Genetic diversity of Brazilian Brahman cattle by pedigree analysis

Abstract: The objective of this work was to evaluate the genetic diversity of Brahman cattle in Brazil with pedigree analysis. Genealogical records of a subpopulation were used considering all pedigree information (Pt) and the pedigree information divided into two periods (P1, from 1994 to 2004; and P2, from 2005 to 2012) or according to the raising system (Ppt, animals on pasture; or Pst, on stable). Estimates were obtained for average inbreeding coefficients, generation intervals (GI), number of equivalent known generation (CGE), number of founders (Nf), effective number of founders (fe), effective number of ancestors (fa), and founder genome equivalents (fg). The average inbreeding coefficients were 11.97, 7.79, 11.95, 11.74, and 11.31% for Pt, P1, P2, Ppt, and Pst, respectively. Average GI was 4.4 years, whereas CGE was 3.18. The fe values were similar to those of fa, which were greater than those of fg. The fe/fa and fg/fe ratios were close to 1, which indicates no genetic bottleneck and small losses by genetic drift. The genetic diversity in the Brazilian population of Brahman breed is not significantly reduced.

摘要：本研究旨在通过系谱分析（pedigree analysis）评估巴西婆罗门牛（Brahman cattle）的遗传多样性。研究采用某亚群的系谱记录，分别设置全系谱信息组（Pt）、按时间划分为两个时期的系谱信息组（P1：1994年至2004年；P2：2005年至2012年），以及按饲养体系划分的系谱信息组（Ppt：放牧饲养个体；Pst：舍饲饲养个体）。本研究获得了多项参数的估算值，包括平均近交系数、世代间隔（generation intervals, GI）、等效已知世代数（equivalent known generation, CGE）、奠基者数（founders, Nf）、有效奠基者数（effective number of founders, fe）、有效祖先数（effective number of ancestors, fa）以及奠基者基因组当量（founder genome equivalents, fg）。Pt、P1、P2、Ppt与Pst组的平均近交系数分别为11.97%、7.79%、11.95%、11.74%及11.31%。该群体的平均世代间隔为4.4年，等效已知世代数为3.18。有效奠基者数（fe）与有效祖先数（fa）的数值相近，且二者均大于奠基者基因组当量（fg）。fe/fa与fg/fe的比值均接近1，表明该群体未发生遗传瓶颈，且遗传漂变导致的遗传损失较小。巴西婆罗门牛种群的遗传多样性未出现显著降低。