amino acid, growth, lysine requirements, finishing pigs


The objective of this study was to determine the standardized ileal digestible (SID) Lys requirement for growth and carcass performance of 225- to 280-lb finishing pigs. A total of 253 pigs (DNA 600 × 241, initially 224.9 lb BW) were used in a 23-d trial. Pens were blocked by BW and were randomly assigned to diets with 7 or 8 pigs per pen and 8 pens per treatment in a randomized complete block design. Diets were corn and soybean meal-based and fed in meal form. Dietary treatments consisted of 0.45, 0.55, 0.65, or 0.75% SID Lys. Increasing SID Lys increased (quadratic, P < 0.05) ADG and ADFI, resulting in pigs fed 0.55% SID Lys having the greatest final BW. A marginal significant improvement (quadratic, P < 0.10) was observed in F/G and caloric efficiency with increasing SID Lys. A marginal significant increase in carcass yield (linear, P < 0.10) and reduction (quadratic, P < 0.10) in backfat was also observed with increasing SID Lys. Carcass ADG increased (linear, P < 0.05) and carcass G:F was marginally improved (quadratic, P = 0.063), resulting in pigs fed 0.55% SID Lys having the greatest HCW. Furthermore, there was a marginal significant improvement (quadratic, P = 0.053) in carcass caloric efficiency on NE basis with increasing SID Lys. For ADG, quadratic polynomial (QP) model resulted in the best fit (BIC = 361.7) predicting 95, 98, and 100% of maximum growth at 0.50, 0.55, and 0.62% SID Lys, respectively. The QP and broken line linear (BLL) models had a comparable fit for F/G (BIC = 278.2 vs. 279.3, QP and BLL, respectively) with the QP model predicting 95, 98, and 100% of maximum feed efficiency at 0.48, 0.54, and 0.63% SID Lys, respectively. The BLL model predicted no further improvement in F/G over 0.55% SID Lys. In summary, the SID Lys requirement to obtain 100% of maximum response in this experiment was 0.62 and 0.63% for ADG and feed efficiency, respectively.


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