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Abstract：
This study evaluated the association between the proportion of Brahman genetics and productivity of Brahman-Angus cows at weaning using a 31-yr dataset containing 6,312 cows and 5,405 pregnancies. Cows were contemporaneously reared and enrolled in yearly breeding seasons under subtropical conditions of North-Central Florida. They were evenly distributed in six-breed groups (G) according to the proportion of Brahman genetics: G0% to 19%, G21% to 34%, G38% (Brangus), G41% to 59%, G63% to 78%, and G81% to 100%. The proportion of cows calving (84.9%) did not differ across the six-breed groups. However, cows in the G81% to 100% weaned fewer calves (90.8%) than cows in the G0% to 19% and G21% to 34% (95.7%, each). The weaning rate of cows in the G38% (94.3%), G41% to 59% (94.2%), and G63% to 78% (93.0%) was intermediate between these three breed groups. The preweaning calf mortality was greater for cows in the G81% to 100% (9.2%) than cows in the G0% to 19% and G21% to 34% (4.3%, each), but intermediate for cows in the G38% (5.7%), G41% to 59% (5.8%), and G63% to 78% (7.0%). Cows in the G81% to 100% also weaned lighter calves (220.6 kg) than cows in the G0% to 19% (245.2 kg), G21% to 34% (250.2 kg), G38% (247.9 kg), G41% to 59% (252.5 kg), and G63% to 78% (245.2 kg). Cows in the G0% to 19% weaned lighter calves than cows with 21% to 78% of Brahman genetics. The 205-d adjusted weaning weight evidenced the less productive results of cows in G0% to 19% and G81% to 100% compared with other genetic groups, as they calved at the fastest and slowest rate, respectively. Thus, the 205-d adjusted weaning weight eliminated this bias. Additionally, younger cows weaned lighter calves; and male calves were heavier at weaning than female calves. Both parity order of cow and calf sex altered the magnitude of the described association between breed group of cows and calf weaning weights. Overall, after adjusting for weaning rate and age of calves at weaning, the number of kilograms produced per cow submitted to reproduction was less for cows in the G0% to 19% (191.1 kg) and G81% to 100 (181.8 kg) compared with cows in the G21% to 34 (197.0 kg), G38 (195.9 kg), G41% to 59 (199.7), and G63% to 78 (196.2). Cows in the G81% to 100% were the least productive. Thus, a proportion of Brahman genetics between 21% and 78% ensured superior productivity of Brahman-Angus cows subjected to subtropical conditions.
摘要：
这项研究使用包含6,312头母牛和5,405个怀孕的31年数据集，评估了Brahman遗传学比例与断奶时Brahman-Angus母牛的生产力之间的关系。在佛罗里达州中北部的亚热带条件下，奶牛在每年的繁殖季节同时饲养和登记。根据婆罗门遗传学的比例，它们平均分布在六个品种组（G）中：G0％至19％，G21%到34%，G38%(Brangus),G41%到59%，G63%到78%，和G81%到100%。在六个品种组中，产牛的比例（84.9％）没有差异。然而,G81%至100%的奶牛断奶的小牛(90.8%)比G0%至19%和G21%至34%的奶牛(95.7%，each).奶牛断奶率在G38%(94.3%),G41%至59%(94.2%)，G63％至78％（93.0％）介于这三个品种之间。G81%至100%(9.2%)的奶牛断奶前小牛死亡率高于G0%至19%和G21%至34%(4.3%,each),但在G38%(5.7%)的奶牛中，G41%至59%(5.8%)，和G63%至78%（7.0%）。G81%至100%的奶牛也断奶较轻的小牛(220.6公斤)比G0%至19%(245.2公斤)的奶牛断奶。G21%至34%(250.2公斤)，G38%（247.9公斤），G41%到59%(252.5公斤)，和G63%到78%(245.2千克)。G0%至19%的奶牛断奶较轻的小牛比具有21%至78%的婆罗门遗传学的奶牛。与其他遗传群体相比，经过205天调整的断奶体重证明了G0％至19％和G81％至100％的奶牛的生产率较低，当它们以最快和最慢的速度产牛时，分别。因此，205-d调整后的断奶重量消除了这种偏差。此外,年轻的母牛断奶较轻的小牛；雄性小牛断奶时比雌性小牛重。母牛和小牛性别的均等顺序都改变了所描述的母牛品种与小牛断奶重量之间的关联程度。总的来说,在调整断奶时小牛的断奶率和年龄后，与G21%至34(197.0kg)的奶牛相比，G0%至19%(191.1kg)和G81%至100(181.8kg)的每头牛生产的千克数较少，G38（195.9公斤），G41%到59(199.7)，G63%到78（196.2）。G81%至100%的奶牛生产力最低。因此，婆罗门遗传学的比例在21％至78％之间，确保了在亚热带条件下婆罗门-安格斯奶牛的生产力更高。
