only different

in Herd 2 where cows in Treatment III had a significantly

30

Table 3.—-Reproductive performance for cows assigned to Treatments I,
II, and III during 1973-74.

 

 

 

Treatment
Ave.
I II III
Interval to first
observed estrus a b
(days) 57 (388) 59(383) 59(110) 58(881)
Interval to first
insemination (days) 73e(376) 82(372) 83(101) 78(849)
Interval to con- f
ception (days)C 99 (304) 105(298) 112(83) 103(685)
Interval from first
insemination to
conception (days) 28(304) 25(298) 30(83) 30(685)
Inseminations
per conceptionc 1.8(304) 1.7(298) 1.7(83) 1.7(685)
Percent pregnantd 77(304) 75(298) 65(83) 75(685)

 

aMean value.
b .
Number of observations.

cCows open longer than 250 days excluded.

dAs a percent of cows assigned in the study that became
pregnant.

eSignificantly different than Treatments II and III (p < .05).

f . . . .
Significantly different than Treatment III (p < .05).

31

longer interval than cows in Treatments I and II (p < .01;
Appendix Table 3). Herds in which cows averaged 51 days
or less to first estrus were not different from each other
as determined by Scheffe's interval. Also, herds in which
cows averaged 54 days or longer to first estrus were not
different from each other. Data analysis by first insemi-
nation intervals showed that cows bred at less than 40 days
postpartum averaged 36 days to first estrus (Table 4).
Cows that had longer intervals to first insemination had
associated longer intervals to first estrus, ranging from
42 days for the 40-60 day first insemination period to 100
days for the 120 day or greater period.

The least squares model for interval to first estrus

was as follows:

= u + Ti + Sj + Z + R + TS.. + TZ. +

Yijlmn 1 n1 1] il

SZjl + TSZijl + e

ijlm

Symbols for variables are described in Appendix
Table 2, parts 2 and 3. The treatment X season X herd size
interaction was significant (p < .05; Appendix Table 4).
Herds within herd size was highly significant (p <,.0005).
Least square adjusted means for interval to first estrus
are given in Appendix Table 5 for treatments, seasons,
herd size, and herds. The multiple correlation coefficient

(r2) was .16.

32

Table 4.--Reproductive performance for cows first insemi-
nated at various 20 day postpartum intervals.a

 

b c d e f

 

IFI Number IFE IFI ITC IFITCg I/ch
<40 10 361 36 92 56 2.4
40-60 180 42 52 86 34 1.9
61-80 254 51 7o 97 27 1.7
81-100 129 70 90 115 25 1.6
101-120 72 77 108 126 18 1.6
121+ 40 100 140 155 15 1.4
Total—Ave. 685 58 78 103 30 1.7

 

aCows open longer than 250 days excluded; only cows
that conceived are used.

bInterval to first insemination periods (days post-
partum).

cNumber of cows first inseminated during that
period.

dInterval to first observed estrus (days).
eInterval to first insemination (days).
fInterval to conception (days open).

gInterval from first insemination to conception
(days).

h . . .
Inseminations per conception.

lAverage values per period.

33

Interval to First Insemination

The average interval to first insemination for cows
in Treatment I was 73 days, which was significantly shorter
(p < .05) than the 82 and 83 days for cows in Treatments II
and III (Table 3). The 849 cows (89% of the cows assigned)
that had a first insemination were used for the calculations
of these unadjusted treatment means.

Herd means for interval to first insemination are
in Appendix Table 6. Significant differences (p < .05)
among treatments existed within Herds l, 7, and 8 where
cows in Treatment I had shorter intervals than cows in
Treatments II and III. Herds in which cows averaged 72 to
91 days to first insemination were not different from each
other (p < .05) and herds in which cows averaged 66 to 79
days to first insemination were similiar as determined by
Scheffe's interval.

The interval to first insemination ranged from 72
to 94 (mean 84) days for cows among the 12 herds in 1972
(Appendix Table 6), and herd means were not different. Cows
in ten herds had shorter intervals to first insemination in
1973-74 than in 1972.

Analysis of intervals to first insemination
(Table 4) showed that cows bred at less than 40 days post-
partum averaged 36 days to first insemination. Successive
20 day intervals had mean values of 52, 70, 90, 108, and

140 days to first insemination respectively.

34

The least squares model for interval to first

insemination (Appendix Table 7) is given below:

=p+Ti+Sj+Z+R +TS..+TZ.+SZ.+

Yijlmn 1 n1 1] il 31

TSZ.. + b x + b x2 + b x + b x2 + e

131 1 1 2 1 3 2 4 2 ijlmn

Description of variables are given in Appendix Table 2
parts 2 and 3. Treatments and herds within herd size had
significant effects (p < .05) on interval to first insemi-
nation. The multiple correlation coefficient (rz) for
interval to first insemination was .70 indicating that
70 percent of the variation in interval to first insemi-
nation was accounted for by the variables listed. Cows in
Treatment I had shorter intervals than cows in Treatments II
and III. The linear and quadratic terms of interval to
first estrus and number of times detected in estrus before
first insemination also had a significant effect (p < .01).
Regression equations for these are plotted in Figures 1
and 2. Each additional day to first estrus (from 20 to 100
days) resulted in .75 additional days to first insemination
(Figure 1). Also as the number of estrous cycles before
first insemination increased, the interval to first
insemination increased (Figure 2). Least square adjusted
means are given in Appendix Table 8.

The percent of cows first inseminated during various
20 day postpartum intervals is shown in Table 5. This table

shows how closely treatment assignments were followed.

35

Figure 1. Least squares regression of interval to first
insemination on interval to first estrus.

Y 78.06 + .69137557(58.6 - IFE) +
.00123752(58.6 - IFE)2

r = .70

INTERVAL TO FIRST INSEMINATION (DAYS)

200

ISO

ISOI'

I40

l20

IOO

80

60

20

 

36

LEAST SQUARES REGRESSION OF INTERVAL TO

_ FIRST INSEMINATION ON INTERVAL TO FIRST ESTRUS

A
Y-78.06 + .69I37557(58.6- IFE) + .oou23752 (58.6- IFE)’

L l 1 l I 1 J

 

20 40.80 am IOO‘I‘ZO‘MO
INTERVAL TO FIRST ESTRUS (DAYS)

37

Figure 2. Least squares regression of interval to first
insemination on number of estrous periods before
initial insemination.

Y

78.06 + 49.l(l.67 - #Estrous Periods) -
6.59(l.67 - #Estrous Periods)2

r = .70

38

LEAST SQUARES REGRESSION OF INTERVAL TO FIRST
INSEMINATION ON NUMBER OF ESTROUS PERIODS

BEFORE INITIAL INSEMINATION

A
Y- 78.06 + 49.I I l.67 -# Estrous PorIods )‘6.59( I.67- # Enron: Periods)!

ISOI'
l50'
I40b
ISOL
I20"
IIO'
IOO'
90'
80’
70"

50’

INTERVAL TO FIRST INSEMINATION ( DAYS)

30-
20L
Io-

 

 

I 2 8 4
NUMBER OF ESTROUS PERIODS
BEFORE FIRST INSEMINATION

Ta

IE

10

12

pa:

fi:

39

Table 5.--Percent of cows in Treatments I, II, and III
first inseminated at various 20 day postpartum
intervals.a

 

 

 

b Treatment
IFI Total
I II III
c d
<40 3 (10) --- --- 1(10)
40-60 37(113) 17(51) 19(16) 26(180)
61-80 31(95) 42(126) 40(33) 37(254)
81-100 17(51) 21(61) 20(17) 19(129)
101-120 9(26) 12(36) 12(10) 11(72)
121+ 3(9) 8(24) 8(7) 6(40)
Total 100(304) 100(298) 100(83) 100(685)

 

aOnly cows that eventually conceived are used;
cows Open longer than 250 days excluded.

b
partum).

Interval to first insemination periods (days post-

cPercent of cows in a treatment group that had a
first insemination during that postpartum interval.

dNumber of cows inseminated.

40

Three percent of the cows in Treatment I were bred before
40 days postpartum. Thirty-seven percent of the cows in
Treatment I were bred between 41-60 days after calving
while 17 and 19 percent of cows in Treatments II and III
were bred during this period. During the 61-80 day period

for Treatment II, 42 percent of the cows were inseminated.

Estrous and Insemination Intervals

The interestrual intervals prior to insemination,
and insemination intervals are given in Table 6. There
were no differences among groups for intervals between
estrous periods prior to initial insemination (average 31
days). However, the interval between first and second
insemination in the abnormal cows was significantly longer
(p < .05) than for normal cows (Treatments I and II).

Estrus and insemination intervals amOng herds are
in Appendix Table 9. The interval between first and second
estrus (range 29 to 52 days), and the interval between
first and second insemination were different for cows among
herds (p < .05). Other intervals were not different. No
data on estrus and insemination intervals were collected
for the 1972 period.

The interval from first estrus to first insemina-
tion also varied for cows among herds as shown in Appendix
Table 10. Herd means ranged from 9 to 38 days, and treat-
ment averages were 17, 23, and 24 days respectively.

Longer herd intervals from first estrus to first

Ta}

TrI

ins
est
Tre
ins
ins
fir

est

41

Table 6.--Days between estrus and inseminations for cows
in Treatments I, II, and III.a

 

Estrus
Intervals Insemination Intervals

 

 

b

Treatment 1-2 2-3 3-4 1-2C 2-3 3-4 4-5 5-6

 

Days Days
I 32 27 26 36 35 39 37 26
II 35 32 28 38 36 31 3o 31
III 34 31 39 51d 36 39 23 14
Average 33 30 29 39 36 36 33 28

 

aCows Open longer than 250 days excluded.
bInterval between first and second estrus periods.
cInterval between first and second insemination.

dSignificantly different than Treatments I and II
(p < .05).
insemination were usually indicative of early postpartum
estrous detection rather than late postpartum inseminations.
Treatment means, however, do tend to reflect the first
insemination interval. Data analyzed by intervals to first
insemination show that cows that had longer intervals to
first insemination also had longer intervals from first

estrus to first insemination (Table 4).

Int

of

110‘
de'
m

COI

in'
(IN
NO
in

fi

ex
br
br
ra

amI

Ta]

42

Interval to Conception

The interval to conception (days Open) for 1973-74
of 99 days for cows in Treatment I was significantly shorter
(p < .05) than the 112 days for cows in Treatment III but
not different than the 105 days for cows in Treatment II as
determined by Dunnett's t test (Table 3). Within herds,
treatment differences were only observed in Herd 1 where
cows in all three treatments were different from each other
(Appendix Table 11). The 83 days Open for cows in Herd 12
and the 121 days open for cows in Herd 7 were different
(p < .05) from each other, but not different from cows in
all other herds as determined by Scheffe's interval. The
interval to conception during 1972 ranged from 90 to 133
(mean 111) days among the 12 herds (Appendix Table 11).
No differences were observed as determined by Scheffe's
interval. The simple correlation between interval to
first insemination and interval to conception was .46 and
.42 for 1972 and 1973-74 respectively.

Increasing the interval to first insemination
(Table 4) resulted in longer intervals to conception,
except for cows bred less than 40 days postpartum. Cows
bred between 40-60 days had less days open than did cows
bred prior to 40 days postpartum (86 vs 92 days). The
range in interval to conception was from 86 to 155 days
among 20 day intervals to first insemination.

The least squares analysis of variance (Appendix

Table 12) for interval to conception shows that none of

7

U!

m
Tai
11
in
0p

‘ .

t0

43

the main effects significantly (p < .05) affected the
variable. However, interval to first insemination and its
interactions with number of inseminations and interval from
first insemination to conception were significant (p < .05).
The interval from first insemination to conception and its
interactions with interval to first estrus and number of

estrous periods before first insemination were also

significant (p < .05). From these the following model was
derived.
Yijklm = u + Ti + Sj + Hk + Z1 + TSij + THik + Tzil +
Sij + SZjl + szl + TSHijk + TSZijl + le3 + bZXS +

b3X3X5 + b4X3X3 + b5X5X2 + b6X5X1 + eijklm

Variable symbols are described in Appendix Table 2 parts

1 and 3. The multiple correlation for days open was .99
which indicates most of the variation was accounted for in
the model. Adjusted least square means are in Appendix
Table 13, but none were different within a variable. The
linear regressions of interval to first insemination and
interval from first insemination to conception on days
Open are plotted in Figures 3 and 4. Each additional day
to first insemination resulted in an increase of .96 days
open as determined by this least squares regression. Each
additional day in interval from first insemination to

conception resulted in an additional 1.06 days open.

