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This is to certify that the

thesis entitled

MUSCLE GROWTH AND MATURITY PARAMETERS
OF BOARS AND BARRONS

presented by

Bradley K. Knudson

has been accepted towards fulfillment
of the requirements for

 

 

Master's degree in Animal Science

    

Major professor

Date ’7 3"

0-7539 MS U is an Affirmative Action/Equal Opportunity Institution

 

 

 

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tonsil USE 0i:

 

 

 

MJSCLE GROWTH AND MATURITY PARAMETERS
OF BOARS AND BARROWS

By

Bradley Karl Knudson

A Thesis
Suhnitted to the Deparflnent of Anhnal Science
and to the Graduate School of
Nfichigan State University in Partial Fulfilhnent

of the Requiranents for the Degree of

Nhster of Science
Michigan State University

East Lansing, Michigan

May, 1983

A3 7‘ c.9577

ABSTRACT

Muscle Growth and Maturity Parameters
of

Boars and Barrows

By

Bradley Karl Knudson

The objectives of this study were to evaluate the whole
body canposition, bone and inuscle Inaturity differences
between boars and barrows. Treaflnents consisted of sex and
end weights of (l) barrow to 105 kg, (2) boar to 105 kg, (3)
boar to 118 kg, (0) boar to 132 kg and (5) boar to 105 kg.
Boars at 105 kg had 45% less backfat, were 2.9% longer and
had shnilar longisshnus area as barrows of sinfllar weight.
At the sane backfat thickness boars were greater than 41.0
kg heavier than barrows. The ratio for total weight to
total length of the tibia was greater in the boars (105 kg)
than barrows. There was no differences in growth rate
between boars and barrows to 105 kg. Boats achieved their
inaxhnun daily gain at a weight 24 kg heavier than the weight

barrows reachedlnaxhnwn daily gain.

WENEMENI’S

A sincere appretiation is extended to Dr. Maynard
Hogberg for his patience and guidance in expanding the
knowledge of this farm boy from Minnesota, into the scope
necessary to be a scientist. The encouraganent I received
from Dr. Maynard Hogberg, his faith in me as a student and
the many hours he has contributed towards my graduate study
and this manuscript are greatly appreciated.

I am also indebted to Dr. R. A. Merkel for his
friendship, wisdom and direction during my research project
and his critical reading of this manuscript.

To Dr. W. T. Magee I am greatful for his continual
patience and assistance in computer progranming and
interpretation of statistical analysis.

The friendship of Dr. Dave Ellis and the added dimension
he has contributed to my graduate study will always be
remembered.

To Dr. R. H. Nelson I express my gratitude for the use of
the facilities and the financial support that have allowed
me to advance my education.

A special thank you is extended to Mrs. Janet Mulvaney
for her persistance in typing this manuscript.

To Don R. Mulvaney for his friendship and continual
assistance throughout my graduate study, I extend my deepest
gratitude.

Thanks are due to Mrs. Dora Spooner for her support in
the laboratory, to Mr. Bruce Carrothers and his staff for
their cooperation in carrying for the experimental animals
animals and to Mr. Tom Forton for his many hours of
assistance at slaughter time.

To Ms. Jane E. Hensing I am forever thankful for the
moral support and assistance given towards the completion of
this work.

To my parents I dedicate this manuscript for all the

encouragement and support I have received throughout the
years.

ii

TABLE OF CONTENTS

List of Tables . . . . . . . . . .

List of Figures . . . . . . . . . . .
Introduction - . . . . . . . . . . .
Literature Review . . . . . . . . . . .

Definition of Growth . . .
thhods of Studying Growth
Whole Body Growth . . . .
Develownental Patterns . .
Bone, Muscle and Fat Developme
Postnatal Muscle Growth . .

t

o o o e o a o o o 0

Bone Growth . . . . . . .
)1 Boar and Barrow Comparisons . . .
/< Growth Rate . . . . . . .

k Composition . . . . . . .

Experimental Procedures . . . . . . . . . .

Experunental Design . . . . .
Slaughter Procedure and Sanple Collection
Preparation of Frozen Muscle Sample . . .
Analysis of Muscle Samples
Analysis for Nuclei Density
Bone Measurements . . . .
Statistical Analysis . . .

Results and Discussion . . . . . . . .

Live Body weight . . . . . . . . .
*Carcass Measurements . . . . . . . .
Muscle Chemical Composition . .
Muscle Nucleic Acid Measurements .
Carcass Composition Data . . . . . . . .
Tibia and Radius Data . . . . . .
7k Growth Rate of Boars and Barrows

Sunmary

iii

Page
iii

iv

Page

Appendix A. Breeding Records and Diets . . . . . . . 30
Appendix B. Laboratory Procedures and Reagents . . 32
Appendix C. Nuclei in Myofiber . . . . . . . . . . . 92
Appendix D. Bone Measurements . . . . . . . . . . . . 94
Appendix E. Equations to Graph Figures . . . . . . . 100
Bibliography . . . . . . . . . . . . . . . . 101

iv

LIST OF TABLES

Table: Page
1. Average Final Live Weight and Dressing Percentage

of Each Group . . . . . . . . . . . . . . . . 37
2. Mean Carcass Measurements of Each Group . . . . . . 33
3. Mean Brachialis Muscle Weight, Fat Free Muscle

10.

ll.

12.

13.

Weight Total Fat, Percentage Moisture, Protein,
Fat and Fiber Diameter by Group . . . . . . . . . . 42

Mean Semitendinosus Muscle Weight, Fat Free Muscle
Weight, Total Fat, Percentage Moisture, Protein, Fat
and Fiber Diameter by Group . . . . . . . . . . . . 43

Mean Longissimus Muscle Weight, Fat Free Muscle Weight,
Total Fat, Percentage Moisture, Protein, Fat and Fiber

Diameter by Group . . . . . . . . . . . . . . . . 44
Mean Brachialis Nucleic Acids and Muscle Weight by

Group D O O O O I O O O I O I O I O O 51
Mean Semitendinosus Nucleic Acids and Muscle

weight by Group C O O O O O O O O O O O O O O O 52

Mean Longissimus Nucleic Acids and Muscle Weight
by Group . . . . . . . . . . . . . . . . 53

Carcass Composition of Fat Free Muscle, Fat, Bone
and the Ratio of Fat Free Muscle to Bone for Groups
I, II, III, Iv and v O O O O O O O O O O O O I O O 57

Mean Percentage Bone and Skin on the Carcasses of
Groups I, II, III, IV and V . . . . . . . . . . . . 62

Mean Soft Tissue Weight, Percentage Moisture, Fat
and Protein in the Carcasses of Groups I, II, III,
Iv and v 0 O O O O O O O O O O O I I O I 63

Effect of Sex and Live weight change In Boars on
Tibia Bone Measurements . . . . . . . . . . . . . . 69

Effect of Sex and Live weight Change In Boars on
Radius Bone Measurements . . . . . . . . . . . . . 70

LIST OF FIGURES

Figure:

I. The Carcass Measurements of Boars From 105 to
145 kg, Live Weight . . . . . . . . . . . . . . .

II. The Fat Free Muscle Weight Increase of The
Brachialis, Sanitendinosus and Longisshnus
Muscles In Boars From 105 to 145 kg, Live Weight

111. Average Carcass Composition of the 105 kg
Boars and 105 kg Barrows . . . . . . . . . . . .

IV. Total Fat Free Muscle, Total Fat and Total Bone
In Boars Fran 105 to 145 kg, Live‘Weight . . . .

V. Total Weight, Ratio of Weight to Length and Total
Length of the Tibia . . . . . . . . . . . . . . .

VI. Total Weight, Ratio of Weight to Length and Total
Length of the Radius . . . . . . . . . . . . . .

, -—'--~.~\

1;¢,VII. The Average Daily Gain of Boars and Barrows Fran
7 5 to 29 weeks Of Age 0 O I O O O O O O O I O O O

lfi“VIII. Growth Curves of Barrows and Boars . . . . . . .

vi

Page

41

58

60

64

65

72

74

INTRODUCTION

"The animal breeder requires of the comparative
anatomist not onlya descriptive statement of what has been
done in evolution, but also an indication of how he can best
produce the form he requires; it is clear that it is in
experimental anatomy or the physiology of anatomy that the
solution of these problems will be found. Just as the
sciences of chemistry and botany have formed the basis of
advancement in soils and crop husbandry respectively, so the
science of physiology should form the basis of animal
husbandry in the future. Farm animal physiology has as its
objective the obtaining of control over the functions of the-
animal body in order to increase the efficiency in the
output of eggs, offspring,imilk, meat and wool and to
maintain good health throughout a long life-time of high
production." These statements by John Harrmond (Harrmond
I932, 1954) recorded more than fifty years ago suggest that
research in animal physiology would become essential for
increasing the efficiency of animal production. This
concept has been adopted by scientists and the research
achievements have continued in achieving a more complete
understanding of the physiological control mechanisms, as
well as using this knowledge to improve the efficiency of

animal production.

The swine industry has adopted genetic principles in
perfonnance testing prograns to select boars with the
genetic ability to sire barrows that will grow efficiently
to a desiredtnarket weight.

The National Swine Inmrovanent Federation (1981)
recommendation to test seedstock to 105 kg is based on the
belief that the physylogical growth of boars and barrows is
shnilar. Current research data, however shows that growth
and body canposition differences do exist between boars and
barrows raised to a cannon weight. Kuhlers et a1. (1976)
reported that boars had .06 on less backfat than barrows at
68 kg and .12 on less backfat at 136 kg. They concluded that
to predict the fat depth of barrows at any given weight,
boars should be nwasured at a weight 22.7 kg heavier than
barrows. Hines (1966) found no significant differences in
the growth rate between boars and barrows carried to shnilar
weights. However, average backfat thickness and percentage
primal cuts did vary. This would‘indiate that a maturity
differencelnay exist between boars and barrows when canpared
at shnilar weights.

The research study reported in this Inanuscript ‘was
designed to uneasure the growth, canposition and rnuscle
Inaturity differences between boars and barrows. 'The purpose
of obtaining these quantitative nwasures was to accurately
determine at which weight the swine industry should test
boars, to attain maximun growth and leanness of a 105 kg

barrow.

LITERATURE REVIEW

Definition of Growth

The growth phenomenon is one of the primary factors of
animal agriculture and a detailed understanding of muscle,
fat and bone development during postnatal growth is
essential for improving the efficiency of livestock
production.

Reviewing the past definitions of postnatal growth will
allow a general overview of this area and aid in allowing
the complexities to remain in focus. Pomeroy (1955)
discussed the definition by Schloss (1911) who defined
growth as a "correlated increase in mass of the body in
definite intervals of time in a way characteristic of the
species." Pomeroy (1955) pointed out that this definition
indicates "that growth in weight of an organism is a
function of the species, subject to individual variation."
The definition does not, however take into consideration
that an increase in body mass that is characteristic of a
species is dependent on an optimal level of nutrition
(Palsson, 1955). The increase in weight until mature size
is reached is growth. Development is the change in body
conformation and shape during which various functions and
faculties cane into full being (Hamnond, 1940). The

increase in weight catagorized as growth is a complex and

highly integrated process, that may be referred to as the
production of new biochemical units through metabolic and
biological synthesis. In quantitative terms, growth is the
increase in living substance and includes one or more of the
following three processes: cell multiplication, cell
enlargement or incorporation of material taken fran the
envirorment (Brody 1945).

