Chronic infection with Trichostrongylus vitrinus in sheep. Some effects on food utilisation, skeletal growth and certain serum constituents.

The effect on food utilisation and skeletal growth of daily infection for 90 days with 2500 Trichostrongylus vitrinus larvae was investigated. Controls were killed initially or fed ad libitum. Food intake, digestibility of dry matter and nitrogen and content of body fat, protein, water and minerals were determined, and selected bones examined chemically and histologically. Serum constituents were determined weekly. Digestibility of food dry matter and nitrogen were reduced during weeks 3 and 5 after initial infection but subsequently recovered. Deposition of fat, protein, calcium and phosphorus in the body was reduced by 36, 58, 67 and 78 per cent respectively. Gross efficiency of utilisation of metabolisable energy was reduced by 36 per cent. Bone changes were associated with a reduction in osteoblastic activity. Hypoalbuminaemia, hyperglobulinaemia and hypophosphataemia were present in infected sheep. There were no significant changes in serum calcium or urea concentrations. It is concluded that the effects of continuous intakes of T vitrinus and T colubriformis larvae on host metabolism are essentially the same.