Investigation of nitrogen balance in dairy cows and steers nourished by intragastric infusion. Effects of submaintenance energy input with or without protein.
1983
Orskov, E. R. | MacLeod, N. A. | Fahmy, S. T. | Istasse, Louis | Hovell, F. D.
English. peer reviewed
Show more [+] Less [-]English. Two dairy cows were maintained by intragastric infusion of volatile fatty acids and casein. Except when fasting, the casein-nitrogen was held constant, while total gross energy supply was varied from zero during fasting to 650 kJ/kg body-weight (W)0 . 75. One cow was estimated to attain zero N balance at an energy intake of 255 kJ/kg W0 . 75 and the other at 307 kJ/kg W0 . 75, which was calculated to be substantially below the estimated energy required for zero energy balance. When the cows were later given an N-free infusion for a period preceding the trial, N balance occurred at 98 kJ/kg W0 . 75 for one cow and 115 kJ/kg W0 . 75 for the other. Four steers were similarly nourished by intragastric infusion and the energy nutrient increased from 0 at fasting to 450 kJ/kg W0 . 75. The protein was held constant at 1 g N/kg W0 . 75 except at fasting. The energy level at which N balance occurred was 154 (SE 38) kJ/kg W0 . 75 or approximately equal to the energy content of the protein. The practical implications of these findings are discussed.
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