Daily Water Requirement of a Herd

Water is the nutrient stock run short of first, and the one least often measured. A lactating dairy cow drinks 110–150 L a day, a beef cow 40–70 L, a finishing pig 8–12 L, a laying hen about a quarter of a litre. Multiply by the head count and the daily demand follows immediately — 120 dairy cows at 115 L each need 13,800 L, near enough fourteen cubic metres, every single day.

Water intake and dry matter intake are tied together tightly enough that one limits the other. A cow that cannot drink stops eating within hours, and milk production — which is itself about 87% water — falls the same day. Restricted water is one of the fastest ways to lose production and one of the hardest to spot, because the animals show nothing except eating less. Anything that limits access counts as restriction: a frozen or fouled trough, too few drinking spaces for the group, a bully at the waterer, or a supply line sized for the average rather than the peak.

Demand is not constant across the year or the day, and the daily average is the wrong figure for sizing anything. Consumption rises steeply with temperature — a beef cow at 32 °C can drink twice what she drinks at 10 °C — and with the dry matter content of the ration, so stock on hay drink far more than the same stock on lush spring pasture, which is largely water already. Within the day, cattle drink in bouts after feeding and in the afternoon heat, so peak hourly draw can be several times the daily total divided by twenty-four.

Size the supply against the peak and the storage against the failure. A well that meets average daily demand exactly will fail on the hottest afternoon of the year, which is the afternoon it matters most; trough capacity and recovery rate have to cover the bout, not the day. And a herd has no reserve of its own — a pump that stops on a summer weekend is a welfare emergency within a day, which is the argument for storage, for a backup, and for an alarm that reaches somebody.