Figure 3.

r

Least squares regression of interval to con-
ception on interval to first insemintion.

A

Y
2

30.0 +

.99

44

.96189967(IFI)

Tn nnmanTInM ( nAYQ\

lthFD\/Al

INTERVAL T0 CONCEPTION I DAYS)

l80

I60

I40

I20

I00

80

60

j

 

45

LEAST SQUARES REGRESSION 0F INTERVAL T0
CONCEPTION 0N INTERVAL T0 FIRST INSEMINATION

?- 30.0 +.96l89967 ( I Fl)

L l L l 1 l l l l A

40 60 80 I00 I20 I40 l60
INTERVAL T0 FIRST INSEMINATIONIDAYSI

Figure 4.

46

Least squares regression of interval to
conception on interval from first insemination
to conception.

A

Y
2

75.0 + 1.06054090(IFITC)

= .99

INTERVAL TO CONCEPTION (DAYS)

INTERVAL T0 CONCEPTION (DAYS)

47

LEAST SQUARES REGRESSION OF INTERVAL TO CONCEPTION
0N INTERVAL FROM FIRST INSEMINATION T0 CONCEPTION

22°F
2|0-
200'
I90*
l80
I70
ISO
I50
I40
I30
l20
HO
IOO
90
80
70'
60’
50'
40*
30-

    

9- 75.0 + |.06054090( IFITC)

 

l l l 1 1 l I

l

 

. 2O 40 so 80 IOO l20 I40
INTERVAL FROM FIRST INSEMINATION T0 CONCEPTIONIOAYS)

48

Interval From First Insemination to Conception

 

The interval from first insemination to conception
averaged 30 days for all cows that conceived during the
1973-74 study period (Table 3), treatment means were not
different. The intervals for cows among herds ranged from
15 to 44 days and were not different (Appendix Table 14).
The intervals from first insemination to conception during
1972 ranged from 5 to 47 days for cows among herds (Appendix
Table 14).

The number of days from first insemination to con—
ception decreased with longer first insemination intervals
from 56 days for cows first bred before 40 days to 15 days
for cows first inseminated after l20 days (Table 4).

The least squares table for interval from first
insemination to conception is in Appendix Table 15. The

following model was used.

Yijklm = u + Ti + Sj + Hk -I- 21 + TSij + THik + TZil +
. I 2
Sij + SZjl + szl + TSHijk + Tszijl -I- le3 + b2X3 +

b3x4 + b4x2x6 + b5x4x6 + eijklm

Variable symbols are described in Appendix Table 2
parts 1 and 3. The multiple correlation coefficient was
.99 with interval to conception accounting for the major
portion of the variation as evidenced by the simple corre—

lation of .82 between the two. Although no main effects

49

were significant, the interval to conception was highly
significant (p < .0005) and the linear regression is
plotted in Figure 5. Each additional day open was
associated with an increase of .98 days in interval from
first insemination to conception. The linear and quadratic
terms of interval to first insemination were also signifi-
cant (p < .01), and the regression equation is plotted in
Figure 6. From the range of 35 to 120 days postpartum,
each additional day to first insemination results in a
linear decline of .98 days from first insemination to con-
ception as determined by least squares regression.
Adjusted mean values for housing, treatments, herd size,

and season are given in Appendix Table 16.

Percent Conception at Various Inseminations

Percent conception by years and treatments is shown
in Table 7, and Appendix Taxles l7 and 18. Table 7 shows
the percent conception at the first four inseminations for
cows assigned to the three treatment groups. Only 2 percent
(15 cows) of the cows that conceived within 250 days post-
partum required more than four inseminations, and data from
these cows are not shown in this table. Conception rate
at first insemination averaged 56 percent and was not
different among treatments. Percent conception at second
insemination also was not different among groups. Percent
conception at third and fourth insemination for cows in
Treatment 11 was significantly higher (p < .05) than cows

in Treatments I and III.

50

Figure 5. Least squares regression of interval from
first insemination to conception on interval
to conception.

A

Y

r2 = .99

-75.0 + .985885(DO)

51

$52: ZOEhEOZOo O... I_<>mm._.z.

 

 

 

00. CV. ON. 00. 0m 00 ov IN.
2 m

a .m

m u

.0. m m

.3 m H

.8 m w

mlu I...

.8 m m

0 S

l 3

Oh N W

S |

.8 ( W

.....

82 383. + 0.2. I a» . cm 0
< N

ZOFQNOZOO Oh I_<>mm._.z. ZO 29.550200 0...
ZO_._.<Z=>_me_ Ema-n. 20m... I_<>mw._.z_ m0 ZO_mmwm@wm mwmdaom km<wu_

Figure 6.

52

Least squares regression of interval from first
insemination to conception on interval to first
insemination.

A

Y 27.1 - .9829226(76.6-IFI) - .00085991

(76.6-IFI)2

= .99

I‘l-I-l—n‘ a- -

l‘nl—f‘ nl—l‘nf-(‘nln‘l Al'—

I Ffln‘r “A.

53

$29 2222.232. 5m... 2. 442.32.
8. 882 889.0»

éé'aé

1
O

co E III 8
(swomoudz-IONOO 01

NOLLVNIWBSNI lSHId WOHJ 'IVAHBLNI

O

l

 

. cm
«A r... I 062.8308. 1...: I 32833015 .0

20.._.<z_s_mmz. #9:... O...
I_<>mm._.z_ ZO ZOFn—wozonv O... 202.42.2mmz. PmmI

20m.“— 4<>mw._.Z_ m0 zo_mmwmomm mum—(Dom .5qu

54

Table 7.--Percent conception at the first through fourth
inseminations for all cows and cows in Treat-
ments I, II, and III.

 

 

 

Insemination Treatment
Number I II III Ave.
1 55a(l68)b 56(166) 58(48) 56(382)
2 59(80) 60(79) 66(23) 60(182)
3 50(28) 770(41) 58(7) 63(76)
4 57(10) 91C(11) 60(3) 66(30)

 

a . .
Percent conce1v1ng.

bNumber conceiving.

cSignificantly higher than Treatments I and III
(p < .05).

Percent conception at first insemination was vari-
able among herds for 1972 and 1973-74 (Appendix Tables 17
and 18). Conception rate at first insemination ranged from
39 to 75, and 40 to 73 percent for 1972 and 1973-74,
respectively. No differences were observed among treatments
within herds during 1973-74. Conception rates at first and
succeeding inseminations were similar for 1972 and 1973-74
(Appendix Tables 17 and 18). Percent conception by various
20 day first insemination intervals for normal (Treatments I
and II) and abnormal (Treatment III) cows is shown in

Tables 8 and 9.

55

Table 8.--Percent conception at first insemination for
normal (Treatments I and II) and abnormal
(Treatment III) cows bred at various 20 day
postpartum intervals.a

 

 

IFIb NormalC Abnormald Total
<40 509(10)f -—— 50(10)
40-60 46(164) 37(16) 45(180)
61-80 60(221) 58(33) 60(254)
81-100 54(112) 71(17) 56(129)
101-120 61(62) 70(10) 63(72)
121+ 70(33) 57(7) 67(40)
Average 56(602) 58(83) 56(685)

 

aOnly data from cows that eventually conceived were
used; cows open longer than 250 days excluded.

bInterval to first insemination (days).

CTreatments I and II (cows bred at first estrus
after 40 or 60 days respectively).

dTreatment III (cows clinically abnormal at
parturition).

e . . . . . .
Percent conceiVing at first insemination.

fTotal number of cows inseminated during that
period.

56

Table 9.--Percent conception at the first through fourth
inseminations for cows first bred at various 20
day postpartum intervals.a

 

 

 

IFIb Insemination Number
1 2 3 4

<40 50C(5)d 40(2) --- 100(3)
40-60 45(81) 58(57) 60(25) 71(12)
61-80 60(152) 56(57) 62(28) 76(13)
81-100 56(72) '70(40) 65(11) 67(4)
101-120 63(45) 63(17) 80(8) ---
121+ 67(27) 61(8) 100(5) -e—

 

aCows open longer than 250 days are excluded and
only data from cows that conceived were used.

bInterval to first insemination periods (days post-
partum).

C . . . . .
Percent conceiVing at that insemination.

dNumber conceiving at that insemination.

57

Ten normal cows were bred before 40 days postpartum
(Table 8), and half of them conceived at first insemination.
Abnormal cows bred first at 41-60 days postpartum had a
37 percent conception rate compared with a 46 percent con-
ception for normal cows bred during that period. Percent
conception reached 60 percent at the first insemination
interval of 61 to 80 days and was above 55 percent for the
other periods. Conception rate at first insemination was
not different between normal and abnormal cows (p > .05).
Conception rate at second insemination (Table 9) was above
55 percent for all periods except for five cows first bred

at less than 40 days postpartum.

Percent Pregnant

 

Percent pregnant, defined as percent of cows
assigned that were diagnosed or considered pregnant, for
treatments and herds during 1973-74 is shown in Tables 1
and 3. In Treatment III, 65 percent of the cows assigned
became pregnant which was significantly less (p < .05) than
the 75 percent pregnant in Treatments I and II (Table 3).
The percent of cows pregmant for all treatments among herds
ranged from 55 to 83 percent with an average for all herds
of 71 percent (Table 1). Percent pregnant was not calcu-
1ated for the 1972 data. Non-pregnant cows were usually

culled.

58

Inseminations per Conception

Fertility as measured by inseminations per con-
ception averaged 1.7 for cows in all treatments during
1973-74 (Table 3). Treatment means were not different.
Within herds, treatment differences occurred in Herds 2
and 10 (Appendix Table 19). Cows in Treatment I required
more inseminations in Herd 2, and cows in Treatment III
required more in Herd 10. Herds means ranged from 1.4 to
2.0 inseminations per conception but were not different.

Inseminations per conception ranged from 1.3 to
2.4 (mean 1.8) for cows among herds during 1972, but were
not different from each other as determined by Scheffe's
interval (Appendix Table 19).

Cows in each successive 20 day first insemination
interval required fewer inseminations per conception
declining from 2.4 for cows bred at less than 40 days to
1.4 for cows bred after 121 days postpartum (Table 4).
The simple correlation of inseminations per conception and
interval to conception was .67.

Housing was the only main variable that signifi-
cantly (p < .05) affected inseminations per conception
(Appendix Table 20). The model was determined to be as

follows:

= u + Ti + sj + H + z + TS.. + TH. + T2 +

k 1 1] 1k i1

+ TSZi. + b X + b x2 +

SHj + $2. + HZ 31 l 4 2 4

k1 3k

b3x3x6 + b4X5X6 + b2X4X6 + eijklm

59

Variable symbols are described in Appendix Table 2
parts 1 and 3. The multiple correlation coefficient was
.81 indicating that most of the variation was accounted
for. The linear and quadratic terms of interval to con-
ception, and the interactions of 150 day milk yield with
interval to first insemination, interval from first insemi-
nation to conception, and interval to conception were
significant (p < .05). Other factors approached signifi-
cance (Appendix Table 20). Adjusted least square means are
given in Appendix Table 21. Cows housed in free stalls
averaged 1.85 insemination per conception, and cows in
stanchions averaged 1.59 insemination per conception, a

significant difference (p < .05).

