– S. L. Boyles, L. J. Johnson, W. D. Slanger, B. J. Kreft, and J. D. Kirsch, originally published in the Canadian Journal of Animal Science
Twenty-six of 52 heifers with an average liveweight of 700 pounds were dewormed by intraruminal injection of oxfendazole and placed in drylot on January 31. The other 26 animals served as controls. All heifers were pastured starting on June 14 and the treatment heifers were dewormed in the same manner as at the start of the experiment on July 1 and July 31.
The groups started out with similar total worm eggs per gram of fecal sample, but the dewormed heifers had fewer counts each month thereafter. The drylot average daily gain of the treated heifers was higher (P = 0.01) and less variable (P = 0.12) and by May 29 these animals were heavier by 26 pounds (P = 0.10). The treated animals did not gain as fast on pasture (P = 0.20), but the gain continued to be less variable (P = 0.09). Age at puberty was not different. Number of open heifers in the treated group was 4 vs. 15% for the control group (P = 0.18).
Deworming resulted in faster feedlot gains and more uniform gains during both drylot and pasture.