Interrelationship between helminths and nutrition: with reference to gastrointestinal nematodes in sheep

Abstract

The plane of nutrition and the adverse effects of gastrointestinal nematodes are clearly inter-related. The parasites usually influence the nutrition of the host by causing a reduced feed intake. The reduction is roughly proportional to the dose of infective larvae. The reasons for the anorexia are not known. A reduction in protein digestability is also seen with certain species, due to their pathological effect on the mucosa of the abomasum or small intestine. Nematodes appear to increase the basal metabolic rate, decreasing the amount of energy available for production. The utilisation of minerals is impaired with hypophosphataemia being widely reported. Nitrogen metabolism is also affected leading to hypoalbumenaemia, hypergammaglobulinaemia and increased albumen/globulin ratio. Total plasma protein is usually reduced.

Animals on a high plane of nutrition are better able to withstand nematode infestation than animals on a low plane. The protein level of the diet seems especially important. With certain parasites, the mineral and fibre levels of the diet have marked influences on the pathological effects of the parasites.