Milk Production

 

Milk production records were collected and analyzed.
The 305 day 2X-ME milk yield ranged from 13,176 to 18,236
(mean 14,914) pounds among herds for cows calving in 1972
and completing more than 250 days of lactation (Appendix
Table 1). The actual herd milk production averages from
September 1973 to October 1974 ranged from 10,848 to 16,546
pounds (mean 14,040; Appendix Table 1). Significant
differences existed among herds (p < .05). The overall
average milk production per cow for the first 150 days of
lactation was 8,174 pounds which projected to an expected
305 day 2X-ME yield of 14,478 (Table 10). Lactation curves

for treatments and interval to conception periods for the

60

Table lO.--Summary of data for 1972 and 1973-74 for herds
participating in the early breeding project.

 

 

 

1973-74
1972
All Cows TRT. II & III
Number of cowsa 834 976 549
Age at calving (mons.) 48 48 48
Interval to first b
estrus (days) —— 58 59
Interval to first c
insemination (days) 84 78 82
Interval to concep- d
tion (days)e 111 103 107
Inseminations per
conceptione 1.8 1.7 1.7
Interval from first
insemination to con-
ception (days)e 28 30 25
Milk production
(pounds)f 14,913 14,478 --
Percent culled 3O 29 32

Percent pregnant

 

aTotal cows calving in 1972, and number of cows
assigned 1973-74.

bData not obtained for 1972.

CSignificantly longer than all cows 1973-74
(p < .001) .

dSignificantly longer than all cows 1973-74
(p < .01).

eCows open longer than 250 days excluded.

f305 2X-ME.

61

first 180 days of lactation are plotted in Figures 7—9.
Curves were not different among treatments or interval to
conception periods. The lactation curve for cows open less
than 40 days was omitted due to small numbers. The average
milk yield per day per cow for the first 180 days of
lactation averaged 52.5 pounds overall and was not differ-
ent among treatment groups (Table 11). Milk per cow per
day by interval to conception periods (Table 12) was also
not different.

The least squares table for 150 day milk yield is
given in Appendix Table 22. The following model was deter-

mined.

2
31 + b1X7 + b2X7 + eijlmn

The variable symbols are described in Appendix Table 2
parts 2 and 3. The multiple correlation coefficient was
.53. The simple correlation between age and milk yield
was .42. The age effect was highly significant (p <
.0005) in both the linear and quadratic terms. The
regression curve for age is plotted in Figure 11. Treat-
ments, herd size, herds within herd size, and the three-
way interaction of treatments, seasons, and herd size all
significantly affected 150 day milk yield (p < .01). The
least squares adjusted means for treatments, seasons, and

herds are given in Appendix Table 23.

62

AHHH mcfiqv HHH ucmspmmue.

AHH wcflqv HH ucwfiummua

II
0

AH mcflqv H ucmsummue u a
HHH

ma. u N0 .mxm»<acm~omoooo. + mlms<avaohmoo. I Amwaocsmnm. + o~.m6 n 2
am. I N0 .mxmwaovaamaoooo. + mlms4ovmmmvoo. I Amwaocmmam. + oa.~m n HH»
«m. n N0 .mlm54ovmmmooooo. + Nxmwaovaoamoo. I 2mw<acsmo~. + mm.mm u Ha

.HHH can .HH .H mucmEummHB cfl m3oo How mw>uzo coflumuoma mop omH .5 munmam

63

.00.

 

Bo2< .nq 3522mm» 2.
38 mo... 3350 20:484.. :5 0m.

ZO....<...0<I_ “.0 m><o
. 0.0. . 0.! . 0W. . 0.0. . 0.00. OWN. 0W0. ohmm. 0.0..

0.00

0.00

0.0..

0.00

 

(SONnOd) AVG 83d >I'IIIN

64

.v mcflq. mxma mmIom cofiummocou cu Hm>umucH n

.m mafia. whoa mhIom coHumwocou ou Hm>umucH u

III [3

.m mafia. mmmo mmIov coaummocoo ou Hm>umucH u <
om. u NH .m.m»<ovmmmaoooo. + «.mwaovmommoo. I .mwmovmomm. + Hm.m6 u 6m
om. u m0 .m.mwaovhmmaoooo. + «.mwaavmmasoo. I .msaavsahm. + RN.4m u mm

om. u «0 .m.msaavmmmooooo. + m.mw¢ovmomaoo. I .mwaovmmoso. + mm.mm u mm

.H mam>nmucw Eduummumom mmv
om msofium> mcHHSG wm>flmocoo umnu mzoo How mm>uso coflumuoma amp oma

.m musmflm

65

.00.

q

 

d

H mI.<>mw...z. 20km<akmoa >40 0N 000.m<> 02.130
00200200 #4:... 0300 00.... mw>mao 20:40.04; >40 00.

20:40.04... “.0 m><0

.N0. .Yv. .0N. .00. 0.00 00» 000 0.00 0.0.

d 1

8....

.8...

l

00¢

0.00

0.00

I 0.0b

I 0.00

 

(SONnOcI) AVO 83d >I‘IIIN

66

mm.
mm.
om.

ma.

.m mafia. mama +oma cowummocou on Hm>nmucH n

.A mafia. mama mmHIovH cofluamocoo 0» Hm>umucH n

0 II [:3

.8 mafia. mama mmHIoma :oflummocoo 0» H8>umucH u

.m mafia. mama mHHIooa nodummocou on Hm>uwucH n <
u m0 .m.m»4ovflamaoooo. + ~.m»<a.ommmoo. I .mwaavnamw. + mo.am u mm
n my .m.mw<ovmmoaoooo. + «.mw¢o.ommmoo. I .mwaavmmma. + mm.mm 0 em
I m0 .m.m»¢ocammooooo. + ~.mw¢avmmn~oo. I .m2405448H. + mm.am n 8m
I N0 .m.mw<ovommooooo. + ~.m»«aqum~oo. I .mwaocmoma. + ~o.mm n mm

.HH mam>umucfl Eduummumom amp
om msofium> mcflusw cm>flwocoo umnu msoo now mm>uzo coaumuoma mun oma

.m wusmflm

67

H 0442.002. 2:...m4n....00n. >40 0N 030E4> 02.030
00200200 ...4....—. 0300 10... 002.00 20....4...04I. >40 00.

20....4...04I. II.0 0>40

 

 

.00. .N0. .44. .0N. .00. 0.00 0.Nh 0.40 0.00 0.0. 0.,
1 I I I I I I I I I I I I I I I I I I I I%Oo
.68
L
0
I 0.04
0 4 I 0 0 O I.
arrI - I D 0 0 .
I I l../I. D 0 I 000
d I” 4.4%.qu .44 O .0 I 04 .iVm
a no 661/ 2L6... a. .
a m _. uIIUaf a . ”IN-0‘. a I- 0.8
. n D n - I.
o I I 0.04.
I000

 

(SONnOd ) AVG 83d >I'IIW

Ta

Tr

per

dat
com
197
the
can

08;:

Cha

Cep

rang

68

Table ll.--Average milk yield per day during the first 180
days of lactation for cows in Treatments I, II,

 

 

and III.
Average Number
Milk Yield Number Observations
Treatment (lbs.) of Periods Per Period
1 52.8:.75a 35b 58.0C
II 52.5i.86 35 58.3
III 51.6:.92 35 15.2
All 52.5:.77 35 131.5

 

aMean:S.E.
bNumber of five day periods used to determine mean.

cAverage number of observations (weights) used per
period.

An overall summary of reproductive and lactation
data for 1972 and 1973-74 is presented in Table 10. When
cows in Treatments II and III were compared with means for
1972, no differences were observed. However, when cows in
the early bred group (Treatment I) were included, signifi-
cantly shorter intervals to first insemination and to con—
ception (p < .01) were noted. Means were tested by standard
"t" test. Thus the only two variables that we had hOped to

change (interval to first insemination and interval to con-

ception) were actually different.

Cull Reasons and Frequencies

 

Percent of cows culled per herd during 1973-74

ranged from 16 to 41 percent (Table 1), indicating the

69

Table 12.—-Average milk yield per day during the first 180
days of lactation for cows that conceived during
various 20 day postpartum intervals.

 

Average Number

 

Days Open Milk Yield Number of of Observations
Interval (Pounds) Periods Per Period
<40 63.7:2.47a 24b 1.2C

40-60 51.0:1.22 35 10.9

61-80 53.8:0.98 35 23.3

81-100 53.0:0.95 35 18.3
101-120 54.0:0.84 35 15.1
121-140 50.5:l.09 35 9.7
141-160 56.1:1.07 35 7.2
161-180 56.1:0.99 35 14.0

 

aMean:S.E.

bNumber of five days periods used to determine

mean .

CAverage number of observations (milk weights) used
per period.

Figure 10.

70

Least squares regression of 150 day milk yield
on age at calving.

A

Y 8174 + 148.4336(46.6 - AGE) - .84744(46.6 -

AGE)2

I‘ll-‘1‘ \

IRA hflv I‘ll I! VIE. “Int-\-

ISO DAY MILK YIELD( POUNDS)

I5,000 ’

I4,000
I 3,000
I2 .000
l |,OOO
I 0,000
9,000
8,000
7,000
6,000
5,000
4,000

71

LEAST SQUARES REGRESSION OF I50
DAY MILK YIELD ON AGE AT CALVING

Y-8I74 + I48.4336(46.6-AGE)-.84744I46.6-A0£)'

 

l l 1 l 1 I j l I

30 50 70 9O IIO
AGE AT CALVING (MONTHS)

72

variation in culling intensity on the various dairy farms.
Herd 9 had a high culling rate because grade cows in the
herd were sold in order to purchase registered cows. In
Herd 8 a large number of cows were sold because the herds-
man left, and the owner was unable to manage the larger
herd by himself. Culling rate during 1972 varied from 8
to 35 percent among herds with an overall culling rate of
29 percent (Table 1).

Low milk production accounted for the greatest
incidence of cows culled for each treatment group, and also
for all cows in 1973-74 (Table 13).

Sterility and infertility, and cows sold for dairy
purposes accounted for equal number of cows sold (18% or 50
cows). The only cull reasons that were different among
treatments were sterility and interfility, and "other"
which differed between Treatments I and II (p < .05). Cows
culled per treatment were 24, 31, 37 percent respectively
and percent culled for Treatment I was significantly less
than for Treatments II and III (p < .05).

I Cull reasons and frequencies for cows calving in
1972 are also in Table 13. Dairy purposes and milking
problems were not listed as cull reasons in 1972, and are
therefore included in "other" reasons. Again, low milk
production was the greatest reason for culling (39% of cows
culled). Sterility or infertility accounted for 24 percent
of the cows culled, and 28 percent were sold due to "other"

reasons. Overall culling rate for both years was 29 percent.

73

Table l3.--Cull reasons and frequencies for all cows during

1972, and for all treatments and cows during

 

 

 

 

 

1973-74.
Treatment and Year
1973-74 1972
I II III Ave. Ave.
Sterility
or infer- a b c
tility 23 (23) ' 15(19) 17(8) 18(50) 24(58)
Injury,
disease,
died 12(12) 12(16) 21(10) 14(38) 9(23)
Low
production 31(31) 23(30) 27(13) 27(74) 39(94)
Dairy d
purposes 20(20) 19(25) 15(7) 19(52) --
Milk d
problemse 6(6) 12(16) 6(3) 9(25) ~-
Other 8(8)c 18(23) 14(7) 13(38) 28)69)
Total 24f(100)g 31(129) 37(148) 29(270) 29(244)

 

aPercent of the

b

Number culled.

cows culled in a treatment group.

cSignificantly different than Treatment II (p <

.05).

dNo category for this reason in 1972.

eHard milkers, mastitis, udder problems.

fPercent of cows culled per treatment.

9Number of cows culled per treatment.

DISCUSSION

The 13.7 percent incidence of abnormal cows at or
following parturition is close to the 15 percent expected.
Morrow gt gt. (1966) reported a 29 percent incidence of
abnormal cows, but they included milk fever, acute mastitis,
and ketosis (non-reproductive abnormal conditions) in their
classification.

