Livestock Water Requirements

Daily water need per animal starts from a widely-cited extension-service planning rate -- North Dakota State University Extension's own AS1763, "Livestock Water Requirements," which publishes per-head daily intake by species and weight class. This calculator normalizes those figures into gallons per 100 lbs of body weight per day so intake scales cleanly with Average Weight -- that base rate varies by Species, then scales with Average Weight and is multiplied up for hot weather. Head Count scales the totals directly: Daily Total, Weekly Total, and Monthly Total all rise in step with how many animals are on water, since every other factor only changes the per-head rate rather than the herd size itself. Average Weight moves per-head consumption proportionally (a 2,000 lb animal drinks roughly twice what a 1,000 lb animal of the same species does), and Species shifts the baseline rate itself. The ordering is not what size alone would suggest: swine sit at the highest gallons-per-100-lbs rate, sheep and goats next, then cattle, with horses lowest, following the per-head figures published by NDSU Extension (AS1763, adapted from the NRC requirement tables).

Water intake tracks metabolic rate and dry-matter intake rather than scaling linearly with body size, so a smaller animal drinks more per 100 lbs than a larger one does. Ambient Temperature applies a smoothly interpolated multiplier: water needs hold at the base rate through moderate temperatures, rise as it warms past 70°F, and reach roughly double the base rate at 100°F, while cold weather below freezing modestly reduces intake. Recommended Tank Size is set at twice the calculated Daily Total, giving a buffer for a hot spell or a water-system outage without running dry. Treat these as planning figures -- actual intake varies with humidity, forage moisture content, lactation status, and individual animal variation.