Water metabolism of dairy cattle.

Lactating dairy cows metabolize large amounts of water and are affected rapidly by water deprivation. Total body water, half-life of body water, size of component pools, and exchanges among them have been quantitated in several studies. The data underscore the dynamic nature of water metabolism in lactating cows. Water is lost in milk, urine, feces, and various forms of evaporation. Sources of water include drinking, feed, and metabolic (oxidation) water. Factors that have been shown to influence drinking behavior include eating pattern, water temperature, whether water is given in a trough or water bowl, flow rates into water bowls, animal dominance if water bowls are shared, and stray voltage. Important environmental factors modulating water consumption of dairy cattle are DMI, nature of the diet, milk production, temperature, and humidity. Equations have been proposed to predict water consumption based on measures of some of these variables. Water is of paramount importance both physiologically and nutritionally; therefore, it is not surprising that its metabolism indirectly may affect many feeding and management decisions. Ample water of acceptable quality must be provided to maximize milk production.