This dissertation has been microfilmed exactly as received. Mic 60-6414

VANSTAVERN, Bobby Dale. AN INVESTIGATION OF PORK CARCASSES AND MUSCLE COM­ POSITION.

The Ohio State University, Ph.D., 1960 Food Technology

University Microfilms, Inc., Ann Arbor, Michigan AN INVESTIGATION OF PORK CARCASSES

AND MUSCLE COMPOSITION

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

BOBBY DALE VANSTAVERN, B.S. Agr., M.Sc.

******

The Ohio State University 1960

Approved by

Adviser Department of Animal Science PREFACE

The swine industry and indeed the entire livestock and meat

industry is striving to produce and offer to the consumer a

meat product that will more nearly fulfill present day needs for

adequate nutritive value and decreased calories. This has called

for drastic changes in all phases of production, processing, and merchandising. Along with these changes have come problems

that can be solved only when sufficient facts are known. The

cumulative efforts of all segments of the industry are directed

toward the improvement of the product to the mutual well being of all concerned.

This study was designed to establish some of the relation­

ships that might exist between current production practices and

the nature of the resulting product. If it can be determined

that there need be no concern in this area, then this work will have contributed to the general effort.

Research of this nature cannot be accomplished without the wholehearted support and cooperation of many departments and many individuals.

The writer is especially grateful to the Institute of

Nutrition and Food Technology for providing laboratory space and facilities for this work. To Dr. Ralph M. Johnson, the

«

ii Laboratory Director, I owe more than is possible to express. His

advice, counsel, and personal encouragement contributed significantly

to the efforts reflected in this manuscript.

Appreciation is extended to Dr. F. E. Deatherage and the

Department of Agricultural Biochemistry for advice in the formu­

lation of the project and for the use of special items of labora­

tory equipment.

I am indebted to the Department of Animal Science Meat

Laboratory whose facilities for handling large numbers of research animals made a project of this nature and scope possible.

Sincere appreciation is extended to Dr. V. R. Cahill for his suggestions and encouragement and for sharing the responsi­ bilities of the author while this work was in progress.

I am grateful to my adviser, Professor L. E. Kunkle, for his continued effort in every phase of my graduate training and for his special interest, advice, and encouragement in the completion of this investigation.

Thanks are extended to Dr. C. R. Weaver of the Statistics

Laboratory, Ohio Agricultural Experiment Station, for his generous contribution of time and effort to the statistical presentation of the data.

iii The combined efforts of the persons responsible for the operation of the Ohio Swine Evaluation Station program and The

Ohio State University Meat Laboratory contributed significantly to this research project.

I share with my wife, Sue, who has been so patient and helpful throughout the course of my advanced studies and who has contributed to the accomplishment of this work as well as pre­ paring this manuscript, any feeling of personal achievement that might have been attained.

iv TABLE OF CONTENTS

Page

INTRODUCTION ...... 1

REVIEW OF L I T E R A T U R E ...... 4

Influence of Age and Nutrition on Carcass Composi­ tion ...... 4

Rate of Growth and Its Effect on the Carcass ...... 5

Genetic Aspects of Growth Rate and Carcass Composi­ tion ...... 8

Emphasis on Chemical Composition ...... 11

Variations Found in Single Muscles ...... 16

PROCEDURES AND TECHNIQUES ...... 18

Source of Animals ...... 18

Slaughter Procedure ...... 19

Carcass Measurements ...... 19

Cutting Procedures ...... 19

Moisture Determination ...... 20

Determination of Fat ...... 21

Iodine Number Determination ...... 22

Free Fatty Acid Values ...... 23

Determination of pH ...... 23

Nitrogen Determination ...... 24

Protein Values ...... 24

Calculation of Calories ...... 25

v TABLE OF CONTENTS (Continued)

Page

RESULTS AND DISCUSSION ...... 26

Experimental Animals ...... 26

Chemical Relationships with Days of Age ...... 28

Fat Relationships ...... 31

Relationships with Muscle Development ...... 37

Loin Eye Size ...... 38

Lean Cuts ...... 40

Primal Cuts ...... 42

Effect of Sex ...... 45

SUMMARY ...... 48

BIBLIOGRAPHY ...... 51

APPENDIX ...... 57

Calculation of Protein ...... 57

Calculation of Percentage Intramuscular Fat ...... 57

Formula for Feeds ...... 58

Tabulated Chemical Data ...... 60

Carcass Information ...... 62

AUTOBIOGRAPHY ...... 65

vi LIST OF TABLES

Table Page

1 Breeds of Swine Represented by the Study ...... 27

2 An Arbitrary Grouping of Age Range Showing Numbers of Hogs in Each Group ...... 28

3 Chemical Factors Observed in Relationship to Days of Age ...... 29

4 The Relationship of Days of Age and Muscle Composi­ tion ...... 30

5 Degree of Pork Carcass Fatness and Its Relationship to the Nature and Amount of Ether Extract from the Longissimus Dorsi Muscle ...... 32

6 Backfat Thickness Gradations Showing Number of Individuals at Each Level ...... 33

7 Percentage Fat Trim Gradations Showing Number of Individuals at Each Level ...... 36

8 Factors Studied in Relation to Carcass Muscle Development ...... 38

9 The Relationship of Loin Eye Size to Days of Age and Selected Chemical Factors of the Longissimus Dorsi Muscle ...... 39

10 Size of Loin Eye and Number of Individuals in Each Arbitrary Grouping ...... 40

11 The Relationship of Percentage Lean Cuts to Days of Age and Selected Chemical Factors of the Longissimus Dorsi Muscle ...... 41

12 Percentage Lean Cuts and Number of Individuals in Each of the Levels ...... 42

13 The Relationship of Percentage Primal Cuts to Days of Age and Selected Chemical Factors of the Longissimus Dorsi Muscle ...... 43

vii LIST OF TABIES (Continued)

Table Page

14 Percentage Primal Cuts and the Number of Indi­ viduals at Each Level ...... 44

15 Effect of Sex on Selected Chemical Factors of the Longissimus Dorsi Muscle ...... 46

16 The Moisture, Fat, Protein, and Calorie Content of the Longissimus Dorsi Muscle ...... 60

17 Cutting Data for the Pork Carcasses ...... 62

viii CHAPTER I

INTRODUCTION

Agriculture, like many other American industries, is presently in a period of very rapid change. The family-type, general farm is being replaced by larger, more highly specialized farming units. There is evidence of increased mechanization at every level. This general trend has affected all phases of American agriculture: production, marketing, processing, and consumer buying.

The changes in the swine industry reflect the effects of this general shift in the American way of life. Swine producers are striving to produce hogs that will gain well and reach market weight at an early age. This, of course, facilitates a system of multiple farrowing and allows the specialized unit to realize greater returns from investment.

The increase in consumer popularity of vegetable shortening over lard has made it desirable for the swine producer to select and produce hogs that will yield a greater percentage of their carcass in the demanded cuts and a lesser amount in the form of fat for lard.

The diet-conscious American people, in addition to rejecting lard as their favorite shortening, have insisted that they prefer to buy leaner meats when they fill the family food basket. Considerable research effort has been directed toward the selection, breeding, and production of hogs that tend to fulfill the requirements stated above. The characteristics of the muscle tissue of hogs that gain rapidly and reach market weight at an early age are not so well known. Could it be that in emphasizing rapid muscle development we are producing pork that is higher in moisture and hence lower in protein than was formerly the case? If so, this would tend to support recent retailer claims that pork from "meat type" hogs does not "hold" as well in the display case as other pork. Is the quantity of intramuscular fat or marbling, long associated with pork quality less in hogs that are marketed at a younger age? Is there a relationship between muscle development and the chemical composi tion of pork muscle that would tend to influence pork processing and the nutritive value of the resulting product? These and other questions are currently being asked and there seems to be insufficient evidence to provide adequate answers. An elucida­ tion of these factors would be of interest and concern to every phase of the swine industry.

THE PROBLEM

The purpose of this study has been (1) to investigate the effect of age upon the chemical composition of pork muscle,

(2) to relate certain chemical constituents to degree of muscle development, (3) to study the effect of degree of fatness upon the muscle composition, and (4) to establish the relationship of sex and muscle characteristics. CHAPTER II

REVIEW OF LITERATURE

Influence of Age and Nutrition on Carcass Composition. Early investigators working with the selection and production of meat animals were cognizant of the variable composition of the result- ing carcasses. Moulton, Trowbridge and Haigh (40) concerned themselves with the changes in chemical composition of the beef carcass as a result of age and different planes of nutrition.

They observed that the total empty animal shows an increase in fat content and a decrease in other constituents with age and plane of nutrition. In their work, when a comparison was made on a fat-free basis, the animal showed a striking change in composition depending on age alone. The animal reached a maxi­ mum water content in six months and a maximum nitrogen content at eleven months of age.

Ellis and Zeller (17) studied the influence of a low fat ration upon the composition of the body fat of hogs. They re­ ported that the fat in the muscle is more unsaturated than the stored fat. Fatty acids found in greatest quantities were oleic, palmitic, and stearic.

