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

The objectives of the study were to measure progesterone (P4) 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 P4 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 P4 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 P4 concentration and body condition score. Plasma and adipose tissue P4 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 P4 concentrations increased (P < 0.05) with increasing concentrations of epinephrine. These results demonstrate that substantial quantities of P4 are sequestered in adipose tissue, depending on the reproductive state, and indicate that lypolysis may result in the release of P4 from this tissue, thereby influencing plasma P4 concentrations.