Optimal Threonine:Lysine Ratio for Growing Pigs of Different Sexes |
W. H. Chang, J. H. Lee, K. N. Heo, I. K. Paik, In K. Han |
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Abstract |
This study was conducted to investigate the effects of threonine:lysine ratios on growth performance, apparent nutrient digestibility and blood urea nitrogen (BUN) concentration, and to estimate the optimal threonine:lysine ratios for growing barrows and gilts. A total of 150 pigs (Landrace횞Yorkshire횞Duroc, 16.75 0.42 kg average body weight, 75 barrows and 75 gilts) was randomly allotted into six treatments in a 2횞3 factorial design. Six diets were formulated to contain 1.12% lysine for barrows and 1.33% lysine for gilts with three threonine:lysine ratios (50, 60 and 70%) for both barrows and gilts. Throughout the whole experimental period (16 to 56 kg body weight), there was no interaction between sex and dietary threonine:lysine ratio in average daily gain (ADG), average daily feed intake (ADFI) and feed conversion rate (FCR). Between sexes, there was a clear sex-effect showing better growth performance of barrows. Barrows consumed more feed (p<0.01) and grew faster (p<0.01) than gilts. For barrows, there was a trend to improved ADG and FCR with increasing threonine:lysine ratio. For gilts, there was a trend to improved ADG and FCR up to threonine:lysine ratio of 60%, but not significant. There was no interaction between sex and threonine:lysine ratio in nutrient digestibilities of growing pigs except for crude ash (CA). Between sexes, there were differences in nutrient digestibilities, except for calcium for which gilts showed higher a digestibility (p<0.01). Among dietary threonine:lysine ratios, there were no differences in nutrient digestibilities. Mean values of essential amino acids (EAA), non-essential amino acids (NEAA) and total amino acids (TAA) digestibilities were not affected by sex and dietary threonine:lysine ratio. There was no evidence of an interaction between sexes and dietary threonine:lysine ratio. Between sexes, total BUN concentration was lower in gilts than barrows (p<0.05). It was concluded that a 70 and 60% dietary threonine:lysine ratio for barrows (1.12% lysine) and gilts (1.33% lysine) tended to result in better growth performances and nutrient utilization and lower BUN concentration than other threonine:lysine ratios. |
Keywords:
Sexes; BUN; Growing Pig; Growth Performance; Amino Acid Digestibility; Threonine:Lysine Ratio |
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