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The role of ammonia in exercise-induced fatigue is reviewed. Implications for integrated activity of developing hyperammoneic states, caused by various precipitating conditions such as exercise, liver dysfunction, hypoxia, hyperoxia, and chemical poisoning are described. The central role of ammonia in diverse important metabolic pathways indicates its ubiquitous role in a spectrum of activity ranging from elite exhaustive performance of sportsmen and -women to life-threatening organ dysfunction. The action of ammonia and metabolites from associated pathways in producing seemingly dangerous short term conditions, but inducing possible long term protection against degenerative processes associated with ageing (free radical-induced cellular damage) indicate the paradoxical position of ammonia and its associated metabolic pathways for health and disease processes.

SUMMARYA series of five field trials with cattle was carried out to study the comparative efficiency of utilization of urea and biuret in various maintenance and production nutritional situations. It was shown that in maintenance diets with energy intake above 8 Meal/head/day and where half of the nitrogen requirements of the animals was contributed by one of the two non-protein nitrogen (NPN) sources, biuret was utilized 30% more efficiently than urea. No difference in the degree of utilization of urea or biuret was apparent when the energy was reduced to 6·7 Meal/head/day. On the other hand, a high intake of nitrogen in production rations had a masking effect on the nitrogen contribution of the NPN sources and no significant differences in bodyweight gain were recorded.

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