Date of Award
Doctor of Philosophy (PhD)
Animal Science (Animal, Dairy, and Poultry Sciences)
L. Lee Southern
This research was conducted to obtain a better understanding of the amino acid needs of finishing pigs. Twelve experiments were conducted using the urea nitrogen method to determine the lysine requirement of gilts and barrows. Two experiments were conducted to determine the optimum ratio of total sulfur amino acids to lysine for finishing pigs (74 to 111 kg); and three experiments were conducted to evaluate the net energy content of low crude protein, crystalline amino acid supplemented diets for finishing pigs (70 to 117 kg). The lysine requirement of gilts, as determined by the urea nitrogen method, decreased as body weight increased from 20 to 80 kilograms; whereas, the lysine requirement of barrows decreased as body weight increased from 20 to 35 kilograms, and then remained similar as body weight increased from 35 to 80 kilograms. The optimum ratio of total sulfur amino acids to lysine for late finishing pigs is.40 to.47 for growth performance and muscling traits as determined by serum urea nitrogen concentrations, average daily gain, feed intake, feed efficiency, fat-free lean, lean gain per day, and retained energy in fat-free lean as protein. However, the optimum ratio to minimize fat traits is.65. Finally, finishing pigs fed low crude protein, crystalline amino acid supplemented diets with reduced net energy (either by dietary fiber addition or dietary fat removal) had similar growth performance, carcass characteristics, organ weights, organ energy expenditures, and lean and fat composition of the carcasses as pigs fed low crude protein, crystalline amino acid supplemented diets (without reduced net energy) or as pigs fed diets in which amino acids were provided from an intact protein source (i.e., soybean meal). Thus, lysine requirements can be determined by the urea nitrogen method; the optimum ratio of total sulfur amino acids to lysine for finishing pigs is not greater than.47 to obtain maximum growth performance and muscling traits; and the reduction of the net energy content of low crude protein, crystalline amino acid supplemented diets was not an effective means of reducing fat in finishing pigs.
Knowles, Theresia Alice, "Amino Acid Requirements and Crystalline Amino Acids for Finishing Pigs." (1997). LSU Historical Dissertations and Theses. 6542.