PSIII-14 Cotton gin byproduct in growing diets for beef steers

Abstract The purpose of this study was to evaluate the performance of beef cattle during the stocker phase when fed different concentrations of cotton gin byproduct (CGB). Angus steers [n = 50; initial body weight (BW) = 349 ± 66 kg) were stratified by BW and grouped in slatted floor pens (10 steers/pen). Steers were assigned randomly within pen (2 per pen) to one of five diets containing 0, 10, 20, 30, and 40% CGB (dry matter basis). Diets were balanced for protein and energy, and the steers were fed for 84 d. Steers were weighed on d -1, 0, 28, 56, 83, and 84 for the stocker phase with d -1 and 0, 83 and 84 averaged to give start and end BW. Following the growing period, steers were switched to the same finishing diet and fed for an additional 55 d prior to being transported to PA for harvest and carcass data collection. Data were analyzed using procMIXED of SASv9.4 to determine the significance of linear, quadratic, cubic, and quartic trends. During the growing phase, dry matter intake increased linearly (P = 0.0017) with 10.16, 11.23, 11.59, 11.86, and 11.96 kg/d for 0, 10, 20, 30, and 40% CGB, respectively. Average daily gain tended to increase (P = 0.0631) with a cubic trend, increasing with the first addition of CGB, declining at the intermediate levels, and then increasing again at the 40% level (1.34, 1.54, 1.36, 1.39, and 1.52 kg/d for 0, 10, 20, 30, and 40% CGB, respectively). Feed efficiency showed a similar cubic trend (P = 0.10) with 0.133, 0.138, 0.119, 0.117, and 0.128 for 0, 10, 20, 30, and 40% CGB, respectively. Within the finishing phase, average daily gain was significant (P = 0.026) as a quadratic trend with 1.54, 1.25, 1.18, 1.20, and 1.33 kg/d for 0, 10, 20, 30, and 40% CGB, respectively. Diets did not differ (P 0.10) for dry matter intake (10.08 kg/d), feed conversion (8.31), or feed efficiency (0.130). Treatment did not influence (P 0.10) marbling or other carcass measurements. Data suggest CGB supported good animal gains with only minor impact on feed intake and feed efficiency for stocker steers up to an inclusion rate of 40%.