title: Evaluation of a strategic deworming program in dairy heifers in Quebec based on the use of moxidectin, an endectocide with a long persistency.
abstract: Two different deworming strategies based on the use of moxidectin, a broad spectrum endectocide with persistency against Ostertagia ostertagi, were evaluated in grazing dairy heifers. Eighty-four heifers unexposed to parasitic infection were randomly allocated to 3 different groups: untreated (Group 1), treated at 3 and 10 weeks after turnout with 0.5 mg/kg/body weight (BW) of topical moxidectin (Group 2), or treated at turnout and 10 weeks later with 0.5 mg/kg/BW of topical moxidectin (Group 3). The heifers were turned out on June 6 (Day 0) to a naturally contaminated pasture divided into 3 sections by an electrical fence. Each group of heifers was put on a different section of pasture. The trial ended when they were housed on October 29 (Day 143). The results of this experiment confirmed the beneficial effect of 2 strategic treatments with moxidectin pour-on under field conditions in Quebec. The parasitological parameters showed a statistical difference in terms of mean fecal egg counts between treated and control groups (ANOVA, P < or = 0.006). After turnout, pasture larval counts were consistently higher for Group 1 compared with counts for Group 2 or 3. All heifer groups gained weight during the trial period, but the weight gain profile of both treated groups was significantly higher than that of the untreated controls (ANOVA, P < 0.03). During the trial period, Group 2 and Group 3 gained 77.7 kg BW and 73.2 kg BW, respectively, while Group 1 gained only 57.9 kg BW, despite the fact that heifers of Group 1 received a greater quantity of supplementary feed while on pasture.
authors.affiliation: Ayerst Veterinary Laboratories, 400 Michener Road, Guelph, Ontario N1K 3E4.
authors.forename: J
authors.initials: J
authors.lastname: Elsener
authors.forename: A
authors.initials: A
authors.lastname: Villeneuve
authors.forename: L
authors.initials: L
authors.lastname: DesCôteaux
mesh_terms: D000018:Abomasum / Q000469:parasitology; D000704:Analysis of Variance; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D000969:Antinematodal Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000517:prevention & control; D005243:Feces / Q000469:parasitology; D005260:Female; D018942:Macrolides; D010028:Ostertagia / Q000187:drug effects*; D010029:Ostertagiasis / Q000188:drug therapy / Q000517:prevention & control / Q000662:veterinary*; D013997:Time Factors; D015430:Weight Gain / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D000969:Antinematodal Agents; D018942:Macrolides; C027837:moxidectin