Effects of dried distillers' grains inclusion on performance, feed efficiency, carcass traits and health of feedlot lambs.

The use of agro-industrial by-products in ruminant diets has increased as a strategy to improve the sustainability of livestock production systems. This study evaluated the biological feasibility of replacing soybean meal with dried distillers' grains with solubles (DDGS) at a practical dietary inclusion level in feedlot lamb diets. Twenty-four Santa Inês ewe lambs (27.08 ± 2.89 kg initial body weight) were assigned to a completely randomized design with two dietary treatments: a control diet without DDGS and a diet containing 6.27% DDGS (dry matter basis). The experimental period consisted of 21 days of dietary adaptation followed by 52 days of evaluation. Productive performance, feed intake, feed efficiency, in vivo carcass traits, parasitological indicators, hematological variables, and serum biochemical parameters were evaluated. Dietary inclusion of DDGS did not affect average daily gain, final body weight, body condition score, Longissimus muscle area, backfat thickness, dry matter intake, feed conversion ratio, or feed efficiency (p > 0.05). However, lambs fed the DDGS diet showed lower dry matter intake relative to body weight (p = 0.021). Parasitological indicators, including eggs per gram of feces, Famacha© score, and packed cell volume, were not affected by dietary treatment. Most hematological and serum biochemical variables were also unaffected. Lambs fed the DDGS diet exhibited lower leukocyte and neutrophil counts (p < 0.05), whereas serum urea concentration was higher (p = 0.035), likely reflecting the higher dietary crude protein content. Overall, replacing soybean meal with DDGS at a commercially relevant inclusion level maintained productive performance, carcass characteristics, and the evaluated hematological and serum biochemical indicators in feedlot lambs under intensive tropical production conditions.