Estimação de parâmetros genéticos de produção de leite e de gordura da raça Pardo-suíça, utilizando metodologias freqüentista e bayesiana

• Ano de defesa: 2006
• Autor(a) principal: Yamaki, Marcos
• Orientador(a): Torres, Robledo de Almeida
• Banca de defesa: Ribeiro Junior, José Ivo , Carneiro, Antônio Policarpo Souza
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Zootecnia
• Departamento: Genética e Melhoramento de Animais Domésticos; Nutrição e Alimentação Animal; Pastagens e Forragicul
• País: BR
• Palavras-chave em Português: REML; Amostrador de GIBBS; Bovino de leite; Máxima verossimilhança restrita; Teoria bayesiana
• Palavras-chave em Inglês: REML; GIBBS sampler; Dairy cattle; Restricted maximum likelihood; Bayesian theory
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::GENETICA E MELHORAMENTO DOS ANIMAIS DOMESTICOS
• Link de acesso: http://locus.ufv.br/handle/123456789/5720

First lactation data of 6.262 Brown-Swiss cows from 311 herds, daughters of 803 sires with calving between 1980 and 2003 were used to estimate genetic parameters for milk and fat production traits. The components of variance were estimated by restricted maximum likelihood (REML) and bayesian methods, using animal model with uni and two-traits analisys . The estimation by REML was obtained with the software MTDFREML (BOLDMAN et al. 1995) testing unitrait models with different effects to covariables and considering contemporary group and season as fixed effect. The best fitting obtained on unitrait analisys were used on two-trait analisys. The estimative of additive variance was reduced when lactation length was included on the model suggesting that the animals were been fitted to the same base on the capacity of transmit a longer or shorter lactation length to the progeny. Therefore, fitting to this covariable is not recommended. On the other side, the age of calving has linearly influenced milk and fat production. The heritability estimates were 0,26 and 0,25 to milk and fat yield respectively with genetic correlation of 0,95. the high correlation among these traits suggests that part of genes that acts on milk yield also respond to fat yield, in such way that selection for milk yield results, indirectly, in increase on fat yield. The estimation by Bayesian inference was made on software MTGSAM (VAN TASSELL E VAN VLECK, 1995). Chain lengths were tested to obtain the marginal posterior densities of unitrait analisys, the best option of chain length, burn-in and sampling interval was used on two-trait analisys. The burn-in periods were tested with the software GIBANAL (VAN KAAM, 1998) witch analysis inform a sampling interval for each burn-in tested, the criteria for choosing the sampling interval was made with the serial correlation resulting by burn-in and sampling process. The heritability estimates were 0,33 ± 0,05 for both traits with genetic correlation of 0,95. Similar results were obtained on studies using the same methodology on first lactation records. The stationary phase adequately reached with a 500.000 chain length and 30.000 burn-in iteractions.