It was shown by Callow (10) that the chemical composition of the various tissues of the pig show variations as growth proceeds. The fat content of the fatty tissues shows a well- marked increase with advancing age. The chemical nature of the fat also undergoes progressive changes. In all cases, the fat

becomes more saturated with Increasing age, and as a result, the

iodine number drops. This drop is more noticeable in the muscu­

lar tissue than in the outer layers of backfat.

The quantity of intramuscular fat varies with the age of

the pig and the position in the body from which the muscle was

obtained. The rate of deposition of fat was greatest near the

head and least near the tail (13).

Work by The Food Investigations Board (18) showed that after

20 weeks of age, the saturation of each depot of fat attains a specific value and that there is little subsequent change.

This value, however, was influenced by the rate at which the

fat was deposited. A pig with a rapid rate of fat deposition had a more saturated fat. This same group reported that sex plays a part in the rate of deposition and that hogs (castrated males) tend to have a more saturated fat than gilts.

Rate of Growth and Its Effect Upon the Carcass. Comstock et al.

(14) state that rapid growth of swine is important to the pork producer for several reasons: "Faster growing pigs require less feed per unit of gain in weight. Overhead costs of labor is smaller when growth is rapid and there is less risk involved." 6

The work of McMeekan involving growth and development of the pig and its resulting carcass characteristics offers evidence of early concern for this area of study.

We believe that these characters (bone, muscle, fat, and offals) are the result of growth and developmental changes occurring within the body, that differences in the rate and order and extent of development of particu­ lar parts and particular tissues are responsible for the differences in the form and composition, and in consequence, in the meat quality of individual animals, of animals of different weights, of different breeds, and to a large extent even of different species. (38)

According to McMeekan, muscle exceeds all other tissue in growth from birth to 24 weeks at which point it is overtaken by fat. Between 24 and 28 weeks, about 50 per cent more fat than muscle is being laid down in the body (38).

This author further states that the percentage of fat in the muscle increases with age and that the percentage of water decreases. He also observed that the fat becomes more saturated as the animal ages. In addition, the fiber diameter increases as the age of the animal increases (38).

Joubert (24) found that the greatest growth rate occurred at an early age and that as the animal grows older, muscle fibers increase in diameter.

Young animals fattening slowly have the largest partition percentage for protein in the muscle (24). Gains in live weight per unit of dry feed fed falls off as rate of fattening is increased. Callow (8) explains that this Is because the protein that Is laid down Is associated with over three times Its weight of water, whereas fat Is laid down as such. High partition percentages for protein will thus be associated with greater gains in carcass weight per pound of dry food fed.

Further work by Callow Indicates that chemical fat in the muscle increases in a regular manner during fattening but that there are factors other than level of fatness that influence this intramuscular fat (8).

Dickerson (15) indicates that rate of gain and carcass composition are both determined by the growth rate of constitu­ ent tissues. "Changes in the character of hog carcasses will inevitably result if rate of growth is changed more for some tissues or parts than for others." He believes that if carcass composition is to be compared, it should be done at a constant age rather than at a fixed weight.

Callow indicates that sex can modify the rate of fattening even when the increase in carcass weight is the same. Hence growth rate is not a good indicator of merit unless the nature of the growth is known (9).

The rate of oxidation of the fat in the fatty tissues of pork was investigated by Lea (35). He states that the chemical composition of the fat is one of the factors involved with rate of oxidation and that the rate at which the fat was deposited influences the chemical composition. The inherited characteristics of the individual animal was also considered to be a factor. Ac­ cording to Judge (26), meaty carcasses with minimum amounts of fat were found to yield soft, slightly marbled muscles at a slightly higher rate than did less meaty, fatter carcasses. Neither the age at slaughter nor the sex of the hog affected muscle type.

Genetic Aspects of Growth Rate and Carcass Composition.

Having observed some of the effects of rapid growth rates, in­ vestigators became concerned with the heritability of these characteristics. Krider et_ al. (32) reported that heritable differences in weight of pigs increased steadily from 5 per cent at birth to 24 per cent at 180 days of age. These workers suggested that the 180-day weight, being more highly heritable, would be a preferable measure of growth rate to the 150-day weight which had been used.

Palmer et_ al. (44), in a rather comprehensive report on the genetic differences in the biochemistry and physiology in­ fluencing food utilization for growth in rats, observed that rats of a well-founded, low efficient strain had a higher moisture percentage and a higher protein percentage than those of a high efficient strain. High efficiency rats became fatter than low efficiency ones. Within each strain, males had a higher moisture and a higher protein percentage than did females but females were consistently fatter. All rats became lower in moisture with increasing age.

"Knowledge of the physiological changes associated with the alterations in body weight due to selection may give insight into the mechanisms controlling normal development and may further our understanding of the genetic situations controlling growth," states

Fowler (20) in prefacing work on the growth and carcass composi­ tion of strains of mice. She observed that mice selected over a long period for large body size had a higher fat percentage and a lower moisture percentage than either a control line or a strain selected for small body size when tested at 6, 9, and

12 weeks of age. Between 13 and 107 days, the water/protein ratio decreased in all strains with increasing age. The per­ centage of protein decreased slightly in the large line after

40 days of age. "Some of the differences in carcass composi­ tion within a strain can be attributed to different growth rates, so that at any absolute age each line being at a relatively different stage of development will have a different carcass composition." (20) She cautions that a breeding program that emphasizes increase in protein is unlikely to yield maximum rate of improvement if selection is based on total body weight and 10

If the character of the weight gain is unknown. This is true

because the relative amount of fat, protein, and water con­

tributing to total carcass weight may vary even though the

absolute rate of increase in weight is similar.

Noffsinger et al. (41) state that the relative rate of fat versus muscle deposition in swine differs considerably depending

on age and size of animal. These workers found a straight line

relationship between backfat thickness and body weight for each of four genetic lines of swine.

Some carcass characteristics of swine in the eighth genera­

tion of production under four combinations of full and limited

feeding were investigated by Brunstad and Fowler (5). They indicate that the plane of nutrition on which the animal is raised represents a major part of the environmental effect of performance. The genotype of an animal impels it to follow a particular line of development; however, if the ration received varies in amount, differing patterns of development may result even when the hereditary make-up is exactly the same. They observed a highly significant positive correlation between age and primal cut yield when level of feeding was the main cause of the variance in age. Older animals yielded a higher percentage of primal cuts than younger animals. 11

Emphasis on Chemical Composition. Many of the studies cited

earlier in this review included statements regarding chemical

composition and factors that might cause variation. The work

cited in this section will emphasize the factors and their effect.

Dukes (16) reports a great variability in the composition of muscle tissue. He cites the following figures: water, 75 per cent; protein, 18-20 per cent; carbohydrate, 1 per cent

(mainly glycogen); soluble material (non-protein and non­ carbohydrate , 3-5 per cent; fatty acids 0.5-1 per cent minimum).

Some early work with the variability of pH in pork tissue was done by Sair and Cook (51). They concluded that one of the characteristics of pork with a high pH value was that it held moisture much more effectively than when the pH was low.

PH 5.2 was cited as the value where loss of moisture was at its maximum.

Winkler (57) studied the relationship between pH and tender­ ness. Toughness was at a maximum at pH 5.0-6.0 and at lower or higher levels the meat was more tender. There was less variation in the pH of pork than there was in beef.

The pH value of the meat is also related to the color (58).

A pH of 5.5 was deemed to be the optimum point. Below this, the meat was light and above this value the meat became darker in color. 12

Bate-Smith (4) states that: "The pH of the flesh plays a vital role in every phase of Meat Technology. In pork, the expected variation in pH is 5.4-6.7. Within these limits of variation, pH has a marked effect on both the physical and biological properties of meat." According to this investiga­ tion, meat with a high pH is dark in color, slimy, and yielding to the touch. In addition, salt will not readily penetrate the tissues and the high pH favors enzyme activity and bacterial growth.

Jacobson and Fenton (28) observed no relationship between the small variations found in the pH of beef and level of nutri­ tion, age of animal, or type of muscle.

Scaife (52) reported that there is a marked pH variation within individual muscles of the pig and that this variation seems to be related to pigment concentration since, when it re­ mains relatively constant, there is insignificant variation in pH. The nature of pH studies is complex. Scaife offers this advice:

In the sampling of muscles for pH determination certain precautions are clearly necessary if fallacious values are not to be obtained. In the case of pig muscles an additional variation within individual muscles occurs over and above the effects of oxygen penetration and variations in connective tissue. Such variations in ultimate pH can be quite large and in view of these findings the significance of many of the deductions based upon ultimate pH of pig muscles must be treated with some reserve. 13

Palsson and Verges (45), working with lambs varying from 9

to 41 weeks of age, observed that the percentage of fat in the

longissimus dorsi muscle appeared to be more dependent on age

of the animal than upon the plane of nutrition. These workers

also reported that the iodine number of the fat in the longissimus

dorsi was more affected by age of the animal than by the state of

fatness. The percentage of moisture in the muscle decreased with

increasing age.

