Effects of Yeast and Exogenous Fibrolytic Enzyme Additives on Lamb Performance and Feed Efficiency

Yeast and fibrolytic enzymes serve as additives incorporated into the nutrition of ruminants to regulate rumen fermentation and increase the digestibility of fiber, thereby enhancing the efficiency of rumen fermentation. Two experiments were conducted to assess the impact of five diets: a control diet without additives, diets with yeast (Saccharomyces cerevisiae) or exogenous fibrolytic enzymes (EFE), and diets with a blend of 0.7yeast + 0.3EFE or 0.7EFE + 0.3Yeast (based on recommended levels in g/kg of total DM). In the first experiment, 40 five-month-old Santa Ines lambs (mean weight 25.0 ± 1.3 kg) were distributed in a completely randomized design (5 treatments and 8 lambs) for 81 days to evaluate performance, ingestive behaviour, and serum metabolites. In the second experiment, 25 Santa Ines male lambs weighing 25.7 ± 4.1 kg were housed in metabolic cages, in a randomized design with 5 treatments and 5 lambs, evaluating digestibility, nitrogen balance, and rumen pH. EFE supplementation increased intakes of dry matter (DM), total digestible nutrients (TDN), and apNDF (mean of 38.1, 5.26, and 27