Maintenance of acquired immunity to Trichostrongylus colubriformis in Merino sheep that are losing weight.
The effect of loss of weight on maintenance of acquired immunity to Trichostrongylus colubriformis in Merino sheep was assessed in 2 experiments. Adult Merino sheep with previously acquired immunity to T colubriformis were housed in individual pens. Sheep were infected 3 times weekly with 2000 T colubriformis larvae. A diet based on chopped oaten and lucerne hay (experiment 1) or a pelleted diet based on lucerne hay and grain products (experiment 2), was offered in amounts to sustain a moderate gain in body weight, or was reduced step-wise to cause a loss in body weight. Worm egg counts were determined weekly. The reduction in feed on offer resulted in a mean weight loss of 4.0 kg over 9 weeks (experiment 1) or 4.8 kg over 7 weeks (experiment 2). Based on worm egg counts, there was no indication of a change in immunity to T colubriformis in either of the experiments. These results suggest that acquired immunity to T colubriformis in adult sheep that are exposed to infection is maintained during periods of moderate loss of weight associated with inadequate nutrition.
van Houtert
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MF
CSIRO Division of Animal Health, Pastoral Research Laboratory, Armidale, New South Wales.
Watson
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DL
Barger
I A
IA
D000821:Animal Feed / Q000592:standards; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D000909:Antibodies, Helminth / Q000276:immunology; D001835:Body Weight / Q000502:physiology; D004435:Eating / Q000502:physiology; D002523:Edible Grain / Q000592:standards; D005243:Feces / Q000469:parasitology; D007110:Immunity, Active; D008297:Male; D010270:Parasite Egg Count / Q000662:veterinary; D012756:Sheep; D012757:Sheep Diseases / Q000276:immunology* / Q000503:physiopathology; D014253:Trichostrongylosis / Q000276:immunology / Q000503:physiopathology / Q000662:veterinary*; D014254:Trichostrongylus / Q000276:immunology*; D015431:Weight Loss / Q000502:physiology*
D000909:Antibodies, Helminth