Parasites in lactating dairy cattle: Epidemiology and response to treatment

Gastrointestinal nematodes rarely cause signs of clinical disease in adult cattle. However, they have been shown to exert a negative impact on production in lactating animals, as seen by improved production following elimination of the worms using anthelmintics. The epidemiology of bovine gastrointestinal nematodes and chorioptic mange was investigated through a one-year longitudinal study in 38 Canadian dairy herds from four different provinces (Prince Edward Island, Quebec, Ontario and Saskatchewan). For each of the herds included in the study, fecal egg counts from eight randomly selected animals and whole herd mange scores were performed on a monthly or quarterly basis. Larval cultures were performed once, and all producers were interviewed regarding herd management practices using a standardized questionnaire.

The 28 herds from the two eastern locations were also enrolled in a clinical trial of the effect of treatment with eprinomectin pour-on solution at calving on production. (Abstract shortened by UMI.).