Seleção para características de leite e corte em animais da raça Guzerá nos rebanhos de duplo propósito

• Autor(a) principal: Canda, Rabia António
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/4797
• topic: Duplo propósito; Zebu; Melhoramento; Correlação; Dual purpose; Zebu; Improvement; Correlation; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::GENETICA E MELHORAMENTO DOS ANIMAIS DOMESTICOS

Phenotypes and EPD estimates for milk and growth traits of Guzera cattle, from the database of National Program for Improvement of Guzera for Milk (PNMGuL) and the Brazilian Association of Zebu Breeders (ABCZ), were used in this study. The EPD were estimated for dairy traits (milk, fat and protein yield) from 7636 lactations adjusted for 305 days of 4924 cows and for growth traits (weights at 205, 365 and 550 days of age) from 172,764 records. Analyses were performed with the MTDFREML program, using animal model. For milk traits the models included calving year, season of birth, genetic groups as fixed effects, age at calving as covariate, and animal and permanent environmental as random effects. Genetic evaluations for fat and protein yield were performed using a bi-trait analysis with milk yield as second trait. For growth traits, animal, maternal and permanent environmental were included as random effects and contemporary group as fixed effect. Genetic and phenotypic trends were performed using REG and MEANS procedures, available on SAS Statistical Software. The trends were obtained evaluating phenotypic and EPD averages, by birth year. Phenotypic trends for dairy traits were evaluated from 1994 to 2009 and for growth traits from 1993 to 2009. Genetic trends for dairy and growth EPDs were evaluated from 2000 to 2009. Pearson correlations between dairy and growth EPDs were performed using the CORR procedure of SAS. The phenotypic and genetic trends were, respectively, 24.3 Kg/year and 5.2 Kg/year for milk yield, -2.3 kg/year and 0.2 kg/year for fat yield, - 1.1 kg/year and 0.1 kg/year for protein yield, and 2.0 kg/year and 0.6 kg/year for 205 days weight. The phenotypic trends were 6.3 kg/year and 8.3 kg/year for 365 and 550 days weight, respectively, and genetic trends was 1.3 kg/year for 450 days weight. In general, the genetic changes have altered phenotypic means, although lower than expected. The EPD correlations between dairy and growth traits were positive with low to moderate magnitude, and differences were observed between males and females, being the values higher for males. These correlations are indicating that probably selection for both simultaneously do not result in losses for dairy or growth traits. However, caution should be taken because correlations were obtained using EPD values.