Summary

1. Water is the most important essential nutrient supplied to dairy cattle. 2. However, at times and in some dairy farms, quality and provision of water may not be optimal to maximize animal performance and health. 3. Too often dairy producers and their consultants have insufficient understanding of water nutrition of dairy cattle. 4. Two main questions should be examined: a) Is water intake normal, depending on physiological state of the animal and its environment? b) Are anti-quality factors present in water that may affect water intake, or normal metabolic or physiological functions of animals? 5. Assessing whether or not water intake is normal must be done by measuring water intake (e.g., with in-line flow meters) of groups of animals with specific definable characteristics (e.g., dry matter intake rate, milk yield, dry matter content of the ration, and sodium intake). Specific approaches for measuring water intake are suggested. 6. If water intake, feed intake, and animal performance are sub-optimal; careful evaluation of the quality of water should be initiated by conducting a laboratory analysis for anti-quality factors. 7. Anti-quality factors (constituents in excess or unwanted compounds) that may affect water intake and animal performance include: total dissolved solids, sulfur, sulfate, iron, manganese, nitrate, toxic compounds (e.g., heavy metals, pesticides), and deleterious microorganisms. 8. The pH of water (6 to 9 range), calcium, magnesium, and hardness of water are not believed to affect the intake of water or animal performance. 9. Various treatment methods to remove unwanted constituents (anti-quality factors) from water are surveyed. No single method will remove the potential broad spectrum of unwanted constituents. 10. Practical guidelines for evaluation of water nutrition, as well as placement and management of water receptacles are discussed