EFFICACY OF INSECTICIDAL EAR TAGS ON FLY CONTROL AND MILK PRODUCTION OF DAIRY COWS

Twenty Holstein cows were blocked into two groups of 10 cows each to evaluate an insecticidal ear tag (8% fenvalerate) on fly control and milk production. One group received one tag in each ear while the control group remained untagged. Each group was allowed access to an exercise-pasture lot of similar size. Forages were fed in the lots and grain was fed in the barn at milking. Tagging resulted in a 99.9% reduction in horn flies over the 16 wk of the trial. However, other flies (house, stable and face) were not controlled to the same extent. As horn fly numbers decreased the number of the other flies increased on tagged cows. Tagging resulted in an overall increase in milk yield by 1.06 kg/d for the trial but not all weeks of the trial showed significant responses. Milk fat and protein percentages were not different between tagged and control animals. Key words: Diptera, dairy cattle, milk production, fenvalerate, ear tags, fly control