Forty Pelibuey × Kathdin lambs (35.5 ± 0.4 kg) were used in a 56-day feeding experiment to assess the effects of feeding different levels of chromium-enriched live yeast (Cr-YC) on growth performance, dietary energetics, carcass traits and visceral organ mass. The Cr-YC source contained 5.5 × 109 colony forming units (CFU) and 0.40 mg of Cr per gram. Treatments consisted of a dry rolled corn-based finishing diet supplemented with 0, 1, 2 or 3 g Cr-YC/lamb.day. Total daily dosages were: 5.5 × 109 CFU and 0.4 mg; 1.1 × 1010 CFU and 0.8 mg Cr, and 1.65 × 1010 CFU and 1.2 mg Cr for supplementation levels of 1, 2 or 3 g Cr-YC/lamb.day, respectively. There were no treatments effects on dry matter intake. As the level of Cr-YC supplementation increased, average daily gain, gain to feed and dietary net energy were linearly increased, and observed/expected dry matter intake was linearly decreased. Chromium-enriched live yeast supplementation increased empty bodyweight (EBW), gastrointestinal fill and full viscera weight, but did not influence organ weights as a proportion of EBW (g/kg EBW). Cr-YC level did not affect carcass length, backfat thickness, kidney, pelvic and heart fat or body wall thickness, but increased hot carcass weight and longissimus muscle area. In general, treatment effects on percentage yield of wholesale cuts (tissue weight as a percentage of cold carcass weight) were small. However, Cr-YC decreased percentage flank. Chromium-enriched yeast supplementation enhances growth rate, longissimus muscle area, and dietary energetic efficiency in finishing feedlot lambs.
