EFFECT OF FASCIOLA-HEPATICA ON PRODUCTIVITY OF BEEF STEERS FROM PASTURE THROUGH FEEDLOT

A total of 142 crossbred beef steers were included in a study of the e ffect of Fasciola hepatica on productivity. A bistadial study was desi gned which consisted of a grazing phase and a feedlot phase. The grazi ng phase was designed to use induced subclinical liver fluke infection s in beef steers to determine the influence of immature liver flukes ( up to 10 weeks post-infection) on beef production while animals are on pasture. Upon subsequent entry into the feeding phase, the objective was to evaluate the effect of treating fluke-infected steers with an i vermectin/clorsulon combination or ivermectin alone in terms of perfor mance and on hematological values. This trial demonstrated the benefit of treating liver fluke-infected feeder cattle with ivermectin/clorsu lon at entry into the feedlot even though all liver flukes were not ad ults at the time of treatment and the fluke infection level was subcli nical. Economic benefit can be anticipated in feeder cattle if natural infections are similar to the artificial infection used in this field study.