Response to index selection for temperate dairy cattle breeds in tropical Sri Lanka

This study aimed to predict selection responses for breeding objective traits based on large-scale dairy farms rearing temperate dairy breeds in Sri Lanka. Responses were predicted selecting 10% of bulls at 4 and 9 years of age assuming the availability of progeny records for the selection of older bulls. When economic weights were expressed relative to the trait genetic standard deviation, milk yield (MY, 74%) had the highest relative emphasis on selection. Favourable responses were only observed for MY and calving interval reflecting the high selection emphasis on MY to counteract with other traits. Predicted responses relative to the current mean varied from -0.67% (protein yield) to 0.40% (MY). Progeny selection increased the accuracy at the expense of higher generation interval. Predicted increase in profit due to genetic improvement was slightly higher under progeny testing compared to family selection (2,624 vs 2,506 rupees or 14.1 vs 13.5 USD per cow per year).