Characterization of changes in temporal concentrations of fibroblast growth factor 21 (FGF21) before and after parturition in multiparous beef cows

The objectives of this experiment were to characterize the secretion of Fibroblast Growth Factor 21 (FGF21) in beef cows during the last month of gestation, parturition, and early lactation and correlate these concentrations with metabolites. Pregnant, multiparous cows (n = 30) fed a TMR to meet or exceed NRC requirements were weighed and blood samples collected on days -14, -7, 0, 14, 28, and 60 relative to parturition. Samples were assayed for concentrations of FGF21, glucose, BUN, and NEFA. Individual average daily gain (ADG) was calculated for the experimental period. As previously shown in dairy cows, concentrations of FGF21 increased as parturition neared with concentrations of FGF21 increasing (P = 0.003) from day -14 (447 ± 120 pg/ml; mean ± SE) to 0 (790 ± 87 pg/ml). After parturition, concentrations of FGF21 decreased (P < 0.0001) by Day 14 (299 ± 88 pg/ml) to concentrations no different than day -14. Concentrations of FGF21 were maintained (P = 0.85) after parturition to Day 28 (288 ± 88 pg/ml). At Day 60, concentrations of FGF21 tended (P = 0.08; 391 ± 87 pg/ml) to increase compared to concentrations on Day 28. Concentrations of FGF21 and ADG tended (P = 0.09) to be negatively correlated on Day 56. Concentrations of glucose increased (P = 0.002) between day -14 and 0 and then decreased (P = 0.04) between Day 0 and 14. Concentrations of BUN increased (P = 0.0006) from day -14 to 0, decreased (P = 0.03) between Day 0 and 14, then continued to decrease (P < 0.0001) from Day 28 to 60. Finally, concentrations of NEFA decreased (P < 0.0001) from day -14 to 0 then increased (P = 0.04) by Day 14 to concentrations maintained (P = 0.94) to Day 28. There was no correlation (P ≥ 0.42) between metabolites and FGF21 on Day 0. However, on Day 60 concentrations of FGF21 tended (P = 0.09) to be negatively correlated with concentrations of glucose, positively correlated with concentrations of BUN (P = 0.0004), and not correlated with concentrations of NEFA (P = 0.30). These data indicate that FGF21 can be used as a biomarker to indicate reproductive and nutritional status in the beef cow.