Jacobson and Fenton (27) investigated the palatability,

cooking data, moisture, fat, and nitrogen of beef from dairy

cattle of different ages (32, 48, 64, and 80 weeks) and on

different levels of nutrition. They found that there was a

decrease in moisture content of the muscle with increasing

age. They associated this decrease of moisture with an increase

in the percentage of fat. These investigators reported that the

total nitrogen expressed on a dry, fat-free basis showed a highly

significant difference between the &ge groups.

Callow (8) observed that the percentage of chemical fat

in the muscular tissue rises as the percentage of fatty tissue

in the carcass increases. There is considerable variation in

individual animals which, according to this investigator, indi­ cates that factors other than general level of fatness influences

the chemical composition of the muscle tissue. Kemp £t al. (30) reported that ham fat from barrows had a

significantly lower average iodine number than ham fat from

gilts and that free fatty acids were negligible in fresh pork

samples. Palmer and co-workers (43) observed that the keeping

quality of frozen pork declined with a decrease in saturation

or higher iodine number values. Watts (54) states that the

susceptibility of any natural fat to oxidative rancidity depends upon its degree of unsaturation and Gibbons (21) says that the hardness of fat depends on age of the animal and the rate of deposition -- the more rapid the deposit of fat, the lower its iodine number. The work of Callow and Searle (11) substantiates this view. They report that there is a tendency for the per­ centage of fat within the muscle to increase as the carcass gets fatter and for the iodine number to decrease. According to these workers, the iodine number of the fat is higher for the muscular tissue than for the fatty tissue.

Callow (12), working with lambs, reported that early maturing muscles have higher iodine numbers than late maturing muscles.

He reported that iodine numbers of muscular tissue varied from

51.5 to 61.7.

Merkel e_t al. (39) observed a high moisture content in the muscles of pigs fed alfalfa hay and 62 per cent total digestible nutrients. Accompanying this high moisture were higher iodine 15

numbers for the backfat but the quantity of intramuscular fat

was not significantly affected by the ration.

Kelly and co-workers (29) studied the effect of antibiotic

supplementation for swine and reported that most of the differences

in composition appeared to be due to changes in the moisture and

fat with the percentage protein remaining more nearly constant.

Pierce (46) reported no significant difference in chemical

composition, moisture, protein, and fat of the lean tissue in pigs

fed antibiotics and control pigs.

Baker (3) suggests that the water/protein ratio in fresh pork remains relatively constant and is 3.5-3.6.

Hankins et_ a U (22) reported that there is little variation

in the gross chemical composition of fat-free muscle from cattle, hogs, and sheep. It is when fat has been deposited, to a

greater or lesser extent, within the muscle tissue that important variations in the proportions of moisture, protein, fat, and ash begin to appear.

Kropf (33) studied the effect of protein level and quality in swine rations on growth and carcass development. He reported

that carcasses from pigs fed a 16 per cent good quality protein ration (proper balance of essential amino acids) had higher

levels of carcass protein, greater muscular development, and 16

decreased fatback thickness when compared with a 12 per cent

protein or a 16 per cent poor quality protein ration. The

intramuscular fat of the longissimus dorsi was lowest and the

percentage moisture was highest for the 16 per cent good quality

protein group.

Reith et_ al. (47) found no relation between protein content

and the age of the animal. The data, however, showed a slight

correlation between fat content and percent protein.

Watts (54) reported that the type and amount of fatty acids

can be influenced by the ration. However, she observed more

differences between individuals on the same ration than there

was between individuals on different rations.

Hartman and Shorland (23) state that the muscle fat of

lambs contains over 3 per cent of C20 unsaturated acids or

about three times as much as the fat from fatty tissues. These workers indicate that the pattern of distribution of fatty acids between different tissues is not predictable since there are so many variables involved.

Variations found in single muscles. In work reported by

Kielanowski ejt al. (31) the longissimus dorsi muscle was divided into six equal lengths and analyzed for percentage fat. The highest relationship of the sections to the entire muscle was obtained for the section situated at the last three ribs. Barrows showed a mean value of 2.19 per cent while the value for gilts was reported as 1.88 per cent.

Mackey and Oliver (36) observed that pork chop characteris­ tics differ, not only due to variation among animals, but due to position of the chop within the loin.

Weir (56) found that the anterior and posterior parts of the loin muscle are more tender than the center. CHAPTER III

PROCEDURES AND TECHNIQUES

Source of Animals

Animals for this study were made available through the

normal functioning of the Ohio Swine Evaluation Station.* These

animals were considered to fit the experimental design of this

project since there were available approximately the same number

of gilts and barrows. This made possible a comparison of the

sex influence. Then, too, all hogs in the evaluation program

are self-fed the same ration so that the effect of nutrition o is controlled. Nine breeds are represented in the study.

A pair of pigs, litter-mate barrow and gilt, from a quali­

fied litter are brought to the Evaluation Station by participating

breeders. This pair of pigs is penned together and fed to

approximately 210 pounds. Feed efficiency and rate of gain are

determined for each pair of pigs. When the individual pig

reaches the predetermined weight, it is weighed out and trans­

ported to The Ohio State University Meat Laboratory for subse­

quent slaughter and test cutting.

^Outlines of the objectives and policies of the Ohio Swine Improvement Association are available through the Department of Animal Science, The Ohio State University.

^The complete ration is given in the Appendix to this report.

18 19

Slaughter Procedure

The pigs were held overnight in the Meat Laboratory holding

pens. During this time they had access to water but feed was

withheld. Dressing was the modified packer style, i.e. head

removed, carcass split, but ham facing and leaf fat remain with

the carcass. Hot carcass weight was recorded and carcasses were

chilled at approximately 38°F. for 48 hours.

Carcass Measurements

Carcass length and average backfat thickness were determined

as recommended by the Reciprocal Meat Conference (48).

Cutting Procedure

Both sides were weighed to the nearest one-tenth pound

immediately before cutting and this weight recorded as chilled

carcass weight. This weight was used in calculating percentage

primal cuts, percentage lean cuts, and percentage fat for lard.

Primal cuts as used in this report refer to the skinned ham,

trimmed loin, fresh belly, and New York style shoulder. Lean

cuts include all four of the above except the fresh belly.

The carcasses were cut into wholesale cuts and trimmed

following the procedure as suggested by the Reciprocal Meat

Conference (49). Loin eye area was determined by tracing the

muscle exposed by breaking the untrimmed loin between the tenth and eleventh rib. This technique has been described by Cahill (6). 20

These tracings were subsequently measured with a compensat­ ing polar planimeter.

Samples for chemical analysis were taken as quickly as possible after wholesale cut weights had been recorded. To provide for uniform sampling procedures, the eleventh to thirteenth rib section was taken from the same loin that was traced for ’’size of loin-eye" determination. This 3-rib section was immediately boned and the longissimus dorsi muscle freed of all external fat and connective tissue. The trimmed muscle section was wrapped in freezer paper and frozen at -22°C. until the laboratory analysis could be performed.

Moisture Determination

The frozen muscle samples were removed from the freezer and allowed to soften slightly at 5°C. while still tightly wrapped. As soon as these samples could be sliced, a portion was removed from both ends of the muscle section and one from the center. The remaining sample was returned to the freezer and held for further determination. The still frozen sections were diced, mixed and ground three times through a Hobart

Kitchen-Aide grinder attachment. The samples were well mixed between grindings. As the sample was ground for the third time, it was caught in a 2-ounce bottle with a screw-type lid and allowed to come to room temperature before weighing. 21

The juice that had escaped from the ground tissue while thaw­ ing was absorbed when the sample was thoroughly stirred.

Duplicate samples of approximately 9 -grams were weighed in tared disposable aluminum pans and allowed to oven dry at 100-

102°C. for 16-18 hours or until consecutive weighings showed no change in weight of the sample. The dried samples were cooled in a desiccator and a dry weight was recorded. The difference between fresh weight and dry weight was recorded as moisture and expressed as percentage moisture of the sample. This procedure is essentially the same as described by the Association of

Official Agricultural Chemists (2).

Determination of Fat

The duplicate dried samples used for moisture determination were finely ground by mortar and pestle and transferred to previously dried and weighed extraction thimbles. The thimbles containing the samples were weighed, placed in the Soxhlet ex­ traction apparatus, and extracted with anhydrous ethyl ether until subsequent weighings revealed no change in weight. Ex­ ploratory work revealed that 6-8 hours extraction time was sufficient for these samples and all samples were extracted for

8 hours to avoid repeat weighings. The extracted samples were oven dried at 100°C. for two hours, cooled in a desiccator and weighed. The difference in weight before and after extraction was recorded as fat and reported as percentage fat on a dry- weight basis. 22

It was difficult to obtain quantitative transfer of the dry

pulverized samples from the mortar to the extraction thimbles.

It was decided that by employing a simple ratio that the per­

centage fat present in the original fresh sample could be cal­

culated. The following ratio was employed:

Wt. of dry sample extracted m Wt. of original moisture-free sample Wt. of fat extracted Fat in original sample

The percentage fat could then be expressed on a fresh weight basis

from the fresh weight of the sample used for moisture determina­

tion.

