The addition of external water to fresh grassdoes not affect dry matter intake, feeding behaviour and rumen characteristics in dairy cows

Fresh grass is often a fodder of high nutritive value for ruminants, but its intake is limited in spite of its high digestibility. The high water content of fresh grass could limit grass DM intake by cows. The effect of external water on intake, feeding behaviour and rumen fill was studied in dairy cows fed indoors with fresh perennial ryegrass offered ad libitum. Three treatments were compared: fresh grass as harvested (C: control); C with water added to the grass (SW: surface water) and C with perfusion of water in the rumen after each distribution (PW: perfused water). Grass was offered to cows at 14:00 h, 19:00 h on each day and 07:00 h the following morning. Free access was given to drinking water. In treatment SW, the DM content of the offered grass was reduced from 161 to 117 gkg -1 on a fresh basis (P < 0.02) without changing the chemical composition of the grass on a DM basis. Compared to C and PW, the fresh matter intake and its rate of intake increased in SW (+ 36 and 39%, respectively), but the grass DM intake (16.4 kg DMday -1 ), the rate of DM intake (35.3 g DMmin -1 ), the daily eating time (468 min) and rumination time (515 min) were not modified. Perfusion of water into the rumen did not affect intake or feeding behaviour. The weight of the rumen contents (150 kg) and their DM content (115 gkg -1 fresh matter), rumen fluid osmolality, as well as proportions of free water and bound water and turnover rate were not modified by the treatments. In conclusion, for dairy cows fed on grass, important inputs of external water do not affect feeding behaviour, rumen fill nor grass DM intake. dairy cows / fresh grass / surface water / intake / behaviour / rumen fill Rsum -L'addition d'eau externe l'herbe verte n'affecte pas la quantit de matire sche ingre, le comportement alimentaire ou les caractristiques du rumen chez la vache laitire. L'herbe frache est un aliment de bonne valeur alimentaire pour les ruminants mais son ingestion par les vaches laitires reste limite au regard de sa digestibilit. La forte teneur en eau de l'herbe frache pourrait limiter la quantit ingre de MS d'herbe. L'effet de l'eau externe la plante sur l'ingestion, 3