Evaluation of the pour-on administration of eprinomectin on milk yield and somatic cell counts in dairy ewes naturally infected with gastrointestinal nematodes

The effect of pour-on eprinomectin administration on milk yield and somatic cell counts was studied in dairy ewes located on twelve farms in mainland Greece. On each farm, the selected ewes were randomly divided into three similar groups. Group 1 consisted of 10-15 untreated ewes (control group), Group 2 consisted of 10-13 ewes treated with a single dose of eprinomectin at Day 0 and Group 3 consisted of 6 ewes repeatedly treated with eprinomectin at Days 0, 42 and 70. Faecal egg counts and coprocultures were performed on Days 0, 7, 14, 28, 42, 56, 70, 84 and 98. The milk yield and somatic cell counts were measured. The topically administered eprinomectin was highly effective against gastrointestinal nematodes up to 42 days post treatment (94.1% and 99.7% for Groups 2 and 3, respectively). This beneficial effect was extended from Day 42 to 98, in ewes of Group 3. Ewes treated once or thrice presented an increase of daily milk yield by ca. 5% (50 mL/day) and 11% (105 mL/day), respectively, compared to untreated ewes. At the same frame, a significant decrease in somatic cell counts was observed in the eprinomectin treated ewes compared to the untreated ones. In conclusion, this study confirmed the high antiparasitic efficacy and the beneficial effect of pour-on eprinomectin on the milk yield and somatic cell counts in dairy ewes under semi-intensive management.