Abstract

MEZA-NIETO, Martín A. et al. Associations between variants A and B of β-lactoglobulin and milk production and composition of Holstein and milking tropical criollo cows. Agrociencia [online]. 2012, vol.46, n.1, pp.15-22. ISSN 2521-9766.

Genetic variants of β-lactoglobulin (β-LG) A and B have been associated with milk production and composition, which can vary between dairy breeds. The aim of this study was to determine the relationship of genetic variants of β-LG with milk composition and production of Holstein cows (H) and Tropical Milking Criollo (TMC). Three hundred and fifty milk samples of H cows and 64 of TMC were characterized. Individual information on production and reproduction records of both breeds was collected. The chemical composition of each sample was determined by mid-infrared spectroscopy and somatic cell count (SCC) by flow cytometry. An analysis of variance was conducted with mixed models to study the effect of β-LG phenotype on the chemical composition of milk, SCC, milk production, fat and protein adjusted to 305 d and milk yield at the day of sampling. In the statistical model, the random effect of the cows father and the fixed effects herd-year-season, phenotype and number of birth were included, besides the covariates days in milk and cow age. β-LG phenotype was found to have a significant effect on chemical composition of milk. The percentage of fat, protein, nonfat and total solids were significantly (p≤0.05) higher in BB phenotype for both breeds. The milk yield/production fitted to 305 d was higher (p ≤0.05) for AA phenotype of H cows.

Keywords : β-lactoglobulin; variants A and B; milk; Holstein cows; Tropical Milking Criollo.