Substituição da proteína dietética por proteína derivada da indústria sucroalcooleira na dieta de cordeiros na fase de terminação

Abstract

The liquid yeast, a by-product of the alcoholic fermentation of sugarcane, has potential for use as an alternative protein source in ruminant feeding, contributing to sustainability and cost reduction in animal production. This study aimed to evaluate the effects of replacing soybean meal with liquid yeast in the diet of feedlot lambs on intake, nutrient digestibility, ruminal and blood parameters, microbial protein synthesis, feeding behavior, productive performance, and quantitative and qualitative characteristics of carcass and meat. Five experimental diets were evaluated, containing 0, 25, 50, 75, and 100% replacement of soybean meal by liquid yeast on a dry matter basis. In the first trial, ten crossbred lambs were distributed in a double 5×5 Latin square design for 105 days. In the second trial, 30 non-defined breed lambs (15 males and 15 females) were used, allocated in a randomized block design, considering initial weight and sex as blocking criteria. The inclusion of liquid yeast influenced dry matter and nutrient intake, fitting quadratic models, and showed significant linear effects on digestibility, absorbed purines, and microbial protein synthesis, indicating improved nutrient utilization up to the 25% replacement level. No differences (p > 0.05) were observed in zootechnical performance, intake, feed and protein efficiency, average daily gain, or loin eye area. However, an increase was observed in backfat thickness, hot and cold carcass weights, cold carcass yield, muscle tissue proportion, and muscle-to-fat ratio, along with a linear reduction in adipose tissue yield. It is concluded that liquid yeast can totally or partially replace soybean meal in the diet of feedlot lambs without impairing performance or meat quality, representing a nutritionally efficient and viable alternative for sheep production.