Controlled field trial on the anthelmintic effectiveness of the morantel sustained-release bolus in grazing calves.
The direct and indirect anthelmintic efficacies of the morantel sustained-release bolus given to calves were assessed in a 154-day controlled field trial. A permanent calf pasture (divided into 2 lots) and naturally parasitized calves were used. The medicated calves were given the bolus at the time they were placed on the pastures. Control calves did not receive anthelmintic therapy. The effectiveness of the bolus to control parasitic gastroenteritis was determined by monitoring various parasitologic determinants. The treated calves had significantly (P less than 0.01) reduced numbers of fecal nematode eggs for every posttreatment sampling period when compared with the control calves. Tracer calves, used periodically during the study to indicate pasture larval infectivities, had equivalent worm burdens at the beginning of the trial (treated vs control pasture). Tracer calves, added later in the study to the lot with treated calves, harbored 83% to 94% fewer nematodes than did their counterparts in the lot with the controls. Plasma pepsinogen concentrations, reflective of abomasal worm burden size and/or activity, were significantly higher (P less than 0.01) in the control than in the treated calves from day 54 until trial termination. At trial termination, the treated calves weighed an average of 27.8 kg more and harbored 80.9% fewer nematodes than the control calves. The morantel sustained-release bolus is an anthelmintic delivery device that has therapeutic and prophylactic antinematode activities. To achieve its optimum performance, the bolus must be used so that the epizootiologic patterns of the predominate parasitic nematodes are effectively disrupted. Generally, internal nematode parasitisms in the calf flourish during the animal's first springtime grazing period.(ABSTRACT TRUNCATED AT 250 WORDS)
D000284:Administration, Oral; D000818:Animals; D001835:Body Weight; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy*; D002986:Clinical Trials as Topic / Q000662:veterinary; D003692:Delayed-Action Preparations; D005243:Feces / Q000469:parasitology; D007411:Intestinal Diseases, Parasitic / Q000188:drug therapy / Q000662:veterinary*; D008297:Male; D009015:Morantel / Q000008:administration & dosage / Q000627:therapeutic use*; D009349:Nematode Infections / Q000188:drug therapy / Q000662:veterinary*; D010270:Parasite Egg Count / Q000662:veterinary; D010435:Pepsinogens / Q000097:blood; D011743:Pyrimidines / Q000627:therapeutic use*; D012621:Seasons; D013045:Species Specificity
D003692:Delayed-Action Preparations; D010435:Pepsinogens; D011743:Pyrimidines; D009015:Morantel