Evaluation of ivermectin on performance of beef cattleon pasture in Alberta
Canadian Veterinary Journal
Canadian Veterinary Medical Association
Parasitic nematode infections may cause slow growth rates (poor performance) in young beef cattle and weight loss in older animals (1,2). Treatment with one of the new broad-spectrum anthelmintics is commonly used to control or alleviate the effects of clinical or subclinical parasitic gastroenteritis in cattle (1,3). However, the economic benefit of anthelmintics, especially in cases of subclinical parasitisms, is still debatable (4,5), particularly for cow/calf beef producers (6). Numerous papers have described the activity of ivermectin in cattle experimentally infected with nematode and arthropod parasites (7). Field trials using counts of parasite eggs in the feces of cattle before and after treatment with ivermectin have confirmed the efficacy under field conditions (7). Early season treatment of cattle at three, six and nine weeks after turnout is generally recommended as an effective prevention of gastrointestinal helminthiasis (8). Alternatively, a sustained-release bolus can be implanted in cattle at turnout (8,9). This latter approach is more convenient for farmers, but more expensive than conventional treatments (9). The disadvantage of the 3-6-9 treatment program is that farmers must collect and treat their cattle three times. Because of the residual effect of ivermectin against reinfection that lasts approximately two weeks, Eysker (9) recommended treatment at three and eight weeks after turnout. In the present study, we determined the efficacy of ivermectin on naturally acquired nematode infections in yearling beef cattle treated 29 and 64 days after turnout on pasture, on the basis of fecal egg counts and growth rates.
Kennedy, M.J., and D.R. ZoBell. 1988. Evaluation of ivermectin on performance of beef cattle on pasture in Alberta. Can. Vet. J. 29:566-567.