Effects of hexachlorethane on the milk yields of dairy cows in north Florida infected with Fasciola hepatica.

Hexachlorethane was evaluated as a fasciolicide in dairy cattle under field conditions. After treatment with hexachlorethane, Fasciola hepatica-infected cows had a significant (P = 0.05) average daily milk yield increase (90 to 120 days after treatment) of + 4.2 kg/day (+ 5.0 kg/day for single treatment and + 4.0 kg/day for double treatment) over daily yields of the previous lactation. Nontreated controls and noninfected treated animals did not have significant gains over yields of the previous lactation. A 73.0% efficacy was observed against egg production by F hepatica after a single treatment of 90 g of hexachlorethane/animal. After a 2- to 3-month interval, a second treatment produced a combined treatment efficacy against fluke egg production of 91.2%.