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Management freemartinism because the male twin may have been aborted at an earlier stage of gestation,” Selk said. “These so-called hidden freemartins can be difficult to identify if purchased as replacement heifers.” This is a major reason why OSU Division of Agricultural Sciences and Natural Resources animal scientists and OSU Cooperative Extension agricultural educators recommend producers cull any non-pregnant replacement heifers soon after their first breeding season. Another reason is that female cattle nursing twin calves will require an estimated 13% more energy intake to maintain body condition. “Be aware the additional suckling pressure on the cow will extend the post-calving anestrus period,” Selk says. “Therefore, cows nursing twins will take longer to rebreed for next year’s calf crop.” In some cases, Selk says producers may want to consider early weaning of twin calves to allow the birth mother to cycle in time with the other cows in the herd. Otherwise, the producer may be headed for management headaches during the next breeding season. I Stotts is a communication specialist with the Oklahoma State University Division of Agricultural Sciences. 148 | JUNE/JULY 2018