This invention provides methods for improving reproductive performance of lactating dairy cows and other mammals. The method in the case of cows comprises feeding to the cows, a composition comprising conjugated linoleic acids (CLAs), cis-9, trans-11 and trans-10, cis-12. When these CLAs are fed daily to dairy cows starting at or prior to calving, and continued after parturition, an improvement in reproductive performance is observed.