Iodine Number Determination

Since this investigation concerns the characteristics of

the loin muscle, one of the measurements desired was that of

the saturation of the intramuscular fat. To obtain samples of

this fat for iodine number determination, it was necessary to

extract it under conditions which would assure minimum change in

the saturation. This was accomplished by grinding a fifty gram

sample and extracting it with two volumes of 95 per cent ethanol

at 55°C., under nitrogen for 20 minutes. The extract was then

filtered and the sample extracted with ethanol-ether (2 volumes-

1 volume). This extraction was repeated three times, each for

fifteen minutes at 55°C. and under nitrogen. The filtrate from each extraction was combined. The solvent and most of the mois­

ture was removed by flash evaporation under vacuum at 55°C. for 23 one hour. The solute was then taken up in chloroform. Chloro­

form insoluble material was removed by filtering through glass wool and the last traces of moisture were removed with anhydrous magnesium sulfate.

Duplicate 5 milliliter quantities of the chloroform-fat solution were evaporated to dryness in previously weighed alumi­ num drying pans. The pan and its contents were subsequently cooled and weighed and the difference in weight was recorded as the weight of fat in 5 milliliters of the solution. Five milliliters of solution were then used for iodine number determina­ tion which was performed as recommended by the Association of

Official Agricultural Chemists (2).

Free Fatty Acid Values

Free fatty acid values were determined from duplicate 3 Ml. aliquots of the chloroform-fat solution. The chloroform was slowly evaporated and the fat taken up in 25cc. of ethanol.

Phenolphthalein was used as an indicator and the fatty acids titrated with .01 normal sodium hydroxide. Free fatty acids were expressed as stearic acid in one gram of fresh pork tissue.

Determination of pH

Approximately 10 grams of comminuted muscle tissue was added to 100 Ml. of distilled water and mixed thoroughly by means of a

Waring blendor. 24

The pH of this homogenate was determined by the use of a

Beckman pH meter equipped with an external glass electrode.

Nitrogen Determination

Samples for nitrogen determination were obtained from the ground samples subjected to extraction for iodine number determinations. These samples were dried, finely ground through a Wiley mill and subjected to ether extraction for 6 hours to assure that they were fat-free. The fat-free samples were again dried to remove all solvent and moisture. Duplicate 0.25 gram samples of the dried, fat-free tissue were used for nitrogen determination employing the Kjeldahl procedure as described by

Foulk £t al. (19).

Protein Values

Protein values on a moisture-free, fat-free basis were cal­ culated by multiplying the nitrogen content by the factor 6.25.

Reith (47) indicates that there is no great risk in this because the factor 6.25 for meat protein as proposed by Kjeldahl has never been seriously questioned. This would tend to indicate that common usage has made this factor acceptable. By a consideration of the moistur£ and fat content of the sample, protein was also expressed on a fresh weight basis.^

JSee Appendix for detailed description of this procedure. 25

Calculation of Calories

Calories per 100 grams of muscle tissue were calculated by multiplying the protein content by 4 and the fat content by 9.

The sum of these figures is the protein and fat calories per

100 grams of the sample. This procedure was suggested by The

American Heat Institute Foundation (1). CHAPTER IV

RESULTS AND DISCUSSION

Experimental Animals

In a report of this nature, it is difficult to consider

all of the many variables that exist. It is known that there

are heritable differences in growth rate, nature of growth,

and muscle characteristics. These heritable differences have

been shown to exist between breeds and between individuals of

the same breed. Nine breeds are represented in this study.

However, the effect of breed cannot be adequately determined,

since there are insufficient numbers of individuals of each breed. Table 1 shows the breeds represented and the number of animals of each breed.

Within-breed variation is present in the study, since,

in general, the hogs of each breed came from more than one breeder. This factor is difficult to evaluate under the condi­

tions of this investigation. Hence, it is suggested that the animals in this study represent market weight hogs of different breeds and different lines within breeds as is the case with

the daily hog slaughter of the Packing Industry. However, it

should be noted that there has been a degree of selection in

the breed lines of this study. The variation of any one characteristic studied may have been reduced from that of the

total population.

26 27

TABLE 1

BREEDS OF SWINE REPRESENTED BY THE STUDY

Breed Total Number of Animals Per Cent

Yorkshire 32 36.78

Hampshire 20 22.99

Landrace 16 18.39

Berkshire 6 6.90

Poland China 4 4.60

Spotted Poland China 3 3.45

Duroc 3 3.45

Tamworth 2 2.30

Chester White 1 1.15

No attempt has been made to study the environment of the individual hogs used in this work. They were all fed the same ration under the same conditions of management. (The ration is listed in the Appendix of this report.) They were all fed to a similar weight of 200-210 pounds. It seems then, that any differences observed can be studied with respect to rate of weight gain or, for convenience, "days of age." Table 2 reflects the age range represented. It may be observed that while the range is narrow, it does include many of the hogs normally marketed at the slaughter weight used in this investi­ gation. 28

TABLE 2

AN ARBITRARY GROUPING OF AGE RANGE SHOWING NUMBERS OF HOGS IN EACH GROUP

Days of Age Number of Animals Per Cent

129-139 9 10.34

140-149 20 22.99

150-159 33 37.93

160-169 16 18.39

170-179 7 8.05

180-183 2 2.30

Chemical Relationships with Days of Age

A characteristic of today's meat-type hog is that it pro- duces a maximum amount of muscle as efficiently and as rapidly as possible. As a result of this emphasis, one of the criteria used in selection is the rate of weight gain. Animals selected on this basis tend to reach market weight at a relatively younger age. The literature indicates that age of the animal and rate of growth have an influence on the composition of the resulting product. The chemical factors of muscle composition listed in Table 3 were studied with respect to days of age to determine

If any definite relationships could be observed within the range of ages represented by this Investigation. Ranges and mean values will show the degree of variation In the factors studied.

TABLE 3

CHEMICAL FACTORS OBSERVED IN RELATIONSHIP TO DAYS OF AGE

Factor Number of Range Mean Observations

Days of Age 87 129-183 153.80

Percentage Moisture 87 69.67-75.86 73.74

Percentage Ether Extract, Fresh 87 0.69-6.18 2.75

Percentage Ether Extract, Dry 87 2.77-20.70 10.33

Percentage Protein, Fresh 87 19.76-24.81 22.75

Percentage Protein, Dry 87 90.57-99.85 96.97

Percentage Nitrogen 87 14.49-16.63 15.49

Iodine Number 87 44.64-82.36 61.48

Free Fatty Acid Value 84 .0858-.2924 0.1556

PH 73 5.12-6.38 5.50

Calories per 100 gms. 87 101.29-148.50 115.74 The individual values of the factors listed in Table 3 were plotted graphically with days of age. For the most part, no relationships were observed. Table 4 reflects the correla­

tion coefficients for those factors where a statistical trend was indicated by the graphs (42).

TABLE 4

THE RELATIONSHIP OF DAYS OF AGE AND MUSCLE COMPOSITION

Number of Correlation Factor Observations Coefficient

Free Fatty Acid Values 84 -.1274

Percentage Protein, Dry Basis 87 -.0894

Percentage Protein, Fresh Basis 87 -.1139

Percentage Ether Extract, Fresh Basis 87 +.0490

Calories per 100 grams 87 -.0202

The low correlation coefficients indicate that within the scope of this investigation there is no significant relationship between days of age and any of the factors studied. This may be interpreted to mean that rate of weight gain of market hogs to 200-210 pounds has no influence on percentage moisture, percentage ether extract, percentage protein, fat saturation, free fatty acids, caloric content, or the acidity of the result­ ing muscle. 31

Fat Relationships

The work has shown that within the range o£ animals studied,

we cannot explain observed variations on the basis of age or

weight gain. Consequently, an investigation of other factors

seemed appropriate. A question of concern to all people

associated with the swine industry centers around the relation­

ship of degree of carcass fatness to the quantity and nature

of the fat within the muscle. This degree of carcass fatness

was measured by backfat thickness and by percentage fat trimmed

from the carcass during the course of carcass cutting as sug­

gested by The Reciprocal Meat Conference (49). Ether extract

was considered to be an accurate measure of intramuscular fat.

Backfat thickness and fat trim were studied in relationship

to ether extract expressed on a fresh basis and also on a

moisture-free basis. In addition, iodine numbers and free

fatty acid values were compared with respect to carcass fatness.

All factors were tabulated and plotted graphically. Correla­

tion coefficients were computed for those factors where a statisti­

cal relationship was indicated. Table 5 presents the results of this phase of the investigation. 32

TABLE 5

DEGREE OF PORK CARCASS FATNESS AND ITS RELATIONSHIP TO THE NATURE AND AMOUNT OF ETHER EXTRACT FROM THE LONGISSIMUS DORSI MUSCLE

Degree of Fatness Number of Correlation as Measured by: Factor Studied Observations Coefficient

Backfat Thickness Percentage Fat Trim 87 +.7073*

None Backfat Thickness Ether Extract, Fresh 87 Indicated

Backfat Thickness Ether Extract, Dry 87 None Indicated Backfat Thickness Iodine Number 87 -.3158* None Backfat Thickness Free Fatty Acid Value 84 Indicated

Backfat Thickness Calories per 100 Gms. 87 +. 1404

Percentage Fat Trim Ether Extract, Fresh 87 +.4513*

Percentage Fat Trim Ether Extract, Dry 87 +.4546*

Percentage Fat Trim Iodine Number 87 -.2805* None Percentage Fat Trim Free Fatty Acid Value 84 Indicated

Percentage Fat Trim Calories per 100 Gms. 87 +.4168*

*Significant at .01 level.

