This study aimed to evaluate nutrient intake and digestibility, enteric methane emission and nitrogen utilization efficiency in Nellore cattle ranked by residual feed intake (RFI). Twenty‐four Nellore bulls at 466 ± 24 days of age and with 352 ± 14.6 kg of body weight, classified as low and high RFI, were evaluated. Animals were kept in individual pens for three periods of 28 days and variables were measured. Data were analyzed as repeated measures over time, considering as fixed effects RFI class, period and RFI class x period interaction, and linear (co)variate of age. No significant differences in dry matter or nutrient intake were detected between RFI classes, but total digestible nutrients intake tended to be lower in low RFI animals, and apparent nutrient digestibility was higher in high RFI animals. Partial efficiency of growth tended to be lower in high RFI animals. RFI class did not interfere with enteric methane production or microbial protein synthesis, but fecal nitrogen output was higher in low RFI animals. The greater efficiency of low RFI animals is consequence of lower maintenance requirements, since energy from higher nutrients digestibility in high RFI animals was spent on metabolic processes other than body tissue deposition.

中文翻译：

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Nellore 肉牛剩余采食量、消化、摄食行为、肠道甲烷排放和氮代谢之间的关联

本研究旨在评估 Nellore 牛的营养摄入量和消化率、肠道甲烷排放量和氮利用效率，按剩余饲料摄入量 (RFI) 排序。评估了 24 头 466 ± 24 日龄、体重 352 ± 14.6 kg 的 Nellore 公牛，分为低 RFI 和高 RFI。将动物在单独的围栏中饲养 3 个 28 天的时间段并测量变量。数据被分析为随着时间的推移重复测量，考虑固定效应 RFI 类、周期和 RFI 类 x 周期相互作用，以及年龄的线性（共）变量。在 RFI 类别之间未检测到干物质或营养素摄入量的显着差异，但低 RFI 动物的总可消化营养素摄入量往往较低，而高 RFI 动物的表观营养素消化率较高。高 RFI 动物的部分生长效率往往较低。RFI 类不干扰肠道甲烷的产生或微生物蛋白质的合成，但低 RFI 动物的粪便氮输出量更高。低 RFI 动物的更高效率是维护需求较低的结果，因为高 RFI 动物中较高营养物质消化率产生的能量用于身体组织沉积以外的代谢过程。