Winter Survival of Some Cattle Parasites on a Kentucky Pasture with Observations on the Effects of Low-Level Phenothiazine Treatment

Abstract

Observations over 4 winter intervals (1953-54 through 1956-57) averaging 7 months in length indicated the survival of the free-living stages of Ostertagia ostertagi, Nematodirus helvetianus, Cooperia oncophora, C. punctata, Trichuris sp., and Moniezia sp. on blue-grass pasture in central Kentucky. There was no evidence that Haemonchus sp. and Oesophagostomum radiatum over-wintered on pasture. Low-level phenothiazine medication of successive groups of heifers on 1 pasture during the intervening summer grazing seasons showed a species-selective action on the nematodes. Of the 3 predominant species, O. ostertagi and C. oncophora were effectively controlled, but the development and survival of N. helvetianus were favored. This was shown by the numbers of each of these species that survived the succeeding winter intervals on the treated pasture in comparison with the control.