Influence de périodes de stress thermique modéré sur le temps de rumination,la production laitière et le nombre de traites de vaches au pâturage, traites par un robot mobile.

peer reviewedGrazing dairy cows milked by an automatic system (AS) experienced mild heat stress (HS) periods, twice during the summer. The daily temperature humidity index (THI) during these periods were higher than 72. Milk production, as well as milking frequency, rumination time and milk fat to protein ratio (F/P) during these periods were compared to adjacent periods with mean THI of 61. The daily milking frequency, the total number of visits to AS and the milk production were significantly higher in HS periods (2.12 vs 1.97, 2.99 vs 2.69, and 19.7 vs 18.5 kg milk per cow, respectively). There were significant interactions between times and periods for milking frequency and number of visits, while the daily rumination time was significantly lower (339 vs 419 min) and the F/P in milk tended to be decreased (1.17 vs 1.23). These results could be explained by changes in cow behaviour during HS periods.Innovative and sustainable systems combining automatic milking and precision grazin