Invited Review: Nutrition and management of cows: Supplementation and feed additives1,2

ABSTRACT Reproductive efficiency is the primary factor affecting profitability of a cow-calf enterprise. Our objective was to review how nutrition affects reproduction in beef females and subsequent calf performance. Body condition is an indicator of nutritional status, and when used in conjunction with BW change, it can be a useful method to assess reproduction. Body energy reserve at calving is the most important factor influencing pregnancy rate in beef females. Energy and protein are the nutrients required in the greatest amounts and are the first priority in nutritional programs to optimize reproduction. Beef females underfed or in poor body condition lack ovarian activity as a result of suppression of pulsatile release of luteinizing hormone under the control of gonadotropin-releasing hormone. Factors affecting postpartum interval to estrus and pregnancy rate include breed type, suckling status, age, dystocia, energy and protein supplementation before and after calving, and BCS before and after calving. Management strategies that influence when a beef female calves during the calving season affect future productivity of both dam and offspring. Feeding an ionophore results in earlier puberty in beef heifers. The effect of feeding fat pre- or postpartum on reproductive performance in beef females has been researched, but results are inconclusive. Prenatal nutrition appears to have potential effects on subsequent performance of female and male offspring. There is no single feed ingredient that can be fed to enhance reproduction in beef cows when a diet is deficient in any nutrient or when beef females are in poor BCS.