PROTEIN EVALUATION OF RABBIT MEAT by ANNE MARGARET SCHLUTZ, B.A. A THESIS IN FOOD AND NUTRITION Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE IN HOME ECONOMICS Approved Accept/ed Dean of the Gradu^/^ Schokl December, 1974 (Lops2 ACKNOWLEDGEMENTS I would like to express sincere appreciation to Mrs. Clara McPherson for her counsel and able assistance and also to Dr. S. P. Yang. I also thank Drs. John Pelley and Willis Starnes, and Harvey Olney of the Texas Tech University School of Medicine for their assistance and encouragement, and also my parents. 11 TABLE OF CONTENTS ACKNOWLEDGEMENTS ii LIST OF TABLES iv Chapter I. INTRODUCTION 1 Statement of the Problem 1 Purposes 2 Hypothesis 2 II. REVIEW OF LITERATURE 3 The Potential Value of Rabbit Meat 3 History of Rabbit Meat 6 Description of Rabbit Meat 8 Nutritive Value of Rabbit Meat 9 III. METHODS AND PROCEDURES 19 Selection of Meat Samples 19 Chemical Analyses 19 The Bioassay 21 Statistical Analysis of Data 25 IV. RESULTS AND DISCUSSION 26 Chemical Analyses 26 Amino Acid Analyses . ^ 26 Rat Growth Experiment 28 V. SUMMARY AND CONCLUSION 37 Summary 37 Conclusions 37 LIST OF REFERENCES 39 11• 1• LIST OF TABLES Table Page 1. Comparison of Farm-Raised Rabbits and Wild Rabbits 10 2. Composition of Raw Domesticated Rabbit Flesh 11 3. Composition of Rabbit Meat 13 4. Nutritional Value of Rabbit and Other Meats 15 5. Composition of Experimental Diets 23 6. Protein, Fat and Moisture Content of Cooked Tissues 24 7. Essential Amino Acid Content of Rabbit, Chicken, Beef, Pork, Cod, and Casein and the FAO Amino Acid Pattern (gm/lOO gm Protein) 27 8. Effect of Feeding Young Rats an Other­ wise Adequate Diet Containing 9% Protein from Different Sources 29 9. Analysis of Variance of Mean Weight Gain of Young Rats 30 10. Differences in Weight Gains (g) Among Rats Fed an Otherwise Adequate but Protein-Free Diet for 28 Days or the Same Diet Supplemented with 9% Pro­ tein from Chicken, Rabbit, Beef, Pork, Cod or Casein 30 11. Analysis of Variance of Mean Food Consumption of Young Rats 31 12. Differences Among Food Intakes (g) of Rats Fed an Otherwise Adequate but Protein-Free Diet for 28 Days or the Same Diet Supplemented with 9% Pro­ tein from Chicken, Rabbit, Beef, Pork, Cod, and Casein 32 IV Table Page 13. Analysis of Variance of Mean PER of Young Rats 33 14. Differences Among Protein Efficiency Ratios for Various Protein Sources .... 33 15. Analysis of Variance of Feed Efficiency of Young Rats 34 16. Differences in Feed Efficiency (g) Among Rats Fed an Otherwise Adequate but Protein-Free Diet for 28 Days or the Same Diet Supplemented with 9% Pro­ tein from Chicken, Rabbit, Beef, Pork, Cod or Casein 35 CHAPTER I INTRODUCTION Animal products are the most efficient source of dietary protein (1,2). The classical solution to protein deficiencies has been to add meat, milk, and/or eggs to the diet. Unfortunately, the distribution of meat cannot be im­ proved since the consumption of animal protein is determined largely by income, cultural patterns, and religions (3). The need for low cost quality proteins has prompted research for new sources. Recently the breeding of rabbits for human consumption has greatly increased (4). It seems feasible that in the future, rabbit meat, as a source of inexpensive high quality protein, may be more abundantly used in the American diet as well as the diets of people in other countries. Statement of the Problem Humans inherently possess dignity and pride and do not willingly eat foods which they consider to be inferior. Rabbit meat was consumed to a large extent during wartimes by civilians since it was not considered a meat and thus was not rationed. Another negative implication dates back to ancient times when man believed he developed the charac­ teristics of the animal he ate. If he ate a lion, he would be fierce and strong; if he ate a rabbit, he would be meek and mild (5). Therefore, rabbit dishes may have adverse connotations dating back not only to prewar days, but to times of primitive man. One may think of rabbit meat as the strong, gcimy-flavored hare usually hunted in the wilds. However, the commercially bred rabbits which consist of all white meat are different from the wild hare, and are quite acceptable for human consumption. Since there is contra­ dicting information in the literature concerning the protein quality of domesticated rabbit, an accurate evaluation of the protein content is needed to prove its value as an ac­ ceptable protein source for man. Purposes This study was undertaken to evaluate the quality of domesticated rabbit by determination of: 1) total protein, fat and moisture content, 2) amino acid content, and 3) the protein efficiency ratio (PER) by a bioassay procedure. Hypothesis In determining the protein quality of rabbit the following hypotheses were tested: 1) There is no difference in protein quality of rabbit and that of chicken. 