Strategic effects of early season treatments with Moxidectin on trichostrongylosis in young calves.
This study was conducted to evaluate the effects of strategic early season treatments with Moxidectin on trichostrongyles in first-season grazing heifer calves on a permanent pasture. Three groups of Black-Pied Friesian heifer calves were turned out in early May on a permanent pasture naturally infected with trichostrongyle larvae. Two of these groups were treated with Moxidectin at turnout or at turnout and again 8 weeks later, while one group served as untreated controls. For the first three weeks of the experiment all animals grazed together in one flock on one pasture. Subsequently, the pasture was divided into three comparable plots, which from then and until housing in mid October were grazed by each calf group. The results showed that the treatments significantly suppressed faecal egg excretion in the early part of the season, leading to reduced herbage infectivity and parasitism over the rest of the season. Results from faecal egg counts determined at genus level revealed that the persistent activity of Moxidectin appeared to be longer against Ostertagia spp. than against Cooperia spp. Two Moxidectin treatments, given at turnout and on week 8, protected the calves to a higher degree than a single Moxidectin treatment given at turnout. However, there was also a significant effect of only one Moxidectin treatment which possibly could be explained by a low overwintered larval population and a drought period in the early summer.
Yang
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X
Danish Centre for Experimental Parasitology, Royal Veterinary and Agricultural University, Frederiksberg, Denmark.
Satrija
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F
Nansen
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P
D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D000900:Anti-Bacterial Agents; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000469:parasitology; D005243:Feces / Q000469:parasitology; D007814:Larva / Q000254:growth & development; D018942:Macrolides / Q000627:therapeutic use; D010063:Ovum / Q000378:metabolism; D010435:Pepsinogens / Q000097:blood; D012621:Seasons; D014251:Trichostrongyloidea / Q000187:drug effects* / Q000254:growth & development; D014253:Trichostrongylosis / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*
D000871:Anthelmintics; D000900:Anti-Bacterial Agents; D018942:Macrolides; D010435:Pepsinogens; C027837:moxidectin