Effect of the inbreeding on reproductive and productive traits in Mantiqueira type cattle

[摘要] - Genealogies of 2070 animals and records from the first five lactations of 1406 cows of the Mantiqueira type cattle, daughters of 113 sires, were analyzed to estimate the frequency of inbred animals, the inbreeding average per generation and the possible effect of inbreeding increase on reproductive and productive traits. The evaluated traits were age at first calving (IPP), calving intervals (IDP), total milk production (PL) and lactation period (DL). Models for PL, IDP and DL included the fixed effects of year-season of calving were used, linear and quadratic effects of the age of the cow as covariate and the random animal effects, permanent environment and error. The fixed effect of lactation period was included also in the PL analysis. Year-season of calving as fixed, and animal and error as random were fit in the mode for IPP. Restricted maximum likelihood methodology was used in the analyses. Trends of inbreeding were estimated by generation. Significant increases of inbred animals and average levels of inbreeding coefficient were observed with the latter varying between 0.33 and 7.34% and increasing up to the last generation. Linear effects of inbreeding on breeding values for PL and IPP and quadratic effect for IDP and DL were found. Inbreeding influenced negatively the breeding values for all traits being responsible for reductions in PL and DL and increases in IPP and IDP. Poor efficient breeding programs and the fact that the herd is closed are important factors for the continuous increase in the level of inbreeding and number of inbred animals.

[学科分类] 兽医学

[关键词] animal model;dairy cattle;inbreeding;Mantiqueira type;REML methodology   IntroduçãoA criação do ecótipo Mantiqueira no Núcleo de Pesquisa Zootécnica Geraldo José Rodrigues Alckmin do Instituto de Zootecnia da Agência Paulista de Tecnologia dos Agronegócios da Secretaria de Agricultura e Abastecimento;do Estado de São Paulo (NPZGJRA/IZ/APTA/SAA-SP);foi iniciada por volta do ano de 1952;ao ser adquirido um grupo de aproximadamente 50 animais;oriundos de rebanhos dos Estados de Minas Gerais e São Paulo