The data indicates that backfat thickness as measured in

this study is not significantly related to the degree of marb­

ling present in the loin eye as determined by ether extraction.

This is in conflict with the accepted view that carcasses with 33 thick backfat are inclined to possess more marbling than thinner carcasses. It is in agreement, however, with the observations of Callow (8) that factors other than the general level of fat­ ness influence the amount of intramuscular fat.

Correlation coefficients indicate that the percentage of fat trim is more closely related to the ether extract of the muscle tissue than is the backfat thickness. This is an interesting observation and one that is not completely understood. The percentage fat trim as identified in this work includes the fat trimmed from the major cuts in carcass cutting as well as the leaf fat and ham facing of the carcass. Merkel et_ al. (39) observed that the amount of leaf fat was not necessarily related to backfat thickness. There seems to be a relationship between leaf fat and ether extract of the muscle tissue since the amount of fat trimmed from the cuts is a function of backfat thickness. A highly significant correlation coefficient of

+.7073 was shown in this study for backfat thickness and per­ centage fat trim. The physiology of this relationship is not clear.

A study of the number of calories per 100 grams of muscle tissue indicates that ether extract influences calories as would be expected. Accordingly, there is no significant dif­ ference in calories based upon backfat thickness while percentage fat trim shows a highly significant positive relationship. 34

Iodine number is commonly considered to reflect the degree

of unsaturation of the fat. The values obtained in this investi­

gation reflect the iodine number of fat extracted from the

muscle tissue. Callow and Searle (11) observed that iodine

number for fat from muscular tissue is higher than for fat from

fatty tissue and that the iodine number will decrease as the

carcass gets fatter. This seems to be true in this work.

Iodine number of the fatty tissue was not investigated but

the mean value obtained for muscular tissue is slightly higher

than that reported by Callow (8) for fatty tissue of the pork

carcass. It may be concluded from the negative correlations

expressed for iodine number and degree of fatness in Table 5

that as the carcass increased in fatness, the iodine number became smaller. This, of course, indicates that the intra­ muscular fat from fatter hogs is more highly saturated; hence,

it should be a firmer fat. Whether or not the unsaturation of

intramuscular fat from less fat hogs is a factor in the appearance

and shelf life of retail pork cuts is not known. Palmer's

(43) report that the keeping quality of frozen pork declined with a decrease in saturation lends validity to an assumption of this nature. No attempt was made to evaluate firmness or

shelf life of carcasses or cuts in this study. 35

It must be considered that the variation in backfat thick­ ness of the hogs represented by this report was not great.

Table 6 presents the range in backfat thickness and the number of individuals within each gradation. It is significant to note that a representative number of these carcasses would be considered as overly fat in terms of present grading standards while none of the samples would be evaluated as needing more fat. A correlation coefficient of -.1244 for backfat thickness and days of age fails to show a significant relationship.

TABLE 6

BACKFAT THICKNESS GRADATIONS SHOWING NUMBER OF INDIVIDUALS AT EACH LEVEL

Gradations of Backfat Thickness (Inches) Number of Individuals Per Cent

1.00-1.10 1 1.15

1.10-1.20 1 1.15

1.20-1.30 9 10.34

1.30-1.40 9 10.34

1.40-1.50 19 21.84

1.50-1.60 14 16.09

1.60-1.70 12 13.80

1.70-1.80 12 13.80

1.80-1.90 9 10.34

1.90-2.00 1 1.15 36

The information presented in Table 7 serves to indicate the variation in percentage fat trim from hogs of this study. The number of animals within each range is given. A correlation co­ efficient of -.1492 for percentage fat trim and days of age fails to show a significant relationship between these two factors.

TABLE 7

PERCENTAGE FAT TRIM GRADATIONS SHOVING NUMBER OF INDIVIDUALS AT EACH LEVEL

Per Cent Fat Trim1 Number of Individuals Per Cent

13.0-14.0 1 1.15

14.0-15.0 0 —

15.0-16.0 1 1.15

16.0-17.0 3 3.45

17.0-18.0 6 6.90

18.0-19.0 6 6.90

19.0-20.0 8 9.19

20.0-21.0 6 6.90

21.0-22.0 15 17.23

22.0-23.0 13 14.94

23.0-24.0 13 14.94

24.0-25.0 5 5.75

25.0-26.0 6 6.90

26.0-27.0 3 3.45

27.0-28.0 1 1.15

^Based on chilled carcass weight. 37

Relationships with Muscle Development

Another aspect of this investigation was a consideration of the composition of the muscle as it is related to muscularity in the animals. As stated previously, there presently is increased emphasis upon the production of hogs that may be identified by the term "meat-type." These hogs are appraised in part by their amount of muscling. That these hogs are of greater value in terms of yield of high priced cuts cannot be questioned. The relationship between extent of muscle develop­ ment and muscle components that may be important in processing and merchandising is not so well known. To assist in elucidat­ ing this area of interest, several relationships were studied.

It was necessary to arrive at some definition of muscling or muscle development before comparisons could be made. A con­ sideration of present practices indicated that the criteria most often used in carcass research and in selection were square inches of loin eye measured at the tenth rib, percentage primal cuts and/or percentage lean cuts. Accordingly, these same criteria were used in this study.

The factors listed in Table 3 that were investigated with reference to carcass development are shown in Table 8. For convenience of reference, the range and mean value of each factor is given. 38

TABLE 8

FACTORS STUDIED IN RELATION TO CARCASS MUSCLE DEVELOPMENT

Factor Range Mean

Day8 of Age 129-183 153.80

Percentage Moisture 69.67-75.86 73.74

Percentage Nitrogen 14.49-16.63 15.49

Percentage Protein, Dry 90.57-99.85 96.97

Percentage Protein, Fresh 19.76-24.81 22.75 pH 5.12-6.38 5.50

Iodine Number of Intramuscular Fat 44.64-82.36 61.48

It seems pertinent to discuss each measure of muscling or meatiness and its relationship to the factors studied. All values for each relationship were plotted graphically and cor- relation coefficients were determined where a trend was observed.

A statistician scrutinized all graphs and determined those that required statistical treatment before conclusions could be drawn.

Loin Eye Size

Table 9 presents the factors studied with respect to loin eye size and, where applicable, correlation coefficients are given. 39

TABLE 9

THE RELATIONSHIP OF LOIN EYE SIZE TO DAYS OF AGE AND SEIECTED CHEMICAL FACTORS OF THE LONGISSIMUS DORSI MUSCLE

Factor Number of Correlation Observations Coefficient

Days of Age 87 +. 1447

Percentage Moisture 87 +.1725

Percentage Nitrogen 87 None Indicated

Percentage Protein, Dry 87 -.1515

Percentage Protein, Fresh 87 +.0801 pH 73 None Indicated

A lock at the data in Table 9 quickly shows that within the scope of this investigation, there is no significant relation­ ship between degree of muscling as measured by the size of the loin eye and any of the factors observed.

Table 10 presents the gradations in loin eye size and the number of individuals witbin each range.

While the range in loin eye size is quite wide, it should be noted that more than sixty percent of the individual measure­ ments are between 3.50 and 4.50 square inches. This fact must be considered in evaluating the results of this study. It can 40 be concluded, however, that In pork carcasses from hogs weighing

200-210 pounds, there Is no relationship between the size of the loin eye and days of age, percentage moisture, percentage nitrogen, percentage protein expressed on a dry or fresh basis, or the pH of the resulting muscle.

TABLE 10

SIZE OF LOIN EYE AND NUMBER OF INDIVIDUALS IN EACH ARBITRARY GROUPING

Square Inches Loin Eye Number of Individuals Per Cent

2.50-3.00 3 3.45

3.00-3.50 13 14.94

3.50-4.00 37 42.53

4.00-4.50 21 24.14

4.50-5.00 9 10.34

5.00-5.50 2 2.30

5.50-6.00 2 2.30

Lean Cuts

Another method of evaluating meatiness is a consideration of the percentage yield of the lean cuts. This includes the fresh skinned ham, the trimmed loin, and the New York style shoulder.

Table 11 presents the results of the investigation with respect to this characteristic. 41

TABLE 11

THE RELATIONSHIP OF PERCENTAGE LEAN CUTS TO DAYS OF AGE AND SELECTED CHEMICAL FACTORS OF THE LONGISSIMUS DORSI MUSCLE

Number of Factor Correlation Coefficient Observations

Days of Age 87 +.1817

Percentage Moisture 87 +.3728*

Percentage Nitrogen 87 -.0983

Percentage Protein, Dry 87 +.0071

Percentage Protein, Fresh 87 +.0097

PH 73 None Indicated

*Signifleant at .01 level.

