Reduce anthelmintic treatment of heifers to limit the risk of development of resistant gastrointestinal strongles.

In order to limit selection pressure on digestive strongles during anthelmintic treatments and thus reduce the risk of resistance development, targeted treatment strategies aimed at defining the lot and animals to be treated were developed in dairy heifers in their first year of grazing. The choice of the lots to be treated was based on the evaluation of the parasite risk linked to the animals' management style using a simulation tool and that of the animals to be treated within the lots on weight gain during grazing or when entering the stall. The validation of this approach was carried out by a study in 23 heifer batches: treatment of half of the animals (those with lower growth) allows for similar results in terms of growth and parasite infestation to those of a treatment of all the animals.

Bibliography :

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

Merlin A., Chauvin A., Lehébel A., Brisseau N., Froger S., Bareille N., Chartier Ch. End-season daily weight gains as rationale for targeted selective treatment against gastrointestinal nematodes in highly exposed first-grazing season cattle. Preventive Veterinary Medicine, 138:104-112. DOI: 10.1016/j.prevetmed.2017.01.011.

Merlin A., Shaw R.C., Chauvin A., Bareille N., Chartier Ch. Significance of anti-CarLA salivary IgA antibody in first grazing season cattle naturally infected with gastrointestinal nematodes. Veterinary Parasitology, 243:36-41. DOI: 10.1016/j.vetpar.2017.06.006.

Merlin A., Ravinet N., Madouasse A., Bareille N., Chauvin A., Chartier Ch. Mid-season targeted selective treatments based on flexible weight gain threshold for nematode controle in dairy calves. Animal 12(5):1030-1040. DOI: 10.1017/S1751731117002312.