Retained placenta and uterine infection were the
major reasons for assignment to Treatment III, although
there was wide variation among herds. Kjome (1975)
reported 14.7 and 17.5 percent incidence of retained
placenta and metritis, respectively, for cows in Michigan
dairy herds. I

The average of 58 days to first estrus for all
cows was longer than reported by Morrow gt gt. (1966), and
Whitmore gt gt. (1974), but is within the range of 30-72
days reported in Wisconsin Research Bulletin 270 where
several studies were summarized. Pelissier (1972) in a
study of 24 commercial herds reported that 58 percent of
the cows were in estrus by 60 days postpartum. Cows in the
three treatment groups had similar intervals to first

estrus, however, Morrow gt gt. (1969) and Buch gt gt.

74

75

(1955) reported longer intervals to first estrus for
"problem" or ”abnormal” cows. However, both studies had
shorter overall intervals to first estrus than observed in
the present study. Variation in estrus detection methods
among herds existed (Appendix C, Tables 4a, 4b, and 4c).
Herds within herd size, significantly affected interval to
first estrus, but season, and herd size did not as deter-
mined by least squares analysis. Some investigators have
reported an effect of season and herd size on interval to
first estrus. The low multiple correlation coefficient
indicated that much of the variation was not accounted for
in the model.

The average interval to first insemination was
longer than expected for Treatments I and II. Ideally,
cows bred at first estrus after 40 days postpartum would
average 51 days to first insemination (assuming all cows
had 21 day estrous cycle, were detected in estrus, and
bred). Accordingly, cows bred at first estrus after 60
days would average 71 days to first insemination. However,
since cows in both treatments averaged 58 days to first
estrus, the interval had to be longer than the ideal, which
it was. The actual intervals from first estrus to first
insemination was 17 and 23 days for cows in Treatments I and
II, respectively. The actual interval to first insemination
was 72 and 83 days for cows in Treatments I and II. It was
thought that abnormal cows would probably be inseminated

later in the postpartum period than Treatment II cows.

76

However, they were bred just as soon as Treatment II cows,
indicating that the abnormal conditions were promptly
treated and corrected. Herd differences were evident.
Eleven herds actually achieved a shorter interval to first
insemination for cows in Treatment I. The herd where cows
failed to achieve this had 68 and 63 days to first insemi-
nation for cows in Treatment I and II. The 63 days to first
insemination for cows in Treatment II in this herd was 12
days shorter than the next shortest herd interval. Least
squares regression analysis revealed that treatments and
herds had a significant effect, but season of calving and
herd size did not.

The estrus and insemination intervals of approxi-
mately 31 days indicated that approximately 50 percent of
the estrous periods were undetected. Estrous detection did
not appear to improve once breeding had started because
intervals between inseminations were just as long as inter-
vals between estrus before the first insemination. The 30
days between inseminations is similar to the 45 percent of
"delayed returns to insemination" (intervals of 26 days or
longer) reported by Olds (1969). Admittedly, early
embryonic mortality, and anestrous cows would also tend to
lengthen the overall intervals between insemination beyond
the expected 21 days. Wide herd variation existed in
estrous and insemination intervals.

The interval to conception (days open) and calving

interval are considered as the same measurement in the

77

study, i.e., calving interval equals days Open + 280 days.
The days open for cows in Treatment I, II, and III corre-
spond to 12.5 (Treatment I) to 13 (Treatment III) month
calving intervals, all longer than the 12 month calving
interval that is considered desirable (Speicher and
Meadows, 1967; Louca and Legates, 1968). Cows in one herd
achieved a twelve month calving interval, i.e., 85 days
open. Cows in seven herds had shorter calving intervals in
1973-74 than in 1972. Cows in three herds had calving
intervals of similar length between years and cows in two
herds had longer calving intervals. Although cows in
Treatments II and III had the same interval to first
insemination, cows in Treatment III had a longer period of
days open because of longer intervals between inseminations,
especially between first and second insemination. Morrow
gt gt. (1969) found an average 126 days open for abnormal
cows and 106 days for normal cows. Ten of the dairymen
said the overall reproductive performance for 1973-74 was
the same or better than previous years. Nine of the herds
reported a decrease or no change in abortions compared with
previous years. Thus, early breeding did not result in
decreased reproductive efficiency.

Least squares regression of days open revealed that
season of calving or housing type did not have significant
effects. The least squares significant interactions for
days open can be observed since longer intervals to first

insemination required fewer inseminations per conception

78

and shorter intervals from first insemination to conception.
The other interactions of interval from first insemination
to conception are probably due to the high correlation
between interval from first insemination to conception and
days open.

The .42 correlation between interval to first
insemination and interval to conception is lower than the
.60 correlation reported by Olds and Cooper (1970). The
correlation of .82 between interval from first insemination
to conception and interval to conception is similar to the
.80 correlation reported by the same workers. Also the .96
and 1.06 additional days open for each additional day to
first insemination or from first insemination to conception
are similar to the .94 and .97 days reported by them.

Least squares analysis of interval from first
insemination to conception showed no effect of treatment,
season, housing type, or herd size. Increasing the inter-
val to first insemination decreased the interval from first
insemination to conception. This may be due to physio-
logical causes, or it may also be because cows that were
bred late were given less opportunities to conceive, i.e.,
only cows that conceived on first few inseminations were
kept in the herd, others were sold, thus shorter intervals
from first insemination to conception and less inseminations
per conception resulted.

Percent conception at first and second insemination

was not different among treatments. Fertility at first

79

insemination is usually reported lower for cows bred

early. Although this was not evident in Treatment I
(perhaps the cows were not bred early enough), it is
evident when observed by first insemination intervals.
Percent conception was lower in cows bred before 60 days
postpartum compared to cows bred after 60 days. This was
even more evident in abnormal cows. Pelissier (1972)
reported that cows with retained placenta had a 30 percent
conception rate at first insemination. Erb and Ehlers
(1957) also reported higher percent conception at first
insemination for normal cows. Overall conception rate for
abnormal cows at first insemination in this study was
equivalent to normal cows. The 56 percent conception at
first insemination for all cows is similar to that reported
by others (Olds and Cooper, 1969; Bozworth gt gt., 1972;
Whitmore gt gl., 1974; Spalding gt gt., 1975). Percent
conception at first and succeeding inseminations varied for
cows within herds.

The overall 1.7 inseminations per conception is
consistent with that reported by others (Morrow gt gt.,
1966; Boyd gt gt., 1954; and Bozworth gt gt., 1972). It
is lower than the 2.4 inseminations per conception reported
by Pelissier (1972) in a California field study. Treatment
means were not different for inseminations per conception.
Morrow gt gt. (1969) and Pelissier (1972) reported than
abnormal cows required more inseminations per conception.

It has also been reported that early bred cows require more

80

inseminations. This is observed in the data analyzed by
interval to first insemination periods, but is not observed
for cows in Treatment I. Interval to conception was corre-
lated with inseminations per conception (r = .67). The
interaction of milk and several reproductive parameters on
inseminations were significant but undefinable. Likewise
no logical explanation of why cows in free stalls required
more insemination than cows in stanchions was found,
although cows housed in free stalls were in smaller herds
(a possible explanation).

The differences in annual milk yield by periods can
be attributed to several things. The 1972 production records
are selective because only pregnant cows that milked over
250 days are included. Thus all cows that milked less than
that are excluded, which included most of the cows sold for
low production. The 1973-74 data includes all cows and was
taken directly from DHIA forms. Less difference is observed
if the 1972 yield is compared with the 1973-74 estimated
305 day yields for pregnant cows.

Average milk yield per day, and the 180 day lacta-
tion curves did not show differences for cows among treat-
ments or interval to conception periods. Various studies
(Erb gt gt., 1952; Gaines and Davidson, 1926; Sanders, 1927;
Louca and Legates, 1968) indicated that gestation does not
affect milk production until after the first five months of

pregnancy. If this is the case, one would not expect to

81

see a difference in 180 day yield for cows in treatments or
interval to conception periods.

Least squares analysis did show an effect of
treatments, but not conception periods, on 150 day milk
yields. The treatment effect was probably due to abnormal
cows having lower production during the early part of the
lactation, and never quite catching up. Age affected yield
as would be expected. Herd and herd size differences were
observed. Herd yields were variable within herd size cate-
gories which probably accounts for herd size variation.

The 29 percent culling rate for both 1972 and
1973-74 is close to the 30 percent annual culling rate often
quoted (Foley gt gt., 1972). Low milk production was the
major reason for culling with sterility and/or infertility
the second major cause which agrees with the culling reasons
reported by Erickson (1972)- Bozworth gt gt. (1972)
reported a 22 percent culling rate in Kansas herds due to
sterility or infertility which approximates the 18 and 24
percent found in this study. Although more cows were
culled for sterility and infertility in Treatment I, cows
in Treatment I had similar pregnancy rates and insemina-
tions per conception as cows in Treatment II. The differ-
ence may exist because fewer total cows were culled in
Treatment I, although the numbers culled for sterility were
similar. The overall lower culling rate for Treatment I
tends to refute the once-held belief that early bred cows

were more likely to be culled. Although there appeared to

82

be more abnormal cows culled, the difference was not
significant. However, there was a lower percent of abnormal
cows which subsequently became pregnant.

It is possible that the actual occurrence of
abnormal and culling frequencies is different than is
reported here. Data were summarized and calculated as
reported on the bi-weekly reports from the cooperating
dairymen. Therefore, the data are subject to all the

biases that affect field study experiments.

SUMMARY

Cows in twelve cooperating dairy herds in south
central Michigan were assigned to be bred at either first
estrus after 40 days (Treatment I) or 60 days (Treatment II)
postpartum. Cows clinically abnormal at parturition
(Treatment III) were assigned to be bred when diagnosed as
normal by the herd veterinarian. Thirteen percent of the
cows were assigned to Treatment III with retained placenta
and uterine infection accounting for 68 percent of those
assignments. Fewer cows in Treatment I were culled than in
Treatments II and III. Low production was the greatest
cause for culling in all groups. Sterility and infertility
was the second major cause.

Interestrual intervals and intervals between
inseminations averaged 31 days for all cows, an indication
that approximately 50 percent of the expected estrous
periods were not observed. Interval to first estrus was
58 days, and was not affected by treatment.

Cows assigned to Treatment I averaged 73 days to
first insemination which was shorter than the 82 and 83
days for Treatments II and III, respectively. In eleven

herds, cows assigned to Treatment I had shorter intervals

83

84

to first insemination than those assigned to Treatment II.
All cows averaged 84 days to first insemination in 1972
which was the pretreatment control period. Treatment and
herds within herd size significantly affected interval to
first insemination as determined by least squares analysis.

Interval to conception was 99 days for cows in
Treatment I which was less than 112 days for cows in
Treatment III, but not different than 105 days for cows in
Treatment II. These correspond to 12.5 to 13 month calving
intervals. Only one herd achieved a 12 month calving
interval, but 10 herds had calving intervals shorter or
similar to those for 1972. Therefore, breeding some cows
earlier reduced overall days open. Interval to conception
was affected by interval to first insemination and interval
from first insemination to conception and their interactions
with other reproductive measurements as determined by least
squares analysis.

Intervals from first insemination to conception and
inseminations per conception for cows were similar between
treatments and years indicating no detrimental effects of
early breeding. Least squares analysis revealed that
interval to first insemination, interval to conception, and
the interactions of 150 day milk yield with interval to
first estrus and interval to conception significantly
affected the interval from first insemination to conception.
Inseminations per conception were affected by housing type,

interval to conception, and 150 day milk yields interactions

85

with interval to first insemination, interval from first
insemination to conception, and interval to conception.
Conception rate for all inseminations was 55 percent or
above, and was not affected by treatments.

When the data were grouped by 20 day intervals to
first insemination, ignoring treatments, a significant
effect was noted for all intervals studied. As the inter-
val to first insemination increased, there was an associated
increase in interval to first estrus, and interval to con-
ception, but a decrease in interval from first insemination
to conception and inseminations per conception. However,
cows first inseminated less than 40 days postpartum had more
days open than cows first inseminated from 40-60 days post-
partum, indicating that breeding before 40 days was un-
desirable.

