Adipose tissue progesterone concentrations in dairy cows during late pregnancy and early lactation

The objectives of the study were to measure progesterone (P-4) concentrations in subcutaneous adipose tissue from the tailhead of dairy cows in various reproductive states, and to examine the effect of epinephrine-induced fat mobilization on P-4 release from adipose tissue in vitro, Blood samples and adipose tissue biopsies were taken from 12 cows twice during late pregnancy and three times during early lactation. Concentrations of P-4 in adipose tissue were higher (P < 0.005) during pregnancy than at any of the non-pregnant stages examined and, in general, the relative changes with reproductive state reflected changes in plasma P, concentration and body condition score. Plasma and adipose tissue P-4 concentrations were positively correlated (P < 0.001) at estrus and during the luteal phase of the estrous cycle. When adipose tissue samples from eight cows were incubated as explants in vitro and challenged with epinephrine, non-esterified fatty acid (NEFA) and P-4 concentrations increased (P < 0.05) with increasing concentrations of epinephrine. These results demonstrate that substantial quantities of P-4 are sequestered in adipose tissue, depending on the reproductive state, and indicate that lypolysis may result in the release of P-4 from this tissue, thereby influencing plasma P-4 concentrations.