University of Florida, Gainesville 32611-0910, USA.
J Anim Sci. 2009 Dec;87(12):3877-86. doi: 10.2527/jas.2008-1553. Epub 2009 Aug 14.
The influence of additive and nonadditive genetic effects and temperament on 4 postweaning feed intake and growth traits was evaluated in a group of 581 bull, heifer, and steer calves born in 3 Florida herds in 2006 and 2007. Calves had breed compositions ranging from 100% Angus (A) to 100% Brahman (B). They were randomly allocated to 24 pens each year by herd (Brooksville, Gainesville, Marianna, FL), sire group (A, 3/4 A 1/4 B, Brangus, 1/2 A 1/2 B, 1/4 A 3/4 B, and B), and sex (bull, heifer, and steer) in a GrowSafe automated feeding facility at Marianna. Calves were fed a concentrate diet during the 21-d adjustment and the 70-d trial periods. Individual feed intakes were recorded daily, and BW, chute scores, and exit velocities were recorded every 2 wk. Traits were phenotypic daily residual feed intake (RFI), mean daily feed intake (DFI), mean daily feed conversion ratio (FCR), and postweaning BW gain. Phenotypic RFI was computed as the difference between actual and expected feed intakes. Calves were assigned to 3 RFI groups: high (RFI greater than 0.9 kg of DM/d), low (RFI less than -0.9 kg of DM/d), and medium (RFI between mean +/- 0.9 kg of DM/d; SD = 1.8 kg of DM/d). The mixed model included the fixed effects of contemporary group (herd-year-pen), RFI group (except when trait was RFI), age of dam, sex of calf, age of calf, B fraction of calf, heterozygosity of calf, mean chute score, and mean exit velocity. Brahman fraction and heterozygosity of calf were nested within sex of calf for RFI and within RFI group for DFI, FCR, and postweaning BW gain. Random effects were sire and residual. Feed efficiency tended to improve (decreased RFI) as the B fraction increased. However, calves required larger amounts of feed per kilogram of BW gain (larger FCR) as the B fraction increased. Postweaning BW gain tended to decrease as the B fraction increased. Temperament traits were unimportant for all traits except exit velocity for DFI, suggesting perhaps a lack of variation for temperament traits in this herd, or that calves became accustomed to the level of handling pre- and postweaning, thus decreasing behavioral differences among them.
在佛罗里达州的三个牧场中，2006 年和 2007 年出生的 581 头公牛、小母牛和阉牛小牛中，评估了添加和非加性遗传效应以及气质对 4 种断奶后采食量和生长性状的影响。小牛的品种组成从 100%安格斯（A）到 100%婆罗门（B）不等。他们每年根据牧场（布鲁克斯维尔、盖恩斯维尔、玛丽安娜，FL）、 sire 组（A、3/4A1/4B、布郎格斯、1/2A1/2B、1/4A3/4B 和 B）和性别（公牛、小母牛和阉牛）随机分配到 24 个畜栏中，在玛丽安娜的 GrowSafe 自动化饲养设施中进行。小牛在 21 天的调整期和 70 天的试验期间内喂食浓缩饲料。每天记录个体采食量，每两周记录一次体重、滑道评分和出口速度。性状为表型每日残差采食量（RFI）、平均每日采食量（DFI）、平均每日饲料转化率（FCR）和断奶后体重增加。表型 RFI 计算为实际采食量与预期采食量之间的差异。将小牛分为 3 个 RFI 组：高（RFI 大于 0.9 千克 DM/d）、低（RFI 小于-0.9 千克 DM/d）和中（RFI 在平均值 +/-0.9 千克 DM/d 之间；SD=1.8 千克 DM/d）。混合模型包括当代群体（牧场-年份-畜栏）、RFI 组（除了性状是 RFI 时）、母畜年龄、小牛性别、小牛年龄、小牛的婆罗门分数、小牛的杂合度、平均滑道评分和平均出口速度的固定效应。婆罗门分数和小牛的杂合度嵌套在小牛的性别内，用于 RFI，嵌套在 RFI 组内用于 DFI、FCR 和断奶后体重增加。随机效应为 sire 和残差。随着 B 分数的增加，饲料效率趋于提高（RFI 降低）。然而，随着 B 分数的增加，小牛每公斤体重增加所需的饲料量（较大的 FCR）增加。随着 B 分数的增加，断奶后体重增加趋于减少。气质性状除了 DFI 的出口速度外，对所有性状都不重要，这表明该群体的气质性状可能缺乏变异性，或者小牛在断奶前后适应了处理水平，从而减少了它们之间的行为差异。
