Research shows feeding cull cows for an extra 30 days before slaughter may increase average daily gain. However, this practice may have the most benefit in terms of reducing antibiotic residues in meat.

According to a study reported in the May Journal of Dairy Science, 31 percent of cows treated with procaine penicillin G exceeded the 10-day meat withdrawal time by about three days.

Althought it may be more costly to feed cull cows for an extra month, it may help minimize residue violations.

“The importance of reducing antibiotic residues outweighs the increased cost of additional feeding of cull cows,” says Mike Looper, one of the study’s authors.