132 Performance response of the grow-finish pig (38 to 142 kg) fed different levels of tryptophan:lysine in diets containing 40% dry distiller grains with solubles

Abstract

Abstract Dried distiller grains with solubles (DDGS) is a popular protein source in grow-finish swine diets to replace soybean meal. An experiment was conducted at the South Dakota State University commercial swine research facility to determine the effect of standardized ileal digestible (SID) Trp:Lys ratio in grow-finish swine diets containing 40% DDGS compared to a standard corn-soybean meal diet. A total of 1,170 pigs (38.6 ± 0.2 kg initial BW) were utilized in a 98-d trial (9 pens per treatment). Pens of pigs were randomly allotted to 1 of 4 DDGS dietary treatments providing SID Trp at 15, 18, 21, and 24% of Lys or a corn-soybean meal diet (18%). Diets were isocaloric, with lysine at 100% of the requirement. From d 0 to 82, increasing Trp:Lys ratio in DDGS diets improved (P < 0.01) BW, ADG, and ADFI with no effect on F:G. Pigs fed the corn-soybean meal diet had greater (P < 0.01) BW, ADG, ADFI, and F:G compared to the DDGS diets with the exception of the ADFI of the 24% Trp:Lys treatment. From d 82 to 98, increasing SID Trp:Lys in DDGS diets had no effect on performance. Overall (d 0 to 98), increasing SID Trp:Lys in DDGS diets increased (P < 0.02) final BW and ADG, but pigs failed to perform to the same degree as the corn-soybean meal diet. Increasing SID Trp:Lys in DDGS diets resulted in an increase in hot carcass weight (P < 0.01); however, diets containing DDGS had decreased (P < 0.02) hot carcass weight, dressing percentage, percent lean, and loin depth compared to pigs fed the corn-soybean meal diet. These results indicate that increasing the SID Trp:Lys in diets containing 40% DDGS improved performance in early grow-finish phases with no effect in late finishing, but performance was inferior to standard corn-soybean meal diets.