Milk production of grazing dairy cattle after a single anthelmintic treatment.

The prevalence of nematode infections in lactating dairy cattle was determined by faecal egg counts and cultures from over 350 cows selected at random from twelve herds. The mean egg count was 3 eggs per gram (epg) and 43% of the cows sampled were passing detectable concentrations of eggs (greater than 6 eggs) in their faeces. In June 1976 171 cows in 10 herds were treated with 7.5 mg/kg fenbendazole and their milk production compared over the following 2 months with that of 164 untreated cows in the same herds. Anthelmintic treatment had no significant influence on milk production in any of the herds. The contrasting results of this study and recent studies in the United States of America are discussed.