Modeling the Effects of Standardized Ileal Digestible Tryptophan:Lysine Ratio on Growth Performance of 65- to 275-lb Pigs

Authors

M. A. Goncalves, Kansas State University, ManhattanFollow
M. D. Tokach, Kansas State University, ManhattanFollow
S. S. Dritz, Kansas State University, ManhattanFollow
K, J. Touchette, Anjinomoto Heartland Inc., Chicago
N. M. Bello, Kansas State University, ManhattanFollow
J. M. DeRouchey, Kansas State University, ManhattanFollow
J. C. Woodworth, Kansas State University, ManhattanFollow
R. D. Goodband, Kansas State University, ManhattanFollow

Keywords

amino acid ratio, growth, tryptophan, finishing pig

Abstract

The objective of this study was to model the effects of standardized ileal digestible (SID) Trp:Lys ratio on growth performance of 65- to 275-lb pigs. The present experiment, along with three previous experiments from Gonçalves et al. (2014), were used in the analysis. For all studies, dietary treatments consisted of SID Trp:Lys ratios of 14.5, 16.5, 18.0, 19.5, 21.0, 22.5, and 24.5%. The experiments were 21 d in duration and used corn and soybean meal-based diets with 30% dried distillers grains with solubles formulated to be deficient in Lys at the end of each of the experiments. In the current experiment, a total of 975 gilts (337 × 1050; PIC, Hendersonville, TN) were used with initial BW of 234.1 ± 6.8 lb and final BW of 274.9 ± 10.4 (mean ± SD). Pens of pigs were blocked by weight and assigned to one of the seven dietary treatments in a randomized complete block design. There were 6 pens/treatment with 20 to 24 pigs per pen. For 235 to 275 lb-pigs, increasing SID Trp:Lys improved ADG (quadratic, P < 0.022), ADFI (linear, P < 0.001), and F/G (linear, P < 0.001). Data from all experiments were then combined for analysis using linear and non-linear mixed models with random effects of experiment and weight block nested within experiment allowing for heterogeneous variances. Competing models included broken-line linear (BLL), broken-line quadratic (BLQ), and quadratic polynomial (QP). In the combined analysis for ADG, QP was the best fitting model and estimated SID Trp:Lys requirement at 23.5% (95% CI: [22.7, 24.3%]). In the combined analysis for F/G, BLL and BLQ had comparable fit and estimated SID Trp:Lys requirements at 16.9% (95% CI: [16.0, 17.8%]) and 17.0% (95% CI: [15.0, 18.9%]), respectively. Thus, the estimated mean requirements for SID Trp:Lys for 65- to 275-lb pigs ranged from 16.9% for optimum mean F/G to 23.5% for maximum mean ADG. Furthermore, 95% of the maximum estimated mean ADG was obtained by feeding 17.6% SID Trp:Lys and 98% of the maximum estimated mean ADG was obtained by feeding 19.8% SID Trp:Lys.

Recommended Citation

Goncalves, M. A.; Tokach, M. D.; Dritz, S. S.; Touchette, K, J.; Bello, N. M.; DeRouchey, J. M.; Woodworth, J. C.; and Goodband, R. D. (2015) "Modeling the Effects of Standardized Ileal Digestible Tryptophan:Lysine Ratio on Growth Performance of 65- to 275-lb Pigs," Kansas Agricultural Experiment Station Research Reports: Vol. 1: Iss. 7. https://doi.org/10.4148/2378-5977.1115