It can be observed that the only factor showing a significant relationship with percentage lean cuts is the percentage mois­ ture in the muscle. Since percentage lean cuts reflects to a degree the relative amount of lean to fat in the carcass, it seems logical to expect this relationship. This indicates that as the animal develops, the major change in muscle composition is that of moisture and that the protein content remains relative­ ly unchanged. Although ether extract was not studied with respect to lean cuts directly, it may be concluded from a study of Table

5 that as percentage lean cuts increase, ether extract will decrease since percentage lean cuts is influenced by percentage fat trim. 42

TABLE 12

PERCENTAGE LEAN CUTS AND NUMBER OF INDIVIDUALS IN EACH OF THE LEVELS

Per Cent Lean Cuts Number of Individuals Per Cent of Total Sample

45.00-46.00 1 1.15

46.00-47.00 5 5.75

47.00-48.00 7 8.05

48.00-49.00 15 17.24

49.00-50.00 10 11.50

50.00-51.00 11 12.64

51.00-52.00 11 12.64

52.00-53.00 11 12.64

53.00-54.00 7 8.05

54.00-55.00 3 3.45

55.00-56.00 3 3.45

56.00- + 3 3.45

Table 12 presents the percentage lean cuts and the number of

Individuals represented at each level.

Primal Cuts

Percentage primal cuts Is often used In appraising carcass merit. Table 13 shows the relationship to percentage primal cuts of the factors studied. 43

TAB1E 13

THE RELATIONSHIP OF PERCENTAGE PRIMAL CUTS TO DAYS OF AGE AND SELECTED CHEMICAL FACTORS OF THE LONGISSIMUS DORSI MUSCLE

Number of Correlation Factor Observations Coefficient

Days of Age 87 +.2019

Percentage Moisture 87 +.3479*

Percentage Nitrogen 87 -.0725

Percentage Protein, Dry 87 None Indicated

Percentage Protein, Fresh 87 +.0425 pH 73 +.0779

Ether Extract, Fresh 87 -.5525

Iodine Number of Intramuscular Fat 87 +.3977*

*Signifleant at .01 level.

It may be observed that in relationship to percentage primal cuts, percentage moisture and iodine number are the only factors studied that show a significant positive correlation. As would be expected, there is a significant negative correlation with percentage ether extract. This can be interpreted to mean that the greater the percentage of primal cuts, the less the quanti­ ty of intramuscular fat in the loin eye. This is in agreement 44 with the work of Judge (26) where he observed that meaty car­ casses yielded soft, slightly marbled muscles at a higher rate than did less meaty ones.

Table 14 shows the percentage of primal cuts and the number of Individuals at each level.

TABLE 14

PERCENTAGE PRIMAL CUTS AND THE NUMBER OF INDIVIDUALS AT EACH LEVEL

Per Cent of Cent Primal Cuts Number of Individuals Total Sample

60.00-61.00 2 2.30

61.00-62.00 6 6.90

62.00-63.00 6 6.90

63.00-64.00 11 12.64

64.00-65.00 16 18.39

65.00-66.00 13 14.94

66.00-67.00 15 17.24

67.00-68.00 9 10.34

68.00-69.00 4 4.60

69.00-70.00 3 3.45

70.00- + 2 2.30 45

A review of the data dealing with meatiness and other selected factors seems to make a few observations appropriate.

1. Within the limits of this investigation, neither loin eye

size, percentage lean cuts, nor percentage primal cuts is

affected by rate of weight gain as measured by days of

age.

2. Significant relationships cannot be shown for meatiness

and the percentage protein of the muscle whether it is

expressed on a fresh weight basis or on a moisture-free

basis.

3. The meatier carcasses show a significantly higher moisture

content in the muscle.

4. There is a decrease in the percentage of ether extract

or intramuscular fat as meatiness increases.

5. No relationship can be observed between meatiness and the

pH of the muscle.

6. The intramuscular fat of meatier carcasses tends to be

less highly saturated.

Effect of Sex

Certain chemical factors of the muscle were studied to learn their association, if any, with the sex of the animal.

The carcasses of thirty-nine barrows and forty-eight gilts comprised the study. Table 15 presents the results of this investigation. 46

TABLE 15

EFFECT OF SEX ON SELECTED CHEMICAL FACTORS OF THE LONGISSIMUS DORS I MUSCLE

Mean Values Factor Barrows (39) Gilts (48)

Percentage Moisture 73.67 73.79

Percentage Ether Extract 2.86 2.66

Percentage Nitrogen 15.56 15.44

Iodine Number of Intramuscular Fat 61.12 61.77

It has been Indicated by work of The Food Investigations

Board (18) that barrows have a more saturated fat than gilts.

Iodine number for the intramuscular fat in this study shows that the average for barrows is 61.12 and for gilts is 61.77.

These values fail to indicate any significance when analyzed statistically.

Palmer et_ al_. (44) observed that in rats, males were higher in moisture and higher in percentage of protein than were females, while females were higher in fat. Kielanowski et al.

(31) state that barrows showed a mean value of 2.19 per cent fat in the longissimus dorsi while gilts had a mean value of

1.88 per cent. The average moisture for barrows in this study 47

was 73.67 per cent while for gilts it was 73.79. Barrows showed

a mean fat percentage of 2.86 while gilts yielded 2.66 per cent

fat in the longissimus dorsi. These values are not statistically

different but the trend is in agreement with the work of

Kielanowski.

A per cent nitrogen of 15.56 for barrows and 15.44 for

gilts, expressed on a fat-free, moisture-free basis, is not

significant and indicates that there is no difference in

percentage protein of the muscle of barrows and gilts.

This investigation has been directed to an understanding

of the effect of the selection of hogs for rapid weight gain

and increased meatiness on the resulting pork product. Informa­

tion of this nature is of practical interest to swine producers, meat processors, and meat merchandisers. Research workers and

those responsible for guiding the development of the swine industry have long been concerned with the many factors that cause variation in the muscles of pork. It is realized that the conclusions indicated by the data of this study are subject to the limitations of the investigation. Some new trends and relationships have been observed, while others have only been confirmed. SUMMARY

The composition of pork muscle was investigated in an attempt to elucidate some of the factors contributing to its variability. The longissimus dorsi muscle from 87 hogs of variable but known ages was analyzed for moisture, ether extract, and protein. The iodine number of the intramuscular fat was determined as well as the quantity of free fatty acids present.

Graphical analysis and correlation coefficients indicate that there is no significant relationship between percentage mois­ ture of the muscle and the age of the animal, within the range of ages studied. The same is true with respect to ether extract whether expressed on a fresh or a moisture-free basis. Like­ wise, there is no significant difference in protein content expressed as nitrogen, as protein on a fat-free, moisture- free basis, or as a percentage of the fresh tissue. Iodine number determinations show a wide variation (44.6-82.3) but no relationship to age of the animal could be shown. The same was true for quantity of free fatty acids where the range of values was from .0858 per cent to .2924 per cent expressed as stearic acid.

An investigation of the pH of the muscle failed to show a significant relationship with days of age.

48 Caloric value of Che muscle based on protein and fat con*

tent was not related to age of the animal.

Another phase of the investigation was directed to a study

of carcass meatiness and its relationship to muscle composition.

The size of the loin eye, the percentage yield of primal cuts,

and the percentage yield of lean cuts was used as a measure

of carcass meatiness or muscle development. No relationship was observed between loin eye size and percentage moisture,

percentage protein, or the pH of the muscle. Percentage mois­

ture waa significantly correlated with the yield of primal cuts

(+.3479) and also with the yield of lean cuts (+.3728). Ether

extract showed a negative correlation with primal cuts (-.5525) and a similar relationship was apparent for yield of lean cuts.

This leads to the conclusion that meaty hogs produce muscle

that is higher in moisture and lower in intramuscular fat than

less meaty hogs.

A study of meatiness and days of age failed to show a signifi­ cant relationship for either of the three measures of meatiness.

Backfat thickness and percentage fat trim were considered to be two measures of carcass fatness. When these factors were correlated with the amount of intramuscular fat, a significant relationship was shown for percentage fat trim but not for back- fat thickness. This indicates that intramuscular fat is influenced 50 by factors other than backfat thickness and that the deposition of Intramuscular fat cannot be accurately predicted from back­ fat thickness alone.

There were 39 barrows and 48 gilts represented by the study. No statistically significant difference could be shown between barrows and gilts with respect to intramuscular fat, iodine number, moisture content, or percentage protein.

The results of this investigation are not final. There are many questions yet unanswered: (1) What would be the situation if the age of the hogs was held constant and weight was permitted to vary? (2) How do the retail cuts respond to the environment of the retail meat case? (3) Is there a difference in the nutritional value of the pork? (4) How does the pork respond to processing techniques? These, and many other equally pertinent questions, provide the stimulus for further investigation. BIBLIOGRAPHY

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31. Kielanowski, J., L. Lassota and Z. Osinska. Fat Content in the Longissimus Dorsi Muscle of Bacon Carcasses (Roczn. Nauk. rol., 1954, 69, B 33-44), Abstr. in Jour. Sci. Food Agr.. 6, 1955.