Reviewing these concepts allows the realization that
growth in the biological sense is more than simply an
increase is size. In a living organism, growth is a canplex
differentiated increase in cell nunber and cell size, and
may be altered genetically and (or) nutritionally.

Methods of Studying Growth

The direction taken to study postnatal growth of animals
is generally divided into three separate areas. The first
area considered, is the increase of body mass in time.
usually described on a whole body basis by the live weight
growth curve (Fowler 1968). The construction of live weight
growth curves are used extensively for comparative species
study and to construct mathematical models of growth
prediction (Brody 1945).

The second category that is studied pertains to the
change in the form of the animal resulting from differences
in the relative growth rates of the component parts of the
body (Fowler 1968). This area of growth requires a

comprehensive anatomical dissection of experimental animal

carcasses into bone, fat and Inuscle to provide the
docunented work necessary. Canplete carcass dissection work
was utilized in sheep (Hannond 1932) and carried out in pigs
(McMeekan 1940 a, b, c). Due to the time consuning,
laborous and painstaking work of this procedure, continual
effort has led to experhnents exploring the possibility of a
procedure that would provide canposition data, but would not
be as time oonsuning as the entire carcass dissection
technique. Hankins and Ellis (1934),' established the
reality of a high correlation betweenlnean backfat thickness
and the chanically detennined anount of fat in the carcass.
This concept was further studied by Hazel and Kline (1952),
‘who found the average of four backfatrneasuranents supported
a .81 correlation with percentage carcass fat. They also
developed the steel backfat probe that is still widely used
throughout the swine industry for nmasuring backfat
thickness. In a different type of approach to detennine the
amount of body fat Brown et a1. (1951), Whiteman et a1.
(1953), Pearson et al. (1956) and Morris and Moir (1964)
found that specific gravity wasrnore accurate in detennining
body fat than backfat thickness. Pearson et a1. (1956)
concluded that the specific gravity technique should be
regarded as a useful, although not a necessarily precise
[nethod for estimating carcass canposition. Aunan and
'Winters (1952) developed a core technique to detennine

carcass composition. They removed a core sample between the

fifth and sixth rib of the carcass and found a correlation
of .79 between the fat to lean ratio in the core, and the fat
to lean ratio in the carcass. After removing the ham from
the carcass Smith et al. (1957) separated out the fat and
observed a correlation of .89 between the percentage
defatted han and the percentage lean cuts in the carcasses
of 300 barrows.

There have been nunerous attempts to develop a technique
that would similate the accuracy of the total body
dissection technique utilized by John Harrmond (1932). No
other technique has provided a more thorough procedure to
record the different components of body composition than the
total carcass dissection.

The third and final area studied as a component of
growth is at the cellular level. Leblond (1972) proposed
three different postnatal cellular growth patterns and a
fourth one for muscle. Robinson (1969) has found an
increase in the amount of nucleic acids as a function of
postnatal growth in myotubes. In studying adipose tissue
growth in young pigs, Anderson and Kauffman (1973) have
reported the increase in adipose tissue mass up to 2 months
was primarily due to an increase in adipose cell nunber.
Fran 2 to 5 months the increase was due to hyperplasia and
hypertrophy however, after 5 months there was continual cell

enlargement but no significant increase in cell nunber.

Working with growing bone Owen, Triffitt and Melick (1973)
have observed the formation of new bone by osteoblasts
differentiating into osteocytes.

Whole Body Growth .

Under nonnal circunstances a signoidal curve is produced
when growth of body weight is plotted against tune. This
relationship of postnatal growth is found to be consistent
across species, with only a variation in thne (Brody 1945).
The first phase of the sigmoidal curve begins with the
growth after parturition, and is described as a slow
accelerating growth. This phase is followed by a rapid
growth phase during which puberty occurs. The rapid growth
phase eventually reaches alnaxhnun rate and then levels off
at mature weight. Mature weight is maintained with only a
slight decrease over time under normal circunstances. Most
studies with pigs occur during the period of rapid growth.
Clausen (1953) reported that rapid growth occurs to the peak
‘weight of 70 to 80 kg, Doornenbal (1972) referenced work by
Oslage and Fliegal (1965) that showed from studying the
modern pig (barrows and gilts of Improved German Landrace
breeding) that the entire interval fran weaning to 130 kg
Inust be regarded as a period of intense growth. Davey and
Morgan (1969) and Doornenbal (1972) have also reported that
rapid linear growth occurred in swine until 40 wk which

represents 130 to 150 kg. The economic importance of rapid

growth is clear, due to the high relationship between rapid

gains and efficient feed utilization of relatively lean pigs
(Oslage and Fliegal, 1965).
Develoanental Patterns

The postnatal develoanent of the differentiated tissues
fran the prenatal blastocyte, in swine and other anhnals,
matures in the well known order of nervous tissue, bone,
Inuscle and fat (Palsson 1955). Huxley (1932) first studied
the differentiation of the various tissue canponents to
whole body growth using the following equation, Y = aXb.
Through the use of this equation Huxley was able to predict
the weight of an organ or tissue within a species knowing
virtually only body weight. The logarithnic conversion of
this equation has been used to detennine growth coefficients
to canpare the relative growth rates of carcass canponents
(Tulloh 1964; Elsley et a1. 1964; Davies (1974a) and
specificrnuscles and bones (Davies (1974b; Richnond and Berg
1982a; Richmond et al. 1979). With the logarithmic equation
Elsley et al. (1964) calculated growth coefficients from
data by McMeekan (1940 a, b, c) and Palsson and Verges
(1952). Elsley et a1. (1964) reported, fran these
calculations, that body growth followed a developmental
pattern of the head and necklnaturing first, the forelimb,
hindlhnb and the thorax being intennediate in develoanent
and the pelvis and loin maturing last. The cranial to
caudal and proximal to distal development, with hindlimb

deveIOping later than forelimb and the lunbar area as the

latest developing is widely supported for nmscle and bone
growth (McMeekan, 1940 a, b; Davies, 1974b; Richmond et al.,
1979; Riclmond and Berg, 1982a). Muscle differentiation of
swine is postulated (Davies, 1974b; Richmond and Berg,
1982a) to occur at a relative high hnpetus early in life for
Inuscles essential for basic function of locanotion, while
the muscles responsible for greater propulsion and body
stability develop later in life. The early differentiation
was found to occur before 23 kg live weight by Richnond and
Berg (1971c).

Comparing muscle development by breed of swine, Davies
(1974b) reported a significant increase in Inuscle
development in the hindlimb and spinal regions, but less
developnent in the forelhnb and neck in the Pietrain
canpared to the Large White. Experhnental use of Huxleys'
allanentric equation also indicated that the Pietrain was
more mature in muscle development than the Large White, at
sinfilar body weights (Davies (1974b). These findings
indicate that a intraspecies difference exists in muscle
developnent between the Pietrain and Large White.

Classifying the developmental differences of certain
Inuscles in swine, with growth coeffients, Richnond and Berg
(1982a) reported that the brachialis was less than 1 and the
longisshnus and sanitendinosusrnuscles were greater than 1.
Davies (1974b) who worked with the Pietrain and Large White

disagrees with these findings, and reported a growth

10

coefficient for the sanitendinosus equal to 1. Butterfield
and Berg (1966) working with cattle found a growth
coefficient for the semitendinosus significantly greater
than 1 early in life, but not different from 1 in later
phases of growth. Mulvaney (1981) reported that in swine
there was a greater impetus for growth in the longissimus at
45 kg than at 22 kg live weight and the semintendinosus and
brachialis had less impetus for growth at 45 kg than at 22 kg
live weight. Richmond and Berg (1971c) found that
differential growth of a certain muscle was also influenced
by the sex, reporting that barrows muscle growth
differentiation is more prolonged than in gilts.
BoneJ Muscle and Fat Development

In addition to anatomical location, developmental
differences also occur in the growth rate of the major
tissues of the animal body, i.e. bone, muscle and fat. The
greatest proportion of bone growth occurs earlier
postnatally than either muscle or fat. Fat continues to
increase in mass longer throughout body growth than muscle.
This pattern was not only demonstrated in swine (McMeekan,
1940a; Cuthbertson and Pomeroy, 1962; Cole et al., 1976) but
has also been shown in sheep (Hanmond, 1932; Palssonland
Verges, 1952) and cattle (Berg and Butterfield, 1976).

Throughout the rapid growth period the impetus of bone
growth is maintained at a steady state (McMeekan, 1940a;

Berg and Butterfield, 1976). Differential growth of an

11

individual bone occurs in the order of length followed by
thickening UMdMeekan, 1940a; Cuthbertson and Paneroy, 1962).
The growth of a singlelnuscle develops in a pattern shn-
ilar to bone by first lengthening and then thickening
(McMeekan, 1940a). '
During the rapid growth period the rate oflnuscle growth
exceeds fat deposition. Near the end of this periodlnuscle
grows at a slower rate and the incorporation of
triglycerides into adipose tissue increases to a rate that
is greater than muscle growth. Relative to live body
weight, the intercept of fat deposition andlnuscle accretion
has met with disagreement among researchers. Harrmond (1933)
reported the intercept of fat and lean occurred at 80 kg
live weight in the British bacon pig; Clausen (1953) found
the intercept to occur at 95 kg for ‘Danish Landrace.
Doornenbal (1972) reviewed work by Oslage and Fliegal (1965)
that observed with the Improved German Landrace that the
ratio of protein to fat does not change fran 90 kg to 120 kg
live weight. These findings are supported by Witte and
Stringer (1969) and Doornenbal (1972). McMeekan (1940a) in
a canprehensive study reported thatlnuscle exceeds fat to 24
wk in swine and fran then on fat is deposited at a greater
rate. In studying bone growth McMeekan (1940a) found that
there is a greater quantity of bone thanrnuscle and fat fran

birth to 4 wk, in swine.

12

It is widely accepted that as body weight increases
percentage carcass yield and fat increase, percentage
carcass protein and bone decrease and percent carcaSSInuscle
increases to a point and then decreases (McMeekan, 1940a;
Buck, 1962; Stant et al., 1968; Richnond and Berg, 1971a;
Doornenbal; 1971). McMeekan (19403) has reported that at
birth the pig carcass consisted of 30%muscle and 5% fat. As
live weight increased from 52 to 100 kg carcass muscle
decreased from 44 to 39% and fat increased fran 32 to 43%,
respectively» ‘Weiss et al. (1971) in swine observed carcass
bone to decrease fran 32 to 15% as body weight increased
fran 1 to 137 kg. Buck (1962) studied percentage lean in
barrows and gilts from 68 to 118 kg and found that the
percentage lean increased less fran 91 to 118 kg than fran
68 to 91 kg live weight. At 91 kg live weight, pigs have sex
of the muscle and 66% of the fat present at 114 kg live
weight (Richnond and Berg, 1971a). In swine as live body
weight increases the carcass uneasuranents of backfat
thickness, longisshnus Inuscle area and length increase
prbportionally (Wallace et al., (1959; Usborne et al., 1968;
Meeker, 1973). Buck (1962) and Usborne et a1. (1968)
reported that as live weight increases daily gain also
increases and the efficiency of feed conversion decreases.

