Effect of exogenous progesterone administration on luteal sensitivity to PGF during the early development of the corpus luteum in mares and cows.

The research studies the impact of administering additional progesterone at ovulation and during the early stages of the corpus luteum (CL) development on its later response to a single Prostaglandin F2 alpha (PGF2a) administration in mares and cows. The study found that such treatment increases CL’s sensitivity in mares but not in cows.

Methods Used

• Fertility data from a UK equine clinic was retrospectively used to conduct the study.
• The mares were divided into three groups: control (single ovulations), double ovulation (asynchronous double ovulations), and PRID group (single ovulations and immediate post-ovulation treatment with intravaginal progesterone device).
• All mares were given d-cloprostenol (PGF) at different times (88 hr, 96 hr, 104 hr, or 112 hr) after the last ovulation.
• Nine non-lactating Holstein cows were used in the study. They were also divided into two groups: control and CIDR group. Control group received GnRH administration, while the CIDR group had an intravaginal progesterone device inserted.
• All cows were administered PGF at 120 hr post-ovulation.

Results Found

• Among mares, those with double ovulation (66.7%) and those treated with exogenous progesterone (68.4%) showed a significantly higher complete luteolysis rate than mares with single ovulation (35.6%) at 104 hr post-ovulation.
• In cows, treatment with CIDR did not increase the luteolytic response in 120 hr post-ovulation.

Conclusions Drawn

• The study concluded that increasing the concentration of progesterone during the early luteal development can influence the degree of complete luteolysis in mares.
• However, this increased progesterone concentration did not have a similar effect in cows.