Effect of Water Restriction on Nitrogen Metabolism in Bovine Fed Two Levels of Nitrogen

Abstract

Twelve Aberdeen Angus steers averaging 250 kg in weight were randomly assigned to a replicated 2 × 2 factorial experiment during two periods and were offered daily water either free choice or 60% of free choice and 4 kg of diets containing either 80 g or 60 g of nitrogen. When the nitrogen intake was reduced by 20 g per day, the average ad libitum water consumption decreased 1.5 liter. Fecal water and urine volume were significantly (P < 0.05) reduced by restricting the water intake. Total serum protein concentration and hematocrit level indicated no detectable reduction in total body water due to the restriction of water intake. Feeding 80 g compared with 60 g of nitrogen significantly (P < 0.05) improved the digestibility of dry matter, gross energy, and nitrogen-free extract when water was allowed ad libitum, but the digestibility of crude protein was increased at both water intake levels. Steers fed the low level of nitrogen had significantly (P < 0.05) greater apparent digestibility coefficients for dry matter, crude protein and nitrogen-free extract when water was restricted but a significantly (P < 0.05) lower digestibility of crude fat. Restricting the water intake tended to increase nitrogen retention at both levels of nitrogen intake but these values were not significantly (P < 0.05) different from the free-choice water values. Blood urea concentration was increased significantly (P < 0.05) by water restriction at both levels of nitrogen intake.