title: Unexpected Decrease in Milk Production after Fenbendazole Treatment of Dairy Cows during Early Grazing Season.
abstract: Gastrointestinal nematodes (GIN) infection can impair milk production (MP) in dairy cows. To investigate whether MP would be optimized by spring targeted-selective anthelmintic treatment in grazing cows, we assessed (1) the effect on MP of an anthelmintic treatment applied 1.5 to 2 months after turn-out, and (2) herd and individual indicators associated with the post-treatment MP response. A randomized controlled clinical trial was conducted in 13 dairy farms (578 cows) in western France in spring 2012. In each herd, lactating cows of the treatment group received fenbendazole orally, control cows remained untreated. Daily cow MP was recorded from 2 weeks before until 15 weeks after treatment. Individual serum pepsinogen and anti-Ostertagia antibody levels (expressed as ODR), faecal egg count and bulk tank milk (BTM) Ostertagia ODR were measured at treatment time. Anthelmintic treatment applied during the previous housing period was recorded for each cow. In each herd, information regarding heifers' grazing and anthelmintic treatment history was collected to assess the Time of Effective Contact (TEC, in months) with GIN infective larvae before the first calving. The effect of treatment on weekly MP averages and its relationships with herd and individual indicators were studied using linear mixed models with two nested random effects (cow within herd). Unexpectedly, spring treatment had a significant detrimental effect on MP (-0.92 kg/cow/day on average). This negative MP response was particularly marked in high producing cows, in cows not treated during the previous housing period or with high pepsinogen levels, and in cows from herds with a high TEC or a high BTM ODR. This post-treatment decrease in MP may be associated with immuno-inflammatory mechanisms. Until further studies can assess whether this unexpected result can be generalized, non-persistent treatment of immunized adult dairy cows against GIN should not be recommended in early grazing season.
authors.affiliation: IDELE, French Livestock Institute, UMT Cattle Herd Health Management, Nantes, France.|LUNAM Université, Oniris, Nantes-Atlantic College of Veterinary Medicine and Food sciences and Engineering, UMR BioEpAR, Nantes, France.|INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France.
authors.forename: Nadine
authors.initials: N
authors.lastname: Ravinet
authors.affiliation: LUNAM Université, Oniris, Nantes-Atlantic College of Veterinary Medicine and Food sciences and Engineering, UMR BioEpAR, Nantes, France.|INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Chartier
authors.affiliation: LUNAM Université, Oniris, Nantes-Atlantic College of Veterinary Medicine and Food sciences and Engineering, UMR BioEpAR, Nantes, France.|INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bareille
authors.affiliation: INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France.|LUNAM Université, Oniris, Nantes-Atlantic College of Veterinary Medicine and Food sciences and Engineering, UMR BioEpAR, Nantes, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Lehebel
authors.affiliation: LUNAM Université, Oniris, Nantes-Atlantic College of Veterinary Medicine and Food sciences and Engineering, UMR BioEpAR, Nantes, France.
authors.forename: Adeline
authors.initials: A
authors.lastname: Ponnau
authors.affiliation: LUNAM Université, Oniris, Nantes-Atlantic College of Veterinary Medicine and Food sciences and Engineering, UMR BioEpAR, Nantes, France.|INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France.
authors.forename: Nadine
authors.initials: N
authors.lastname: Brisseau
authors.affiliation: LUNAM Université, Oniris, Nantes-Atlantic College of Veterinary Medicine and Food sciences and Engineering, UMR BioEpAR, Nantes, France.|INRA, UMR1300 Biology, Epidemiology and Risk Analysis in animal health, Nantes, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Chauvin
mesh_terms: D000818:Animals; D000969:Antinematodal Agents / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000469:parasitology; D005243:Feces / Q000469:parasitology; D005260:Female; D005273:Fenbendazole / Q000627:therapeutic use; D007774:Lactation / Q000502:physiology*; D010028:Ostertagia / Q000502:physiology; D010029:Ostertagiasis / Q000150:complications / Q000188:drug therapy; D010270:Parasite Egg Count; D011897:Random Allocation; D012621:Seasons
chemical_list: D000969:Antinematodal Agents; D005273:Fenbendazole