Replacement of soybean meal with urea in forage cactus diets for lambs: Nitrogen balance, performance, blood parameters, carcass traits, and meat quality

Abstract

This study aimed to evaluate the effect of replacing soybean meal with urea in diets based on forage cactus (Opuntia stricta) (Haw.) on the nutrient intake, digestibility, nitrogen balance, blood parameters, performance, carcass traits, and physicochemical and sensory characteristics of the meat of Santa Inês lambs in a feedlot. Forty Santa Inês lambs were used, with an initial body weight of 22.2 ± 2.1 kg, distributed in a completely randomized design. The treatments were diets with 400 g/kg DM forage cactus and increasing levels of urea (0, 7.3, 14.6, and 21.9 g/kg dry matter [DM]) to replace soybean meal. The lambs were confined for 75 days. The lambs with elevated urea levels in the diet showed an increase (P < 0.05) in the intake of crude protein and non-fibrous carbohydrates. As the urea level increased, there was a quadratic increase (P < 0.05) in the amount of urinary nitrogen (N), retained N (% of ingested), serum triglycerides, and albumin. As the urea level increased, there was a linear decrease (P < 0.05) in the average daily gain, empty body weight, cold carcass weight, and the leg muscularity index. The ether extract in the lamb meat and the internal body fat increased (P < 0.05) by adding urea to the diet. In conclusion, in diets with 400 g/kg DM forage cactus, decreases weight gain and cooking losses of meat from Santa Inês lambs in feedlots.