EFFECTS OF DIETARY AMINO-ACID CONTENT BETWEEN 20 AND 50 KG AND 50 AND 100 KG LIVE WEIGHT ON THE SUBSEQUENT AND OVERALL PERFORMANCE OF PIGS

Twenty-four gilts and 24 castrated males were used to investigate the effects of dietary amino acid content between 20 and 50 kg (0.423 or 0.765 g lysine/MJ DE) and 50 and 100 kg (0.423 or 0.612 g lysine/MJ DE) on the subsequent performance, carcass characteristics and internal organ weights. Between 20 and 50 kg, pigs offered the high-amino acid diet grew 18% faster (P < 0.001), and were 23 to 24% more efficient (P < 0.001) in utilization of feed and energy than those offered the low-amino acid diet. During 50 to 100 kg, however, pigs previously offered the low-amino acid diet tended to gain more rapidly and efficiently (P = 0.09) than those offered the high-amino acid diet, and there were no differences in the performance of the two groups between 20 and 100 kg. Similarly, pigs offered the high-amino acid diet to 50 kg tended to have better carcass characteristics and heavier (P < 0.001) liver and kidneys at 50 kg. However, the diets offered between 20 and 50 kg had no effect on these criteria at 100 kg. Between 20 and 100 kg, pigs offered the high-amino acid diet during 50 to 100 kg tended to gain faster (P= 0.08), and were more efficient (P < 0.01) in utilization of feed and energy than those offered the low-amino acid diet. The results indicated that the performance of pigs between 20 and 50 kg may have little effect on the overall rate and efficiency of growth or carcass quality.