The effect of a daily intake of Ostertagia circumcincta larvae on body weight, food intake and concentration of serum constituents in sheep

Abstract

The effect of daily doses of Ostertagia circumcincta larvae on food intake, growth rate and concentration of serum constituents was studied in two experiments. In the first (expt A) three groups of six sheep were dosed daily with 1000 (group I), 3000 (group III) or 5000 (group V) larvae and killed after eight weeks. A fourth group of eight worm-free sheep were group housed as controls for food intake and growth rate. In the second (expt B), two groups of eight lambs (ALC and ALI) were fed ad libitum and the latter dosed daily with 4000 larvae. A third group of eight sheep (PF) were pair-fed to the intake of group ALI. All sheep were killed after 14 weeks. Intakes above 1000 larvae/day adversely affected performance without inducing overt clinical signs of parasitism. Groups I, III and V consumed 6.1, 6.7 and 27.9 kg dry matter (DM) respectively per kg gain in body weight. In expt B infection lowered DM intake by 20 per cent and body weight gain by 16 per cent. Food consumed per kg gain in body weight was 17.4, 10.4 and 11.9 kg DM for groups ALI, ALC and PF respectively. Mean worm burdens at slaughter were 9358, 29,200, 37,323 and 18,450 for groups I, III, V and ALI respectively; a high percentage of fourth stage larvae being present in group ALL Worm egg concentrations in faeces were similar in all infected groups and were not related to worm burden or performance. Serum pepsinogen concentrations were elevated with larval intakes above 1000 larvae/day and may be of value in giving an early indication of subclinical ostertagiasis. Slight hypoalbuminaemia occurred in groups V and ALI from about week 7. Changes in Ca and P concentrations were small and inconsistent. There were no significant differences in serum total protein, globulin or urea N concentrations between groups.