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Anthelmintics remain the main or even exclusive tool used to control gastrointestinal strongles (GIST) in young cattle on pasture. However, their non-rationalized use (frequency and period of treatment) represents a double risk: the emergence of resistant worms and the disruption of the development of antiparasitic immunity in cattle. Rationalisation of the use of anthelmintics requires the development of indicators to target interventions on the most infested animals or those suffering the most from infestations. The aim of this study was to evaluate the value of a simple indicator, the growth rate during the first grazing season, to identify the most parasitized animals.

The grazing of heifers (months of exit, supplementation, duration of grazing) made it possible to divide 12 batches of animals (291 animals) into 3 levels of exposure to IMS (low, medium, high). The variability of their individual growth was explained by individual parameters (level of parasite infestation measured by an IMS antibody level and diarrhea score) as well as by group parameters (exposure level). The higher the level of parasite infestation, the lower the growth rate of the heifers, and this correlation was only found in groups with moderate to high exposure to IBS. These results indicate that identification of at-risk batches from heifers and parasitized animals based on their growth performance is possible with a view to selective anthelmintic treatment.

Partners: this work was carried out in collaboration with units at INRA (UMR 1348 and UE 0326) and the Chambers of Agriculture and with funding from the INRA GISA Strep metaprogram and the AEI Chair.

Associated publication :  Merlin A., Chauvin A., Madouasse A., Froger S., Bareille N., Chartier C. Explaining variability in first season grazing heifer growth combining individually measured parasitological and clinical indicators with exposure to gastrointestinal nematode infection based on grazing management practices. Veterinary Parasitology, 2016, 225, 61-69.   doi:10.1016/j.vetpar.2016.05.006

Contacts

Scientific contacts :

•  Aurélie Merlin, Christophe Chartier UMR BIOEPAR

Associated Department : Santé animale

Associated Centres : Angers-Nantes Pays de la Loire, Rennes Bretagne-Normandie