Considerations in the Use of Crystalline Amino Acids in Swine Diets

164 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1988.A series of experiments were conducted to evaluate the effects of reduced-protein, amino-acid-supplemented diets on pig performance, carcass characteristics, heat production and nitrogen and energy balance. Pigs from weaning to market weight fed diets reduced in protein by two to four percentage units below recommended levels exhibited inferior performance and carcass characteristics in comparison to pigs fed adequately. Pig performance and carcass characteristics were improved to a level equal to pigs fed the higher-protein diets when the reduced-protein diets were supplemented with the required indispensible amino acids. However, pigs fed the reduced-protein, amino-acid-supplemented diets tended to have greater backfat thickness than pigs fed diets of higher-protein content.Energy and nitrogen balance studies revealed that maximum nitrogen retention was achieved only when the reduced-protein diets were supplemented with both the deficient indispensable amino acids and a source of nitrogen for the synthesis of dispensable amino acids. Apparently, in the absence of adequate nitrogen, the pig retains excess ingested energy as lipid, thus contributing to a fatter carcass.Despite the measurement of a lower heat production when pigs were fed reduced-protein diets, they did not consume more feed than pigs fed the higher-protein diet. When pigs were restricted-fed in a thermal-stress environment, the lower heat production by pigs fed the amino-acid-supplemented diet resulted in greater feed efficiency than that of pigs fed the higher, i.e., recommended level, protein diet. This was not apparent when pigs were fed ad libitum. Pigs fed the reduced-protein, amino-acid-supplemented diet produced inferior carcasses compared to pigs fed the higher-protein diet.Evaluation of amino acid supplementation in diets for gravid gilts suggests that diets containing free- and protein bound-amino acids should be fed more frequently than a diet containing only intact protein. Threonine and(or) dispensable amino acid supplementation of a lysine- and tryptophan-supplemented corn diet did not permit gravid gilts fed the diet to reach the nitrogen retention level attained by gilts fed a 12% crude protein diet. This supports the hypothesis that one or more additional amino acids is limiting.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD