Body size and its effects on productive efficiency of cows with predominant Nellore genetic composition

ABSTRACT. This study was developed to evaluate productive efficiency during the lactation period of cows with predominant Nellore genetic composition based on their body size. Cows were divided into the following categories: light (≤ 316 kg), moderate (≥ 317 and ≤ 400 kg), or heavy (≥ 401 kg). Body weight change and total gain from birth to 210 days of age of calves born from heavy cows (0.155±0.03 and 111.6±5.1 kg) were higher than those of calves born from light (0.064±0.03 and 91.0±4.3 kg) and moderate (0.144±0.03 and 97.7±4.0 kg) cows. Calf production index differed (p < 0.05) with the herd of heavy cows (93.5±3.2 kg), producing 57.4 and 19.7% more kilograms of calf than light (59.4±2.7 kg) and moderate (78.1±2.4 kg) cows, respectively. Heavy Nellore cows produce heavier calves and have a better reproductive performance, which lead to a better calf production index. However, they require a larger area for the same herbage allowance. Calves born from heavier Nellore cows gain more weight from birth to 210 days of age and are heavier from 210 to 270 days of age.

摘要。本研究旨在基于体质量指标，评估以内洛尔牛（Nellore）为主要遗传背景的母牛在泌乳期的生产效率。试验将母牛划分为三类：轻型（体重≤316 kg）、中型（体重≥317 kg且≤400 kg）以及重型（体重≥401 kg）。重型母牛所产犊牛的体重变化量（0.155±0.03）及初生至210日龄总增重（111.6±5.1 kg）均高于轻型组（0.064±0.03、91.0±4.3 kg）与中型组（0.144±0.03、97.7±4.0 kg）的犊牛。犊牛生产指数差异显著（p < 0.05），其中重型母牛组的犊牛生产指数为93.5±3.2 kg，其犊牛总产重较轻型组（59.4±2.7 kg）与中型组（78.1±2.4 kg）分别高出57.4%与19.7%。内洛尔重型母牛可产出更重的犊牛，且繁殖性能更优，进而获得更高的犊牛生产指数。但此类母牛在同等饲草供给量下需要更大的饲养面积。由重型内洛尔母牛所产的犊牛，从初生至210日龄的体重增长更快，且在210至270日龄时体重更高。