Efficacy of Levamisol on milk production of dairy cows: a field study.

Twelve hundred ninety-six cows on 88 farms were alternately injected at calving with Levamisol or saline. Each farm was visited every 2nd wk from May to October to administer treatments to cows that would calve prior to our next visit and to collect fecal grab samples from cows for worm egg counts. Production records were collected for each cow for their first 6 mo of lactation. Fecal worm egg counts were reduced in cows treated with Levamisol for the first 2 mo postcalving. Daily milk produced was higher in cows treated with Levamisol by 1.24 kg. Milk fat and protein percentages were not different between treatment groups; however, milk fat production was higher in cows treated with Levamisol for the first 2 mo post-calving. Cows treated with Levamisol produced 235 kg more milk than control cows during their first 6 mo of lactation and were projected to produce 339 kg more milk for a 305-d lactation. Month of calving improved milk production by cows treated with Levamisol. Cows treated with Levamisol and calved in months May to July showed the highest improvement in milk production while cows that were treated with Levamisol and calved in months August to October showed no significant improvement in production. Injection of cows with Levamisol at calving improves milk production and reduces gastrointestinal worm burdens.