Fibroblast Growth Factor 21 Has a Diverse Role in Energetic and Reproductive Physiological Functions of Female Beef Cattle

SIMPLE SUMMARY: Fibroblast growth factor 21 (FGF21) has been identified in multiple mammalian species as a marker of energetic stress that has the potential to negatively impact nutritional and reproductive performance. However, the role of FGF21 in regulating energetic and reproductive physiology of cattle selected for meat production has yet to be characterized. Within this report, we have conducted a comprehensive evaluation of the role FGF21 plays in female beef cattle throughout the production process. We have revealed that FGF21 plays an expansive role in beef cattle during various developmental and physiological processes. Moreover, this is the only work that has investigated the role of FGF21 in pubertal development, mammary secretions, or postpartum return to reproductive cycles in beef cattle—all other reports have been performed in dairy cattle breeds. In conclusion, FGF21 plays a role in physiological functions in beef cattle that can be applied to advance the understanding of basic scientific processes governing the nutritional regulation of reproductive function but also provides a novel means for beef cattle producers to select parameters of financial interest. ABSTRACT: Fibroblast growth factor 21 (FGF21) has been identified in multiple mammalian species as a molecular marker of energy metabolism while also providing negative feedback to the gonads. However, the role of FGF21 in regulating the energetic and reproductive physiology of beef heifers and cows has yet to be characterized. Herein, we investigated the temporal concentrations of FGF21 in female beef cattle from the prepubertal period to early lactation. Circulating concentrations of FGF21, non-esterified fatty acids, plasma urea nitrogen, glucose, and progesterone were assessed. Ultrasonography was employed to determine the onset of puberty and resumption of postpartum ovarian cyclicity as well as to measure backfat thickness. Finally, cows and calves underwent the weigh-suckle-weigh technique to estimate rate of milk production. We have revealed that FGF21 has an expansive role in the physiology of female beef cattle, including pubertal onset, adaptation to nutritional transition, rate of body weight gain, circulating markers of metabolism, and rate of milk production. In conclusion, FGF21 plays a role in physiological functions in beef cattle that can be applied to advance the understanding of basic scientific processes governing the nutritional regulation of reproductive function but also provides a novel means for beef cattle producers to select parameters of financial interest.