Short Communication: Return to Normal Oestrous of Mongrel Bitches Treated with Medroxyprogesterone Acetate as a Contraceptive

Abstract

The bitch is a seasonally monoestrous animal (exhibiting one oestrous cycle in season) (Tomaskovic et al, 1997).The oestrous cycle is traditionally divided into stages based on anatomical, behavioural, hormonal and cytological criteria. These stages and their corresponding function phases are prooestrus (follicular, phase),oestrus, metoestrus, or dioestrus (luteal phase) and anoestrus (quiscenf phase of the ovaries) (Tomaskovic et al, 1997). The duration of the oestrous cycl in the bitch is considerably longer with aJ prolonged anoestrus phase of about two to ten months irrespective of whether pregnant or not (Schaefers-Okkens and Kooistra, 2010). Unlike other domestic animals, it is not clear how folliculogenesis in the bitch is prevented and restarted ati the luteal phase (Tomaskovic et al 1997). Although, Schaefers-Okkens and Kooistra (2010) reported that basal plasma FSH concentration increases during the progression of anoestrus strongly suggests that FSH increase is a key event in ovaria folliculogenesis in the dog. Medroxyprogesterone Acetate (MPA) is one of the progestins developed for human use and has therefore been extensively tested in dogs and cats especially at high multiples of human dose (Romagnoli and Concannon, 2003). It could be used to either suppress or postpone the oestrous cycle based on the dosage and the time of administration (Romagnoli and Concannon, 2003; Romagnoli, 2006). The recommended dosage for MPA in the bitch is 2.5-3.0mg/kg intramuscularly every 5 months, while it is 2.0mg/kg intramuscularly every 5 months for the queen (Romagnoli, 2006). Great caution must be exercised due to potential serious side effects associated with progestin administration such as uterine pathology, mammary tumour, increased prolactin, growth hormone secretion, and blood sugar level, masculinization of female fetuses in the bitch, adrenocortical suppression in the bitch and queen, local skin alterations and behavioural modification (Romagnoli, 2006). The aim of this study is to observe the return to normal oestrous cycle in mongrel bitches treated with depot-injection of MPA as a contraceptive.

KEY WORDS: Oestrous, bitches, medroxyprogesterone acetate, contraceptive.