Effects of the Intestinal Nematode Trichostrongylus Colubriformis on Ruminal Acetate Metabolism in Young Sheep

Rates of production and oxidation of ruminal acetate were measured in young sheep (1) infected with T. colubriformis; (2) kept worm-free and pair-fed to (1); and (3) kept worm-free and given feed ad lib. Both voluntary food consumption and the production rate of acetate were reduced by up to 76 per cent in sheep on treatment (1) compared with (3). Acetate production rate was 30 per cent lower in infected than in pair-fed sheep, indicating there was an effect of the parasite on ruminal fermentation additional to the effects of reduced feed intake. The percentage contribution of acetate to blood CO2 was lower in infected than in pair-fed animals. Rates of irreversible CO2 loss from blood suggested that, apart from a reduction associated with decreased feed intake, the energy expenditure of sheep was not markedly affected by the parasite.