Efficacy of estradiol or GnRH in combination with progesterone intravaginal devices to control the follicular wave dynamics and resulting fertility in lactating dairy cows.

This study was conducted to compare efficacy of treatments with EB or GnRH and different quantities of exogenous progesterone (P) for synchronization of time of ovulation on follicular growth and pregnancy in lactating dairy cows. In Experiment 1, 40 cows were treated with EB or GnRH and 1.9 or 3.

A simple pharmacokinetic model linking plasma progesterone concentrations with the hormone released from bovine intravaginal inserts.

On the basis of pharmacokinetic modeling, this study provides some insights into predicting in vivo plasma progesterone concentrations when using bovine intravaginal inserts for systemic progesterone delivery. More significantly, this contribution is the first attempt to build a simple pharmacokinetic model that links plasma progesterone concentrations with the hormone released from bovine intravaginal inserts. After evaluating three rival pharmacokinetic models and considering some phenomena involved in the intravaginal administration of progesterone, a primary pharmacokinetic model having a good data fitting capability with only two adjustable parameters is proposed to the above mentioned task.

Pharmacokinetics of progesterone in lactating dairy cows: gaining some insights into the metabolism from kinetic modeling.

Progesterone pharmacokinetics were analyzed for plasma hormone concentrations ranging from linear to saturated metabolism in lactating Holstein cows with differing daily milk yields. The adequacy of 2-coupled first-order (bi-exponential equation), hyperbolic (Michaelis-Menten equation), and sigmoidal (Hill equation) kinetic models to describe the experimental progesterone pharmacokinetic profiles was examined on a statistical basis. After nonlinear regression and statistical analysis of the data-fitting capability, a simple one-compartment model based on Hill equation proved to be most adequate.