No effects on milk yield per day for the first 180
days of lactation were observed for treatments or intervals
to conception. Lactation curves for the first 180 days of
lactation were not affected by treatments or intervals to
conception. Least squares analysis of 150 day milk yields
revealed significant treatment, and herds within herd size
effects.

Season affected none of parameters measured. Age
at calving affected only 150 day milk production. Herd
variation existed for all parameters measured. At the end
of the study, 11 of the c00perating dairymen planned to

continue breeding some cows early, an indication that their

86

participation in the study convinced them of the benefits

of early breeding.

APPENDICES

APPENDIX A

WEEKLY REPORT FORM FOR FIELD STUDY

APPENDIX A

WEEKLY REPORT FORM FOR FIELD STUDY

 

 

 

 

 

 

 

 

 

 

 

Herd Name Date
Instructions:
1. Information should be updated daily
2. When cows have calving or reproductive problems, write the
information in the column concerning problem cows. The vet
can also use this area for comments when he makes herd visits
3. Forms should be returned to MSU every two weeks when new
forms are received.
Day & Cows in Cows Calved Cows Bred Cows with Calving
Date Heat Today Today Today Problems or
Reproductive Problems
Sunday
Monday
Tuesday
wednesday
Thursday
Friday
Saturday

 

 

 

 

 

87

APPENDIX B

SAMPLE COMPUTER PRINTOUT FOR ASSIGNED MINIMUM
INSEMINATION DATES, AND ACTUAL

INSEMINATION DATES

ed >d<3¢muu

INN“ mix 2» 0.

9 .0w «muckoo

m$5
msx ”mam“
4&0“ onw dwmtm>oz

\wAvm" «ISAmV

4504 ed 00020000

wuH>mwm adeh

whoa

450“

.3 .5.
“WMMJRee

Juan

abmu

odd

esu
.na

.0“

eo~

.o~

unu>~mm ozouwm

>¢¢32<5 Suva eom

oknuu :son and
«unabuo 45¢“ .04
bmauac :hoa on~

\nwuwnee .ee
ammoeue seed .8

mnou eon

AVMWNeea .~a

msou .o
0&0“ .94
ago“ emu
hmsusq skew .om

«mozm>oz

hmnund

Ibnmm

>435

Inuit

«weapon

Inuar

munchuo

>42

4uma4

>¢1=dnuu

>405

undo muu>aum hmuuu

mmmtnu<
mamz ere:

whoa

:so«
450“
:sa«
whoa
mkwu

«sou

ms¢d
whoa
chad
“sad
0~o«
nuau
4504

“so“

waud haw: hmyuu be ommxu

00940 ZOHB<ZH£mmZH 440904 02¢ .00840

.04 mzaa
4th02 20::

new bmaoaa

ova >405
ad >405
ed >435

.cn >maazea
.en .»aum

agree: 2w13
.mu 44202
.~« wzaa
.- «weapon
0» 4uua¢
.o >¢¢auouu
.oa >«aach
eon 02:5

.0 >435

ZOHBfiZHSmmZH SDSHZHS DMZUHmm¢ 00h BDOBZHmm “0800200 mnmz<m

m XHDmemfl

zzeoI
>mH20I
uuuwzoI
mmJooaaI
«ozumoI
«Lazaro
02022400
wuouuoI
:hwnI
wuuzmoo
unauoI
woaeauoI
upaxmnu
wo<oI
>ueoaeo
qeuzeI

4400240

z¢<0I4Odhz

«00:07

00
30

0

BE!

APPENDIX C

SAMPLE OF QUESTIONNAIRE SENT TO COOPERATING

DAIRYMEN, AND THEIR RESPONSES TO QUESTIONS

10.

APPENDIX C
SAMPLE 0F QUESTIONNAIRE SENT TO COOPERATING

DAIRYMEN, AND THEIR RESPONSES TO QUESTIONS

How many cows are in your herd?

At what age do you try to have your heifers freshening?
What type of housing do you have?

Describe the method of heat detection used on your farm:

Number of times checked per day:
Who does the heat checking:

Time spent per observation:
Place or area where observed:
Signs looked for:

Other comments:

How good a job do you think you do in heat detection?
(Circle one)
Good Fair Poor
How many days after calving do you wait before starting
to observe for signs of heat?
Do you record heat dates for the herd? (Circle one)
Yes No

How has this study affected your heat detection
methods?

Before the study, when did you normally try to breed
your cows after calving?

Who does the insemination on the farm?
Is any natural services used? How much?

 

 

89

ll.

12.

13.

14.

15.

16.

17.

18.

90

Is there a period of time you don't breed your cows so
as to miss calving in the summer, and to hit fall
freshenings? (Circle one)

Yes No
When do you not breed?
Do you plan to continue breeding some cows at first
heat after 40 days? (Circle one)

Yes No

If Yes, about what percent do you plan to breed
early?
How will you determine which cows to breed at 40 days.

 

How useful was the computer printout in the study?
Did you follow it fairly closely?

How would you say this year’s reproductive performance
compares with previous years? (Circle one)

Same Better Worse

Did you observe any differences in the occurrence of
the following conditions? (Check apprOpriate answer)

Increased Decreased No Change

 

 

 

Metritis
Abortion
Calving Problems
Cystic Cows

Do you have a program of regular veterinary visits for
the following: (Check appropriate answer)

Yes No

Postpartum Exams
Pregnancy Diagnosis
Reproductive Problems
Examination of Heifers
Before Breeding

How often do the regular visits occur?

Compare this year's nutrition level with last years:
(Circle one)
Same Higher Lower

What is the average length dry period for cows in
your herd?

19.

20.

21.

22.

23.

24.

91

What is your rolling herd average?

Have you noticed a change in milk production during the
year? (Circle one)

Increase Decrease No Change

Estimate the percentage of cows culled from your herd
for the following reasons:

Percent
Low Production
Sterility or Reproductive Problems
Dairy Purposes
Other Reasons

Have there been any major changes in your dairy
Operation since September 1, 1973? (i.e., new
facilities, large number of cows bought or sold, major
herd health problems, change of herdsman, etc.)
Describe, change, and tell effect, if any.

Please give us your evaluation of the study as con-
ducted.

Would you be interested in continuing this study for
two more years? (Circle one)

Yes No

92

Question Number

 

ggttg On Questionnaire
1 1
2 2
3 3
4a 4
4b 5,6,8
4c 4,7
5 9
6 10
7 10
8 11
9 12
10 13
11 14
12 15
13 16
14 17
15 l8
16 19
17 20
18 21

19 22

93

Table 1.--Herd size.

 

 

Number of Herds Size Range
3 40-60
5 61—80
3 81-100
1 101+

 

Table 2.--Age at first calving (goal).

 

 

Number of Herds Age (Months)
3 24
2 27
1 25-27
6 24+

 

Table 3.--Types of housing.

 

 

Number of Herds Type
7 Free Stall
3 Stanchion
1 Loose
1 Combination Loose and Stanchion

 

94

 

uozmc4 oz H

 

 

 

 

roeum peace a
mnoq xaaz N 003804 oz 4
.mmmcmso>u0z
.mcfluusm .mmo ocwuwmm.
HOH>mcmm Hmsmsca n m H va m
new: pwnmsom v mIm H m v
0608:6840 cases m MIN H mIm m
unflosmum HO mcfiucsoz OH nozmcd Oz v m N
mcmwm momma mo .02 .mmuscwz. 0549 women mo .02 amo\mwafla mpumm mo .02
mm>ummno msmflm coaum>u0mno mom usmmm 0849 >00 umm pwxowno muses

 

.moonums cowuomumv msuumMII.mv manna

95

Table 4b.--Estrus detection methods.

 

Estrus Detection

 

Effect of Study on

 

Days Postpartum

 

 

 

 

 

 

 

 

Efficiency Estrus Detection Before Observing
(Self-Judgment) Methods for Estrus
No. of No. of No. of
Herds Efficiency Herds Effect Herds Days
6 Good 1 No Answer 5 All Observed
6 Fair 7 No Effect 3 20-30
0 Poor 4 More Aware 3 30
1 35-40
Table 4c.--Estrus detection methods.
Record Estrus Number of People Area
Dates Responsible Observed
No. of No. of No. of No. of
Herds Response Herds People Herds Place
12 Yes 3 One 2 No Answer
0 No 5 Two 10 Barn Lot
4 A11a

 

aNo specific

person responsible.

96

Table 5.--Usua1 interval to first postpartum insemination.

 

 

Number of Herds Interval (Days)
1 it
1 40,a 60-90b
1 50-60
7 6O
2 60-90

 

*When veterinarian says ready.
aWhen breeding cows for calving during base period.

bRegularly.

Table 6.--Herd insemination responsibility.

 

 

Number of Herds Inseminator
9 One person
2 Two people

1 A.I. Technician

 

97

Table 7.--Natura1 service use.

 

 

 

 

Used in Herd Extent Used
Number of Herds Response Number of Herds Use
10 Yes 1 10%
2 No 4 Heifers
1 Clean up
2 After 2nd
Service
1 After 3rd
SerVice
1 30-50% after

lst Service

 

Table 8.--Breed year around.

 

 

Number of Herds Response
9 Yes
2 No

1 No Answer

 

98

.Eduummumom mmmn ow umumm manumm umuHmw

 

 

 

 

 

umzmcd oz m
AMHHmso 06:0 HHe H
oonm H
mEmHQoum mchwmum mo
wuoumHm suH3 mzou H om H
umm> mo OEHB m omImm H
20000
mmmm cmHumcHumum> v OMImN m
OH m oz H
:OHuoswoum
mo Hm>wH 30H v pmumum 002 m mm» HH
mHmmm conHowo momma 00 .Oz cumm 00 w mwumm mo .02 mmcommmm mtumm mo .02
cmmum Op msou mHHmm mHHmm mchmmum
SOan mcHEumuwo 300 Ummum ou usmoumm macHucou ou cmHm

 

.mcHUmmun mmHumm How

m:MHm mnsusmII.m mHnma

99

Table 10.--Printout usefulness.

 

 

Number of Degree of Number of Closely
Herds Usefulness Herds Followed
3 Unknown 7 Yes
2 Little-Some 3 Tried
7 Useful 2 No

 

Table 11.--Reproductive performance compared with previous
years.

 

Number of Herds Change

 

4 Better
6 Same
1 Worse

1 No Answer

 

100

Table 12.--Reproductive problems during year.

 

 

 

 

 

Problem Change
Increase Decrease No Change
(No. of Herds)
Metritis l 2 9
Abortions 3 2 7
Calving Problemsa 0 3 9
Cystic Cowsb 4 l 7

 

aCows having dystocia, retained placenta, milk
fever.

bCows having ovarian follicular cysts, and cystic
corpora lutea.

Table l3.--Regulara veterinary care.b

 

 

Number of Herds Response
11 Yes
1 No

 

aMonthly visits.

bConsisting of postpartum examinations, pregnancy
diagnosis, and treatment of reproductive problems.

101

Table 14.--Nutrition level compared with last years.

 

 

 

 

 

Number of Herds Change
2 Better
10 Same
O Worse

Table 15.--Dry period length.

Number of Herds Days Dry
1 Approx. 35
4 40-50
6 60-65
1 No Answer

 

Table 16.--Rolling herd average.

 

Number of Herds

Range (lbs.)

 

10,000 - 11,999
12,000 - 13,999
14,000 - 15,999
16,000 - 17,999

 

102

Table 17.--Change in milk during year.

 

 

Number of Herds Change
6 Increase
3 Decrease
3 No Change

 

Table 18.--Cull reasons and frequencies.a

 

Reason 0-24(%) 25-49(%) 50-74(%) 75-100(%)

 

 

(Number of Herds)

 

Low Production 5 5 2 0
Sterility and

Infertility 3 4 4 1
Dairy Purposes 8 1 2 0
Other Reasons 7 5 0 0

 

aPercent of total cows culled per herd.

bNumber of herds that low production accounted for
less than 25% of total cows culled.

