Anthelmintic Treatment of Nonpastured Dairy Cows in California1

Many dairy cattle are housed under drylot conditions, which generally are not considered conducive to elevated populations of gastrointestinal parasites. Thus, an examination of the potential benefits to be obtained by anthelmintic treatment of lactating cows under these circumstances was initiated. Because there were no statistically significant differences in milk production between control and treated groups, routine deworming cannot be considered economically sound under the management conditions described.