Muscle to bone ratios have been shown to be similar at
birth for sheep, cattle and hogs, and also at the adult

stage (Tulloh, 1964). This suggests that between species,

13

maturity may have a greater effect on the muscle to bone
ratio than body size. Berg and Butterfield (1976) stated
that the growth pattern of bone occurs at a steady, but slow
rate, while muscle grows relatively fast. Therefore, the
ratio of nmscle to bone increases with an increase in body
weight. Edwards et al. (1980) observed a range oflnuscle to
bone ratios in swine fran 2.89 to 5.49, and found that the
leaner carcasses had significantly larger muscle to bone
ratio. I

The sequence of adipocyte developnent in the different
fat depots of redtneat anhnals, fran early to late growth,
is reported to occur in the order of perirenal,
subcutaneous, intermuscular and intramuscular by Lee and
Kaufflnan (1974). Richnond and Berg (1971b) indicated that
fat and lean hog carcasses have the same proportion of
subcutaneous, intennuscular and perirenal fat. Over a two
week period Mulvaney (1981) found a significant increase in
the anount of intranuscular fat in the longisshnus and the
sanitendinosusnnuscles of pigs as early as 45 kg live body
weight. Noffsinger et a1. (1959) has observed that in swine
the thickness of backfat is greater over the shoulder than
the loin.

In a comprehensive review Hamnond (1932) showed that the
plane of nutrition had a profound effect on the anount of
fat in the body. The classical work carried out bylMdMeekan

(1940 a, b) danonstrated the effect of nutrition on growth,

14

by growing inbred Large White pigs along predetermined
planes of nutrition that would represent different growth
curves. Development of (the major body tissues was studied
at 16 wk of age and at a final weight of 91 kg live weight.
McMeekan concluded that different tissues and organs could
be affected by nutrition. Wilson (1954) reexamined
McMeekans' data and reportedly found that the varied levels
of nutrition primarily affected the development of fat.
Fowler and Livingston (1972), Davies (1974a) and Cole et a1.
(1976) reported that fat deposition is not as closely
related to either body weight, carcass weight, or muscle
plus bone weight as are muscle and bone growth. Consistent
with these findings Richmond and Berg (1971a) found that fat
is the major contributor to differences in carcass
canposition.
Postnatal Muscle Growth

Skeletal muscle is a significant canponent of postnatal
body mass of manuals. The carcass of the new born pig
consists of 60% muscle and this level is maintained in the
lean type pig to 16 wk of age (Callow, 1948). On a live body
basis this muscle mass constitutes 40 to 45% of the weight.

The synthesis of muscle begins at the embryonic stage
and originates from the mesoderm (Kelly and Zachs, 1969) as
a spindle shaped, mitotically active, mononucleated cell
population, termed presunptive myoblasts (Holtzer, 1970).

The presunptive myoblast differentiates to a mitotically

15

inactive myoblast cell that is elongated and capable of
myofibrillar protein systhesis (Stockdale and Holtzer,
1961). Myogenesis continues with the fusion of myoblasts to
form the multinucleated myotubes. The next stage of
myogenic development is the differentiation of myotubes into
muscle fibers by the migration of nuclei to the periphery
and the bulk synthesis of the myofibrillar proteins, e.g.,
actin and myosin (Fisclman, 1967; Coleman and Coleman,
1968). Continual maturation of the muscle fiber involves
synthesis, assembly of the myofibrillar proteins,
mitochondrial proliferation, innervation and development of
the sarcotubular systen.

Growth in living tissue is characterized by two methods,
hyperplasia or an increase in cell nunber and hypertrophy or
the increase in cell size. The diploid nuclei located in
the myofiber contains a constant amount of deoxyribonucleic
acid (DNA) (Mirsky and Ris, 1949; Vendrely, 1955; Leblond,
1972). Enesco and Leblond (1962) studying the muscle nuclei
of the rat estimated that each nucleus contained 6.2 pg of
DNA. Therefore, in mononucleated cells an increase in DNA
content would indicate hyperplasia. Enesco and Puddy (1964)
and Leblond (1972) however, have pointed out that skeletal
muscle consists of multinucleated cells (myofibers) and a
increase in DNA content represents an increase in nuclei
ntmber and not necessarily an increase in cell nunber.
Check et al. (1971) discussed how each nucleus within a

myofiber has jurisdiction over a definite mass of myofiber

l6

cytoplasnu The incorporation of additional lnyofibrils
increases this cytoplaanic area and increases the cell size
by hypertrophy. Theretnay bernaxhnun volune of cytoplaan a
single nucleuSInay control and this physiological cell size
concept may be used as a measure of postnatal growth (Moss,
1969; Cheek et al., 1971; Robinson, 1971; Goldspink, 1972).

Extensive docunentation that postnatal muscle growth
occurs prhnarily by hypertrophy oflnyofibers is reported in
the literature. McMeekan (1940a) examined the fiber nunber
per bundle in the longissimus of the pig and found no
significant increase during postnatal growth. Stickland and
Goldspink (1973) supported this previous work in pigs by
finding no significant increase of nwofiber nunber in the
cross section of the longisshnus fran l to 200 d
postnatally. In a different approach using lightrnicroscope
techniques, Swatland and Cassens (1973) and Swatland (1973)
reported thatlnyofiber hyperplasia is canpleted in the fetal
pig by approximately 70 d of gestation. After this time
only hypertrophic growth of the individual myofibers was
found. In addition to the hypertrophy of the myofiber,
determined by an increase in fiber diameter, (Mulvaney,
1981) an increase is reported in total DNA and ribonucleic
acid (RNA) and a decrease in DNA and RNA concentration in
skeletallnuscle of swine, postnatally (Gordon et al., 1966;
Robinson, 1969; Gilbreath and Trout, 1973; Tsai et al.,

1973; Hakkarainen, 1975; Powell and Aberle, 1975; Harbison

17

et al., 1976; Swatland, 1977). Considering thelnitotically
inactive nature of myofiber nuclei the primary source of
additional nuclei is the satellite cell. Mauro (1961) first
detected the presence of the satellite cell, by electron
microscopy, which are located between the plasma membrane
and the basement membrane of the myofiber. By thymidine
incorporation studies it was detennined that the satellite
cell is capable of nfitosis, after which one or both of the
daughter cells fuse ‘with a rnyofiber, thus contributing
additional nuclei (Moss and Leblond, 1971; Snow, 1978). The
absolute as well as relative decrease in nmscle satellite
cell population is reported for the pig, postnatally
(Campion et al., 1981).

The decrease in DNA and RNA concentrations with
increasing age is most accurately explained as a diluting
effect caused by the rapid increase of nwofibrils
(Goldspink, 1972; Tsai et al., 1973). The increase in total
RNA in a tissue during growth is associated with the protein
synthesizing potential (Wannanacher, 1972). In postnatal
growth of pigs the increase in total RNA was associated with
the increase in total protein andtnuscle weight (Powell and
Aberle, 1975).

The anount of RNA synthesized per nucleus is obtained by
the ratio of RNA to DNA. Topel (1971) has observed an
increase of RNA to DNA ratio in the longissimus of a

muscular strain of pigs, and suggested an association of the

l8

ratio of RNA to DNA with protein synthesis. Powell and
Aberle (1975), Millward et al. (1975), Ezekwe and Martin
(1975) and Hogberg (1976) have also demonstrated the RNA to
DVA ratio of muscle is related to protein synthesis
capacity. The relationship of protein to DNA and muscle
weight to DNA, indicative of physiological cell size, have
been found to increase postnatally with age (Robinson, 1969;
Powell and Aberle, 1975; Hogberg, 1976).
.Bone Growth

Bone is in a constant flux of new mineralization and
enzymatic digestion during the growth period and in the
mature animal. This activity is referred to as bone
remodeling and is due to the presence of osteoblasts and
osteoclasts. Osteoblasts are characterized by synthesizing
high levels of collagen and providing alkaline phosphatase
activity (Rasmussen and Bordier, 1974) responsible for bone
mineralization. The osteoclasts contain lysosanal enzymes
including acid phosphatase (Vaes, 1968) and are capable of
synthesizing a substantial amount of hyaluronic acid (Owen
and Shetlan, 1968) which is able to degrade mineralized
matrix (Rasmussen and Bordier, 1974).

Bone, as other living tissues, is dependent on adequate
nutrition, stimuli and cell type to grow and maintain life.
Harris and Innes (1931) have reported that a deficiency of

vitamin D or abnormal mineral intake will interfere with

19

normal cartilage calcification and impair growth. X-ray
analysis of long bone growth regions have illustrated
transverse lines of growth arrest, due to chronic dietary
restriction (Harris, 1933).

Bone growth is also controlled by gonadal hormones.
Shnpson et al. (1944) reported that testosterone» has a
sthnulating effect on epiphyseal growth. Brannang (1971)
has reported the distal bone length of appendages are longer
in steers than bulls during the growth period. Wood and
Riley (1982) in agreanent with this record, have reported
that barrows are taller than boars at the sane weight.

The precursor cells of bone fonnation, skeletoblast
originate fran nusenchwnal stun cells during prenatal and
postnatal life (Young, 1964; Owen, 1967). The skeletoblast
inay differentiate into a prechondroblast type 1 or type II
(Stutznan and Petrovic, 1982). The prechondroblast type 1
cells mature into the chondroblast cells located in the
ephiphyseal cartilage of long bones. The original
skeletoblast cell can differentiate into a osteoprogenitor
cell that can develop into a preosteoblast or a
preosteoclast (Petrovic, 1982). ‘With furtherlnaturation the
osteoblast and osteoclast cells are fonned.

The ephiphyseal cartilage located at the junction of the
diaphysis and ephiphysis at both the proxhnal and distal end
of a long bone is often referred to as the epiphyseal plate.

Under nonnal circunstances the rapidly growing anhnal has a

20

wider epiphyseal plate than slower growing older animals
(Sissons, 1956). The proliferative activity of
chondroblasts originating fran the ephiphyseal plate
cartilage, adds new cells increasing the length of bone
through a sequence of interstitial growth and endochondral
ossification (Dodds and Caneron, 1934). Kernber (1960)
reported that ephiphyseal cartilage cells labeled with
tritiated thwnidine danonstrate passage through the
ephiphyseal plate towards the diaphysis duringlnitosis. The
passage through the plate is followed by hypertrophic growth
and vascularization by blood vessels and connective tissue
incorporation (Han, 1950). Osteoblasts present in this
endochondral hypertrophic growth area initiate the
Inineralization of cartilage rennants (Scott and Pease, 1956)
forming trabecular bone. Osteoclast also function in
trabecular bone, remodeling areas of the new framework by
digesting cartilage rennants (Dodds, 1932).

Thetnapping of bone growth was first initiated by Hales
(1927), who drilled two holes in the diaphysis of a young
chicken bone and danonstrated that bone grew by the addition
of new bone at the ends. Brash (1934) fedlnadder to pigs as
a (method of mapping bone growth. Madder contains alizarin
(Payton, 1932) a compound that is incorporated into the
growing area of bone (Tapp, 1966). The mapping by
tetracycine however, is detected by fluorescence of

histological sections (Hansson, 1967).

21

The appositional formation of bone on a preexisting
surface is referred to as Inanbranous ossification and
accounts for the thickening of bone during growth. Studies
using tritiated thymidine :(Young 1952 a, b) have
danonstrated that a osteoblast cell population located
between the bone surface and periosteun actively deposits
lanellar bone on the surface. The osteoblasts are fonned by
the proliferation and nuturation of osteoprogenitor cells
located under the periosteun (Owen, 1970). New bone cells
are actively fonned on the surface and are included in bone
lacunae as nature osteocytes. Reabsorption and ranodeling
of bone by osteoclast is also present in this process (Lee,
1964).