2) There is no difference in the protein quality of rabbit and that of beef. 3) There is no difference between the protein quality of rabbit and that of pork. 4) There is no difference in the protein quality of rabbit and that of cod. CHAPTER II REVIEW OF LITERATURE The Potential Value of Rabbit Meat Seventy per cent of the world's population is under­ nourished and children in certain areas of the world are still victims of kwashiorkor, which is due to an inadequate supply of high quality protein (6). Although protein is not a limiting factor in the United States, there is evidence that protein quality may be a problem under certain ethnic or low income dietary situations, or due to a lack of educa­ tion (5,6) . Morrison and Campbell proved that high quality ani­ mal protein was a more efficient protein source than vege­ table protein by feeding one group of rats casein, and another group a vegetable diet. (The vegetable diet con­ sisted of 85% soybean and 10% wheat since soybean lacks methionine and wheat lacks lysine). On the higher quality protein diet (casein), less food was needed to meet nutri­ tional quality. When the lower quality protein (vegetable diet) was used, quantity had to make up for quality (7). Bender (8) concluded that an adult diet requires no more than 6% of calories in the form of protein and a mixed vegetable diet can be of equal value to animal pro­ tein. However, diets of lower protein percentage are ade­ quate only when sufficient food is eaten to meet calorie requirements (9). The F.A.O. suggested that by the year A.D. 2000, a threefold increase in total protein supplies would be needed and a fivefold increase in animal protein supplies would be needed in the developing countries. The protein food programs often include encouragement for animal pro­ duction and these activities are frequently supported by international organizations(10). The efficiency with which farm animals convert feed- stuffs into food for man has received much attention. Food conversion ratio is the number of pounds of feed required to produce one pound of live animal tissue (11). Swine, dairy cattle (milk) and poultry (eggs and broilers) are the most efficient converters of feed energy and protein into food for humans. Poultry is intermediate and beef and cattle are the least efficient. The values for energy are of little importance because animal production is needed primarily for protein sources and not as contributors of energy in the human diet (12). Rabbits are good food converters. The commercial­ ized all white meat rabbit gives a well fleshed carcass (13). The feed conversion of an entire rabbit herd which includes young replacement stock is 3.4 to 4 lbs. of feed to produce 1 lb. of body tissue. The feed cost to produce a lb. of edible meat is about 28C. Both feed conversion and feed cost include the total amount of feed for offspring, doe and buck (14). The number of young per year that a doe can produce varies from 24-45 depending on the strain (12). Most commercial meat producers raise 4-6 of 8 fryers each year per individually raised doe (15). In any comparison of food conversion in animals, it should be remembered that the nonruminants consume a smaller proportion of the whole crop. Rabbit is especially effi­ cient in crop consumption as it consumes its mother's milk for 50% of its life. Ninety-eight percent of commercialized rabbits are 8-10 weeks of age when they go to market, and weigh from 2 to 3 lbs. The food efficiency of animals varies with the pro­ portion of body fat they store. Therefore, future needs should be aimed toward producing animals low in fat and high in protein content since much of the fat in meat products is discarded rather than served as food energy (12). In this case, rabbit would be more efficient since it has a lower fat and higher protein content than chicken, beef, pork and lamb (16). Holmes (10) mentions food production per unit acre as an important factor in nutritional efficiency. Crop pro­ duction is superior to any form of animal production when comparing the amount of food produced per unit acre. Never­ theless, there are continuous problems of palatability and acceptability of vegetable protein and the nutritive value still requires critical evaluation. Broilers seem the most productive when compared to pork and beef (10). The production of broilers in 10 weeks, weighing 3 lbs.