Genetic parameters for milk yield in imported Jersey and Jersey-Friesian cows using daily milk records in Sri Lanka

Abstract

Objective: This study was conducted to estimate genetic parameters for milk yield traits using daily milk yield records from parlour data generated in an intensively managed commercial dairy farm with Jersey and JerseyFriesian cows in Sri Lanka. Methods: Genetic parameters were estimated for first and second lactation predicted and realized 305day milk yield using univariate animal models. Genetic parameters were also estimated for total milk yield for each 30day intervals of the first lactation using univariate animal models and for daily milk yield using random regression models fitting secondorder Legendre polynomials and assuming heterogeneous residual variances. Breeding values for predicted 305day milk yield were estimated using an animal model. Results: For the first lactation, the heritability of predicted 305day milk yield in Jersey cows (0.08±0.03) was higher than that of JerseyFriesian cows (0.02±0.01). The second lactation heritability estimates were similar to that of first lactation. The repeatability of the daily milk records was 0.28±0.01 and the heritability ranged from 0.002±0.05 to 0.19±0.02 depending on day of milk. Pearson productmoment correlations between the bull estimated breeding values (EBVs) in Australia and bull EBVs in Sri Lanka for 305day milk yield were 0.39 in Jersey cows and –0.35 in JerseyFriesian cows. Conclusion: The heritabilities estimated for milk yield in Jersey and JerseyFriesian cows in Sri Lanka were low, and were associated with low additive genetic variances for the traits. Sire differences in Australia were not expressed in the tropical lowcountry of Sri Lanka. Therefore, genetic progress achieved by importing genetic material from Australia can be expected to be slow. This emphasizes the need for a withincountry evaluation of bulls to produce locally adapted dairy cows.