Effects of Trichostrongylus colubriformis (Nematoda) on the nutrition and metabolism of sheep. III.* Digesta flow and fermentation

Abstract

The effect of infection with Trichostrongylus colubriformis on the characteristics of digesta flow and fermentation was studied in young Merino sheep fed on a pelleted roughage diet at 540 g/day.

The pattern of elimination of ⁵¹CR-EDTA was compared in six infected and six paired control sheep. The half-times of the water-soluble marker in rumen and caecum-proximal colon were similar, but the transit time of marker through the tubular intestine was significantly greater in the infected sheep.

The distribution of digesta and the pattern of fermentation in the digestive tract was compared in three infected and three paired control sheep under general anaesthetic. The dry matter, water and nitrogen contents of the rumen were decreased, while those of the abomasum, smail intestine and caecum-proximal colon were increased, in infected sheep. The concentrations of volatile fatty acid and ammonia in the digesta indicated that fermentation in the large intestine was increased by infection.

A flow diagram was developed to describe the specific derangements of nitrogen metabolism caused by infection with T. colubriformis.

It was concluded that the combined effects of increased leakage of endogenous protein into, and reduced efficiency of absorption from, the small intestine resulted in a reduction in the net absorption of amino acid nitrogen by infected sheep. The corresponding increase in microbial deamination of protein in the large intestine increased the availability of ammonia, but very little of this ammonia was used for amino acid synthesis as most was converted to urea and excreted.

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*Part II, Aust. J. Agric. Res., 25: 363 (1974).