The Effects of Phenothiazine vs Methyridine on the Weight Gains and Helminth Burdens of Feed Lot Lambs.

The anthelmintic efficiency of methyridine administered subcutaneously was compared with orally administered phenothiazine in a group of feed lot ram lambs. Methyridine caused a greater suppression of total ova counts than did phenothiazine and was particularly superior in regard to Nematodirus and S. Papillosus. Examination of gastrointestinal tracts at the conclusion of the 10 week feeding period indicated that the reduced total ova counts in the methyridine group was for the most part a reflection of reduced numbers of small trichostrongyles of the small intestine. At the conclusion of the trial there was a 45% increase in the mean liveweight gains of the methyridine treated group over the mean of the phenothiazine treated animals. This difference was statistically significant and amounted to 10 lbs. per animal.