Effects of restricting the water intake of dairy cows upon their milk yield, body weight and blood composition

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Abstract
1. Water intake was measured in eight lactating cows. Subsequently n i an experiment of a 4 × 4 Latin square design, each cow received 100, 87, 73 and 60% of its voluntary intake for 6 days followed by an 8-day recovery period.2. Measurements were made of the intake of feed, milk yield and quality, water, Na and K balances, metabolic profiles, and serum and urine osmolalities. The cows were weighed at the beginning and end ofthe experimental periods, and pulse, respiration and rumination rates and rectal temperatures were measured daily.3. Milk yield decreased significantly with increasing water deprivation. A 40% reduction in water intake was associated with a 16% decrease in intake of dry matter and a concomitant 16% decrease in milk yield. The only significant change in milk composition was a small increase in lactose concentration with increasing water deprivation.4. There was no significant reduction in urine output, but the output of water in faeces was reduced and there was evidence of a reduction i n total body water which approximated the reduction in body weight. 5. Concentrations of serum Na and urea-N and serum osmolality increased significantly with increasing water deprivation.