Association between body condition genomic values and feed intake, milk production, and body weight in French Holstein cows

Body condition score (BCS) offers a good estimate of the amount of stored fat on the body, and its variations can be used as a proxy for energy balance. Many coun-tries have implemented a genomic evaluation of BCS, including France, where estimated breeding values are based on an individual BCS determination during the first lactation. In this article, we investigate the degree to which this genomic estimated breeding value based on a single phenotype record per cow might reflect different profiles of body reserves throughout lacta-tion and be used to predict, and perhaps limit, their mobilization during early lactation. We also investigate whether selection on BCS affects other traits. A data set including 686 lactations of 435 Holstein cows from 3 experimental farms not used in the reference popula-tion for genomic evaluation was used to estimate the effects of the BCS direct genomic value (iBCS) on BCS, body weight, feed intake, milk production, and fat and protein contents throughout the lactation period. For each trait, the model included different iBCS regres-sions and an effect of the direct genomic value of the trait itself when available. It thus appeared that cows with a positive iBCS always had a higher BCS than negative iBCS cows, whatever the lactation stage, and that this difference increased during the first 6 mo to reach a difference of 0.8 point. A similar effect was seen regarding body weight, but it was the opposite for milk production, with negative iBCS cows producing slightly more milk (difference of about 3% over lactation). Feed intake increased slightly faster at the beginning of lac-tation for cows with positive iBCS. Therefore, iBCS is a promising tool that could help to limit intense mobi-lization during early lactation. Should feed efficiency be included in the breeding goal, greater attention should be paid to BCS to avoid further body mobilization in early lactation.

Automated summary

Body condition score (BCS) is a good estimate of stored fat on the body and can be used to proxy energy balance. Genomic evaluation of BCS has been implemented in several countries, including France, where estimated breeding values are based on individual BCS determination during the first lactation. This study investigates the use of genomic estimated breeding values based on a single phenotype record to predict and potentially limit body reserve mobilization during early lactation, as well as the effects of selection on BCS on other traits.