Comparison of Spayed Heifer Performance to Intact Heifers Fed Melengestrol Acetate on Feedlot Performance and Carcass Characteristics

Abstract

Summary with Implications Pregnancy and estrous cycle management are critical considerations when feeding intact heifers in the feedyard. Alternatively, producers can opt to spay heifers, which eliminates hormonal fluctuations associated with the estrous cycle. A proportion of U.S. feedlots have spayed heifers on feed, although there is limited data comparing the performance of spayed heifers to intact heifers. A commercial feedlot experiment was conducted to compare performance between spayed and intact heifers fed melengestrol acetate. Intact heifers had greater ADG and tended to have greater DMI compared to spayed heifers, although no difference in feed conversion was observed. Carcass weight and final BW were heavier for intact heifers. Spayed heifers were leaner and had a lower USDA Yield Grade compared to intact heifers. These results indicate that spaying heifers upon feedlot entry and feeding similar DOF as intact heifers does not result in improved performance