Genetic relationships between weight loss in early lactation and daily milk production until 305 days in Holstein cows

International audienceBody mobilization of high-yielding dairy cows is intense after calving and can generate health and fertility troubles. This study aimed to estimate the genetic correlation between body weight loss during the five first weeks of lactation (BWL) and daily milk production (MY24a) in first (L1) and second (L2) lactations Holstein cows. The dataset included 859,020 MY24a and 570,651 body weight (BW) daily phenotypes from 3,989 L1 cows, and 665,361 MY24a and 449,449 BW daily phenotypes from 3,060 L2 cows, recorded in 36 French commercial farms equipped with milking robots including an automatic weighing platform. The genetic parameters of BW and MY24a in L1 and L2 were estimated using a 4-trait random regression model. Genetic correlations between BWL and MY24a ranged from-0.26 to 0.05 in L1, and varied from-0.11 to 0.10 in L2, suggesting that selecting to reduce early body mobilization while maintaining milk production is possible