This is most important with the urea-containing feeds. Death may result. However, drought stressed forage may be deficient. The minimum level suggested is 200,000 units per pound. Don't let internal parasites add an extra burden on your cows.
Current research indicates that the best time to deworm cows is mid-summer.
The parasite load in your cows is controlled and the chance for reinfection is slim because of dry, hot weather. Most dryland corn has been hurt severely. Cattlemen may want to salvage the corn by grazing. Be advised that nitrates can be a problem. A limited number of corn samples indicate that nitrate levels are safe.