[Water requirement of food-producing animals and pets]

In contrast to other essential nutrients there are only few publications dealing with the water requirement of food producing and companion animals. The exact derivation of water requirement and more detailed knowledge about the actual water consumption of each animal is only required if water supply is limited or too expensive to be provided in abundance. In case of limited water supply the water requirement is of special interest in order to prevent negative effects on animal health, performance or welfare. Intentions for water restriction or reasons for an accidental reduced water intake are quite different and variable in animal husbandry or keeping of companion animals. The following conditions only represent a few examples: water restriction in order to keep the litter dry (for example in poultry houses), due to technical problems concerning water supply like blocked-up waterers or failure to estimate the water requirement correctly (e.g. pet rabbits fed on concentrate and carrots without any additional water). Water consumption measured under conventional housing conditions (in litre per kg dry matter intake) varies in a wide range (from < 1:1 up to > 4:1) from one species to another. With higher performance leading to increased feed intake, water consumption usually also rises. For this reason it is very useful to calculate water consumption in relation to dry matter intake only. Besides there are several other factors of practical concern that have great influence on water intake: environmental temperature, intake of nutrients, that must be eliminated via the kidneys (e.g. electrolytes, nitrogen), as well as the amount of water spent for certain products like the sweat in horses or cow's milk. The importance of adequate water supply is best understood regarding the consequences of water deprivation (reduced feed intake, concentration of urine, impaired thermoregulation, reduced renal excretion of metabolic waste products, intake of other fluids that may be critical with regard to hygiene, behavioural problems). Because of the consequences of an inadequate water intake for animal welfare--last but not least--legislation on keeping animals provides guidelines for water supply that are controlled (among others) by veterinary administration.