32. Krider, J. L., B. W. Fairbanks, W. E. Carroll, and E. Roberta Effectiveness of Selecting for Rapid and for Slow Growth Rate in Hampshire Swine. Jour. An. Sci.. 5:3, 1946.

33. Kropf, D. H., R. W. Bray, P. H. Phillips. Effect of Protein Level and Quality in Swine Rations Upon Growth and Car­ cass Development. Jour. An. Sci.. 18:755, 1959.

34. Lawrie, R. A. Factors Affecting tyoglobin Concentrations in Muscle. Jour, of Agr. Sci., 40:365, 1950.

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36. Mackey, Andrea Overman and A. H. Oliver. Sampling Pork Loin for Cooking Tests. Food Res.. 19:298, 1954.

37. McCarthy, John F. and David L. Mackintosh. Some Observations on the pH of Pork Under Various Conditions. Food Tech., 7:167, 1953.

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57. Winkler, C. A. Tenderness of Meat: I Recording Apparatus for Its Estimation, and Relation Between pH and Tender­ ness. Canadian Jour, of Res.. 17D:8, 1939. 56

58. Winkler, C. A. Colour of Meat: I Apparatus for Its Measurement and Relation Between pH and Colour. Canadian Jour. Res.. 17D:1, 1939.

59. Zobrlsky, S. E., D. E. Brady, J. F. Lasley, and L. A. Weaver. Significant Relationships in Pork Carcass Evaluation. I. Lean Cuts as Criteria for Live Hog Value. Jour. An. Sci.. 18:420, 1959. APPENDIX

I. Method for Calculating the Percentage Protein In the Fresh Sample

1. X ■ Weight of fresh sample

2. Wt. of moisture-free, fat-free sample ■ X - (Wt. fat + Wt. water)

Wt. of fat ■ Percentage fat from previous determination x X

Wt. of water * Percentage water from previous determination x X

Having found the weight of the fresh sample:

3. Let Y * Percentage protein in fresh sample

Then: Weight protein in dry, fat-free sample * Weight of fresh sample x Y

. . v „ Weight protein in dry, fat-free sample ln_ And Y Weight of fresh sample x AUU

II. Method for Calculating Percentage Fat on a Fresh Weight Basis

1. Calculate the weight of fat that would have been extracted

from a quantitative transfer of the sample used for moisture

determination. Call this value X.

Weight of sample extracted „ Weight of original sample Weight of fat extracted X

2. Then: Percentage fat on a fresh weight basis (Y) is determined

as follows:

Y - ---r-—— , v- x 100 Fresh Sample Weight

57 58

FORMULA FOR FEEDS

Feed fed to pigs Feed fed to pigs up to 120 lbs. from 120 lbs. up (SES Ration No.l) (SES Ration No.2) Ingredients (15.AX C.P.) (13.7X C.P.)

Coarsely ground, shelled yellow corn 78.5 82.4

Meat and bone scraps 3.0 2.0

Soybean oil meal 14.0 11.0

Dehydrated alfalfa meal 2.5 2.5

Antibiotic-Vitamin- Arsenical antioxidant premix, approx. .5 .5

Trace mineralized salt .5 .5

Mineral mixture 1.0 1.1 TOTAL 100.0 100.0

Estimated Crude Estimated Specifications for ingredients used; Protein X Minerals %

Corn, shelled yellow, U.S. No. 2 8.2 1.2

Meat and bone scraps 50.0 28.0

Soybean oil meal, toasted, solvent extracted 50.0

Alfalfa meal, dehydrated 17.0 9.5 not less than 17«0X crude protein not more than 27.OX crude fibre not less than 100,000 I.U. Vit. A per lb.

Antibiotics - 10 grams of aureomycin hydrochloride per ton of feed 10 grams of PB 10 (Commerical Solvents Corp.) per ton of feed Specifications for ingredients used: (Continued)

Vitamins - 10 milligrams of B^2 Per ton 2.5 grams of riboflavin per ton of feed 10 grams of calcium pantothenate per ton of feed 16 grams of niacin per ton of feed 180,000 units of D per ton of feed

Arsenical - 90 grams of arsenilic acid per ton of feed

Antioxidant - .25 lb. of B.H.T. per ton of feed

Mineral Mixture - 20 lb. of dicalcium phosphate per ton of feed in SES Ration No. 1 23 lb. of dicalcium phosphate per ton of feed in SES Ration No. 2 80 p.p.m. of zinc 60 TABLE 16 THE MOISTURE, FAT, PROTEIN, AMD CALORIE CONTENT OF THE LONGISSIMUS DORSI MUSCLE

Days Caloriei Sex Tattoo % Moisture % Fat % Protein Total of Age 100 Km G 000 160 72.46 3.47 22.36 98.29 120.67 B 100 158 73.00 2.94 23.38 99.32 119.98 G 200 153 71.46 3.26 24.09 98.81 125.70 G 300 153 69.67 4.41 24.81 98.89 138.88 G 400 144 71.69 3.71 23.45 97.85 127.19 B 220 137 72.14 2.40 24.53 99.07 119.72 G 14 172 74.06 2.16 23.76 99.98 113.48 B 24 144 74.48 2.59 22.66 99.73 113.95 B 32 141 73.24 2.12 24.34 99.70 116.44 G 31 146 73.83 2.75 23.26 99.84 117.79 B 040 140 74.08 3.36 22.42 99.82 119.92 G 032 153 75.14 2.11 22.37 99.62 108.47 G 030 153 74.61 2.00 ----- B 031 153 74.24 2.26 G 041 161 73.50 2.32 24.03 99.85 117.00 G 042 162 74.34 2.11 23.01 99.46 111.03 G 120 146 74.42 3.18 21.82 99.42 115.90 G 140 142 74.04 2.79 21.94 98.77 112.87 G 043 160 73.56 2.10 23.84 99.50 114.26 G 100 155 73.52 2.47 23.58 99.57 116.55 B 210 135 73.93 2.51 23.51 99.95 116.63 G 044 155 74.27 2.21 23.00 99.48 111.89 B 110 146 70.17 6.18 23.22 99.57 148.50 B 130 145 74.01 3.05 22.58 99.64 117.77 B 200 135 73.51 1.66 24.33 99.50 112.30 B 400 143 74.15 3.21 21.47 98.83 114.77 G 230 164 72.77 3.01 23.15 98.93 119.69 B 220 164 73.52 3.73 21.85 99.10 120.97 B 240 156 72.98 2.83 23.63 99.44 119.99 B 300 163 73.73 3.14 22.76 99.63 119.30 B 320 150 72.43 3.91 23.52 99.86 129.27 B 330 152 72.20 3.99 23.26 99.45 128.95 G 340 152 73.74 2.28 23.13 99.15 113.04 G 310 155 74.10 2.20 23.11 99.41 112.24 B 00 168 74.18 2.18 22.25 98.61 108.62 B 02 149 75.08 2.16 21.52 98.76 105.52 G 420 154 75.32 1.70 22.48 99.50 105.22 G 430 150 71.36 5.67 22.42 99.45 140.71 G 03 138 73.32 2.58 23.70 99.60 118.02 G 410 158 73.70 3.17 22.00 98.87 116.53 B 440 149 75.51 2.03 21.02 98.56 102.35 G 01 168 74.55 2.59 21.35 98.49 108.71 G 04 156 75.27 1.94 21.95 99.16 105.26 B 10 154 73.96 2.26 23.22 99.44 113.22 B 11 154 74.46 2.84 21.57 98.87 111.84

61 111.26 125.89 100 gm. 114.54 109.44 114.64 117.78 114.28 109.21 118.65 129.57 107.75 106.35 118.79 107.18 116.57 114.37 104.01 122.51 118.06 109.31 121.46 112.06 117.65 120.16 106.40 126.96 101.29 118.55 108.06 103.52 119.10 104.88 Calories/ 99.33 99.57 99.13 99.05 135:20 99.76 Total 99.38 105.92 98.87 99.04 116.84 99.44 99.18 98.75 99.35 98.26 99.42 98.99 99.16 99.35 99.24 99.62 99.70 113.79 99.38 98.93 105.54 98.34 99.99 99.62 99.32 99.00 99.15 111.59 99.0099.1099.20 113.41 103.20 113.78 98.66 22.37 22.14 99.14 22.99 23.45 24.05 23.33 21.56 22.70 23.06 23.28 22.37 99.01 23.1722.92 99.33 21.0321.92 23.53 97.81 23.13 99.65 22.97 99.40 113.30 21.5823.07 99.10 23.8322.64 99.44 23.00 22.06 23.77 23.0322.64 99.59 102.56 22.56 22.74 23.81 22.17 99.40 23.07 ZProtein 2.42 2.50 23.01 5.71 21.27 99.24 136.47 1.82 4.29 21.82 2.52 2.56 ZFat 3.45 21.90 2.95 2.412.01 4.05 21.88 2.03 1.86 1.66 2.41 3.253.22 22.10 2.21 2.66 1.98 1.40 2.38 1.16 2.39 1.36 0.69 3.11 3.38 2.72 19.76 4.08 2.06 73.02 73.82 74.78 TABLE 16 (Continued) 73.93 72.05 5.44 74.61 73.75 74.47 74.57 73.17 73.73 3.69 20.84 73.76 3.76 73.16 73.89 73.37 3.87 74.78 1.99 22.85 74.05 73.75 74.78 1.60 75.86 75.16 73.57 74.46 74.3973.51 2.51 2.29 22.25 23.20 75.00 ZMoisture

