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Control of transitional anestrus in mares by infusion of gonadotropin releasing hormone

Theriogenology 29(6): 1383-1386
Control of transitional anestrus in mares by infusion of gonadotropin releasing hormone
Ten Standardbred mares were divided into two equal groups during transitional anestrus. One group was left untreated, while the other group received a subcutaneous infusion of gonadotrophin releasing hormone (GnRH) at a rate of 100 ng/kg/h for 28 d, delivered via osmotic minipumps (OMP). Ovarian palpations were carried out, and blood samples were collected every 2 to 5 d and assayed for luteinizing hormone (LH) and progesterone concentrations. Volume of the ovary destined to ovulate almost doubled within 7 d of OMP insertion in treated mares, while volume of the contralateral ovary declined by 50% in the same period. Day (.hivin.X .+-. SEM) of ovulation was approximately 5 wk earlier (P < 0.01) in the treated (18.6 .+-. 4.1 d) mares compared to controls (54.8 .+-. 10.8 d). Ovulation was generally associated with an obvious endogenous surge of LH which was followed by a rise in plasma progesterone concentrations. The day of conception in the treated mares (26.6 .+-. 9.7 d) was significantly (P < 0.01) earlier than the controls (67.8 .+-. 16.0 d). The results indicate that fertile estrus can be induced in Standardbred mares during seasonal anestrus using GnRH infusions. This has important implications for improving reproductive efficiency in the horse breeding industry.

Accession: 001554858

DOI: 10.1016/0093-691x(88)90019-2

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