Faria F J C, Filho A E V, Madalena F E, Josahkian L A
Departamento de Zootecnia, FAMEZ-UFMS, Campo Grande/MS, Brazil.
J Anim Breed Genet. 2009 Apr;126(2):148-53. doi: 10.1111/j.1439-0388.2008.00767.x.
Zebu breeds play an important role in cattle production systems in Brazil. To assess the genetic variability from animals in the Herd Books of Nelore, Gir and Guzerat breeds, generation intervals, inbreeding, effective population size and parameters of gene origin (effective number of founders, ancestors and founder genomes) were calculated using pedigree records from 1938 to 1998. Breed subdivision was quantified by Wright's F-statistics. Calculations were separately carried out for consecutive 4-year intervals in the period 1979-98. Generation interval was around 8 years for the three breeds. Total inbreeding increased in all the breeds reaching values of 2.13%, 2.28% and 1.75%. Effective population size decreased from 85 to 68 in Nelore, from 70 to 45 in Gir and remained nearly constant around 104 in Guzerat. The quantities assessing the number of contributing ancestors decreased with time in all the breeds, and in the last analysed period the most important ancestor accounted for 14%, 3.1% and 4.1% in Nelore, Gir and Guzerat, respectively. Results indicate that the studied breeds are suffering from a loss of genetic variability which can result in negative effects on breeding and conservation purposes.
瘤牛品种在巴西的养牛生产系统中发挥着重要作用。为了评估内洛尔牛、吉尔牛和古泽拉特牛品种畜群登记簿中动物的遗传变异性，利用1938年至1998年的系谱记录计算了世代间隔、近亲繁殖、有效种群大小和基因起源参数（有效奠基者数量、祖先数量和奠基者基因组数量）。品种细分通过赖特F统计量进行量化。在1979 - 98年期间，以连续4年的间隔分别进行计算。这三个品种的世代间隔约为8年。所有品种的总近亲繁殖率均有所上升，分别达到2.13%、2.28%和1.75%。内洛尔牛的有效种群大小从85降至68，吉尔牛从70降至45，而古泽拉特牛则几乎保持在104左右不变。在所有品种中，评估贡献祖先数量的指标随时间减少，在最后一个分析期内，内洛尔牛、吉尔牛和古泽拉特牛中最重要的祖先分别占14%、3.1%和4.1%。结果表明，所研究的品种正遭受遗传变异性的损失，这可能对育种和保护目的产生负面影响。
