Impact of non-protein nitrogen supplements on nematode infected sheep

Inadequate nutrition and gastrointestinal nematode parasitism are major constraints to livestock production. In livestock rearing enterprises that rely on low quality roughage for the provision of digestible carbohydrate, the most critical nutritional deficiency is often nitrogen. The provision of non-protein nitrogen in the diet can compensate for this deficiency and enable increased productivity from the available feed resource. Numerous studies have shown that increasing the supply of protein for intestinal absorption can alleviate the detrimental effects of nematode parasites on production and can also result in improved protective immunological responses to infection. In many situations, the practical implementation of such a strategy for improved nematode parasite control is hampered by the high cost and/or unavailability of high quality protein sources for use as ruminant livestock feed. Evidence is presented from studies with young sheep to demonstrate that supplementation with urea can achieve similar qualitative benefits in reducing the effects and level of infection with parasitic nematodes to that achieved with protein supplements. Urea–molasses blocks are a popular low-cost means of delivering non-protein nitrogen and experimental evidence shows that the use of urea–molasses blocks can have a beneficial impact on enhancing the resilience and resistance of sheep to infection with nematode parasites. Consistent with other nutritional studies, urea appeared to confer increased benefits proportional to increasing supplement intake as shown by reduced pathological effects, parasite numbers and faecal egg output. It is suggested that application of these findings in Australian pasture systems may require revision of current systems for the delivery of non-protein nitrogen supplements to increase the level of urea consumed.