Preliminary studies on the use of an oral progestogen to induce oestrus and ovulation in seasonally anoestrous Thoroughbred mares

Abstract

Summary Daily oral administration of 30 mg allyl trenbolone (Regumate) for 10 to 15 days to 61 barren, maiden and lactating Thoroughbred mares which were exhibiting either deep anoestrus, shallow anoestrus, prolonged spring oestrus or lactation anoestrus, resulted in 54 mares (88 per cent) showing oestrous behaviour within 8 days, and 51 mares (84 per cent) ovulating within 18 days, after the last dose of compound. Response rate was lowest in mares in deep anoestrus. Of the 38 Regumatetreated mares which were covered during the induced oestrus, 21 (55 per cent) conceived. The practical value of this form of progesterone withdrawal therapy as a method for hastening the onset of the breeding season in Thoroughbred mares is discussed. Résumé L'administration orale de 30 mg d'allyl trenbolone (Regumate), durant 10 à 15 jours, à 61 juments vides, soit en lactation, soit vierges, soit en anoestrus profond, soit en anoestrus léger, soit en anoestrus prolongé, soit en anoestrus de lactation, suscita chez 54 juments (88%), un comportement d'oestrus dans les 8 jours, et 51 juments (84%) ovulèrent dans les 18 jours succédant à la dernière administration du produit. Le taux de réponse fut plus bas chez les juments en anoestrus profond. Parmi les 38 juments traitées par ce produit qui furent saillies sur la chaleur provoquée, 21 (55%) furent gestantes. La valeur pratique de cette thérapeutique soustractive de progestérone comme méthode pour accélérer le démarrage de la saison de monte che les Pur Sangs, est discutée. Zusammenfassung Bei täglicher Gabe von 30 mg Allyl‐Trenbolon (Regumate) während 10–15 Tagen an 61 Vollblutstuten (leere, laktierende und Maidenstuten), die entweder ausgeprägten Anoestrus, seichten Anoestrus, verlängerten Frühjahrsoestrus oder Laktationsanoestrus zeigten, provozierte bei 54 Stuten (88%) Brunstverhalten innert 8 Tagen und bei 51 Stuten (84%) eine Ovulation innert 18 Tagen nach der letzten Dosis. Die Stuten mit ausgeprägtem Anoestrus reagierten am schlechtesten. Von 38 behandelten und im induzierten Oestrus gedeckten Stuten konzipierten deren 21 (55%). Der praktische Wert einer derartigen Progesteron‐Entzugstherapie als einer Methode zum frühe***ren Beginn der Deckperiode bei Vollblutstuten wird diskutiert.

Estrous cycle characterisation and artificial insemination using frozen–thawed spermatozoa in the bottlenose dolphin (Tursiops truncatus)

“…Similar partial responses (i.e. estrous behavior, but without ovulation post-altrenogest) have also been observed in horses during the anestrous period (Allen et al 1980, Squires et al 1983 Evaluation of ovaries using trans-abdominal ultrasonography has been previously reported in bottlenose dolphins (Robeck et al 1998, Brook 2000, 2001 and recently in killer whales . Brook (2000Brook ( , 2001 was the first to describe follicular growth during natural cycles in the Indo-Pacific bottlenose dolphin and reported a POF diameter of 19.9^1.1 cm.…”

Pharmacokinetic analysis during intravaginal progesterone-releasing devices (PRID®/CIDR®) application in the mare

“…The oily allyl-trenbolone (altrenogest) solution (Regumate ® , Intervet S. A., Beaucouzé, France), thoroughly studied in the mare (Allen et al 1980, Webel and Squires 1982, Squires et al 1992, Bruemmer et al 2000, requires daily administration and manipulation precautions due to its local skin absorption and androgens effects.…”

Management of the transition period: hormone therapy

“…Conflicting reports certainly exist as to the efficacy of progesterone in advancing the first ovulation of the year. However, a majority of controlled research studies indicate that progesterone therapy: 1) will not consistently advance the first ovulation when administered to mares in deep seasonal anoestrus or early transition (Squires et al 1979;Allen et al 1980;Turner et al 1981;Alexander and Irvine 1991); 2) may synchronise the return to oestrus and advance the first ovulation in late transitional mares (Squires et al 1979;Allen et al 1980); and 3) is effective in suppressing the prolonged and often irregular periods of oestrus in transitional mares (Turner et al 1981).…”