Roberson R L, Sanders J O, Cartwright T C
J Anim Sci. 1986 Aug;63(2):438-46. doi: 10.2527/jas1986.632438x.
Birth weight, preweaning gain and weaning weight (adjusted 180-d weight) data, collected at McGregor, Texas, were analyzed for genetic differences. Breedtypes represented in the data were Brahman, Hereford and various Brahman-Hereford crosses. Preweaning gain was calculated as adjusted 180-d weight less birth weight. All statistical models included effects of dam age, year, season and sex. Analyses were performed using a breedtype model and a regression model that redefined breedtype as direct additive, direct heterotic, maternal additive and maternal heterotic effects. Brahman dams produced calves with lightest birth weights. Brahman-sired calves were heaviest at birth compared with those by other sire breedtypes. The estimated Brahman direct additive effect on birth weight was 4.6 kg greater than Hereford. The Brahman maternal additive effect was 7.5 kg less than Hereford. Direct and maternal heterotic effects on birth weight were 2.2 and .6 kg, respectively. Calves from F1 dams had larger preweaning gains than those of the other breedtypes. The Brahman direct additive effect on preweaning gain was 17.7 kg less than Hereford and the Brahman maternal additive effect was 20 kg greater than Hereford. Direct and maternal heterotic effects on preweaning gain were 19.6 and 19.5 kg, respectively. Results of weaning weight analyses were similar to preweaning gain analyses. The largest effects on weaning weight were direct and maternal heterosis, which were 21.6 and 19.8 kg, respectively.
对在得克萨斯州麦格雷戈收集的出生体重、断奶前增重和断奶体重（调整后的180日龄体重）数据进行了遗传差异分析。数据中代表的品种类型有婆罗门牛、赫里福德牛以及各种婆罗门牛 - 赫里福德牛杂交品种。断奶前增重计算为调整后的180日龄体重减去出生体重。所有统计模型都包括母牛年龄、年份、季节和性别的影响。分析使用了品种类型模型和一个回归模型，该回归模型将品种类型重新定义为直接加性效应、直接杂种优势效应、母体加性效应和母体杂种优势效应。婆罗门牛的母牛所产犊牛出生体重最轻。与其他父本品种类型相比，婆罗门牛父本所产犊牛出生时最重。估计婆罗门牛对出生体重的直接加性效应比赫里福德牛大4.6千克。婆罗门牛的母体加性效应比赫里福德牛少7.5千克。对出生体重的直接和母体杂种优势效应分别为2.2千克和0.6千克。来自F1代母牛的犊牛断奶前增重比其他品种类型的犊牛大。婆罗门牛对断奶前增重的直接加性效应比赫里福德牛少17.7千克，婆罗门牛的母体加性效应比赫里福德牛大20千克。对断奶前增重的直接和母体杂种优势效应分别为19.6千克和19.5千克。断奶体重分析结果与断奶前增重分析结果相似。对断奶体重影响最大的是直接和母体杂种优势，分别为21.6千克和19.8千克。
