The aim of this study was to evaluate growth, ruminal and metabolic parameters and feeding behavior of young Nellore males classified based on postweaning residual feed intake (RFI). Fifty-nine Nellore males (290 ± 20 days of age and 294 ± 8.48 kg of body weight) were evaluated for 70 days in a feed efficiency test conducted with the GrowSafe System®, with automatic and daily measurement of individual feed intake and feeding behavior. The animals were weighed every 14 days. Body measures and blood samples were obtained at the beginning and end of the efficiency test. The RFI was calculated as the residual of the regression equation of dry matter (DM) intake on average daily weight gain and mid-test metabolic body weight. The animals were classified as low (n = 25), medium (n = 15), and high (n = 19) RFI. Six low RFI and six high RFI animals were used for determining ruminal parameters and microbial nitrogen. The data were analyzed considering the fixed effect of RFI class and initial age as linear covariate. Low RFI animals consumed less DM to achieve a performance similar to that of animals with medium and high RFI. The different RFI groups did not influence ruminal fermentation parameters, microbial nitrogen, blood metabolites, or body measures. Low RFI animals spent less time at the feed bunk when compared to animals with medium and high RFI for a similar amount of feed consumed per visit. Animals with low RFI are efficient in feed utilization as demonstrated by their good production potential despite lower feed intake, without losses in growth or ruminal and metabolic parameters.

这项研究的目的是评估根据断奶后残余饲料摄入量（RFI）分类的内罗尔幼小雄性的生长，瘤胃和代谢参数以及喂养行为。在由GrowSafeSystem®进行的饲料效率测试中，对59名内洛尔雄性（290±20天大的体重和294±8.48 kg体重的雄性）进行了为期70天的评估，该系统每天自动测量个体的采食量和采食行为。每14天给动物称重一次。在效率测试的开始和结束时获取身体测量值和血液样本。RFI计算为干物质（DM）摄入量回归回归方程在平均日增重和中期测试代谢体重上的残差。动物分为低（n  = 25），中（n = 15）和高（n = 19）RFI。六只低RFI和六只高RFI动物用于确定瘤胃参数和微生物氮。分析数据时，将RFI类和初始年龄的固定影响视为线性协变量。低RFI的动物消耗的DM较少，可实现与中高RFI的动物相似的性能。不同的RFI组不影响瘤胃发酵参数，微生物氮，血液代谢产物或身体指标。与具有中等和高RFI的动物相比，RFI低的动物在饲料铺上花费的时间更少，每次访问消耗的饲料量相近。具有低RFI的动物尽管饲料摄入量较低，但具有良好的生产潜力，因而具有较高的饲料利用率，并且没有损失生长或瘤胃和代谢参数。