Effect of Fenbendazole on Nematode Parasites and on Preweaning Average Daily Gain in Beef Cow Herds

Abstract

AbstractThe objectives of this study were to determine the effects of fenbendazole treatment on nematode parasite control and on the ADG of suckling beef calves. In Exp. 1, seven pastures containing commercial cows were randomly assigned to one of two treatments groups. Cows and calves in treatment 1 received no treatment and served as controls. Cows in treatment 2 were administered fenbendazole 45 to 60 d prior to calving. The calves in treatment 2 were administered fenbendazole at approximately 90 d of age. Fecal samples were collected and calf weights were recorded. Treatment 2 cows (P<.025) and calves (P<.05) had lower fecal egg counts per gram (EPG) than treatment 1 cows and calves. Differences in preweaning ADG were not significant (P>.10), but gains were 15.3% higher for treatment 2 calves. In Exp. 2, treatments 1 and 2 were repeated as described in Exp. 1 except that treatment 2 cows received fenbendazole in deworming blocks. A treatment 3 was added in which cows and calves were administered the same fenbendazole treatment as treatment 2 except that the cows in treatment 3 were administered a second fenbendazole treatment (in suspension) at the time of calf treatment (90 d postpartum). A treatment x time interaction was detected (P<.08) in the cow EPG counts. Treatment 1 EPG counts started at a relatively low value and increased by weaning whereas treatments 2 and 3 cow fecal egg counts started at a higher value and decreased by weaning. Differences in calf preweaning ADG were not significant (P>.10). In conclusion, calves born to cows that were dewormed before calving had lower EPG counts at approximately 90 d of age than calves born to cows that were not dewormed, no significant improvements in calf preweaning ADG were detected, and fenbendazole deworming blocks were as effective in reducing EPG counts as fenbendazole administered as a suspension.