Boar and Barrow Comparisons

Scientific studies canparing growth and canposition
differences of boars and barrows have been reported in the
literature throughout the world. ‘Walstra andl<roeske (1968)
reviewing the literature of thirty five articles fran ten
counties have reported that boars have a higher percentage
lean, a lower percentage fat, are longer, have a more
favorable feed conversion and a lower dressing percentage

"s

than barrows. Turtonp(l969)’anphasizes that castration is
as old as the history of danestication of livestock and was
adopted tornodify the secondary sex characteristics oflnale
anhnals such as sex drive, body fonn, canposition and the

sexual odor or taint in boar carcasses. The Leydig cells of

22

the serniniferous tubules in the testis secrete the
testosterone and other androgens that regulate and maintain
the body characteristics and accessory sex organs of the
male. Turton (1969) reviewed the data across species of
sheep, cattle and hogs and reported that intact males have a
greater fore-end development and a higher bone content than
castrates. This observation agrees with the review by
Prescott and Lanning (1964) that focused specifically on
boars.
Growth Rate

The literature on growth rates for boars and barrows
have reported no difference in growth rate and that boars
grow at a more rapid rate than barrows. The majority of
reports demonstrate that boars grow significantly faster
than barrows (Bratzler et al., 1954; Piatkowski and Jung,
1966; Blair and English, 1965; Burgess et al., 1966; Siers,
1975; Wood and Riley, 1982). Reports by Blair and English
(1965) show an 8.8% greater growth rate in boars, and Wood
and Riley (1982) observed at the same final weight boars
were 20 d younger. A study on seasonal growth (Siers, 1975)
shows a significantly higher growth rate for boars than
barrows during the fall. No difference was found in the
spring, however. Nunerous other researchers have found no
significant difference between the growth rate of boars and
barrows (Winters et al., 1942; Kroeske, 1963; Hines, 1966;

Ontvedt and Jesse, 1968; Hetzer and Miller, 1972; Newell and

23

Bowland, 1972; Pay and Davies, 1973). Prescott and Lanning
(1964) have reported that barrows grew faster than boars.
Reviews by Turton 1962 and‘Wianer-Pedersen (1968) indicate
that when no difference resulted in growth rate between
boars and barrows, there was a consistent pattern of varied
growth. Boars would grow faster than barrows prior to 3 to 4
inonths while barrows would then grow faster thereafter to 6
to 7 nmmths, resulting in no difference in the growth rate
over the entire period. IA possible explanation for this
observation was proposed by Winters et a1 (1942) as the
onset of puberty, which produces sane factors that have a
depressing effect on growth. Prescott and Lanning (1964)
suggest that the depression in growth rate of boars is due
to an increase in nutritional protein requirenent that is
not provided for in the diet.

Results on the efficiency of feed conversion show that
boars are more efficient than barrows (Charette, 1961;
Turton, 1962; Teague et al., 1964; Hines, 1966; Pay and
Davis; 1973; Siers, l975;‘Wbod and Riley, 1982). Bratzler
et al. (1954), however reported no difference in feed
conversion. Blair and English (1965) reported boars to be
7.7% more efficient and Ontvedt and Jesse (1968)
demonstrated a 10% improvement in the efficiency of feed

conversion for boars.

24

‘When feeding different levels of protein Prescott and
Lanning (1967) and‘Wood and Riley (1982) reported that boars
have a nwwe efficient feed utilization and growth rate at
increased protein levels than barrows. Protein levels of
18% fed until 57 kg and then 16% fed to boars have provided
the most beneficial gains (Hays et al., 1966; Newell and
Bowland, 1972). Walstra (1969) has shown that ad libitun
fed boars are Inore efficient, but grow slower than ad
libitun fed barrows. Am restricted intake however, boars
grow faster and maintained a more efficient conversion of
feed. A possible explanation for this observation may be
provided by the studies of Charette (1961), Hines (1966) and
Newell and Bowland (1972) who reported boars consuned
significantly less feed than barrows, indicating boarslnore
closely regulate their feed intake than barrows. Wong et
al. (1968) however, found no significant difference in feed
conversion between boars and barrows.

Composition

Studies on canposition of boars and barrows are
consistent in boars having a greater percentage of muscle
and bone, less fat and a lower dressing percentage (Bratzler
et al., 1954; Zobriskey et al., 1959; Teague et al., 1964;
Prescott and Lanning, 1964; Hines, 1966; Plhnpton et al.,
1967; Prescott and Laning, 1967; Wismer-Pedersen, 1968;
Newell and Bowland, 1972; Fuller, 1980; Wood and Riley,

1982). The lower dressing percentage reported for the boar

25

may be partially due to the removal of the genitals.
Prescott and Lanning (1967) reported boars had 15% greater
muscle, 12% greater bone and 24% less fat in the carcass
than barrows. Boars also had 3% less dressing percentage
and a greater percentage of skin than barrows. Luscanbe
(1962) has shown that boars have 7% greater muscle and 17%
less fat in the carcass than barrows. The rate of protein
deposition of boars is 49% greater per day than barrows when
compared on an ad libitun fed basis (Wood and Riley, 1982).
The ratio of muscle to bone has not been found to be
significantly different even though boars possess a greater
anount of muscle and bone (Newell and Bowland, 1972; Fuller,
1980; Wood and Riley, 1982). It has also been shown that
boars have a greater kidney weight, intermuscular fat and a
thicker skin than barrows (Wood and Riley, 1982).

Carcass measurement of backfat thickness has
demonstrated that boars are leaner than barrows (Bratzler et
al., 1954; Hetzer et al., 1956; Zobrisky et al., 1961;
Charette, 1961; Plimpton et al., 1967; Wong et al., 1968;
Siers, 1975;1Newell and Bowland, 1972). The difference
reported by Prescott and Lanning (1964) was that boars were
14% leaner than barrows while Blair and English (1965)
reported a 23% difference in leanness. In reviewing
literature on sheep and cattle Turton (1969) found a
consistent pattern with previous data reported for the boar-

barrow canparison. Rans were significantly leaner than

26

wethers and bull carcasses had less fat than steer
carcasses. On a ‘weight basis Kuhlers et al. (1976)
demonstrated that at a sinfilar backfat thickness boars are
23 kg heavier than barrows on a live weight basis.
Deanoulin (1973) has recorded an increase of 40 kg in live
weight, when boars were at the same backfat thickness as
barrows. Carcass length is reported to be greater in boars
than barrows by Bratzler et al. (1954), Teague et al.
(1964), Prescott and Lanning (1964), Hines (1966), Plhnpton
et al. (1967), Turton (1969), and Froseth et a1. (1973).
However, Zobrisky et a1. (1959), Wong et al. (1968), and
‘Wood and Riley (1982) have found no significant difference
in carcass length. Longissimus area has met with similar
reports. Bratzler et al. (1954), Zobriskey et al. (1959),
Charette (1961), Blair and English (1965), Prescott and
Lanning (1967), Pay and Davies (1973) and Siers (1975) have
found a significantly larger longissimus muscle area in
boars canpared to barrows, while Prescott and Lanning
(1964), Teague et al. (1964), Hines (1966), and Plhnpton et
al. (1967) have reported no significant difference in
longisshnus area.

The endogenous gonadal honnone production in the boar
has an effect onlnuscle developnent that is not present in
the barrow. The androgens of the boar induce the synthesis
of protein by regulation of the ribonucleic acids and the

protein biosynthesis systen at the nficrosanal level

27

(Kockakian, 1966). This level of androgen inducement of
protein synthesis does not occur at the sane magnitude for
all muscles, as with the withdrawl of the hormones does not
reduce muscle growth to the same extent (Brannang, 1966).
LaFlame et a1. (1973) working with castrated and intact twin
bulls have reported that castration had no significant
effect on concentration of DNA, total protein collagen or
muscle fiber diameter for the longissimus muscle. Wood and
Enser (1982) reported that the moisture content of the
longissimus was greater for the boar than the barrow. Staun
(1963) studying the boar and barrow found no significant
difference in the fiber diameter of the longissimus. This
sane effect was reported for sheep by Moody et al. (1970)
who found no significant difference in the fiber dianeter in
the sernitendinosus or longissunus muscles from rans and
wethers that were slaughtered at the sane average weight.
Reports that are not consistent with these previous findings
were reviewed by Brannang (1971). Jasienski (1929)
demonstrated that muscle fibers of bulls had a larger
dianeter than steers and Schilling (1966) reported that the
longissimus fiber bundles were 15% smaller in steers, when

canpared with genetically identical bulls.

EXPERLMENTAL PROCEDURES

Experimental Design .
Sixty-fivelnale pigs, representing thirteen litters were
used for this research study. The genetic base was derived
from purebred Yorkshire or Duroc sires bred to crossbred
dams (of Yorkshire, Landrace, Duroc, Hanpshire, Chester
White breeding). (Breeding records are given in Appendix
A.1). All experimental pigs were bred and raised at the
lMichigan State University Swine Faun. Thirteen replicates
were used for the trial. Each replicate consisted of five
littennate male pigs selected at 3 wks of age and randanly
assigned to the treannent groups of castration or no
castration and final slaughter weight of 105 kg, 118 kg, 132
kg or 145 kg. Table 1 sunnarizes the experhnental design.

Table 1 Experimental Design

 

Replicate Groups
(five letter
inale pigs)

 

Pig 1 Castrated (at 3 wk) -slaughter wt-105 kga
Pig 2 Boar -slaughter wt-105 kga
Pig 3 Boar -slaughter wt-118 kga
Pig 4 Boar -slaughter wt 132 kg3
Pig 5 Boar -slaughter wt-l45 kga

 

aEmpty Body Weight
28

29

Pigs were started on trial at 4 wk of age and each
replicate (5 pigs) were penned together until slaughter
time. Fran 4 wk to 27 kg pigs were raised in a partially
slatted nursery with a flush gutter and a hovered sleeping
area in an environmentally controlled roan at 21 to 29 C.
Pigs were fed ad libitun in a 1.22 by 2.44 meter pen
allowing .60 square meters of floor space per pig. When
pigs within a pen weighed an average of 27 kg the entire
replicate was relocated until slaughter weight in a
naturally ventilated building with a different pen
arrangement. The 2.44 by 2.74 meter solid board partition
pen allowed 1.34 square meters of solid concrete floor area
per pig. Pigs were fed ad libitun from self feeders and the
pens were bedded with straw and cleaned three times weekly.
Fran weaning until 27 kg a 18% protein diet with 1.08%
lysine was fed and after 27 kg a 16% protein diet with .9296
lysine was fed until slaughter weight was reached. (The
diets are listed in Appendix A.2).