103

.mHuHmaomuuocHnm mcH>om msowuommcHo

.mwuuuqu
n

.omuuomwu powuuw o: oumOchH vacuum 4:0Hmm

 

 

 

 

Hammmo H 00mmnousm HOUHcoz puma muHmo H
mmcmso oz v
mEmHnoum

ochmmnn .m:OHquQm pwmmmuocH H uEmHnoum mmH H
mmoH spawn wmeOHocH H nEmHnoum huHOona H
mmcmno amsmpuwm N
002040 HOHMMQ u0\u:m vcwmsom m
pHOm msoo mo amnesc momma N

mEmHnOum wcH>Hmo pmmmmuocH H
msmHnOum mcHnmmun pmwmmuocH H 00mmnousm mzoo HucOHqup4 m

Hommmm momma mo .02 mmcmno mvumm «0 .oz
muommmm manure

 

.HMO> mcHuav mmmcmso mo uommmmII.mH anoa

APPENDIX D

TABLES

Table D-l.--Age at calving, lactation number, and herd milk
yields for cows in herds participating in the
early breeding project.

 

 

 

Age at Lactation Milk Yield (lbs.)
Herd Calvinga Number
1972b 1974C
1 43:2.4d 2.3:0.17 14,794 14,885
2 53:3.5 3.0:0.28 17,038 16,053
3 50:3.5 2.510.24 18,236 16,367
4 4012.2 2.0:0.17 13,538 12,758
5 50:3.3 2.9:0.26 16,208 14,577
6 46:3.4 2.7:0.27 16,045 16,340
7 52:2.5 2.910.19 14,481 14,096
8 4512.0 2.2:0.16 13,176 15,331
9 5814.1 2.910.26 15,132 10,848
10 50:2.0 2.7:0.14 13,342 11,206
11 5132.5 2.8:0.19 16,013 16,546
12 4812.6 2.9:0.26 15,993 14,116
Ave. 48:0.8 2.6:0.06 14,914e 14,040e

 

days.

b

aAge in months for cows calving in 1972.

305 2x-ME (pounds) for cows calving in 1972 that
were open less than 250 days and lactated more than 250

cRolling herd average September, 1974 from DHIA
records.

dMean : S.E.

eAverage milk yield per cow.

104

105

Table D-2.--Description of variables used in least squares
multiple regression analyses.

 

1. Main effects for least squares analyses of interval to
conception, interval from first insemination to con-
ception, and inseminations per conception

Yijklm = Parameter of interest
0 = Constant (mean)
Ti = Treatment
Sj = Season
Hk = HouSing

Z1 = Herd size
TS.. = Treatment by season interaction
THik = Treatment by housing interaction
TZi1 = Treatment by herd size interaction
Sij = Season by housing interaction
SZjl = Season by herd size interaction
HZ = Housing by herd size interaction
TSH.. = Treatment by season by housing interaction

ijk

TSZijl = Treatment by season by herd size interaction

2. Main effects for least squares analyses of interval to
first estrus, interval to first insemination, and 150
day milk yield

Yijlmn = Parameter of interest
0 = Constant (mean)
Ti = Treatment
Sj = Season
z =

1 Herd size

w
I

— Herds within herd size

106

Table D-2.--Continued.

 

TS..
1:)
Tzil

SZjl

TSZijl

Treatment by season interaction
Treatment by herd size interaction

Season by herd size interaction

= Treatment by season by herd size interaction

3. List of other variables for all least squares analyses

Number of times detected in estrus before
first»insemination

Interval to first estrus
Interval to first insemination
Interval to conception

Interval from first insemination to
conception

150 day milk yield
Age in months at calving
Number of inseminations

Interactions of above variables

Quadratic term of above variables

Error term

 

107

Table D-3.--Interval to first estrus for cows in Treatments
1, II, and III within herd--1973-74.a

 

 

 

Herd Treatment Total
I II III

1 65:4.4b 76:4.7 60:12.0 70:3.2a
2C 57:5.2 63:5.5 ll9:21.6 67_+_4.8a
3 6714.3 74:5.9 57:9 70:3.6a
4 5415.7 4714.5 53:6.7 5113.2b
5 45:4.8 4618.7 57:7.6 46:4.lb
6 5614.9 46:5.8 39:5.7 48:3.4b
7 62:6.1 70:5.2 67:6.1 66:3.7a
8 54:4.1 53:4.1 65:25.2 5432.9b
9 6614.6 73:4.7 80:9.4 7013.1a
10 7115.1 6915.2 71:12.6 70:3.6a
11 37:4.4 3913.9 4214.5 3912.5b
12 4915.0 40:2.8 4714.2 45:2.7b

Ave. 5711.5 59:1.6 59:3.5 5811.1

 

aCows open longer than 250 days excluded.

bMean : S.E.

CSignificant differences exist among treatments in
this herd (p < .05).

dInsufficient numbers to calculate standard error.

eMeans with same letter are not different from
each other.

108

 

 

Table D-4.--Least squares analysis of variance for interval
to first estrus.

Variable D.F. M.S. F. Sign.
Treatment (TRT) 2 176.8 0.2 .82
Season 3 772.3 0.8 .47
Herd Size 3 1342.4 1.5 .22
TRT X Season 6 1121.4 1.2 .29
TRT X Herd Size 6 865.2 0.9 .46
Season X Herd Size 9 1477.7 1.6 .11
TRT X Season X Herd Size 16 1659.1 1.8 .03*
Herds/Herd Size 8 6712.7 7.3 .0005***
Other 5
Error 823 915.3
Total 881

 

109

Table D-5.--Least squares adjusted means for interval to
first estrus.

 

 

 

Codea Treatment Season Herd Size Herds/Herd Sizeb'c
1 2 3 4

1 57.1 62.6 61.3 47.4 72.7 63.2 60.5

2 58.3 58.5 55.5 69.6 51.7 62.3 59.0

3 60.1 57.3 62.9 51.0 50.0 63.8

4 55.5 54.2 50.7

 

aCode for treatments (TRT) 1=TRT1, 2=TRT2, 3=TRT3.

Code for season of calving 1=January-March, 2=
April-June, 3=Ju1y-September, 4=October-December.

Code for herd size 1=Sma11, 2=Medium, 3=Medium-
Large, 4=Large.

bCode for herds/herd size 1 (small)= herds 5,9;

2 (medium)=herds 2, 6, 12; 3 (medium-large)=herds 1, 3, 8;
4 (1arge)=herds 4, 7, 10, ll.

cSignificant differences exist among herds/herd
size (p < .0005).

110

Table D-6.—-Days to first insemination for cows within herds
by years and treatments.a

 

Year and Treatments

 

 

 

 

Herd
1973-74 1972
I II III Total Ave.
1d 71:3.8b 87:4.0 60:12.0 78:3.03'C 85:4.2d
2 66:5.1 75:5.8 119:21.6 76:4.6e’c 85:6.3d
3 74:3.4 85:4.0 82:? 79:2.69'c 87:3.5d
4 74:4.5 81:4.2 78:5.7 77:2.78'c 86:3.7d
5 59:4.6 78:7.4 57:7.6 66:4.0b'c 77:6.3d
6 68:4.7 77:6.1 77:5.1 73:3.5e'C 85:4.3d
7d 86:5.3 99:4.5 73:8.6 91:3.3e 72:3.2
8d 65:3.3 77:2.4 100:4.1 72:2.2‘3'C 30:2.2d
9 76:4.2 79:4.7 90:5.2 79:2.89'c 73:3.8
10 31:5.0 89:5.2 87:10.5 86:3.4e 94:3.7d
11 71:4.2 77:3.1 89:6.6 77:2.59'C 93:3.5d
12 68:3.4 63:2.8 74:13.3 66:2.4b'C 72:3.0d
Ave. 73:1.3 82:1.4 83:3.2 78:0.9 84:1.2

 

within herd (p <

aCows open longer than 250 days excluded.

b

Mean : S.E.

cInsufficient numbers to calculate S.E.

dSignificant differences exist among treatments

.05).

eMeans with same letter are not different from each
other within years.

111

Table D-7.--Least squares analysis of variance for interval
to first insemination.

 

 

Variable D.F. M.S. F. Sign.
Treatments (TRT) 2 765.4 3.2 .04*
Season 3 46.1 0.2 .90
Herd Size 3 315.0 1.3 .27
TRT X Season 6 71.2 0.3 .94
TRT X Herd Size 6 256.8 1.1 .38
Season X Herd Size 9 227.2 0.9 .48
TRT X Season X Herd Size 16 253.7 1.1 .39
Herds/Herd Size 8 579.7 2.4 .01**
Interval First Estrus 1 5365.9 22.3 .0005***
Interval First Estrus2 1 1385.2 5.7 .02*

No. Heats 1 11156.2 46.5 .0005***
No. Heats2 1 8669.9 36.1 .0005***
Other 10

Error 768 239.9

Total 839

 

112

Table D-8.-—Least squares adjusted means for interval to
first insemination.

 

 

 

Codea Treatmentb Season Herd Size Herds/Herd Sizec'd
1 2 3 4
1 75.6 78.8 79.4 79.6 79.4 79.6 76.0
2 79.2 78.7 75.7 76.9 78.6 78.1 81.6
3 79.4 77.0 77.9 76.2 76.5 78.1
4 77.8 79.3 76.5

 

aCode for treatments (TRT) l=TRTl, 2=TRT2, 3=TRT

Code for seasons of calving 1=January-March, 2=
April-June, 3=July-September, 4=October-December.

Code for herd size 1=Sma11, 2=Medium, 3=Medium-
Large, 4=Large.

bSignificant differences within treatments (p <
.05).

cCodes for herds/herd size 1 (small)=herds 5, 9
2 (medium)=herds 2, 6, 12; 3 (medium-1arge)=herds 1,3,8
4 (large)=herds 4, 7, 10, ll.

0
I
.
I

dSignificant differences exist among herds/herd
size (p < .05).

3.

113

Table D-9.--Days between estrus and inseminations for all

cows by herds.a

 

Estrus Intervals

 

Insemination Intervals

 

 

 

 

 

Herd
1-2’3'd 2-3 3-4 1-2C'd 2-3 3-4 4-5 5-6
———————Days Days
1 41 20 -- 40 47 24 -- --
2 42 -- —— 43 35 33 36 23
3 29 20 -- 37 40 48 -- --
4 28 35 22 40 37 37 20 --
5 37 59 -- 47 42 44 —- --
6 32 24 24 54 36 32 20 22
7 52 34 20 43 38 26 33 35
8 28 29 22 33 33 41 27 22
9 39 24 -— 34 33 25 23 24
10 39 37 50 33 30 38 34 30
ll 29 28 31 40 42 42 -- --
12 32 31 25 25 29 34 45 22
Ave. 33 30 29 39 36 36 33 28
aCows open less than 250 days excluded.
bInterval between first and second estrus (days).
CInterval between first and second insemination
(days).

dSignificant differences exist among herds (p <

.05).

114

Table D-10.--Days from first estrus to first insemination

 

 

 

for cows in Treatments I, II, and III within
herds.a
Herd I II III Total
1 6 11 0 8
2 9 12 0 9
3 7 11 25 9
4 20 34 25 26
5 14 32 0 20
6 12 31 38 25
7 26 29 6 25
8 11 24 35 18
9 10 6 10 9
10 10 20 16 16
11 34 38 47 38
12 19 23 27 21
Ave. 17 23 24 20
aCows open longer than 250 days excluded average
in days.

bMean.

