Dietary nitrogen and energy metabolism in the ruminant: Effect of source of nitrogen.

摘要

Three experiments were conducted to determine the effects of dietary nitrogen on the energy status of ruminants and the feasibility of using L-carnitine to prevent the negative effects associated with overfeeding nitrogen. The objectives of the first experiment were to monitor the nitrogen and energy status of cows grazing ryegrass pastures through the measurement of key blood metabolites and insulin and to determine the protein supplementation scheme which would maximize milk yield and maintain plasma urea nitrogen levels below dangerous levels. In the first experiment, the protein supplement that supplied excess total protein exerted negative effects on body condition and plasma nitrogen metabolites but had a minimal effect on plasma energy metabolites and insulin. The nutritional status of the cows post-partum and prior to grazing seemed to have a greater effect compared with the dietary protein supplements on the ability of the cow to maintain condition during early lactation. The second experiment was conducted to investigate the effects of intravenous administration of L-carnitine in sheep, and to determine its ability to ameliorate subclinical hyperammonemia experimentally-induced using an oral urea load test. Results indicated that intravenous administration of L-carnitine (12.72 mmol/kg