150 153 150 172 146 74.68 2.32 134 164156 73.70 73.52 157 74.65 1.40 144 161 72.02 149 ofAge 162 179 162 Days 139 162 140 158 138 155 73.35 158 75.40 181 151 154 152 171 73.85 183 74.19 14 12 13 30 157 74.65 1.71 22.74 99.10 34 31 24 20 21 146 72.26 22 23 166 73.03 32 152 74.46 40 41 33 129 00 168 43 01 168 73.60 2.90 42 159 000 002 004 003 Oil 170 73.30 020 001 163 010 021 022 013014 137023 74.24 148 74.63 012 032 030 031 158 033 024 151 043034 171 042 010Oil 171 73.33 040 it too it

C5B0O0BOM«0O0«WnOWBC5UO««OO0O«0O«MBn0P30Sffl0«OOU 62

TABLE 17

CUTTING DATA FOR THE FORK CARCASSES

Pen No. Backfat Per Cent Square Per Cent Per Cent and Breed Thickness Fat Trim Inches Primal Lean Tattoo (Inches) Loin Eye Cuts Cuts

41-000 Duroc 1.63 21.05 4.68 66.10 51.40 43-100 Yorkshire 1.80 25.28 3.60 61.40 46.71 44-14 Yorkshire 1.47 19.02 4.12 67.20 54.03 46-200 Landrace 1.43 22.13 3.25 64.80 48.42 47-300 Duroc 1.80 23.78 3.36 63.50 48.44 49-400 Sp. Pol. China 1.63 22.54 4.70 65.00 49.93 58-220 Sp. Pol. China 1.77 22.89 3.83 64.40 47.89 58-230 Sp. Pol. China 1.47 19.55 4.79 67.60 52.26 60-220 Poland China 1.47 18.81 5.32 67.80 53.80 63-041 Yorkshire 1.50 21.40 4.08 65.60 50.97 64-042 Yorkshire 1.53 23.23 3.68 62.50 47.94 65-240 Yorkshire 1.83 26.16 3.35 60.90 45.97 65-23 Yorkshire 1.43 21.24 4.87 66.10 52.26 66-24 Yorkshire 1.80 25.60 2.93 62.90 47.07 66-24v Yorkshire 1.60 27.18 3.04 60.60 46.54 69-31 Landrace 1.20 17.98 3.94 68.10 53.25 71-00 Hampshire 1.27 17.70 4.26 69.40 54.82 71-01 Hampshire 1.30 20.50 4.05 66.40 51.74 72-043 Hampshire 1.40 22.76 3.79 63.80 49.01 73-032 Yorkshire 1.40 21.40 4.28 64.10 50.14 74-300 Yorkshire 1.43 20.61 3.85 65.40 51.23 75-044 Poland China 1.43 19.54 5.19 66.70 53.66 75-32 Poland China 1.63 18.80 4.94 66.50 52.63 76-100 Poland China 1.47 , 17.70 5.64 67.90 54.39 77-003 Berkshire 1.37 18.62 4.27 67.70 52.99 77-410 Berkshire 1.60 22.01 3.79 64.20 49.29 78-310 Hampshire 1.80 21.81 4.08 66.30 51.28 81-110 Hampshire 1.30 23.20 2.96 63.50 47.80 81-120 Hampshire 1.30 19.92 3.62 66.10 51.20 82-420 Hampshire 1.23 17.52 4.37 67 .40 53.17 82-040 Hampshire 1.37 22.26 3.22 64.20 48.44 83-34 Hampshire 1.50 21.82 3.90 65.80 50.94 90-31 Hampshire 1.50 21.20 4.52 65.80 52.36 90-30 Hampshire 1.57 21.38 3.55 65.50 51.96 91-440 Hampshire 1.27 16.36 4.63 69.30 55.08 91-140 Hampshire 1.40 20.64 4.32 66.60 52.44 92-32 Hampshire 1.23 15.90 4.84 70.10 56.29 92-00 Hampshire 1.23 16.95 5.73 69.10 56.33 93*41 Hampshire 1.67 23.06 3.85 65.40 51.35 63

TABLE 17 (Continued)

Pen No. Backfat Per Cent Square Per Cent Per Cent and Breed Thickness Fat Trim Inches Primal Lean Tattoo (Inches) Loin Eye Cuts Cuts 93-01 Hampshire 1.73 23.41 4.26 64.30 50.03 94-400 Hampshire 1.70 24.73 3.96 62.20 48.29 94-030 Hampshire 1.23 19.42 4.00 66.70 52.46 95-12 Hampshire 1.23 21.10 3.87 65.10 49.34 95-02 Hampshire 1.27 18.96 3.79 67.20 53.15 96-000 Hampshire 1.70 24.27 4.35 63.20 48.15 96-42 Hampshire 1.70 25.90 3.17 61.90 48.26 97-011 Berkshire 1.43 17.99 4.30 68.60 52.90 97-001 Berkshire 1.47 19.99 3.41 65.40 49.90 98-13 Berkshire 1.60 22.70 3.82 64.00 47.97 98-14 Berkshire 1.47 23.02 3.57 63.70 47.92 99-43 Yorkshire 1.83 26.01 3.37 61.10 48.80 99-03 Yorkshire 2.00 20.72 3.08 61.10 46.50 100-012 Duroc 1.63 22.74 3.99 64.20 50.89 101-20 Landrace 1.67 23.17 3.64 64.60 49.70 101-200 Landrace 1.30 19.13 4.40 66.20 52.01 102-21 Landrace 1.37 22.39 3.17 64.20 50.10 102-210 Landrace 1.53 21.05 3.71 65.10 51.10 103-002 Landrace 1.47 20.93 4.06 66.20 51.69 103-22 Landrace 1.83 25.17 3.23 62.50 47.76 104-022 Chester White 1.73 25.09 3.86 62.40 48.15 105-023 Yorkshire 1.73 24.44 4.21 64.00 50.60 105-011 Yorkshire 1.30 16.64 4.66 68.60 55.77 106-042 Tamworth 1.63 23.48 3.80 64.10 49.81 106-043 Tamworth 1.87 23.25 3.73 64.10 48.77 107-031 Yorkshire 1.33 18.52 3.83 67.90 53.26 107-032 Yorkshire 1.00 13.81 4.36 70.20 57.11 108-024 Yorkshire 1.57 21.66 3.67 66.10 51.48 118-013 Yorkshire 1.73 24.08 3.65 63.60 49.48 118-033 Yorkshire 1.53 21.53 3.97 65.30 50.94 119-014 Yorkshire 1.40 18.96 3.50 67.00 53.47 119-034 Yorkshire 1.50 21.87 3.89 64.50 50.13 120-020 Yorkshire 1.73 24.55 3.52 62.60 48.06 120-33 Yorkshire 1.53 23.92 2.93 63.00 49.23 121-021 Yorkshire 1.57 20.62 4.09 66.80 52.96 121-040 Yorkshire 1.50 19.07 3.84 66.90 52.25 122-010 Yorkshire 1.47 17.90 4.21 68.70 55.92 83-320 Landrace 1.57 22.61 3.80 64.20 48.10 84-04 Landrace 1.40 21.05 3.90 66.10 50.66 84-130 Landrace 1.50 22.00 3.54 63.40 46.92 85-10 Hampshire 1.73 23.68 3.60 63.60 48.99 85-11 Hampshire 1.73 22.72 3.86 64.70 49.57 64

TABLE 17 (Continued)

Pen No. Backfat Per Cent Square Per Cent Per Cent and Breed Thickness Fat Trim Inches Primal Lean Tattoo (Inches) Loin Eye Cuts Cuts 86-330 Yorkshire 1.83 26.53 3.32 61.10 46.07 86-340 Yorkshire 1.43 21.76 3.87 65.10 51.73 87-40 Yorkshire 1.67 23.73 3.33 63.20 48.73 87-430 Yorkshire 1.13 25.23 4.32 61.70 48.02 89-004 Yorkshire 1.67 23.88 3.58 63.30 48.49 89-010 Yorkshire 1.70 22.38 4.31 65.10 50.52 AUTOBIOGRAPHY

I, Bobby Dale VanStavern, was b o m near Union, Monroe

County, West Virginia, October 27, 1929. My primary and

secondary-school education was received in the Monroe County

Schools. In September 1948, I enrolled in the College of

Agriculture, West Virginia University, and was granted the degree Bachelor of Science in Agriculture in June 1952.

Upon graduation, I was commissioned into the United States

Air Force and subsequently served on active duty until August

1954. I received a research assistantship in the Department of Animal Science, The Ohio State University, and began my graduate training in September 1954. The degree Master of

Science was awarded in March 1956. I continued advanced

study for the degree Doctor of Philosophy while serving as part-time instructor in the Meat Laboratory of the Department of Animal Science.

65