Economic evaluation of three anthelmintic strategies for lamb flocks affected by benzimidazole-resistant nematodes

Objective To compare the profitability of three anthelmintic strategies in growing lambs in flocks\with nematodes resistant to benzimidazole anthelmin tics. Method A partial-budgeting analysis was carried out by means of a stochasti c simulation model, which allows inputs to be described as distributions ra ther than as fixed values, and hence permits variation between farms to be considered in the analysis. Results The results show that control of nematode parasites by use of an ef fective anthelmintic provides the highest net returns, yielding a margin ov er ineffectively treated lambs of A$114 per 100 lambs an average. Suppressi ve treatment based on the administration of two controlled-release capsules and monthly with moxidectin resulted in an average loss of A$131 per 100 l ambs in comparison with animals treated with an ineffective anthelmintic. A nalysis of the results from capsule-treated lambs did not take into account the unmeasured benefits associated with less contamination of pastures. Se nsitivity analysis using a stochastic model indicates that apart from the e ffect of treatment on weight gain variation in carcase price greatly influe nces the profitability of all the parasite control programs examined. Conclusion The results suggest that it is economically important for farmer s to adjust their strategy in the presence of anthelmintic resistance. But as a result of uncertainty in the factors influencing economic return, the expected economic benefit is likely to vary substantially.