Effects of Amino Acid Supplementation on Growth Performance for Weanling, Growing and Finishing Pigs

Four feeding trials with 260 pigs were conducted to evaluate the effects of supplementing the diet with different amino acids on growth performance and blood metabolites for weanling, growing and finishing pigs. One hundred twenty weanling pigs (Exp. 1, BW 8 kg), eighty growing pigs (Exp. 2. BW 20 kg), thirty growing pigs (Exp. 3, BW 29 kg) and thirty finishing pigs (Exp. 4, BW 50 kg) were randomly allotted to different dietary treatments according to sex and body weight. Pigs weight and feed consumption were measured at initiation and termination of each trial with 4 weeks. At the end of trial, blood samples from three pigs selected in each pen (Exp. 1) and each pig (Exp. 2) were obtained to determine the level of blood urea nitrogen, glucose, insulin and cortisol in the serum. In Exp. 1, pigs fed diet supplemented both with lysine and methionine had the best feed conversion ratio (p < 0.05), but no significant differences (p > 0.05) were observed in ADG and ADFI. Pigs receiving control diet obtained the obtained the optimal ADG (p < 0.05), ADFI (p < 0.05) and F/G for the whole period. No differences were detected in serum glucose, insulin and cortisol concentrations. In Exp. 2, pigs receiving the control diet exhibited the lowest serum urea nitrogen (p < 0.05), ADG, F/G and serum insulin concentration increased linearly (p < 0.05) with the inclusion of lysine, methionine, threonine and tryptophan in diets. No significant differences (p > 0.05) were detected for glucose and cortisol content in pigs serum among dietary treatments. In Exp. 3 and 4, pigs growth rate increased linearly (p < 0.01), and feed conversion efficiency was also improves by addition of lysine, methionine, threonine and tryptophan. In conclusion, pigs fed diets supplemented with lysine, methionine, threonine and tryptophan together obtained optimal growth performance in growing and finishing periods.