Effect of Restricted Water Intake on Feed Intake, Nutrient Digestibility and Nitrogen Metabolism in Steers

Six steers were used in a replicated 3x3 latin square metabolism study to observe the effects of restricted water intake on feed intake, nutrient digestibility and nitrogen metabolism. Each steer received a full feed of a ground ear corn-urea ration and water free choice (FC), 80% of FC or 60% of FC throughout the experiment. Restriction of water to 60% of FC resulted in a significant (P<.05) reduction in voluntary feed intake. Fecal water, urine output and unmeasured water were significantly (P<.01) correlated to water intake. As water was restricted, the amount of water lost through each of these excretion pathways was decreased. Urine specific gravity paralleled urine osmolality and was negatively (P<.01) correlated to both water intake and urine output. Apparent digestibility tended to be consistently higher when the water intake was restricted but these values were not significantly different from control digestion coefficients. Nitrogen retention tended to increase when water was restricted and was negatively (P<.01) correlated to total nitrogen excreted in the urine. Infusion with a constant amount of urea solution (20% w/v) intravenously resulted in less total nitrogen and less urea nitrogen being excreted in the urine of water restricted steers. These observations indicate that nitrogen recycling was increased due to water restriction.