Water temperature impacts water consumption by range cattle in winter.

Abstract

Water consumption and DMI have been found to be positively correlated, and both may interact with ingestion of cold water or grazed frozen forage due to transitory reductions in the temperature of ruminal contents. The hypothesis underpinning the study explores the potential that cows provided warm drinking water would have increased in situ NDF and OM disappearances and a more stable rumen temperature, drink more water, and lose less BW during the winter. This hypothesis was tested in 3 experiments. In Exp. 1, ruminal extrusa (93.1% DM, 90.2% OM, 81.1% NDF [DM], and 4.9% CP [DM]) were randomly allocated to 1 of 5 in vitro incubation temperatures. In 2 independent trials, temperatures evaluated were 39, 37, or 35°C (trial 1) and 39, 33, or 31°C (trial 2). In Exp. 2, 4 pregnant rumen cannulated cows grazing in January were fitted with Kahne (KB1000) temperature continuous recording boluses for 22 d. Two grazed in a paddock provided cold water (8.2°C) and 2 in a paddock provided warm water (31.1°C). Two in situ trials were conducted placing 6 in situ bags containing 2 g of winter range ruminal extrusa in each of the 4 ruminally cannulated cows and incubating bags for 72 h for measurement of NDF disappearance. In Exp. 3, 6 paddocks ( = 3/water treatment) were grazed by 10 to 13 pregnant crossbred Angus cows from December through February across 3 yr from 2009 to 2012. Water intake per paddock was measured daily and ambient temperature was recorded. Motion-activated cameras were used to determine the time of day water was consumed and the number of cow appearances at water. In Exp. 1, rate and total gas production ( < 0.05) and NDF disappearance ( < 0.001) at 48 h was reduced by each incubation temperature below 39°C. In Exp. 2, ruminal temperature for cows supplied with warm water dropped below 38°C 1.5% of the time whereas ruminal temperature for cows provided cold water dropped below 38°C 9.4% of the time ( < 0.01). Drinking water temperature did not alter in situ OM or NDF disappearance. In Exp. 3, cows with access to warm water consumed 30% ( < 0.05) more water than cows provided cold water. In this study, there were energetic costs to range cows proportional to consumption of water at temperatures less than body temperature. The magnitude of these costs were found to be less than the heat increment because no improvement to BW gain, BCS change, or calf birth weight were found for cows consuming warmed water.