Slaughter Procedure and Sanple Collection

Final weight was determined on an empty body basis as
pigs were allowed to gain 3 to 4% beyond their
predetermined slaughter weight. The pigs were then held
off feed for 12 to 16 h, weighed and slaughtered. At
slaughter time pigs were electrically stunned and bled by

severing the carotid artery and jugular vein. At the

30

cessation of bleeding, pigs were scalded and dehaired in a
dehairing machine. Thirty minutes after stunning, the
brachialis, semitendinosus and longissimus muscles were
removed fran the left side of the carcass. The entire
brachialis and semitendinosus muscles were removed. The
longissimus dorsi was dissected out from the anterior edge
of the hip bone to its cranial termination near the first
rib. Each muscle was weighed and a subsanple of 40 to 50 g
was placed in a plastic bag and rapidly frozen in Dry-ice
and isopentane. A 2 g sanple was also removed fran the
center of the longissimus for nuclei density analysis.
Bone sanples were collected fran the last seven replicates
slaughtered. The tibia-fibula and ulna-radius were removed
from the left side of the carcass and freed of all muscle
and connective tissue. The bones were placed in
polyethylene bags and stored in -30 C blast freezer for
later analysis. After muscles and bones were removed the
carcasses of pigs fran the last five replicates were
eviscerated, perirenal fat removed, head removed at the
atlas joint and the carcass split longitudinally along the
dorsal midline fran tail to atlas joint. Carcass weight
was recorded and the left side of the carcass was separated
into bone, skin and soft tissue (adipose tissue, skeletal
muscle and additional connective tissue). Weights were
recorded on all three canponents. The soft tissues were

ground in a Toledo Model nunber 5520 meat grinder through a

31

4lnn1plate, handtnixed and reground through the 41nn plate a
second thne. During the course of the second grinding 10 -
5 to 6 g subsanples were collected to canprise a 50 to 60 g
sanple which was placed in a plastic bag and stored at -30
C.

The right side of the carcass fran each pig was
chilled for 24 h at 2 C. The carcasses were thentneasured
for length, longisshnus area and backfat thickness at the
tenth rib by standard procedures (NSIF, 1981). Longisshnus
area waslneasured by the gridrnethod, Hillers (1970).
Preparation of Frozen Muscle Sample

The muscle samples collected at slaughter time were
powdered in a -30 C walk in freezer. Two different
approaches to this technique were outlined by Borchert and
Briskey (1965) and Mulvaney (1981). The powdering
procedurelnodified for this analysis consisted of placing
the nmscle sample in a cloth bag and crushing the sanple
into approxhnately 2.0 an dianeter fragnents using a rubber
unallet. The sanple was then placed in a 1KA.Universahnuhle
model M20 high speed impact mill with equal amounts of
crushed Dry-ice for 45 to 60 sec. The powderedrnuscle was
then passed through a twenty nwsh screen. The remaining
muscle fragments were repowdered and sifted through the
screen. The powdered Inuscle sanple was rnixed and a

subsanple was placed back in the plastic bag. The bag was

32

left open for 12 to 16 h to allow the 002 fran the Dry-ice
to escape. Sanples were then sealed and stored in the -30 C
freezer until analyzed.

The ground sanples representing the soft tissues fran
the dissected carcass side (left side) of replicates nine
through thirteen were also prepared in thislnanner.
Analysis of Muscle Samples

The standard AOAC (1980) methods of analyses for
rnoisture (drying oven), ether extract (Goldfisch), and
protein (Kjeldahl x 6.25) were carried out on all the
powdered musclesubsanples and the powdered soft tissue
subsanples representing carcass canposition.

Nucleic acid concentration was determined on all
muscle subsanples using the modified Munro and Fleck (1969)
method carried out by Mostafavi (1978) and Mulvaney (1981).
The details of this procedure are described by Mostafavi
(1978) and are outlined in Appendix B.1.

Muscle fiber diameter was determined on subsanples of
the powderedtnuscle fran each carcass. The procedure‘which
includes 1.0% gluteraldehyde BSS buffer (Appendix 8.2) and
.02 M guanidine-HCL buffer (Appendix 8.3) was described by
Mulvaney (1981) and is presented in Appendix 8.4.

Analysis For Nuclei Density

The nunber of nuclei per unit fiber area was

detennined on the longisshnus sanple fran the carcasses of

eight replicates (replicates 4, 5, 7, 8, 9, 10, ll, 13).

33

The procedure incorporated into the present study is a
modification of the technique utilized by Cardasis and
Cooper (1975) on mice. Approximately 2 g of muscle 2.5 cm
in length were removed fran the center of the longissimus.
A 1 nm thick section of fiber was teased from the sample to
allow rapid penetration by the 1% gluteraldehyde in .1 M
phosphate buffer pH 7.4 (Appendix B.5) solution in which
the sanple was placed for 1 to 2 h. The sanple was removed
from the gluteraldehyde solution spread out with blunt
forceps and then placed in .02 M guanidine-HCL in -05 M
borate buffer pH 9.5 (Appendix B.6). The sample was
inmediately hanogenized at very low speed by a Virtis 45
model Super 30 hanogenizer for 4 min. The fibers were
spread apart in guanidine solution and then allowed to set
at roan temperature for 20 min. At the end of 20 min the
fibers were removed from the guanidine solution and stained
in Mayer Hematoxylin for 45 min. The fibers were then
destained by placing them in a .05 M borate buffer solution
at pH 8.5 (Appendix 8.7) for 55 min. At the end of the
destaining period fibers were placed in deionized H20 for a
minimu’n of 10 min. Twenty fibers were dissected apart fran
the other fibers and placed on a slide coated with 2%
gelatin, one fiber at a time under a Bausch and Lanb model
31-26-84 dissecting microscope. Once twenty fibers were
located, the slide was cleaned using a drop of xylene, air

dried and covered with a drop of mounting solution and a

34

cover slip. The slide was viewed through a light
microscope at a magnification of 480. A micraneter was
located in one eye piece and was calibrated with a stage
rnicraneter forrneasuring the fiber dianeter and the length
of the fiber on which the nuclei were counted. Due to the
poor staining quality of the fibers it was necessary to
separate out at least one hundred fibers to allow for fifty
countable fibers. The nunber of nuclei per unit fiber area
for a sample was calculated on the average of fifty fibers.
The fiber diameter was measured and the nuclei counted
within a 4.83 mm length of the fiber (Diagran in Appendix
8.8). Due to the arrangement of nuclei near the outer
surface of the fiber the nuclei were counted by atnethod of
focusing fran the far side of the fiber to the near side.
Bone Measurements

Due to ossification of the tibia to the fibula and
the ulna to the radius Specific gravity was calculated for
the canbined tibia-fibula and the canbined ulna-radius.
The weight at roan tanperature and the weight subnerged in
0 C water were recorded for each pair of bones to calculate
specific gravity (Specific gravity = (wt 1Ktairlflw: in H20T)'
The radius and the tibia were then split in two halves by
sawing fran the distal to the proximal end. Measurements
for total length, length of diaphysis, proxhnal epiphysis
and distal epiphysis were recorded in nullinwters.

Proximal epiphyseal cartilage width and distal epiphyseal

35

cartilage 'width were recorded as the average of five
rneasuranents (Diagran B.9).
Statistical Analysis

The data were analyzed using the procedure of Least-
squares (Harvey, 1960). Thetnodel used was:

Yijk = u + t. + l. + eiik

1 1
Yijk = an observation for any of the traits considered
u = an effect cannon to all individuals for

a given trait
ti = effect of the ith treaflnent, i= 1...5

1 effect of the jth litter j= 1...13

i
eijk

For a solution of the generalized equations, the restraints

an effect unique for each individual

2t = O and £1 = 0 were imposed to make all the equations

independent.

RESULTS AND DISCUSS 1m

Live Body Weight

The average live body weights for groups I through V are
listed in table 1. There was a significant linear increase
(P<.01) in the live weights of the boars, groups 11 through
V. No significant difference was found between the live
weight of the barrows and the boars groups 1 and 11,
respectively. The similar dressing percentage (Table 1)
between groups 11 and l is in contrast to other studies
(Hines, 1966; Plimpton et al., 1967; Wood and Riley, 1982).
Prescott and Larrming (1967) found that barrows had a 3%
greater dressing percentage than boars. A trend did occur
in this study for a 1% greater dressing percentage in the
barrows.
Carcass Measurements

The carcassuneasuranents of tenth rib backfat thickness
(Table 2) was less (P<.01) in group 11 than group I. The
greater leanness in the boar, than barrow at similar live
weight is substantiated in the literature (Bratzler et al.,
1954; Charette, 1961; Plimpton et al., 1967; Siers, 1975).

The 45% reduction in tenth rib backfat in boars than
canparable weight barrows (groups 11 and 1, respectively) is

greater than the 14% reported by Prescott and Lanning (1964)

36

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38

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39

and the 23% less backfat in the boar canpared to the
castrate, reported by Blair and English (1965). The 2.84 an
tenth rib backfat thickness of the barrow is even greater
than the 2.72 an averagelneasuranent of the boars in group
V. When canpared on a live weight basis the tenth rib
backfat thickness in the barrow is greater than the boars
weighing 41.4 kg more. This 41.4 kg weight difference
between boars and barrows is greater than the 22.7 kg
difference reported by Kuhle‘rs et al. (1976), the weight
difference at which boars had fat thicknesses similar to
barrows.

A greater (P<.09) carcass length in the boar (group 11)
than the barrow (group I) was also found and is consistent
with past work (Bratzler et al., 1954; Hines, 1966; Turton,
1969; Froseth et al., 1973). The boar carcasses in this
study were 2.9% longer than the barrow carcasses. Sane
studies reported no differences in carcass length between
boars and barrows (Zobriskey et al., 1959; Wood and Riley,
1982). There was no significant difference in longisshnus
area (Table 2) between boars and barrows slaughtered at
shnilar *weights (groups 11, and 1, respectively). No
differences in longisshnus area were reported by Prescott
and Lanning (1964), Teague et a1. (1964), Hines (1966) and
Plhnpton et a1. (1967).

In contrast, other studies have shown that boars had a
larger longissimus area than barrows (Blair and English,

1965; Pay and Davies, 1973; Siers, 1975). Blair and English

40

(1965) reported that boars had 14% more longissimus area
while Siers (1975) found the boars had 15%1nore longisshnus
area than the barrow.

Average longisshnus area and tenth rib backfat thickness
increased with the live weight increase in groups 11 through
V (Figure l). Carcass length increased (P<.01) linearly at
a rate of .15 cm/kg of live weight gain. A significant
(P<.05) quadratic inrease was found for longissimus area
fran groups 11 to V. Thernost rapid increase in longisshnus
area over this weight range was .30 omzlkg of live weight
increase fran 118 to 132 kg, while the slowest rate of
increase in longisshnus area was .19 anZ/kg of live weight
increase fran 105 to 118 kg. Both a linear and quadratic
increase (P<.01) was found for tenth rib backfat thickness
in the boars of groups 11 to V. A constant rate of .017 an
increase/kg of gain in tenth rib backfat thickness occurred
in the boars fran 105 to 132 kg. Fran 132 to 145 kg alnore
rapid rate of increase for tenth rib backfat thickness of
.023 am/kg of gain was found.

Muscle Chemical Canposition

There were no significant differences in the brachialis
(Table 3), sanitendinosus (Table 4) or longisshnus (Table 5)
fat freelnuscle weight between boars (group 11) and barrows
(group I) at 105 kg. As previously mentioned, the
longisshnus area between groups 11 and I was also shnilar.

There was however, a trend for a greater brachialis (P<.10)

41

Figure I: The Carcass Measurements 0f Boars From

105 to 145 kg, Live weight.

—— Carcass Length(CL)

‘1“ Longissimus Muscle Area(LMA)

M Tenth Rib Backfat<TRB)

105 118 132
Live Weight (kg)

Equations of Graphs in Appendix E.l

  

145

XP8211

,92.0

90.5%

489.0,J

o
87.5

3.00

A

8
2.003
1.oo§

[-4

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45

and sanitendinosus (P<.12) weight in the boars (group II) as
compared to the barrows (group 1). A quadratic increase
(P<.Ol) is present for the fat free nmscle weight of the
brachialis, sanitendinosus and longisshnus with live weight
increases (groups 11 to V, Figure 11). The increase over
the live weight range for eachlhuscle was .72 g/kg for the
brachialis, 2.9¢ g/kg for the sanitendinosus, and the
longisshnus increased 18.1 g/kg of live weight gain iron 105
to 1#5 kg (groups ll to V).

