Amino acid requirements and low crude protein, amino acid supplemented diets for swine and poultry
The purpose of this research was to determine requirements for amino acids that limit the use of crystalline amino acids, to determine the effects of reducing crude protein, and to evaluate the problems associated with low crude protein diets for swine and poultry. Four experiments were conducted to determine the Lys and sulfur amino acid requirements for 5- to 10-kg pigs. The results of these experiments suggest pigs in this weight range require a diet containing 1.40% true digestible (TD) Lys and the ratio of sulfur amino acids to Lys is not greater than 0.54. Two experiments were conducted to determine the requirement of Lys and sulfur amino acids in 90-kg barrows using plasma urea nitrogen as the response. These experiments indicate a TD Lys requirement of 0.57% and there was no response to TD sulfur amino acid concentrations above 0.27%. Six experiments were conducted to evaluate the Ile requirement of 80- to 120-kg barrows. These experiments indicate a requirement of 0.34% TD Ile in a corn-blood cell diet; however, the requirement may not be greater than 0.24% in barrows fed a corn-soybean meal diet. Two experiments were conducted to evaluate the effects of soybean meal and lowering crude protein in diets for late-finishing barrows. Results suggest that reductions in soybean meal are not the cause of increased carcass fat in pigs fed low crude protein diets. Furthermore, the fortification of a corn diet with crystalline Lys, Trp, and Thr will not support optimal growth or carcass composition. Five experiments were conducted to determine the effects of lowering crude protein in diets for broilers and to evaluate limiting essential and nonessential amino acids. Results indicate that low crude protein diets can support optimal growth of broilers when surfeit Gly is supplied in the diet. The requirement of Gly + Ser appears to be not less than 2.14% from d 0 to 17 posthatching.