Genetic diversity and population structure of Boer and Nubian goats in Mexico

Abstract

In Mexico, since 2010 the Asociación Mexicana de Criadores de Ganado Caprino de Registro has been undertaking annual national genetic evaluations for the Boer and Nubian goat breeds. Mexican pedigree goat farmers are concerned with maintaining a reasonable high genetic diversity and a low level of inbreeding without loss of genetic gain. This study aimed to assess the genetic diversity and to describe the population structure of the Boer and Nubian goat breeds in Mexico using pedigree analyses to support the development of strategies for breeding programs. Herdbook information collected between 1994–2017 for Boer and from 1991 to 2017 for Nubian were utilized. The information included pedigree records on 18,947 animals for Boer (141 flocks) and 13,744 animals for Nubian (99 flocks). The effective number of founders ( f e ) were 504 and 203, and the effective number of ancestors ( f a ) were 253 and 88, for Boer and Nubian, respectively. The ratio f a / f e was 0.50 for Boer and 0.43 for Nubian, indicating the existence of population bottlenecks. The average inbreeding and relatedness coefficients were 1.02 and 0.28 % for Boer and, 1.39 and 1.04 % for Nubian. The number of most influential ancestors that explained 50 % of the genetic diversity in the population were 109 for Boer and 38 for Nubian. The average generation interval estimated through the four gametic paths was 3.27 ± 0.03 yr for Boer and 4.63 ± 0.06 yr for Nubian. Realized effective population size, computed from the individual increase in inbreeding, was 61.3 ± 24.5 for Boer and 69.3 ± 22.8 for Nubian (kids born from 2013 to 2017 were considered as the reference population for both breeds). The average equivalent completed generations, as a measure of pedigree completeness, were 2.02 for Boer and 2.88 for Nubian. The pedigree completeness index increased over time for both breeds. The results revealed the loss of genetic diversity and the presence of genetic bottlenecks for both populations. The study of the genetic diversity on these populations must continue to prevent the decrease in genetic progress and genetic variability. Additionally, a mating policy that simultaneously allows low levels of inbreeding, high levels of genetic diversity and maximum genetic progress, must be designed.