Resumo

ALVARADO, Carlos et al. Effect of the k-Casein Genetic Variant on Milk Yield and Composition in a Holstein Herd in the Tropics. Rev. Fac. Cienc. Vet. [online]. 2006, vol.47, n.1, pp.43-49. ISSN 0258-6576.

To evaluate the effect of k-casein polymorphism on milk yield and composition in a Holstein herd located in the central region of Venezuela, different k-casein genetic variants present in the herd were determined by the isoelectric focusing technique.  A total of  294 milk samples were analyzed using a completely randomized statistical design with  a 2³ factorial arrangement. The allele A of casein was found in 92% of the cows in the herd, while the allele B was found in 52%. When the levels of milk yield of each animal were compared, it was found that those animals with allele A had a higher daily milk yield. The statistical analysis of the results of milk composition from milk samples showed that the k-casein polymorphism found in the Holstein herd has no effect on the content of the main components of milk.

Palavras-chave : k-casein; cow milk; breeds (animals); Holstein; proximate composition; genetic variation; Aragua.