Neville W E, Utley P R, McCormick W C
J Anim Sci. 1985 Mar;60(3):632-43. doi: 10.2527/jas1985.603632x.
The first phase of this study was the production of contemporary straightbred (SB) and reciprocal crossbred (F1) bulls by mating Angus (A) bulls to A and Santa Gertrudis (SG) cows and SG bulls to SG and A cows. Of the bulls produced during the 4-yr period, those used for breeding included 15 A, 15 SG, 8 A X SG and 8 SG X A. For 205-d weight and weight/day of age (W/DA) postweaning, A X SG had higher (P less than .05) performance than SG X A bulls and SG had higher (P less than .05) performance than A bulls. There was no difference (P greater than .05) between SG and A X SG for 205-d weight, postweaning average daily gain (ADG) or postweaning W/DA. Heterosis estimates were 5.2 (P less than .10), 9.9 (P less than .01) and 5.8% (P less than .01) for 205-d weight, postweaning ADG and W/DA, respectively. The second phase of this study was the comparison of SB and F1 bulls for reproductive and progeny performance by exposing them as yearlings to 25 Polled Hereford cows each. There were no differences (P greater than .05) among the four sire groups for proportion of cows exposed that had a calf, had a live calf or weaned a calf. Reproductive performance of sires also was evaluated in terms of number of days (NOD) from the beginning of the breeding period until calves were born. The NOD for calves by SG was greater (P less than .05) than for calves by A or F1 sires. Compared with calves from SB sires, the NOD for calves from A X SG and SG X A sires were 5.0 and 10.6 d (P less than .05) lower. Differences among sires within year and breeding of sire were significant for all preweaning traits and for W/DA postweaning of their progeny. The SG-sired calves were heavier (P less than .05) for birth and 205-d weight and had higher (P less than .05) postweaning ADG than A-sired calves. Mean performance of calves by reciprocal F1 sires did not deviate (P greater than .05) from the mean performance of those by SB sires. Calves by A X SG sires had higher (P less than .05) 205-d weight, postweaning ADG and W/DA than calves by SG X A sires. Results indicated that the primary genetic effects responsible for differences in performance of calves sired by F1 vs SB bulls were mean transmitted and mean heterotic effects.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究的第一阶段是通过将安格斯（A）公牛与A母牛以及圣格特鲁迪斯（SG）母牛交配，以及将SG公牛与SG母牛和A母牛交配，来培育当代纯种（SB）和正反交杂种（F1）公牛。在这4年期间所培育的公牛中，用于繁殖的有15头A公牛、15头SG公牛、8头A×SG公牛和8头SG×A公牛。对于断奶后205日龄体重和日增重（W/DA），A×SG公牛的性能高于（P＜0.05）SG×A公牛，且SG公牛的性能高于（P＜0.05）A公牛。在205日龄体重、断奶后平均日增重（ADG）或断奶后W/DA方面，SG公牛与A×SG公牛之间没有差异（P＞0.05）。杂种优势估计值在205日龄体重、断奶后ADG和W/DA方面分别为5.2%（P＜0.10）、9.9%（P＜0.01）和5.8%（P＜0.01）。本研究的第二阶段是通过将一岁龄的SB和F1公牛分别与25头无角海福特母牛配种，来比较它们的繁殖性能和后代性能。在四个父本群体中，受配母牛产犊、产活犊或断奶犊的比例没有差异（P＞0.05）。还根据从配种期开始到犊牛出生的天数（NOD）来评估父本的繁殖性能。SG公牛所产犊牛的NOD比A或F1父本所产犊牛的NOD长（P＜0.05）。与SB父本所产犊牛相比，A×SG和SG×A父本所产犊牛的NOD分别低5.0天和10.6天（P＜0.05）。对于所有断奶前性状及其后代断奶后的W/DA，年份内父本间以及父本的繁殖情况存在显著差异。SG父本所产犊牛的出生体重和205日龄体重更重（P＜0.05），断奶后ADG也更高（P＜0.05），高于A父本所产犊牛。正反交F1父本所产犊牛的平均性能与SB父本所产犊牛的平均性能没有偏差（P＞0.05）。A×SG父本所产犊牛的205日龄体重、断奶后ADG和W/DA高于（P＜0.05）SG×A父本所产犊牛。结果表明，F1公牛与SB公牛所产犊牛性能差异的主要遗传效应是平均传递效应和平均杂种优势效应。（摘要截选至400字）
