Effects of slow-release urea microencapsulated in a carnauba wax lipid matrix and amino acid blend supplementation on lamb carcass traits

Abstract

Controlled-release urea provides a gradual nitrogen supply, improving microbial protein synthesis and reducing ammonia toxicity in growing lambs. Supplementing with methionine and lysine ensures essential amino acids that can reach the intestine for efficient tissue growth. This combination enhances nitrogen utilization and supports muscle development. Together, they promote better weight gain and feed efficiency. This research investigated carcass traits in 40 male lambs of mixed breed, with an average body weight of 18.3 ± 3.0 kg and four months old. The slow-release urea (SRU) was produced by microencapsulation through a fusion-emulsification process using carnauba wax (Copernicia prunifera) as the coating material. Lambs were distributed into five dietary groups from a completely randomized design (eight animals per treatment): control (without SRU or added amino acids); 4% SRU alone; 4% SRU combined with 1.5% lysine (SRU + L); 4% SRU combined with 1.5% methionine (SRU + M); and 4% SRU combined with 1.5% lysine plus 1.5% methionine (SRU + L + M). The lambs were fed total mixed rations for 60 days, comprising 30% roughage, a silage mixture of Sorghum bicolor and Panicum maximum, and 70% concentrate, including ground corn, soybean meal, mineral supplements, and the specified additives according to each treatment, before being slaughtered for carcass evaluation. Hot (P = 0.001) and cold carcass weight (P = 0.011), cold (P = 0.012), and hot carcass yield (P = 0.013) differed significantly between treatments. The hot and cold carcass weights were higher (16.6 and 16.2 kg, respectively) in animals slaughtered while consuming the control diet (without SRU or amino acids) compared to lambs fed the SRU + methionine diet (12.4 and 12.1 kg, respectively). The association of SRU with the amino acid levels proposed here is not recommended as it does not contribute to the carcass traits of lambs.