Alternative feeding strategies were investigated for Holstein heifers grazing a vegetative red, Trifolium pratense L., and white clover, Trifolium repens L., pasture. A total of 474 grazing heifers were supplemented varying amounts of corn silage, Zea mays, during the breeding season in an effort to improve reproductive performance. Animal response to supplementation, whether on spring or winter pasture, was similar. Corn silage supplemented at 18.8 or 28.8% DM basis of total diet, for winter and spring pastures, respectively, resulted in animal weight gains similar to that of heifers receiving legume pasture only. Serum urea nitrogen and reproductive performance for heifers offered corn silage was similar to heifers offered pasture only. Heifers offered a higher proportion of corn silage, at 35.2 and 56.5% DM basis of total diet, for winter and spring pastures, respectively, had lower body weight gain and tended to have a lower percentage of animals exhibiting estrous and confirmed pregnant after 2 services. Treatment did not influence conception rates, with 85.5% of all heifers gravid within a 2 estrous cycle schedule
