Investigating the trend of blood progesterone concentration following an injection of slow-release progesterone in ewes out of the breeding season

Ali Kadivar; Mohamad Mahdi Kaviani; Pegah Khosravian; Abdonnaser Mohebbi; Najmeh Davoodian

Just Accepted

This article has been peer reviewed and accepted for publication. It is in production and has not been edited, so may differ from the final published form.

Investigating the trend of blood progesterone concentration following an injection of slow-release progesterone in ewes out of the breeding season

Ali Kadivar , Mohamad Mahdi Kaviani, Pegah Khosravian, Abdonnaser Mohebbi, Najmeh Davoodian

Abstract

Context. Progesterone has several applications in the reproductive management of domestic animals. Progesterone treatment in intravaginal devices is one of the most important and widely used methods for estrus synchronization in ruminants, especially in ewes and does. The use of intravaginal devices has disadvantages, including vaginitis and purulent discharge. An alternative solution to overcome these side effects is the use of slow-release progesterone injection. Aim. This study evaluated blood progesterone concentration after injecting three doses of slow-release progesterone (50, 75, and 100 mg) in ewes out of the breeding season. Methods. A total of 18 cross-bred ewes were used in this trial. Ewes were randomly assigned among three groups (6 ewes in each group) which received a single intramuscular injection of 50 (P50), 75 (P75), and 100 (P100) mg slow-release progesterone. Blood samples were collected in 10 times to evaluate progesterone concentration in all three groups. Key results. Progesterone concentration decreased below 1 ng/ml in the P50 and P75 groups 24 h and 72 h after injection respectively, but stayed more than 1 ng/ml in the P100 group for around 7 days after injection. Conclusions. Based on these results, the 100 mg dose is probably better than lower doses to use in estrus synchronization programs in ewes. Implications. Achieving a minimum dose of slow-release progesterone that maintains high blood progesterone levels for an appropriate period of time with a single injection is an easy and economical way to induce and synchronize estrus in ewe.

AN25175 Accepted 05 June 2025