Avaliação genética em bubalinos leiteiros utilizando modelo de regressão aleatória

• Ano de defesa: 2009
• Autor(a) principal: Chaves, Luciara Celi da Silva
• Orientador(a): Torres, Robledo de Almeida
• Banca de defesa: Carneiro, Paulo Luiz Souza , Braccini Neto, José
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado em Genética e Melhoramento
• Departamento: Genética animal; Genética molecular e de microrganismos; Genética quantitativa; Genética vegetal; Me
• País: BR
• Palavras-chave em Português: Búfalos; Persistência da lactação; Produção de leite; Seleção; Tendência genética
• Palavras-chave em Inglês: Buffaloes; Lactation persistency; Milk production; Selection; Genetic tendencies
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::GENETICA E MELHORAMENTO DOS ANIMAIS DOMESTICOS
• Link de acesso: http://locus.ufv.br/handle/123456789/1291

Aiming the evaluation of six measures of milk production persistency and the genetic progress of dairy buffaloes using genetic tendencies of milk production accumulated until 301 days and the milk production persistency in first lactation of buffaloes Murrah breed, 9.219 test day records of milk production originated from the first lactation of 646 dairy Murrah buffaloes, controlled from 1987 to 2006, were used. The productions at the test day were analyzed by random regression model, considering as fixed effects the contemporary group, number of milking, linear and quadratic effects of the covariable buffalo age at calving, random regression coefficient over lactation days, modeled by Legendre orthogonal polynomial of order three, besides the random regression coefficients of the additive genetic and permanent environmental random effects were modeled by the logarithmic function of Ali & Shaeffer. The milk production mean at the test day was 6,63±2,49 kg. The breeding values for milk production of female and male buffaloes along the days in production were growing and negatives at the beginning of the curve until near 30 days of lactation, with highest values within 60 to 90 days. The persistency variable PS1, defined as PS1 = 280 Σ t=61 (VGP1 VGP60), where VGPt and VGP60 correspond to the predicted breeding values at the tth day and at 60 days in production, respectively, was chosen as a criterion of selection for milk production persistency. It was verified that the selection of individuals with higher breeding values for milk production accumulated until 301 days in production (VGP301ac) favors the selection of animals with higher breeding values for milk production at the beginning of the lactation and less persistent and, in addition, the selection of individuals with higher breeding values for persistency, implies in selection of animals with higher breeding values for milk production at the end of the lactation. Analyzing the behavior of the phenotypic tendency, one can verify the growth of 26,91 kg of milk by year, which corresponds to 1,69 % of the general mean of the total milk production. The genetic tendencies of PS1 for male reproducers were negative (-3,41 kg/year) and positive for female reproducers (0,88 kg/year). For the animals, the genetic tendencies indicates a reduction of 2,12 kg of milk by year. For genetic tendencies of VGP301ac, the values were positive for male reproducers (4,71 kg/year), negative for female (-0,16 kg/year) and positive for the animals (1,86 kg/year). The estimated value for genetic tendency of male reproducers correspond to 0,29% of the general mean of milk production.. The results indicate that simultaneous selection for VGP301ac and PS1 implies in the choice of the most persistent and productive animals, and that a higher growth in milk production along the years was done by the improvement of non genetic factors, however there was genetic improvement of male reproducers for milk production in recent years and reduction of milk production persistency.