115

Table D-ll.-—Days to conception for cows within herds by
years and treatments.a

 

Year and Treatments

 

 

 

 

Herd
1973-74 1972
I II III Total Total
1d 78:4.9b 107:5.7 201:28.0 95:4.99'b 105:5.8
2 126:12.2 106:10.7 130:28.5 118:7.Be’b 114:8.2
3 86:7.0 104:8.3 82:C 95:5.5e'b 101:6.6
4 88:7.0 108:8.0 99:9.7 99:4.7e'b 133:8.0
5 100:11.8 101:14.6 87:22.9 99:8.3e'b 98:8.9
6 115:15.2 117:9.6 120:16.6 116:7.5‘9'b 90:5.2
7 119:8.0 112:6.7 130:22.8 121:5.2e 104:5.0
8 93:6.5 111:8.2 110:23.1 101:5.09'b 112:5.5
9 97:7.5 105:8.2 92:9.5 100:5.1e'b 95:8.2
10 117:9.9 101:5.5 129:15.7 111:5.49'b 130:5.3
11 90:9.4 90:6.1 109:10.8 94:4.9‘9'b 112:5.1
12 86:2.7 80:5.3 84:11.7 83:4.7b 103:8.8
Ave. 99:2.7 105:2.3 112:5.4 103:1.7 111:1.9

 

aCows open longer than 250 days excluded.
bMean : S.E.
cInsufficient numbers to calculate S.E.

dSignificant differences exist among treatments in
herd l (p < .05).

eMeans with same letter are not different from each
other within years (p < .05).

116

Table D-12.--Least squares analysis of variance for interval

to conception.

 

 

Variable D.F. M.S. F Sign.
Treatment (TRT) 2 1.68 0.269 .76
Season 3 4.07 0.653 .58
Herd Size 3 2.17 0.348 .79
Housing 1 0.44 0.070 .79
TRT X Herd Size 6 2.66 0.426 .86
TRT X Season 6 2.35 0.376 .89
TRT X Housing 2 3.71 0.594 .55
Season X Herd Size 8 4.24 0.680 .71
Season X Housing 3 6.00 0.961 .41
TRT X Season X Herd Size 16 5.31 0.851 .63
TRT X Season X Housing 6 3.89 0.623 .71
Interval to First
Insemination (IFI) 1 2160.45 346.016 .0005***
Interval from First
Insemination to
Conception (IFITC) 1 3692.00 591.309 .0005***
IFI X Number of Insemi—
nations 1 28.19 4.516 .03*
IFI X IFITC l 64.69 10.361 .001**
IFICT X Interval First
Estrus 1 27.49 4.404 .04*
IFITC X Number of Estrus
Periods 1 24.45 3.917 .05*
OTHER 29 6.24
ERROR 588
TOTAL 679

 

117

Table D-13.—-Least squares adjusted means for interval to

 

 

conception.
Codea Housing Treatment Herd Size Season
1 103.7 103.6 103.3 104.0
2 103.5 103.4 103.6 103.7
3 103.8 104.0 103.3
4 103.5 103.5

 

aCode for housing 1=free stalls, 2=stanchions.
Code for treatments (TRT) 1=TRT1, 2=TRT2, 3=TRT3.

Code for herd size 1=Sma11, 2=Medium, 3=Medium-
Large, 4=Large.

Code for season of calving 1=January-March, 2=
April-June, 3=Ju1y-September, 4=October-December.

118

Table D-14.--Days from first insemination to conception
for cows within herds by years and treatments.

 

Year and Treatments

 

 

 

Herd 1974-74 1972
I II III Total Total

1C 8:3.5b 18:5.8 140:15.0 17:4.3e 21:5.1
2C 59:12.2 25:7.8 8:8.4 40:7.2 29:7.5

3 13:6.0 21:6.7 o 16:4.4e 14:5.3

4 21:6.7 30:7.9 23:9.7 25:4.6e 47:7.5

5 40:13.3 31:12.3 30:30.3 36:8.9e 21:8.7

6 49:14.7 41:8.0 45:16.9 44:6.9e 5:4.6

7 37:8.1 25:5.6 57:19.8 34:5.0e 32:4.8

8 27:6.3 35:7.7 10:9.8 30:4.7e 32:5.2

9 18:6.8 22:8.1 6:5.8 19:4.8e 22:7.9
10 38:9.9 20:5.5 52:15.7 32:5.4e 36:5.3
11 20:7.3 14:5.7 21:11.1 17:4.3e 19:5.0
12 18:2.8 16:5.2 4:4.2 15:4.7e 31:8.3
Ave. 28:2.5 25:2.0 30:5.0 30:1.6 27:1.6

 

aCows open longer than 250 days excluded.
bMean : S.E.

cSignificant differences exist among treatments
within herd (p < .05).

dMeans with same letter are not significantly
different within years (p < .05).

119

Table D-15.--Least squares analyses of variance for interval
from first insemination to conception.

 

 

Variables D.F. M.S. F. Sign.
Treatment (TRT) 2 .96 .1481 .862
Season 3 1.87 .2901 .833
Herd Size 3 1.01 .1550 .926
Housing 1 .00 .000 .996
TRT X Herd Size 6 1.47 .2268 .968
TRT X Season 6 1.25 .1928 .979
TRT X Housing 2 1.88 .2896 .749
Season X Herd Size 8 3.22 .4950 .860
Season X Housing 3 2.94 .4514 .716
TRT X Season X Herd Size 16 4.82 .7406 .753
TRT X Season X Housing 6 2.83 .4345 .856
Interval to First
Insemination (IFI) 1 2745.25 422.1147 .0005***
IFIZ 1 49.47 7.6068 .006**
Interval to Conception 1 14381.96 2211.3949 .0005***
Interval to First
Estrus X Milk 1 25.74 3.9584 .047*
Interval to Conception
X Milk 1 27.19 4.1800 .041*
OTHER 22
ERROR 596

6.50

TOTAL 679

 

120

Table D-16.--Least squares adjusted means for interval
from first insemination to conception.

 

 

Codea Housing Treatments Herd Size Season
1 27.11 27.1 27.3 26.9
2 27.11 27.2 27.2 27.0
3 27.0 26.8 27.4
4 27.2 27.1

 

aCode for housing 1=Free stall, 2=Stanchion.
Code for treatments (TRT) 1=TRT1, 2=TRT2, 3=TRT3.

Code for herd size 1=Sma11, 2=Medium, 3=Medium-
Large, 4=Large.

Code for season of calving 1=January-March, 2=
April-June, 3=July-September, 4=October-December.

121

Table D-l7.-—Percent conception at the first through
fourth inseminations for cows within herds-—

 

 

 

1972.a
Herd Insemination Number
1 2 3 4
1 56b(19)C 100(14) _-d __
2 50(20) 50(10) 60(6) 75(3)
3 73(27) 60(16) 75(3) -—
4 39(18) 50(14) 14(2) 42(5)
5 60(18) 75(9) 100(3) --
6 75(25) 89(8) 100(1) --
7 48(34) 46(17) 50(10) 100(10)
8 45(30) 35(13) 58(14) 50(5)
9 63(20) 58(7) 60(3) 50(1)
10 49(44) 67(30) 80(12) 100(3)
11 66(40) 57(12) 67(6) 100(3)
12 57(21) 56(9) 14(1) 33(2)
Ave. 55(316) 57(149) 54(61) 63(32)

 

aCows Open longer than 250 days excluded (30 cows).
bPercent conceiving.
cNumber conceiving.

dData incomplete due to lost herd records.

122

Table D-18.--Percent conception at the first through
fourth inseminations cows within herds--

 

 

 

1973-74.a
Insemination Number
Herd
1 2 3 4
1 73b(49)C 61(11) 100(7) --
2 45(22) 59(16) 27(3) 50(4)
3 68(30) 71(10) 75(3) 100(1)
4 61(48) 55(17) 57(8) 100(6)
5 46(12) 57(8) 66(4) 100(2)
6 40(19) 61(17) 55(6) 80(4)
7 47(36) 63(26) 73(11) 25(1)
8 50(39) 49(19) 70(14) 83(5)
9 61(22) 57(8) 83(5) 0(0)
10 42(28) 66(25) 46(6) 42(3)
11 67(45) 68(15) 57(4) 100(3)
12 65(32) 58(10) 7(5) 50(1)
Ave. 56(382) 60(182) 63(76) 66(30)

 

aCows Open longer than 250 days excluded (15 cows).
b . .
Percent conceiVing.

c . .
Number conceiVing.

123

Table D-19.-—Inseminations per conception for cows within
herds by years and treatments.a

 

Herd

Year and Treatments

 

 

 

 

1973-74 1972
I II III Total Total

1 1.2:.08b 1.4:.13 3.0:? 1.4:.08e 1.4:.09b

2 2.6:.33 1.6:.19 1.2:.20 2.0:.19e 1.9:.17b

3 1.3:.14 1.5:.17 1.0:? 1.4:.11e 1.4:.14b

4 1.6:.18 1.8:.18 1.5:.19 1.6:.11e 2.4:.22b

5 1.8:.22 2.0:.42 1.7:.67 1.8:.19e 1.5:.11b

6 2.1:.36 2.0:.18 1.7:.29 2.0:.16e 1.3:.09e

7 2.0:.22 1.6:.11 2.0:.27 1.8:.12e 1.9:.13b

8 1.9:.17 1.9:.17 1.3:.25 1.8:.12e 2.2:.18b

9 1.6:.20 1.7:.27 1.3:.25 1.6:.16e 1.7:.21b

10d 2.1:.24 1.6:.15 2.7:.63 2.0:.16e 1.7:.09b

11 1.5:.17 1.4:.15 1.5:.22 1.5:.10e 1.5:.11b

12 1.6:.09 1.7:.21 1.2:.20 1.6:.16e 2.0:.26b
Ave. 1.8:.07 1.7:.05 1.7:.17 1.7:.04 1.8:.05

 

within herd (p <

aCows open longer than 250 days excluded.

b

Mean : S.E.

CInsufficient numbers to calculate standard error.

dSignificant differences exist among treatments

.05).

eMeans with same letter are not significantly
different within years.

124

Table D-20.--Least squares analysis of variance for
inseminations per conception.

 

 

Variable D.F. M.S. F. Sign.
Treatment (TRT) 2 .531 2.36 .09
Season 3 .404 1.79 .15
Herd Size 3 .492 2.19 .09
Housing 1 1.052 4.67 .03*
TRT X Herd Size 6 .443 1.97 .07
TRT X Season 6 .345 1.53 .16
TRT X Housing 2 .529 2.35 .10
Season X Herd Size 8 .270 1.20 .30
Season X Housing 3 .210 0.93 .42
TRT X Season X Herd Size 16 .166 0.74 .75
TRT X Season X Housing 6 .267 0.19 .31
Interval to Conception (ITC)

Interval to Conception 2 .663 2.95 .05*
Interval to First Insemination

(IFI) X Milk 1 .861 3.83 .05*
Interval From First Insemination

to Conception (IFITC) X Milk 1 .863 3.84 .05*
ITC X Milk 1 .864 3.84 .05*
IFITC X Age 1 .817 3.63 .06

ITC X Age 1 .817 3.63 .06

IFITC l .781 3.47 .06

IFI X Age 1 .786 3.49 .06

IFI X IFITC 1 .751 3.34 .07

No. Heats X Age 1 .720 3.20 .07

IFI 1 .722 3.21 .07

ITC 1 .710 3.16 .08

OTHER 23

ERROR 588 .2249

TOTAL 679

 

125

Table D-2l.—-Least squares adjusted means for inseminations
per conception.

 

 

Codea Housingb Treatments Herd Size Season
1 1.85 1.81 1.57 1.59
2 1.59 1.79 1.72 1.78
3 1.58 1.72 1.76
4 1.89 1.78

 

aCode for housing 1=Free stall, 2=Stanchion.
Code for treatments (TRT) 1=TRT1, 2=TRT2, 3=TRT3.

Code for herd size 1=Sma11, 2=Medium, 3=Medium-
Large, 4=Large.

Code for season of calving 1=January-March, 2=
April-June, 3=July-September, 4=October-December.

bSignificant effect (p < .05).

126

Table D-22.--Least squares analysis of variance for 150 day
milk yield.

 

 

Variable D.F. M.S. F. Sign.
Treatment (TRT) 2 8,036,310 4.51 .01**
Season 3 450,871 .25 .86
Herd Size 3 11,339,024 6.36 .0005***
TRT X Season 6 932,910 .52 .52
TRT X Herd Size 6 3,024,745 1.70 .12
Season X Herd Size 8 2,305,886 1.29 .24
TRT X Season X
Herds 16 4,387,599 2.46 .001**
Herds/Herd Size 8 26,952,971 15.11 .0005***
Age 1 180,545,401 101.24 .0005***
Age2 1 179,847,742 100.86 .0005***
OTHER 12
ERROR 613 1,783,227
TOTAL 679

 

 

.1—1.

