SUMMARY

Fabian, J., L. I. Chiba, L. T. Frobish, W. H. McElhenney, D. L. Kuhlers, and K. Nadarajah.

A total of 16 castrated male pigs weighing approximately 20 kg were used in two trials to investigate the effect of grower diets (5.0 or 11.0 g lysine/kg) on growth performance and nitrogen balance. Common finisher 1 and 2 diets were offered when pigs reached approximately 50 and 80 kg, respectively. Pigs were placed in metabolism crates at 43, 70, and 91 kg for the grower, finisher 1 and finisher 2 phases, respectively, to determine nitrogen balance. There were no diet x trial interactions of interest, thus the data sets were combined.

Pigs fed the low-lysine grower diet grew more slowly and less efficiently (P < 0.001) during the grower phase and had more ultrasound backfat (P < 0.01) at the end of the grower phase than those fed the high-lysine grower diet. During the finisher 1 phase, however, pigs fed the low-lysine diet grew more efficiently (P < 0.05) than those fed the high-lysine diet, and the grower diet had no effect on overall weight gain, carcass traits, lean accretion, or meat quality scores. At 43 kg, pigs fed the low-lysine diet had less serum urea nitrogen (P < 0.001), triglycerides (P < 0.05), and total protein (P = 0.07), and more glucose (P < 0.01) than those fed the high-lysine diet. During the grower phase, pigs fed the high-lysine diet consumed more nitrogen (P < 0.001) and had higher apparent nitrogen digestibility (P < 0.05), utilization (P < 0.05), and retention (P < 0.001), but they excreted more fecal (P < 0.05) and urinary (P < 0.001) nitrogen than those fed the low-lysine diet. Pigs fed the low-lysine grower diet had a higher nitrogen utilization (P < 0.05) and tended to have a greater nitrogen retention (P = 0.08) during the finisher 1 phase, and excreted less urinary nitrogen (P < 0.05) during the finisher 1 and finisher 2 phases than those fed the high-lysine grower diet.

The results indicate that pigs subjected to early amino acid restrictions compensated completely in terms of growth performance and body composition. In addition, the restricted pigs exhibited compensatory nitrogen retention and reduced nitrogen excretion during the realimentation phase. Compensatory growth can, therefore, have a positive impact not only on the overall efficiency of pig production but also on the environment.

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