Pedigree analysis in the Brazilian Zebu breeds

Abstract

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.

In-depth pedigree analysis in a large Brazilian Nellore herd

“…Average regular inbreeding levels in Nellore have been reported by Faria et al (2009), and were slightly higher (2.13% in the 1994-1998 period) than those found using VRM in the current study (1.73% in 2007). For other Brazilian Zebu breeds in this same period, Faria et al (2002) reported values of F ranging from 0.98% in the Polled Nellore to 10.13% in the Sindhi breed.…”

Genetic improvement and population structure of the Nelore breed in Northern Brazil

“…The average generation interval was equal to that calculated by Faria et al (2009), slightly lower than those reported by Malhado et al (2008a;, and higher than the intervals observed by Carneiro et al (2009) and Malhado et al (2010) for registered zebu cattle in Brazil.…”

“…The genetic contribution of the 10, 50 and 448 most influential ancestors (founders or not) explained 13.2, 28.0 and 50% of the genetic variability of the whole population, respectively. Faria et al (2009) reported that in Nelore cattle, a small number of ancestors made a substantial contribution to the population, while in Gir and Guzerat the numbers were larger. They describe that during the period from 1994 to 1998 as few as 50 Nelore ancestors explained 56% of the variability observed in the population.…”

“…These methods have provided significant insights into the genetic structure of economically profitable species. Despite these advances, there is still a need for information about pedigree, in order to identify temporal trends and to evaluate inbreeding, effective population size, generation interval, genetic diversity and several other important population parameters (Vercesi Filho et al, 2002, Malhado et al, 2008a, 2008b, 2010Martinez et al, 2008;Faria et al, 2009).…”

Estrutura Populacional Do Rebanho Nelore Criado No Semiárido Do Nordeste Brasileiro

“…Conforme estudo de Faria et al (32) , a utilização de touros por longos períodos na reprodução e em centrais de inseminação contribuem na elevação dos níveis de endogamia e acarretam a redução do tamanho efetivo da população de bovinos Nelore, parâmetros essenciais para o monitoramento da variabilidade genética ao longo dos ciclos seletivos.…”