Resumo

TORRES-VAZQUEZ, José Antonio; VALENCIA-POSADAS, Mauricio; CASTILLO-JUAREZ, Héctor  e  MONTALDO, Hugo H. Genetic and phenotypic trends for milk yield and milk composition traits of Saanen goats from Mexico. Rev. mex. de cienc. pecuarias [online]. 2010, vol.1, n.4, pp.337-348. ISSN 2448-6698.

The objective of the study was to estimate the genetic and phenotypic trends for milk yield (MILK, n = 1041), fat yield (FAT, n = 487), protein yield (PROT, n = 477), lactose yield (LACT, n = 401), fat content (%FAT, n = 487), protein content (%PROT, n = 477) and lactose content (%LACT, n = 401), analyzing first lactation records adjusted to 305-d, obtained between 2000 and 2006 from 10 Saanen goats flocks from Guanajuato, Mexico. Predicted breeding values (PBV) were obtained with single-trait animal models that included phantom parent groups. Genetic trends were estimated as the regression of the PBV on year of birth. Phenotypic trends were estimated as the linear regression coefficients of production records on the year of birth. The annual genetic trends for MILK, FAT, PROT and LACT were 2.99 ± 1.06 kg, -0.21± 0.09 kg, -0.10 ± 0.04 kg and -0.19 ± 0.09 kg, respectively (P<0.05). Annual genetic trends for %FAT, %PROT and %LACT were close to zero (P>0.05). The mean annual genetic trend for MILK was 0.32 % of the phenotypic mean. These results indicate that it is necessary to use more appropriate selection criteria, increasing the emphasis on all the production traits, including fat and protein contents in order to maximize the economic progress in this population, whose main objective is milk production for cheese yield manufacture.

Palavras-chave : Genetic trend; Genetic parameters; Phantom parent groups; Dairy goats.

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