| Autor: |
Berk Z; School of Agriculture Food and Rural Development,Newcastle University,Newcastle upon Tyne NE1 7RU,UK., Laurenson YC; Animal Science, School of Environmental and Rural Science,University of New England,Armidale,New South Wales 2351,Australia., Forbes AB; Scottish Centre for Production Animal Health and Food Safety,School of Veterinary Medicine,University of Glasgow,Glasgow G61 1QH,Scotland., Kyriazakis I; School of Agriculture Food and Rural Development,Newcastle University,Newcastle upon Tyne NE1 7RU,UK. |
| Abstrakt: |
Predicting the effectiveness of parasite control strategies requires accounting for the responses of individual hosts and the epidemiology of parasite supra- and infra-populations. The first objective was to develop a stochastic model that predicted the parasitological interactions within a group of first season grazing calves challenged by Ostertagia ostertagi, by considering phenotypic variation amongst the calves and variation in parasite infra-population. Model behaviour was assessed using variations in parasite supra-population and calf stocking rate. The model showed the initial pasture infection level to have little impact on parasitological output traits, such as worm burdens and FEC, or overall performance of calves, whereas increasing stocking rate had a disproportionately large effect on both parasitological and performance traits. Model predictions were compared with published data taken from experiments on common control strategies, such as reducing stocking rates, the 'dose and move' strategy and strategic treatment with anthelmintic at specific times. Model predictions showed in most cases reasonable agreement with observations, supporting model robustness. The stochastic model developed is flexible, with the potential to predict the consequences of other nematode control strategies, such as targeted selective treatments on groups of grazing calves. |
