Genetic variability of Guzerat cattle raised in northern Brazil, based on pedigree analysis

ABSTRACT Genealogical data comprised 45,711 animals born between 1901 and 2016, with 48,127 animals in the pedigree file. Population structure was analyzed in terms of pedigree completeness, individual inbreeding coefficient (F), generation interval (L), rate of inbreeding (ΔF), effective population size (Ne), effective number of founders (ff), and effective number of ancestors (fa). The herd initially consisted of 13 bulls and 14 cows, and there were variations in the number of selected bulls and cows throughout the analyzed period, with 2,575 bulls, 13,691 cows, and 45,711 births recorded at the end of 2016. In total, 48.81% of the cows had only one progeny. Most dams (47.59%) were between three and seven years old, with a mean L in the population of 7.9 years. According to the results, 52.75% of the cows, 44.92% of the bulls, and 63.71% of the calves of the Guzerat breed in the northern region of Brazil showed some degree of inbreeding, with small-magnitude coefficients (0.56, 0.83, and 0.71% for cows, bulls, and calves, respectively). This fluctuation did not hinder the genetic evolution of the herd in the region. The effective population size does not seem to compromise the maintenance of genetic variability in the breed.

摘要 本谱系数据集涵盖1901年至2016年间出生的45711头动物，系谱文件中共收录48127头个体。本研究从系谱完整度、个体近交系数（individual inbreeding coefficient, F）、世代间隔（generation interval, L）、近交速率（rate of inbreeding, ΔF）、有效群体大小（effective population size, Ne）、有效奠基者数量（effective number of founders, ff）以及有效祖先数量（effective number of ancestors, fa）等维度对群体结构进行了分析。该畜群初始种群包含13头公牛与14头母牛；分析周期内，入选的公牛与母牛数量存在波动，截至2016年末，共记录到2575头公牛、13691头母牛以及45711头新生个体。总计48.81%的母牛仅产下一胎。多数母牛（47.59%）的年龄处于3至7岁区间，群体平均世代间隔为7.9年。分析结果显示，巴西北部地区古泽拉特牛（Guzerat）品种中，52.75%的母牛、44.92%的公牛以及63.71%的犊牛存在不同程度的近交，其近交系数均处于较低水平，其中母牛、公牛与犊牛的近交系数分别为0.56%、0.83%与0.71%。这种近交波动并未阻碍该区域畜群的遗传进化，有效群体大小亦未对该品种遗传多样性的维持造成负面影响。