Submitted to: Journal of Animal Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/2010
Publication Date: 2/1/2011
Citation: Gaines, A.M., Kendall, D.C., Allee, G.L., Usry, J.L., Kerr, B.J. 2011. Estimation of the standardized ileal digestible valine to lysine ratio in 13- to 32-kilogram pigs. Journal of Animal Science. 89:736-742. Interpretive Summary: Amino acid intake is critically important to optimize pig growth, feed efficiency, and carcass lean deposition, as well as minimizing the excretion of nitrogen into the environment. The culmination of three experiments conducted herein demonstrated that a small intestine ileal digestible valine:lysine ratio of 65% appears adequate in optimizing performance in pigs weighing 13 to 32 kg. This information is important for nutritionists at universities, feed companies, and swine production facilities showing them the proper ratio of valine relative to lysine necessary to achieve optimal pig performance, thereby mazimizing nitrogen utilization in the pig and minimizing the excretion of nitrogen into the environment.
Technical Abstract: Three experiments were conducted to determine the optimum standardized ileal digestible Val to Lys (SID Val:Lys) ratio for 13 to 32 kg pigs. In Exp. 1, a Val deficient basal diet containing 0.60% L-Lys•HCl, 1.21% SID Lys, and 0.68% SID Val was developed (0.56 SID Val:Lys). Performance of pigs fed the basal diet was inferior to a corn-soybean meal control containing only 0.06% L-Lys•HCl, but was fully restored with the addition of 0.146% L-Val to a ratio of 68% SID Val:Lys. In Exp. 2, 54 individually housed barrows (21.4 kg) were utilized in a 14 d growth assay. Pigs were offered a similar basal diet (1.10% SID Lys), ensuring Lys was first-limiting and Val second-limiting (55% SID Val:Lys). The basal was fortified with four graded levels of L-Val (0.055% increments) up to a ratio of 75% SID Val:Lys. In Exp. 3, 147 barrows (13.5 kg) were fed identical diets, only with one additional level at a SID Val:Lys ratio of 80% and fed for 21 d. In Exp. 2 and 3, a high protein, control diet was formulated to contain 1.10% SID Lys and 0.20% L-Lys•HCl. In Exp. 2, linear effects of ADG (713, 750, 800, 796, and 785 g/d; P = 0.05) and G:F (P = 0.07) were observed with increasing SID Val:Lys, characterized by improvements to a ratio of 65% and a plateau thereafter. In Exp. 3, quadratic improvements in ADG (600, 629, 652, 641, 630, 642 g/d; P = 0.08) and G:F (P = 0.07) were observed with increasing SID Val:Lys, as performance increased to a ratio of 65%, but no further improvement to a ratio of 80%. Pigs fed the control diet did not differ from those fed a ratio of 65% SID Val:Lys in Exp. 2, but did have improved G:F in Exp. 3 (P = 0.03). To provide a more accurate estimate of the optimum SID Val:Lys ratio, data from the two experiments were combined. Using single-slope broken-line methodology, the minimum ratio estimate was 64 and 65% SID Val:Lys for ADG and GF, respectively. Using combined requirement estimates, the data suggest that a SID Val:Lys ratio of 65% appears adequate in maintaining performance for pigs from 13 to 32 kg.