Yearling Friesian and Boran cattle were given a standard dose of Fasciola gigantica metacercariae designed to produce chronic infection. Their liveweights were then monitored for 23 weeks post-infection. Following standard meat inspection procedures, all the livers from the infected cattle were condemned. At 22 kg per animal, the mean reduction in liveweight gain in infected Borans was significantly greater than in infected Friesians. Compared to the control cattle and based on current sale prices in Kenya, the production losses from the combination of liver condemnations and reduction in liveweight gain constituted a loss in value of US$12.11 (4.92%) and US$23.41 (10.34%) for Friesians and Borans respectively. These data indicate that productivity losses and the economic consequencies of fasciolosis in yearling Boran cattle are much more severe than in Friesians. These findings have implications for assessing the likely benefits of control measures against this parasite.
