Active yeast supplementation on nutritional parameters of ewe lambs fed a high-concentrate diet

This study aimed to evaluate the effects of active yeast supplementation on intake, apparent digestibility, nitrogen balance, and energy use in ewe lambs fed high-concentrate diets. Five Dorper × Santa Inês ewe lambs, with an average initial body weight of 54.1 ± 1.4 kg and 8 months of age, were housed in individual metabolism cages. Treatments included a control diet (without active yeast) and four levels of active yeast supplementation [Active Flora® - ICC, Louisville, Kentucky, USA, 2.0 × 1010 colony-forming units (CFU)], at inclusion rates of 0.15, 0.30, 0.45, and 0.60% of dry matter (DM) intake (kg animal-1 day-1). Diets consisted of 20% corn silage and 80% concentrate, based on DM. The experiment followed a 5 × 5 Latin square design with five animals and five evaluation periods. Each period lasted 15 days, including 10 days for adaptation and 5 days for data collection, totaling 75 days. Data were analyzed using analysis of variance and regression at a significance level of 5%. Results showed a quadratic effect of yeast supplementation levels on DM (P = 0.027) and organic matter (OM) intake (P = 0.029) in g animal-1 day-1, as well as on total carbohydrate intake (P = 0.026). A linear increase was observed in DM (P = 0.041) and OM (P = 0.043) intake in percentage of body weight (BW) and in g kg-1 BW0.75 (P = 0.031 and P = 0.032, respectively), as well as for crude protein (P = 0.037) and non-fibrous carbohydrate intake (P = 0.041). Apparent nutrient digestibility was unaffected by treatments. Nitrogen (N) intake (P = 0.036) and urinary N excretion (P = 0.003) exhibited quadratic responses to yeast levels, while fecal N excretion (P = 0.043) and absorbed N (P = 0.045) increased linearly. Gross energy (GE) intake (P = 0.009), metabolizable energy (P = 0.019), and the metabolizability of ingested GE (P = 0.024) showed quadratic responses to yeast supplementation. However, treatments did not affect fecal GE, digestible energy, or urinary GE. Supplementing active yeast at levels between 0.31% and 0.36% of dietary DM improved intake patterns, nitrogen absorption, metabolizable energy availability, and GE metabolizability without altering the apparent digestibility of nutrients in ewe lambs fed diets containing 80% concentrate.