The quadratic relationship for fat freelnuscle weight of
the longisshnus and the sanitendinosus agrees with the
differential growth rate of individual nmscles reported by
Richnond and Berg (19823) and Davies (1974b). The
brachialis is characterized as an early developinglnuscle,
the semitendinosus as an intermediate maturing muscle and
the longissimus as a late developing muscle (Richmond and
Berg, 19823; Davies, 1974b). In this study a rapid increase
in growth occurred in the sernitendinosus fat free muscle
'weight in the boars frun 118 kg to 132 kg (groups 111 to IV).
The most rapid increase in the longissimus fat free muscle
weight occurred between 132 and 145 kg (group III to V). The
brachialis data in this study does not agree with the work
of Richnond and Berg (1982a) and Davies (1974b) as thelnost
rapid increase of fat free brachialisrnuscle weight did not

occur until the period fran 132 to 1#5 kg (group 111 to V).

46

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47

The percentage of moisture was greater (P<.01) in group
11 than in group I for the brachialis and sernitendinosus
muscles but was not significantly different for the
longissimus. The percentage moisture of .boars (group II)
was 2% greater in the brachialis, 2% greater in the
sernitendinosus and 1% greater in the longissimus, than in
similar weight barrows (group i). No significant difference
was found in the percentage moisture for the brachialis,
semitendinosus or the longissimus from groups 11 to V.

Protein concentration was constant in the three muscles
from pigs in groups I and II and thus, no significant
differences were found between these groups. Similarly no
significant difference was observed in the protein
percentage for the brachialis, sanitendinosus and
longissimus muscles of boars from 105 to 145 kg (groups 11
to V).

The percentage intramuscular fat was significantly
greater in the brachialis (P<.09) and semitendinosus (P<.02)
of group I as compared to group II. Barrows (group I) had
.8% more intramuscular fat in the brachialis and 1.45% more
in the semitendinosus muscles than the boars (group II).
There were no significant differences in longissimus
intramuscular fat between boars and barrows taken to the
same endpoint weight of 105 kg (group ll and 1,
respectively). Total intramuscular fat of the brachialis

and longissimus also was not significantly different for

#8

treaUnent groups 11 and 1. Total intranuscular fat weight
of the sanitendinosus was 29% larger (P<.lO) in group I than
in group II. The percentage intramuscular fat decreased
fran groups 11 to V at a significantly linear rate in the
brachialis (P<.02) and a significant quadratic rate in the
sanitendinosus (P<.09). No significant difference was
observed in the total intranuscular fat for the brachialis,
semitendinosus or the longissimus from groups 11 to V.
Likewise no difference was found in the percentage
intramuscular fat in the longisshnus over the weight range
fran 105 to 145 kg (group ll to V).

Forbes (1968) reported that with an increase of fat free
Inuscle there is a decrease inlnoisture percentage while the
percentage of protein increases. During development this
rate of increase eventually reaches a plateau. The
relationship between protein and fat accretion rates was
found by Bailey and Zobrisky (1968) and Searle et a1.
(1972) to occur at a constant rate during early postnatal
growth but at heavier body weights the rate of fat
deposition is greater than the rate of protein accretion.
Over a two week period at 45 kg live weight Mulvaney (1981)
reported that the brachialis, sanitendinosus and longisshnus
of boars deposited fat at a more rapid rate than protein
accretion. He also observed significant decreases in water

content. The pattern reported by Forbes (1968) in relation

:19

to percentage Inoisture and protein was present in the
canparison of groups 11 and l. The boars (group 11) had a
greater percentage of nmdsture and a lower protein
concentration than barrows (group I) in the brachialis,
sanitendinosus and longisshnus fat freelnusclelnass. With
developnent, Forbes (1968) found that protein concentration
increased whilelnoisture decreased. Applying this concept
to this study, barrows appeared to be further along in
Inuscle developnent than boars of shnilar weight (105 kg).
The developnent front groups 11 to ‘V indicate that the
percentage oflnoisture in the brachialis, sanitendinosus and
longisshnus had plateaued since no significant different was
noted between groups. The decrease in percentage of
intranuscular fat fran group II to V indicates that fatlnay
belnobilized possibly as an energy source or that a diluting
effect occurred by a faster rate of myofibrillar protein
accretion than for fat deposition.

A. greater sanitendinosus fiber dianeter occurred in
boars (group II) than in barrows (group I). The greater
fiber diameter of the semitendinosus from boars is not
consistent with the shnilar fat freelnuscle weight of boars
and barrows at 105 kg. This difference may be due to
biological difference from littermate replication as the
greater fiber diameter of the semitendinosus muscle
approached significance (P<.10) but no significant

difference existed ,for the fiber diameter in the longissimus

50

or brachialisrnuscle between boars and barrows (group II vs
group I). Swatland and cassens (1973) danonstrated that
hyperplasia of muscle fibers is completed prenatally and
that postnatal growth occurs exclusively by hypertrophy.
This indicates that if the sane nunber of fibers are present
in two muscles and fat free muscle weight is similar then
fiber dianeter should be shnilar. This concept is supported
in the present study since fiber dianeter was significantly
(P<.09) different for the longisshnus in the boars fran 105
to 145 kg (group II to V). Although there was a consistent
increase in the fiber dianeter from groups ll through V, it
was not a significant linear response. Fiber dianeter of
the senitendinosus or brachialislnuscles fran groups 11 to V
did not differ significantly even through fat free muscle
weight of the brachialis and senitendinosus increased.
Muscle Nucleic Acid Measurements

The nucleic acid analysis of the brachialis,
sanitendinosus and longisshnus are listed in Tables 6, 7 and
8, respectively. Due to the high variation, there were few
significant differences between groups. Trends are present
that are consistent with other reports (Hakkarainen, 1975;
Harbison et al., 1976). No significant difference existed
in DNA concentration for the brachialis, sanitendinosus or
longisshnuslnuscles fran groups 11 through V. There was a
trend for decreased DNA concentration as live weight

increased fran 105 to 145 kg in all threetnuscles of boars.

51

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54

A trend for a constant decrease in RNA concentration was
also observed for the longisshnus and sanitendinosusrnuscles
of groups 11 through V. This result of decreasinglnuscle
DNA and RNA concentration with increasing live weight due to
growth has been reported in other studies involving pigs
(Robinson, 1969; Tsai et al., .1973; Hakkarainen, 1975;
Harbison et al., 1976). Work by Tsai et al. (1973) and
Hakkarainen (1975) danonstrated that the decrease inlnuscle
DNA and RNA concentration was due to the increased accretion
of myofibrillar proteins in myofibers causing a diluting
effect oflnyonuclei. In all threernuscles tOtal DNA and RNA
trended to increase with live weight gains fran 105 to 145
kg in boars. This increase is referred to as a trend since
no significant differences occurred with the exception of
total RNA in the brachialis and semitendinosus muscles.
Total RNA in the brachialis and semitendinosus increased
significantly (P<.Ol, P<.02, respectively) over the weight
range fran 105 through 145 kg. This increase resulted in a
significant linear response for the brachialis (P<.05) and
the semitendinosus (P<.O7) for total RNA over the weight
range of 105 to 145 kg. Harbison et al. (1976) reported that
total DNA and RNA continued to increase with live weight
gain in pigs fran 23 to 118 kg. The increase in total DNA
appears to precede the increase in total RNA and additional

protein accunulation (Hakkarainen, 1975). The increase in

55

total RNA is a prelude to increased protein accretion
(Hakkarainen, 1975) and may be used as an indirect measure
of protein synthesizing machinery (Wannamacher, 1972). The
source of the additonal DNA is from the incorporation of
daughter nuclei of satellite cells into the myofiber (Mauro,
1961; Moss and Leblond, 1971; Snow, 1978).

In this study there was a greater (P<.O4) amount of
total DNA in the semitendinosus in boars (group 11) than in
barrows (group i, 2M.5 vs 197.1 mg, respectively). No
significant differences occurred for any of the other
nucleic acid measurements between groups 11 and l.

The ratio of RNA to DNA has been used as a indicator of
protein synthesis capacity by Powell and Aberle (1975) and
Millward et al. (1975). The ratio of RNA to DNAwas constant
in all groups in this study. No significant difference was
found between the RNA to DNA ratio for the three muscles in
barrows and boars at 105 kg live weights.

The physiological cell size concept reported by Moss
(1969) does not vary since a significant difference was not
observed for the protein to DNA ratio or the fat free muscle
weight to nuclei ratio between groups I and II or from
groups II to V for the brachialis, semitendinosus or the
longissimus.

No significant difference was found in nuclei density in
the longissimus myofibers (Table 8). There was no

difference in nuclei density of the longissimus myofiber

56

between groups I and II (P<.94) or groups 11 through V
(P<.98).
Carcass Composition Data

The greaterxnuscleinass of boars compared to barrows as
reported by Prescott and Lanning (l967), Fuller (1980), and
‘Wood and Riley (1982) was not found in the present study
(Table 9). No significant difference in fat freelnuscle was
observed between groups II and 1. However, there was a
difference (P<.01) in total fat of the carcass between
groups II and l and this agrees with past studies (Wigner-
Pedersen, I968; Newell and Bowland, 1972). Pigs of group I
had 25.N% fat (Figure III) in the carcass canpared to 17.r%
in group II carcasses. The 26.696 less fat in group 11
compared to group I was greater than the 2W6 difference
between boars and barrows reported by Prescott and Lanning
(1967).

The total fat in the barrow carcasses of group I at 105
kg was the sane mnount as the total fat in the carcasses of
the boars of group V at 145 kg (Table 9). The l“.0 kg
difference in live weight between groups I and V is closely
associated with the #0 kg weight difference in live weight
when boars had the sane fat content as barrows as reported
by Demnoulin (1973). As previously observed in this study,
barrows had similar tenth rib backfat thickness as boars
weighing 41.2 kglnore. There was a significiantly (P<.Ol)

greater weight of carcass skin and total bone in the

57

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58

Figure III: Average Carcass-Compostion Of The

105 kg Boars And 105 kg Barrows.

0
9

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BOAR

' BARROW

FFM-- Fat Free Muscle

XP8211

59

carcasses of group II as compared to group I (Table 9). The
IP% greater weight of total bone in boars (group II) than
barrows (group I) is in close agreanent with the 12%»greater
carcass bone in boars canpared to barrows of sinfllar live
weight as reported by Prescott and Lanning (I967). The 1wx
greater carcass skin weight of group II, than of group Ilnay
be best explained by the greater skin thickness of boars
canpared to barrows reported by Wbod and Riley (I982). The
ratio of fat freernuscle weight to total bone weight between
groups II and I was shnilar in the present study and is in
agreement with other studies (Newell and Bowland, I972;
Fuller, I980).

The average fat free muscle weight for the boars for
groups II through V was increased (P<.Ol) with live weight
gain (Figure IV). A significant linear increase was
observed. There was a 37% (Table 9) increase in fat free
Inuscle fron 105 to 145 kg in boars or a .41 kg increase of
fat freelnuscle/per kg of live body weight increase. Total
fat weights of groups II to V increased at a quadratic rate
(P<.O6). Total fat increased 52% fron groups II through V.
The inost rapid increase in total carcass fat in boars
occurred between 118 and 132 kg at a rate of .236 kg/kg of
live weight. Fron 105 to 118 kg and fron 132 to 145 kg the
total fat in boars increased at a rate of .129 kg/kg of live
weight gain. Total bone and total skin increased at a

significantly (P<.Ol) linear rate from groups II to V.

