A study of the use of injectable altrenogest for the maintenance of pregnancy

Authors: Perkins NR, McConaghy FF, Searle D
Publication: Australian Equine Veterinarian, Volume 40, Issue 1, pp 30-34, Mar 2021
Publisher: Equine Veterinarians Australia

Animal type: Horse
Article class: Scientific Article

---

Abstract:

Introduction: This study aimed to support the registration of the long acting altrenogest injection, NV Readyserve® for the indication of maintenance of pregnancy in mares at risk from pregnancy loss associated with progesterone deficiency.

Materials and Methods: Thirteen mares were included in a randomised, blinded, placebo-controlled study. Mares were monitored for ovulation every 2 days and inseminated with fresh semen within 24 hours prior to ovulation. Mares were treated with altrenogest injection or placebo saline injection 3 mL/500 kg every 5 days from day 5 after insemination. The study veterinarian was blinded to treatment allocation. Pregnancy testing was conducted on days 15, 21, 28, 35, 45 and 60. Mares were recruited on day 21 based on a positive pregnancy test and then administered an abortigenic dose of prostaglandin. On day 60 treatment was stopped and any pregnant mares were administered prostaglandin to result in abortion. Injection sites were monitored daily, foetuses were monitored during pregnancy and examined for gross abnormalities at abortion. The reproductive capacity of the study mares was assessed in the following reproductive season.

Results: All mares in the control group had aborted by day 28 and all treated mares remained pregnant until day 60. Injections were well tolerated with only 2 minor site reactions and there were no effects on any foetus or reproductive capacity of the mares used again in the subsequent breeding season.

Conclusion and clinical significance: The study demonstrated that treatment with altrenogest injection prevented abortion associated with prostaglandin treatment. This study was limited by lack of progesterone measurement. The study supports the use of Readyserve® injection for the maintenance of pregnancy associated with progesterone deficiency.

---