Abstract
This study evaluated the responses of Thin-tailed lambs (TTL) and Texel crossbred lambs (TCL) to different feeding levels in terms of protein metabolism, rumen fermentation, growth performance, and body composition. A total of 20 male growing lambs aged four months were used, consisting of TTL (9.56 ± 0.97 kg) and TCL (15.30 ± 2.84 kg). Lambs were individually housed and fed a complete pelleted diet containing 14.42% crude protein and 70.03% total digestible nutrients (TDN). The experiment used a nested completely randomized design with feeding levels of 4% and 5.5% body weight within each breed group. Texel crossbred lambs had higher dry matter intake, nutrient digestibility, protein retention, and microbial protein synthesis than thin-tailed lambs (P0.05). Higher feeding levels also reduced rumen pH and increased blood urea concentration after feeding (P0.05). Overall, breed exerted a greater influence than feeding level on protein utilization, growth performance, and body composition in lambs.