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 effect of Fasciola hepatica on productivity. A bistadial study was designed which consisted of a grazing phase and a feedlot phase. The grazing phase was designed to use induced subclinical liver fluke infections 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 ivermectin/clorsulon combination or ivermectin alone in terms of performance and on hematological values. This trial demonstrated the benefit of treating liver fluke-infected feeder cattle with ivermectin/clorsulon at entry into the feedlot even though all liver flukes were not adults at the time of treatment and the fluke infection level was subclinical. Economic benefit can be anticipated in feeder cattle if natural infections are similar to the artificial infection used in this field study.