238 Impact of Increasing Standardized Ileal Digestible Tryptophan to Lysine Ratio in Diets Containing 20% Corn Distillers Dried Grains with Solubles fed to Growing-Finishing Pigs

Abstract

Abstract A study was conducted to investigate the optimal standardized ileal digestible (SID) Trp to Lys ratio in diets containing a moderately high level (20%) of corn distillers dried grains with solubles (DDGS) fed to growing-finishing pigs. A total of 2,232 pigs [initial body weight (BW) = 31.41 kg ± 0.53 kg] were allotted to a randomized complete block design with 4 dietary treatments (18 pens/treatment; 31 pigs/pen, mixed gender) and fed experimental diets for 15 wk in a 6-phase feeding program. The level of SID Trp/Lys in each treatment was formulated to 0.15, 0.18, 0.21, and 0.24, respectively, and was manipulated by crystalline Trp inclusion. Within each phase, diets were formulated to be isocaloric and contained equal provisions of SID Lys, sulfur containing amino acids, Thr, and Ile. Diets met or exceeded NRC (2012) estimated nutrient requirements. The levels of SID Thr/Lys (0.65 – 0.70 from grower to finisher) and SID Ile/Lys (0.60 – 0.62 from grower to finisher) were adjusted to a greater level to accommodate the potential negative effects of greater levels of fiber and Leu, respectively, from the inclusion of DDGS. Results were analyzed using the lme4 package of R 4.1.2, and the statistical models included the fixed effect of SID Trp/Lys and the random effect of body weight block. Orthogonal contrasts were used to test linear and quadratic effects of increasing dietary SID Trp/Lys (Table 1). Results indicated that increasing SID Trp/Lys in diets containing 20% corn DDGS improved final body weight (FBW) in a quadratic pattern (128.67, 130.61, 130.83, and 130.37 kg, for diets formulated to SID Trp/Lys at 0.15, 0.18, 0.21, and 0.24, respectively, P < 0.05). Average daily feed intake (ADFI) was quadratically increased with increasing SID Trp/Lys (2.51, 2.57, 2.60, and 2.57 kg/d, respectively, P < 0.05). A linear tendency was observed on average daily gain (ADG) with increasing SID Trp/Lys (0.96, 0.98, 0.98, and 0.98 kg/d, respectively, P < 0.10). In summary, increasing SID Trp/Lys in diets with moderately high levels of corn DDGS improved FBW and ADFI in a quadratic pattern and tended to increase ADG linearly.