EFFECT OF CLIMATE ON MILK-PRODUCTION AND COMPOSITION

Twenty-two Holstein or Montbeliarde dairy cows were pastured on a continuous grazing system for 76 d in the Auvergne. Climatic conditions, milk production and fat and protein contents were measured every day. Milk yield was higher (+0.5 kg/d, P < 0.01) when the mean temperature ranged between 15 and 20-degrees-C than when it ranged between 4 and 10-degrees-C. This difference disappeared when the rainfall was higher than 5 mm/d. In contrast, the fat and protein contents were lower (about -1 g/kg, P < 0.05) when the mean temperature was between 15 and 20-degrees-C. There was no difference in these responses of Holstein and Montbeliarde cows.