title: The economic effects of whole-herd versus selective anthelmintic treatment strategies in dairy cows.
abstract: Current control practices against gastrointestinal nematodes in dairy cows rely strongly on anthelmintic use. To reduce the development of anthelmintic resistance or disposition of drug residues in the environment, novel control approaches are currently proposed that target anthelmintic treatment to individual animals instead of the whole herd. However, such selective treatment strategies come with additional costs for labor and diagnostics and, so far, no studies have addressed whether they could be economically sustainable. The objectives of this study were to (1) investigate the economic effects at farm level of whole-herd versus more selective anthelmintic treatment strategies in adult dairy cows, and (2) determine how these economic effects depend on level of infection and herd size. A Monte Carlo simulation, fed by current epidemiological and economical knowledge, was used to estimate the expected economic effects and possible variation of different control strategies under Belgian conditions. Four treatment strategies were compared with a baseline situation in which no treatments were applied: whole herd at calving (S1), selective at calving with (S2) or without (S3) treatment of the first-calf cows, and whole-herd when animals are moved from grazing to the barn in the fall (housing treatment, S4). The benefit per lactation for an average dairy herd varied between -$2 and $131 (average $64) for S1, between -$2 and $127 (average $62) for S2, between -$17 and $104 (average $43) for S3, and between -$41 and $72 (average $15) for S4. The farmer's risk associated with any treatment strategy, as indicated by the width of the 95% credible intervals of economic benefit of anthelmintic treatment, decreased with increasing level of exposure, as assessed by bulk tank milk ELISA. The order of the different strategies when sorted by expected benefit was robust to changes in economic input parameters. We conclude that, on average, strategies applying anthelmintic treatment at calving outperform a strategy applying treatment at housing. Within the strategies that applied treatment at calving, more selective treatment strategies can be economically sustainable. However, given the large variation in possible benefits within each treatment strategy, decision support systems are needed to account for the multitude of cow, epidemiological, and economic factors that determine the economics of nematode control and select the optimal treatment strategy for a specific farm.
authors.affiliation: Department of Virology, Parasitology and Immunology, Salisburylaan 133, 9820 Merelbeke, Ghent University, Belgium. johannes.charlier@ugent.be
authors.forename: J
authors.initials: J
authors.lastname: Charlier
authors.forename: B
authors.initials: B
authors.lastname: Levecke
authors.forename: B
authors.initials: B
authors.lastname: Devleesschauwer
authors.forename: J
authors.initials: J
authors.lastname: Vercruysse
authors.forename: H
authors.initials: H
authors.lastname: Hogeveen
mesh_terms: D000818:Animals; D000969:Antinematodal Agents / Q000191:economics* / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000191:economics / Q000517:prevention & control*; D003362:Cost-Benefit Analysis; D003612:Dairying / Q000191:economics / Q000379:methods; D005260:Female; D007774:Lactation; D018803:Models, Economic; D009349:Nematode Infections / Q000188:drug therapy / Q000191:economics / Q000517:prevention & control / Q000662:veterinary*
chemical_list: D000969:Antinematodal Agents