60

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61

Total bone increased 3.3% (Table 9) over the live weight
range from 105 to 1145 kg or a .083 kg increase of total
bone/per kg of live weight gain. Total skin of the carcass
increased at a constant rate of .IOQ kg/kg of live weight
Iran 105 to 145 kg. On a percentage basis total skin (6&%)
showed the greatest percentage increase while carcass fat
(52%) was at a greater percentage than either fat free
muscle (37%) or carcass bone (29%) over the weight range
fran 105 to 1&5 kg (Table 9).

The increase (P<.05) in the ratio of fat free nmscle
(Table 9) to total bone from treatment groups 11 to V
indicates that the rate of fat freetnuscle growth continued
to increase at a greater rate than carcass bone, over this
live weight range. 'On a percentage basis total bone (P .08)
decreased significantly fran groups II to V. The decrease
in percentage total bone, even though total bone weight
increased from treatment groups II to V, was due to a
greater rate of increase in fat free muscle and total fat
over this weight range. The 9.3% decrease in total bone
fran 105 to 145 kg live weight was within the range of a 19%
decrease in carcass bone reported by Weiss et al. (1971) in
swine frun l to 137 kg live ‘weight. No significant
difference was observed for percentage total skin from
groups 11 to V.

Tibia and Radius Data
Measurements of bone development were recorded on the

tibia (Table 12) and radius (Table 13).

62

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64

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66

Total weight of the tibia was greater (P<.03) for boars
(group 11) than for barrows'(group I). The radius weight of
boars (group II) and barrows (group I) was not significantly
different. However, a trend for a higher radius weight in
boars was observed (P<.11). The measurements of total
length were consistent for the two bones between boars
(group II) and barrows (group I). work by Brannang (1971)
in cattle for bone weights showed sinfilar results due to
castration. Steers had lighter (P<.01) ulna and radius.
weights than bulls. Brannang (1971) found a greater bone
length of the radius and tibia in castrates which conflicts
with the data in this study. The ratio of total weight to
total length is atneasure of bone thickness. In group II the
ratios of total weight to total length for the tibia and
radius were 17.7 and 22.9, respectively. In group I the
sane ratios for the tibia and radius were 15.0 and 20.9,
respectively, A greater tibia and radius total weight is
observed in group 11 over group I. The greater tibia and
radius weight in group II is consistent with the greater
total carcass bone weight that is found for group 11
compared to group I (Table 9). The difference in total
weight, and no difference in total length between groups 11
and 1, indicates that the greater total weight of the bones
is due to increased bone thickness. This is supported by
the higher total weight to total length of the tibia and

radius for group II canpared to group I.

67

A significant linear increase in total weight of the
tibia (Figure V) and radius (Figure VI) was found as the
live weight increased fran 105 to 145 kg. Ower this weight
range there was a linear increase (P<.Ol) in the total
length of the tibia (Figure V) and radius (Figure VI). ‘When
the ratio of total weight to total length was plotted for
the tibia (Figure: V) and radius (Figure ‘VI) the ratio
continued to increase fran group 11 through group V. The
increase of this ratio substantiates that total weight is
increasing at a greater rate than total length for both the
tibia and the radius. The 13% increase in the tibia ratio
and 16% increase of the radius total weight to total length
ratio, points out that the growth of the tibia and radius
over the live weight range of 105 to 105 kg in boars was due
Inore to an increase in bone thickness rather than an
increase in bone length.

No significant difference was observed for specific
gravity of the tibia or the radius between groups 11 and 1.
Therefore the density of the tibia or radius in boars and
barrows is not different. However specific gravity
calculated for the tibia and radius fran groups II through V
was not constant. While no difference was observed for the
tibia fran 105 to 145 kg (groups 11 to V) in boars, there was
a difference (P<.07) in specific gravity of the radius. The
2%% increased (Table 1J0 .hm the specific gravity of the

radius fran groups II to V was neither linear or quadratic.

68

No differences were observed for any epiphyseal
measurements of the tibia (Table 12) or the radius (Table
1M9. There was however, a trend for a decrease of the tibia
and radius epiphyseal cartilage widths at both the proxhnal
and distal ends for groups II through V. The decrease in the
epiphyseal cartilage widths indicates closure was occurring
in the epiphyseal cartilage and that growth rate of bone
length, for the tibia and radius was decreasing in boars as
they increased fran 105 to 145 kg live weight.

Diaphysis length of the tibia and radius did not differ
between groups 11 and I. There was a difference (P<.0l) in
diaphysis length of the tibia and the radius from groups II
to V. A consistent, but nonlinearly significant increase of
the tibia and radius diaphysis length was observed as boars
increased fran 105 to 145 kg. The increase in diaphysis
length and total length of boars fran groups II to V along
with no increase in epiphyseal length of the tibia and
radius supports the work of Dodds and Caneron (1934) and
Kember (1960) who found that the increase in bone length was
due to a lengthening of the diaphysis, or bone shaft rather
than an increase in epiphyseal length. The 6.7% increase in
diaphysis length is consistent with the 6.7% increase in
total length of the radius, of groups 11 to V. The tibia
increased in total length by 6.5%‘while the diaphysis length
increased by 10% from groups II to V. The percentage
increase in the diaphysis length is considerably greater

than that of total increase of the tibia.

69

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70

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71

Growth Rate of Boars and Barrows

The growth rate of the boars in groups II through V were
analyzed as one group and compared to the growth rate of the
barrows of group I. Fran 5‘wk of age to 105 kg the average
daily gain of the boars and barrows was .782 kg and .796 kg,

respectively. No significant difference in average daily

6...... '-
' “h

 

 

gain between boars and,barrows was, _ob5er_ve_dm (Figure VII).
MW” """“"“”“"‘" ' ~.

Winters et al. (1942), Kroeske (1963), Hines (1966), Ontvedt
and Jesse (1968), Hetzer and Miller (1972a), Newell and

Bowland (1972) and Pay and Davies (1973) also found no
N ..-...

 

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\M . M

in boars than barrows. Winters et al. (1902) indicated that

- r... .9...-
Ho .4-

fl_‘,‘,_,_~.-
\ ......—

the onset of puberty in boars had a depressing affect on

growth rate. The aggressive sexual behavior that occurs
anong some boars after puberty was observed in only 2 boars
in this study. They demonstrated aggressivenes to mount
other pigs in the pens.

Average defilymfiéiflmP199991....19 Figure VII illustrates

 

thwwhjdfl.a...sl.igh-trl'y~ 1351.311” {33? 0f gain than boars
to 15 Wkwfiwifig’ At 15 wk the rate of gain for barrows was
highest, however the rate of gain for boars did not peak
until week 19. The final weight at which boars and barrows
are compared may be a possible explanation for the

inconsistent data for growth rates between these sex groups.

Studies in which boars and barrows were grown to weights

72

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mm um mm mu Hm oa NH ma ma Ha o m m

    

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73

greater than the weight at which barrow gains level off
undoutedly show a difference in gain between boars and
barrows while experiments terminated prior to this weight
generally may show no difference in growth rate. Genetic
ability for growth rate varies throughout the swine
population, thus the rate of gain of all barrows may not
reachlnaxhnun at 15 wk of age. The data in this study does
indicate that the anabolic effects of the testosterone in
the boars results in an increase in average daily gain that
reacheslnaxhnun at a live weight that is 20 kgtnore than the
live weight at which the barrow attains itslnaxhnun rate of
gain.

The increase in live weight at 2 wk intervals for
barrows and boars is graphed in Figure VIIl. A very
consistent rate of increase in live weight occurred for
boars and barrows until week 23 or approximately l05 kg,
live weight. The increase in boars live weight continued to
increase at a steady rate to about 27 wk and then it appears

to have leveled off.

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Amxmmzv mw<

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l)

2)

3)

4)

SUMMARY

Average live weight of the barrows in group I was not
different fran that of the boars in group II. The 13.6
kg weight difference was statistically significant
between groups 11, III, IV and V. A linear increase was

also observed from groups 11 to V.

Tenth rib backfat thickness was I45% less in group II
(boars) than in group I (barrows). When boars and
barrows had the sane backfat thickness boars were
greater than 01.0 kg heavier (group V boars) than

barrows.

A 2.9% greater carcass length was found in boars than in
barrows, however no significant difference occurred in

longisshnus area between groups I and II.

The three carcass measurenents consisting of length,
tenth rib backfat thickness and longisshnus area
continued to increase with live weight increase in boars

fran groups 11 to V. The rate of increase was linear for

75

5)

6)

7)

76

carcass length, while the quadratic response for
longissimus area and tenth rib backfat indicated that
the increase in longissimus area was leveling off
between 132 to 145 kg and the deposition of tenth rib

backfat thickness was beginning to accelerate.

The brachialis, semitendinosus and longissimus muscles
in the barrows of group I and the boars of group II did
not differ in average weight or average fat free muscle
weight. These three muscles continued to increase in a
quadratic response as live weight increased for the

boars in group II to V.

A greater percentage of intramuscular fat and less
moisture was found in barrows than the boars indicating
that barrows were further along in their development

than boars at a similar live weight.

Total DNA in the semitendinosus of the boars (group II)
was greater than that found in the barrows (group 1).
Total RNA increased with a quadratic response in the
semitendinosus and brachialis from the boars as live

weight increased from 105 to 145 kg.

8)

9)

10)

77

The comparison of the barrows and the boars from group I
and II, respectively, resulted in no difference in
dressing percentage, fat free muscle or in the ratio of
fat free muscle to total bone. Boars carcasses had
26.6% less fat, 11% more bone and 17% more skin than

barrows at 105 kg live weight.

With the increase of live weight from groups 11 to V the
fat free muscle mass and the ratio of fat free muscle to
total bone increased at a consistent rate. Total fat
and total skin from the boars over this weight range
increased linearly while total bone increased in a
quadratic response. The increase of fat free muscle to
live weight for boars increased over the weight range
from groups 11 to V by 16% while total fat increased
6.6% and bone increased 3.2%. This greater rate of
increase of fat free muscle in boars than fat indicates
that even at 105 kg boars are continuing to deposit

muscle at a more rapid rate than fat.

On a percentage basis the boars of group II had a
greater percentage of bone and skin than the barrows of
group I. Barrows however, had a higher percentage of

fat.

78

11) Totallnoisture decreased 1.3% and total bone decreased

1.3% in boars over the weight range fran 105 to 145 kg.

12) No difference was found in total length of the tibia or
the radius in the boars (group II) and barrows (group I)
at similar live weight. A difference was observed in
total weight of the tibia between boars and barrows
indicating that the greater bone weight of boars,
compared to barrows was due to a greater thickness of

bone.

13) Total bone weight and length of the radius and tibia
increased linearly in boars fran 105 (group II) to 145
kg (group V). The ratio of bone weight to bone length
for the radius and tibia increased over this weight
range, indicating that bone weight was increasing at a
greater rate than bone length, or that the increase in
bone weight fron 105 to 145 kg in boars was primarily

due to an increase in thickness.

14) A consistent trend for a decrease in the epiphyseal
cartilage width in the radius and tibia in boars fron
105 (group> II) to 145 kg (group V) indicates that

closure of the epiphyseal cartilage was occurring.

15) No difference was found in the average daily gain of

boars or barrows up to 105 kg.

