EFFECT OF WATER-DEPRIVATION ON EATING PATTERNS OF LACTATING COWS FED GRASS AND CORN PELLETS AD-LIB

The present study investigated the effect of 48 h of water deprivation on eating behavior of 12 lactating cows fed grass and corn pellets ad lib. Water deprivation reduced grass and corn pellet intake significa ntly, with corn pellet intake decreasing earlier than grass intake. Th e reduction of feed intake was entirely due to a reduction of meal siz e for both grass and corn-pellet meals. The size of the first meal of the water deprivation period was already reduced by about 30%. Grass-m eal frequency increased, whereas corn-pellet meal frequency decreased during water deprivation. Water deprivation also decreased live weight and milk yield by about 12 and 30%, respectively. All parameters retu rned to baseline values with rehydration. With ad lib access to feed a nd water, 77% of drafts occurred in relation to meals, but the number of meals clearly exceeded the number of drafts. The results demonstrat e that water deprivation rapidly leads to premature meal termination. This is in line with the assumption that an enhanced prandial increase in ruminal fluid osmolality contributes to dehydration-induced hypoph agia. Yet, further studies are necessary to prove this assumption and to better understand the complex relationships between eating and drin king in ruminants. Copyright (C) 1996 Elsevier Science Inc.