PSXIII-11 - Evaluating different doses of rumen-protected or nonprotected tributyrin on performance of feedlot lambs fed a moderate or low-forage diet

The objective of this study was to evaluate performance of lambs when supplemented with different doses and forms of tributyrin in moderate (MF) and low forage (LF) diets. Eighty-four ram lambs were blocked by initial BW (27.9 ± 2.3 kg) assigned into 1 of 2 groups that were fed a MF (40% forage) or LF (10% forage) diet (%DM). Lambs in each block were also assigned to 1 of 6 treatments (n = 7) including a control (no supplementation) or diets that contained 0.1, 0.2, or 0.3% (DM basis) rumen protected (RPT) or 0.1 or 0.3% of tributyrin that was not protected (NPT). Lambs were housed indoor in individual pens and fed once daily for 97 d. At harvest, hot carcass weight (HCW) and back-fat thickness was measured for each lamb. Within diet type (MF and LF), data were analyzed to determine the linear and quadratic response for increasing RPT, the effect of using tributyrin (con vs. RPT and NPT), and the effect of rumen protection (RPT vs. NPT). Treatments fed MF diets did not differ with each other (P ≥ 0.06) for final BW (53.5 kg), ADG (255 g/d), DMI (1.42 kg/d), gain:feed ratio (0.187 kg/kg), backfat thickness (14.1mm), hot carcass weight (24.0 kg), and dressing percentage (45.0%). Also, no differences (P ≥ 0.08) were detected for final BW (56.0 kg) and ADG (0.30 kg/d), DMI (1.56 kg/d), gain:feed ratio (0.190 kg/kg), back-fat thickness (16.8 mm), and HCW (25.5 kg) between treatments fed LF diets. However, lambs fed LF diet with RPT had greater (P = 0.04) dressing percentage than lambs fed NPT (45.9 vs. 44.5%, respectively). We conclude there is no benefit from inclusion of tributyrin in MF diets for lambs whether provided in protected or unprotected form. However, feeding RPT in LF diets for lambs may enhance dressing percentage.