79

16) The point at which average daily gain reached a plateau
‘was different between boars and barrows. In this
genetic pool, barrows leveled off in gain at 15 wk and
boars at 19 wk. When the average daily gain fron 15 to
19 wk was used to calculate the actual weight
difference, boars were approximately 24 kg heavier than
barrows when the peak gain per day was reached.
Researchers that have reported a difference in growth
rate between boars and barrows tnay possibly have
Ineasured gain to a weight that was beyond the point of
Inaxhnun average daily gain for barrows. Other studies
where no difference in gain existed between boars and

barrowslnay have preceded this point.

APPENDICES

Replicate

#UDN

oxooowoxu

12
13

Litter
212..

106
.103
105
124
203
121
102
103
107
108
114
130
137

80

APPENDIX A.1

Breeding Records

Sow No.

and Breeding

163-2 Ch-D

138-2 D-L
126-1 Y-ch
167-2 D-Y
Y11-2 Y

164-2 Ch-H
138-4 D-L
138-3 D-L
117-1 Ch-Y

139-3 Y-H
107-3 Y-D
188-1 Y-D
203-1 Y-L

Boar and

Breeding

Trump-D
Jackson-Y
Billy-Y
Motorhead-D
Mbtorhead-D
Billy-Y
Genesis III-Y
Genesis III-Y
Genesis II-Y
Trunp-D
Trunp-D

Rail III-D

Boran-D

Ch-Chester White; D-Duroc; H-Hampshire; Y-Yorkshire;

L-Landrace

81

APPENDIX A.2

MSU Swine Diet

 

 

Boar
Ingredients, kg Starter Test Station
Ground Shelled Corn 530 680
Soybean Meal (48%) 159 186
Oats 91 ---
Dried Whey 91 ---
Dicalciun PhOSphate 14 16
Calciun Carbonate 9.1 12
Salt 2.3 2.7
MSU-VTM Premix 4.5 5.4
Seleniun-Vit. E premix 4.5 4.5
L-Lysine 2 1.4
Aureomycin 50 -- 0.5
ASP-250 2.2
Calculated Analysis
Metabolizable energy (Kcal) 1400 1431
Protein (%) 18.3 16.8
Lysine (%) 1.08 .92
Calciun (%) .91 .87
Phosphorus (%) .71 .68

1. Procedures

Acids

A. RNA

1.

lo.
11.

12.
13.

14.

l5.
16.

82

APPENDIX B .1

Modified Munro and Fleck (1969)

Nucleic Acid Detennination

for Extracting Muscle and Liver Nucleic

Weigh .2 gm powdered muscle (.1 g powdered
liver) in a corex tube add Zrnl of deionized
H20 and then stopped a: vortex.

Add 5 ml of cold 2.5% l-lClOa, stopper dc vortex
and let stand in ice for at least lOtnin.

Centrifuge for 15 min at 17,000 RPM (RC2-B
Sorval, SS-34 roter) or 34,800 xg.

Discard supernatant.

Break up pellet, (with an applicator stick),
add 5 m1 cold 1% HClOu, stopper and vortex.

Centrifuge for l5tnin at 17,000 REM.
Discard supernatant.

Break up pellet and add 4 ml of .3 N KOH,
stopper and vortex, (Put tape over stopper to
prevent fron popping off).

Incubate for 1 hr at 37C.
Place on ice for 5 min.

Add 5tnl cold 5% PCA, stopper vortex and let
stand in ice for l5tnin.

Centrifuge for 10 min at 17,000 RPM.

Decant supernatant into graduated test
tubes.

Break pellet, add 5 ml of 5% PCA, stopper,
vortex, centrifuge at 17,000 RPMrand decant

supernatant into graduated test tubes (step
13).

Repeat step 14 (save pellet for DNA).

Bring the volune up to 20 ml. This is the
RNA Fraction.

83

.Add .ltnl of Acetaldehyde solution to each
tube and vortex.

Place nurbles on top of tubes and incubate
overnight at 30C (water bath).

Cool to roan tenperature and read at 595 an.

84

B. DNA

1. Breakup the pellet from step 15, add 5 ml of
10% PCA, stopper and vortex.

2. Place marbles on top of tubes and digest at
70C for 25 min.

3. Remove from water bath and place in ice for 5
min. Then stopper and vortex.

4. Centrifuge for 10 min at 17,000 RPM.

5. Decant supernatant into graduated tubes.

6. Break up pellet and add approximately 4.75 ml
of 10% PCA, stopper, vortex and centrifuge
for 10 min at 17,000 RPM.

7. Decant supernatant into tubes (step'5) and
bring the vol up to 10ml. (discard remaining
pellet)

II. Colorimetric Procedures for Nucleic Acid

Determinations

A.

RNA

1.

Pipet (2 ml volunetric) 2 m1 from each RNA
tube into 16 rrm test tubes (do everything in
duplicate). Also set up the blank (using 2
ml of 5% PCA) and the standards (2 ml of each
standards; 12.5, 25, 37.5 and 50 ug/ml).

Add 2 m1 of 1% orcinol reagent to each tube
(must be made up just prior to use) and
vortex.

Place marbles on top of tubes and place the
rack in boiling water for 30 min. Cool by
placing rack in running cold water for 5 min.

Read at room temperature at 680 nm.

Pipet (2 ml volunetric) 2 m1 from each DNA
tube into 10 rrm test tubes (do everything in
duplicate). Also set up the blank (2 ml 10%
PCA) and the standards (2 ml of each
standard; 12.5, 25, 37.5 and 50 ug/ml).

Add 2 ml of 4% Diphenyl Rhine to each tube.

1.

l.

85

SOLUTICNS FCR COLCRIMETRY

Make RNA Standards up in 5% PCA.

'a. 12.5 mg RNA/250 ml 595 PCA so ug/mi

b. 37.5 ml of (a) + 12.5 ml 5% PCA =
37.5 ug/ml

c. 25 m1 of (a) + 25 ml 5% PCA = 25 ug/ml

d. 12.5 ml of (a) + 37.5 ml 5% PCA =
12.5 ug/ml

1% Orcinol

a. Make 10% FeCl (“MW in 6 N HCl.

b. Take 5 ml of (a) and dilute to a l
with 6 nc l-iCl (gives a 0.05% FeCl3
sol.)

c. *Make 1% Orcinol by adding 100 ml
of (b) to l ngrcinol in a volunetric
flask and stirring vigorously with
a magnetic bar for about 20 min.
*(Must be made just prior to use).

Make DNA Standards up in 10% PCA

a. 12.5 mg DNA/250 ml 10% PCA = 50 ug/ml

b. 37.5 ml of (a) + 12.5 ml 10% PCA =
37.5 ug/ml

c. 25ml of (a)+25ml of 10%PCA=
25 ug/ml

d. 12.5 ml of (a) 37.5 ml 10% PCA = 12.5

ug/ml

Diphenyl amine reagent (W/V)

3.

4 gm Diphenyl Amine/100 ml Glacial
Acetic Acid

Acetaldehyde solution

a.

0.4 ml Acetaldehyde concentrate/250

ml H20

KEEP ALL SOLUTIGVS IN A COLD Rm

86

APPENDIX B.2
Gluteraldehyde - BSS Buffer

1% gluteraldehyde 1:3 355 Buffer
BSS Buffer:

- Mix the following compounds with dionized
water and bring final volune up to 1 liter:

8.0076 g NaCl
.2013 g KCl
.1110 g CaCl2
.2033 g MgCl2
.0207 g NaHzPOQ
.1931 g Nazi-1003
.5041 g NaHOO3
.9909 g glucose

87

APPENDIX B.3
Guanidine - HCl Buffer

Make a: l) .02 M guanidine - I-Cl solution
2) .05 M boric acid - KOH buffer

Mix to a pH 9.5

10.

ll.

88

APPENDIX B.4

Fiber Diameter

Weigh approximately 200 mg of, powdered muscle
sanple in 5Inl beaker.

Add 21n1 of F% gluteraldehyde - BSS buffer.
Refrigerate at 4C for 1 hr.
Pipett off liquid portion and discard liquid.

Add 2 ml of .02 M guanidine-HCI buffer and allow
to stand at room temperature for .5 hr.

Pipett off .02 M guanidine-HCl buffer and discard.

Add 2 ml of BSS buffer plus 2 drops of methylene
blue.

Gently shake at 4C for at least 2 d.

‘Runove breaker fran shaker and homogenize for 30
sec using a Virtis 451nodel Super 30 homogenizer.

Put one totwo drops of mixture on microscrope
slide-add cover slip.

Mbasure dianeter of 50 fibers at a total
Inagnification of 400.

89

APPENDIX B.5

1% Gluteraldehyde in .lM Phosphate Buffer pH 7.4

- 1% gluteraldehyde in Phosphate Buffer
- Phosphate Buffer

1. Mix 13.9 g NaHPO,‘ ' 71-120 in 1000 ml

2. Mix 26.8 g Nazi-1P0," 71-120 in 1000 ml

3. Add 19 ml of solution lto 81 ml of solution 2

and dilute with H20 to a total of 200 ml.

90

APPENDIX B.6

Guanadine-HCl in Borate Buffer pH 9.5

- Add .02 M Guanadine - HCl to Borate Buffer until a

pH 9.5 is reached.

91

APPENDIX B.7

.05M Borate Buffer pH 8.5

Mix 31.0 g Boric acid in 1000 m1.
Mix 47.6 g Borax in 1000 ml.
Add 50 m1 of solution 1 to 14.5 ml of solution 2

and dilute with H20 to a total of 200 ml.

92

APPENDIX C.1

Nuclei counting in

longisshnus fiber.

 

94

APPENDIX D.l

The ossification
located between
the tibia-fibula
and the raius-

ulna.

O ..

.TlBAA- FIBULA RADIUS - ULNA

       

96

APPENDIX D.2

Measurements recorded

on the Tibia.

  
  

Ikozwa

J<h0b

4453 .33»; .—

Sm:
mhzmfimmam<m5 mZOm

98

APPENDIX D.3
Measurements recorded

on the Radius.

.2350:

35.02”.-

415.0...

 

...(hmzu

 

wao<m

Ezmsmmamfi: mzom _ M

 

100

APPENDIX E.l

Equations to Graph Figures

intercept '

linear regression coefficient

quadratic ugression coefficient

absicca value (105 kg: 2, 118 kg: 3, 132 kg=4,
145 kg: 5)

Linear response = a + (b)(d)

Quadratic response = a + (b)(d) + (c)(d2 )

0.00’0’

Figure I

Carcass Length = 80.14 + (2.26)d
Longissimus Muscle Area = 32. 32+ (-.684)d + (2.255)d
Tenth rib Backfat = 3. 84 + (-1.105)d + (.183)d

Figure II

Longissimus Muscle = 2247. 60 + (91. 98)d + (124. 4)d2
Semitendinosus Muscle = 437. 34 + (14. 78)d + (29. 21)d
Brachialis Muscle = 112. 21 + (3. 73)d + (4. 99)d

2

Figure IV

Total Fat Free Muscle = 35.06 + (5.201d
Total Fat = 12.90 + (1.21)d + (.691)d
Total Bone = 9.50 + (1.17)d

Figure V

Total Weight
Total Length

252.49 + (25.73)d
17.37 + (.396)d

Figure VI

Total Weight
Total Length

253.38 + (24.21)d
12.85 + (.330)d

Figure VII
Graphed onlnean values

Figure VIII
Graphed onlnean values

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