127

Table D-23.--Least squares adjusted means for 150 day milk yield.

 

 

 

Codea Treatmentb Season Herd Sizec Herds/Herd Sized'e
1 2 3 4
8,489f 8,243 8,156 8,538 8,510 8,524 7,560
8,296 8,169 8,723 7,810 7,910 9,011 7,942
7,737 8,066 7,694 8,102 6,987 8,185
8,218 8,123 9,009

 

aCode for treatments (TRT) 1=TRT1, 2=TRT2, 3=TRT3.

Code for season of calving 1=January—March, 2=Apri1—June, 3=
July-September, 4=October-December.

Code for herd size 1=Sma11, 2=Medium, 3=Medium-Large, 4=Large.
bSignificant differences among treatments (p < .01).
cSignificant differences among herd size (p < .0005).

dCode for herds/herd size 1 (small)=herds 5,9; 2 (medium):

herds 2,6, 12; 3 (medium-large)=herds 1,3,8; 4 (large)=herds 4,7, 10,
ll.

eSignificant differences among herds/herd size (p < .0005).

fPounds.

BIBLIOGRAPHY

BIBLIOGRAPHY

Armstrong, D. V. 1964. Breeding Efficiency in a Southern
California Dairy Herd. M.S. Thesis. Michigan
State University, East Lansing, Michigan.

Ayalon, N., H. H. Harrari, I. Lewis, L. N. Posener, and Y.
Cohen. 1971. Relation of the Calving-to—Service
Interval to Fertility in Dairy Cows with Different
Reproductive Histories, Production Levels and
Management Practices. Refuah. Veterinarith. 28:
155-165.

Boyd, L. J. 1970. Managing Diary Cattle for Fertility.
J. Dairy Sci. 53: 969-972.

Boyd, L. J., D. M. Seath, and D. Olds. 1954. Relationship
Between Level of Milk Production and Breeding
Efficiency in Dairy Cattle. J. Anim. Sci. 13: 89—93.

Bozworth, R. W., G. Ward, E. P. Call, and E. R. Bonewitz.
1972. Analysis of Factors Affecting Calving
Intervals of Dairy Cows. J. Dairy Sci. 55: 334-337.

Britt, J. H. 1975. Early Postpartum Breeding in Dairy
Cows: A Review. J. Dairy Sci. 58: 266-271.

Britt, J. H., and L. C. Ulberg. 1970. Changes in Repro—
dutive Performance in Dairy Herds Using the Herd
Reproductive Status System. J. Dairy Sci. 53:
752-756.

Buch, N. C., W. J. Tyler, and L. E. Casida. 1955. Post-
partum Estrus and Involution of the Uterus in an
Experimental Herd of Holstein-Friesian Cows. J.
Dairy Sci. 38: 73-79.

Carman, G. M. 1955. Interrelations of Milk Production

and Breeding Efficiency in Dairy Cows. J. Anim.
Sci. 14: 753-759.

COOper, T. 1966. Analysis of Sources of Variation in

Calving Intervals of Dairy Cattle. Dissertation.
University of Kentucky, Lexington, Kentucky.

128

129

Erb, R. E., and M. H. Ehlers. 1957. Fertility Rates Among
Normal and Abnormal Cows Bred Following Estrus
Cycles of Various Lengths. J. Dairy Sci. 35: 224.

Erb, R. E., J. W. Wilbur, and J. H. Hilton. 1940. Some
Factors Affecting Breeding Efficiency in Dairy
Cattle. J. Dairy Sci. 23: 549 (abstr.).

Erickson, R. E. 1972. An Analysis of High and Average
Milk Production Dairy Farms. Ph.D. Thesis.
Michigan State University, East Lansing, Michigan.

Everett, R. E., D. V. Armstrong, and L. J. Boyd. 1966.
Genetic Relationship Between Production and
Breeding Efficiency. J. Dairy Sci. 49: 879—886.

Foley, R. C., D. L. Bath, F. N. Dickinson, and H. A. Tucker.
1972. Dairy Cattle: Principles, Practices,
Problems, Profits. Lea and Febiger, Philadelphia.

 

Fuquay, J., A. H. Rakes, L.'C. Ulberg, and D. G. Davenport.
1966. Effect of High Levels of Energy Intake
During Early Lactation on the Reproductive Per-
formance of Dairy Cows. J. Dairy Sci. 49: 447
(abstr.).

Gaines, W. L. 1927. Milk Yield in Relation to Reoccurrence
of Conception. J. Dairy Sci. 10: 117.

Gill, J. L. 1975. Notes for Statistics 423; page 136.

Gwazdauskas, F. C., C. J. Wilcox, and W. W. Thatcher.
1975. Environmental and Managemental Factors
Affecting Conception Rate in a Subtropical Climate.
J. Dairy Sci. 58: 88-92.

Hafs, H. D., L. J. Boyd, and W. D. Oxender. 1973. Ferti-
lity and Sterility. Hoard's Dairyman, Fort
Atkinson, Wisconsin.

 

Hall, J. G., C. Branton, and E. J. Stone. 1959. Estrus,
Estrous Cycles, Ovulation Time, Time of Service and
Fertility of Dairy Cattle in Louisiana. J. Dairy
Sci. 42: 1086-1093.

Hasherut A. I. Center Annual Report. 1971—72. Beitdagan,
Israel.

Hignett, S. L. 1960. The Influence of Nutrition on
Female Fertility in Some Large Domestic Animals.
Proc. Nutrition Soc. 19: 8-15.

130

Hofstad, M. S. 1941. A Study of Breeding Records of One
Large Herd of Dairy Cattle. Cornell Vet. 31:
379-381.

Hurnik, J. F., G. J. King, and H. A. Robertson. 1974.
Estrus and Related Behavior in Postpartum Cows.
J. Anim. Sci. 39: 968 (abstr.).

Kjome, D. J. 1975. Herd Health Problems Affected by Dry
Cow Management on Southern Michigan Dairy Farms.
M.S. Thesis. Michigan State University, East
Lansing, Michigan

Lamb, R. C., C. H. Mickelson, and L. L. Perkes. 1965.
Influence of Sire and Ration on Reproductive Per-
formance of Dairy Cows. J. Dairy Sci. 48: 823
(abstr.).

Lassiter, C. A., and D. M. Seath. 1955. Dairy Calf Losses
in the Kentucky Agricultural Experiment Station
Herd. Kentucky Agric. Expt. Sta. Bull. 622.

Legates, J. E. 1954. Genetic Variation in Services Per
Conception and Calving Interval in Dairy Cattle.
J. Anim. Sci. 13: 81-88.

Louca, A., and J. E. Legates. 1968. Production Losses in
Dairy Cattle Due to Days Open. J. Dairy Sci. 51:
573-583.

Marion, G. B., and H. T. Gier. 1968. Factors Affecting
Bovine Ovarian Activity After Parturition. J.
Anim. Sci. 27: 1621—1626.

Morrow, D. A., S. J. Roberts, K. McEntee, and H. G. Grey.
1966. Postpartum Ovarian Activity and Uterine
Involution in Dairy Cattle. J. Amer. Vet. Med.
Assoc. 149: 1590.

Milk Marketing Board. 1968-69. Report of Breeding and
Production Organisation. 19: 120-122.

Miller, P., L. D. VanVleck, and L. R. Henderson. 1967.
Relationships Among Herd Life, Milk Production,
and Calving Interval. J. Dairy Sci. 50: 1283-1287.

Norman, H. D., and H. W. Thoele. 1967. Effects of Calving
Interval Upon 305-Day Milk and Fat Production. J.
Dairy Sci. 50: 975 (abstr.).

Olds, D. 1969. An Objective Consideration of Dairy Herd
Fertility. J. Amer. Vet. Med. Assoc. 154: 253—260.

131

Olds, D., and T. Cooper. 1970. Effect of Postpartum Rest
Period in Dairy Cattle on the Occurrence of Breeding
Abnormalities and on Calving Interval. J. Amer.
Vet. Med. Assoc. 157: 92-97.

Olds, D., T. C00per, and O. W. Deaton. 1966. Sources of
Variation Affecting Delayed Returns to Service.
J. Dairy Sci. 49: 726-727 (abstr.).

Olds, D., and O. W. Deaton. 1968. Effect of Herd Size on
Fertility and Delayed Returns. Kentucky Anim. Sci.
Research Report 176. University of Kentucky,
Lexington.

Olds, D., and D. M. Seath. 1965. Evaluation of Time to
Breed Cows After Calving. J. Dairy Sci. 41: 841
(abstr.).

Pelissier, C. L. 1970. Factors Contributing to Low
Breeding Efficiency in Dairy Herds. J. Dairy Sci.
53: 684 (abstr.).

Pelissier, C. L. 1972. Herd Breeding Problems and Their
Consequences. J. Dairy Sci. 55: 385-391.

Reid, J. T., J. K. Loosli, K. L. Turk, G. W. Trimberger,
S. A. Adell, and S. E. Smith. 1957. Effect of
Nutrition During Early Life Upon the Performance
of Dairy Cows. Proc. Cornell Nutrition Conf. Feed
Manufacturers.

Salisbury, G. W., and N. L. VanDemark. 1961. Physiology
of Reproduction and Artificial Insemination of
Cattle. W. H. Freeman and Co., San Francisco.

 

Saiduddin, S., J. W. Riesen, W. J. Tyler, and L. E. Casida.
1968. Relation of Postpartum Interval to Pituitary
Gonadotropins, Ovarian Follicular Development and
Fertility in Dairy Cows. Research Bull. 270.

Coll. of Agricultural and Life Sciences, University
of Wisconsin: 15-22.

Sanders, H. G. 1927. The Variation in Milk Yields Caused
by Season of the Year, Service, Age, and Dry Period
and Their Elimination. Part II. Service. J.
Agr. Sci. 17: 502.

Spalding, R. W., R. W. Everett, and R. H. Foote. 1975.
Fertility in New York Artificially Inseminated
Holstein Herds in Dairy Herd Improvement. J. Dairy
Sci. 58: 718-723.

132

Speicher, J. A., and C. E. Meadows. 1967. Milk Production
and Costs Associated with Length of Calving Interval
For Holstein Cows. J. Dairy Sci. 50: 975 (abstr.).

Spike, P. L. 1973. Calving Interval Trends in Michigan
Dairy Herds. M.S. Thesis. Department of Dairy
Science, Michigan State University, East Lansing,
Michigan.

Stott, G. H. 1961. Female and Breed Associated with
Seasonal Fertility Variation in Dairy Cattle. J.
Dairy Sci. 44: 1698-1704.

Tanabe, T., and G. W. Salisbury. 1946. The Influence of
Age on Breeding Efficiency of Dairy Cattle in
Artificial Insemination. J. Dairy Sci. 29: 337-344.

Thatcher, W. W., and C. J. Wilcox. 1973. Postpartum
Estrus as an Indicator of Reproductive Status in
the Dairy Cow. J. Dairy Sci. 56: 608—610.

Trimberger, G. W. 1954. Conception Rates in Dairy Cattle
From Services at Various Intervals After Parturition.
J. Dairy Sci. 37: 1042-1049.

Vandemark, N. L., and G. W. Salisbury. 1950. The Relation
of the Postpartum Breeding Interval to Reproductive
Efficiency in the Dairy Cow. J. Anim. Sci. 9:
307-313.

Whitmore, H. L., W. J. Tyler, and L. E. Casida. 1974.
Effects of Early Postpartum Breeding in Dairy
Cattle. J. Anim. Sci. 38: 339-346.

Wisconsin Research Bulletin 270. 1968. Studies on the
Postpartum Cow. Research Division, College of
Agricultural and Life Sciences, University of
Wisconsin, Madison.

Zemjanis, R., M. L. Fahning, and R. H. Schultz. 1969.
Anestrus the Practitioner's Dilemma. Vet. Scope
14: 15.

"17'1'3111111 (31011117 ITS