Low Crude Protein Diets for Late Finishing Barrows

Abstract

AbstractTwo experiments were conducted with finishing barrows to determine the effect of low CP, amino acid (AA) supplemented diets on growth performance and carcass traits. In Exp. 1, 80 barrows (initial and final BW of 85.5 and 117.5 kg, respectively) were allotted to 4 treatments (5 replicates of 4 pigs per replicate). The dietary treatments were 1) corn-soybean meal diet (C-SBM) with 0.54% true ileal digestible Lys; 2) diet 1 but with crystalline Lys, Thr, and Trp to lower CP (LCP C-SBM); 3) corn-soy protein isolate diet (C-SPI) equal in Lys to diet 1; and 4) diet 3 but with crystalline Lys, Thr, and Trp to lower CP (LCP C-SPI). Daily gain was increased when CP was reduced in pigs fed the SPI diet but decreased in pigs fed the SBM diet (soy source x CP interaction, P < 0.02). Gain:feed was decreased with the decrease in CP in the C-SBM diet but was unchanged in the C-SPI diets (soy source x CP; P < 0.10). In general, pigs fed the SPI diets had less carcass fat and more lean than those fed the SBM diets, but the reduction in CP resulted in more carcass fat and less lean. In Exp. 2, 48 barrows (initial and final BW of 85.3 ± 0.2 and 112.9 ± 2.1 kg, respectively) were allotted to 3 treatments (4 replicates with 4 pigs per replicate). The dietary treatments were 1) C-SBM positive control (PC) diet formulated to 0.54% true ileal digestible Lys; 2) cornbased diet with crystalline Lys, Thr, Trp, and Met (C+AA); 3) negative control (NC), which was diet 2 without the crystalline AA. Pigs fed the NC had lower (P < 0.01) ADG and G:F compared with pigs fed the C+AA or PC. Pigs fed C+AA had lower (P < 0.01) ADG and G:F compared with pigs fed PC. In general, pigs fed the PC diet had less fat and more lean than pigs fed the NC diet, and pigs fed the C+AA diet were intermediate. The results of this research indicate that pigs fed low CP diets supplemented with crystalline Lys, Thr, and Trp may have reduced growth performance and they will have more carcass fat than those fed more conventional diets.