Prepartum and postpartum nutritional management to optimize fertility in beef cattle

Background: The cow-calf sector of the beef industry has a constant challenge to provide cattle with the proper nutritional profile to optimize reproductive performance. Reproduction and nutrition are the two most important factors when considering profitability in this sector of cattle production. Feed costs account for 63% of the total annual cow cost, and, thus, it is evident that nutritional management plays a major role in the financial viability of beef enterprises. Female infertility and other reproductive diseases account for an estimated yearly cost between $441 and $502 million for beef producers. Review: There is evidence suggesting that prepartum nutrition affects subsequent postpartum reproduction in beef cattle. The energy balance of the cows and energy profile of their diet are crucial to reproductive success. Prepartum nutrition is important in ensuring cows remain in a positive energy balance and return to estrus efficiently. Cows grazing native range grass pastures and supplemented (0.3 kg of 41% Crude Protein cottonseed meal) to lose body weight (BW) for 5 months during gestation, had reduced pregnancy rates (29.5% lower) when compared with cows that were fed (1.4 kg of 41% Crude Protein cottonseed meal) to maintain BW. This result suggests that cows that lose weight and energy reserves during gestation may suffer from reduced reproductive performance and pregnancy rates when compared with cows that maintain BW and body condition score (BCS). Postpartum nutrition is an important factor in reducing the postpartum interval to pregnancy and increasing reproductive efficiency in beef cows. When cattle enter a negative energy balance during gestation, they tend to mobilize energy reserves and consequently suffer a reduction in BCS. It has been shown that when cows calve at a poor BCS (4 or less on a 9 point scale), increasing postpartum dietary energy can decrease the interval from calving to pregnancy and increase conception rates. Reproductive success in beef cattle is reliant on proper endocrine function and hormone concentrations. It has been shown that increased concentrations of progesterone (P4 ) and estradiol are linked with increased pregnancy maintenance. Nutrition can influence hormone concentrations. Also, supplemental fats have been shown to increase concentrations of serum cholesterol and could then increase P4 concentration as cholesterol serves as a precursor for P4 production. Cows with higher serum cholesterol concentrations from 2 weeks prior to parturition until 4 weeks postpartum had a decreased interval from calving to resumption of ovarian cyclicity. Yet, it has also been shown that feeding varying amounts of supplemental fats had no effect on P4 concentrations. There is also evidence that cow nutrition at the time of flush can impact embryo development. Recently, experiments have been designed to fill a gap in knowledge on how prepartum plane of nutrition affects beef cow postpartum reproduction and embryo production. Conclusion: Plane of nutrition impacts BW and BCS in beef cattle. Although results are variable, supplementing energy, protein, or lipids has been shown to improve reproductive efficiency. Also, nutrition can influence concentrations of serum and plasma hormones important in reproductive function. Excess dietary intake at the time of superovulation and prior to embryo recovery has been shown to decrease embryo quality. However, there is limited information on the impact of prepartum nutrition on superovulation as well as the recovery and quality of preimplantation embryos.