Research has shown that parasites cost the beef industry over $3 billion annually in lost weight gains, poor feed conversion and increased disease. Most producers dewormed and vaccinated calves earlier in the fall. Parasite-inflicted calves respond poorly to vaccination because they mount a poor immune response. High calf prices and high feed prices greatly magnify the return benefit of parasite control. Several extra pounds at market or slaughter will more than pay for the entire parasite control program.
In our area, we are pregnancy-checking and vaccinating cowherds. This is a great time to administer a parasite prevention program. For the past 10 years most producers have used a pour-on avermectin for control. These topical applications must be absorbed to be effective against internal parasites. In the past, low doses of these products were administered, with only fractional levels being absorbed, contributing to parasites developing resistance to avermectin pour-ons. Even lice are becoming resistant.
There are many effective broad-spectrum products on the market. If a producer has been using a single product for several years, it may be a good time to rotate to another product.
We commonly use oral wormers when pregnancy-checking because the cow is restrained in a chute. These products are hard to administer, but work well on most internal parasites.