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GENERAL ARTICLEprolong oviductal retention of embryos and secondlyoestrogen has direct degenerative effects on ova andmay alter the endometrium.1. OESTROGENSOestrogens are widely used to preventunwanted pregnancies. They act by altering thetransport time of zygotes and thus interfering withimplantation. In some bitches estrogens given duringoestrus results in early luteolysis and this effect maybe mediated either directly upon luteal progesteroneproduction or by inhibition of LH release which isluteotrophic.a. Diethyl Stilbesterol (DES)Injection of DES at a dose rate of 2mg/kgbody weight, up to 25mg once or twice within 5 daysof mating is found to be highly effective interminating pregnancy. However injectable DES isnot available for veterinary practice. Oral DES hasbeen recommended at a dosage of 1 to 2 mg/day for 7days after mating, but oral therapy has not been foundto be completely reliable.b. Oestradiol cypionateIt was an oestrogen compound commonlyused by veterinarians for the management ofunwanted mating. The treatment protocol involved isadministration of 0.25 to 1 mg total dose within 3days of mating. A dose rate of 0.04 mg /kg is 100percent successful in preventing pregnancy inbitches. The total dose should not exceed 1mg.Despite the potentially favourable action ontermination of pregnancy, it has major side effectssuch as permanent bone marrow suppression ordestruction resulting in severe anaemia, leukopenia,thrombocytopenia and death.c. Conjugated oestrogenConjugated oestrogens can be used for thetreatment of misalliance in dogs within 5 daysfollowing breeding. They are mainly isolated frommare's urine and hence it can be called as conjugatedequine oestrogen. Most commonly used for thetreatment of osteoporosis, atrophic vaginitis,atrophic urethritis etc as a complication ofmenopause in woman. Commonly availablepreparation is PREMARIN 0.625mg and 1.25mgtablets. Dosage 1.875mg daily for 3 daysHowever estrogens can result in thedevelopment of pyometra by causing cervicalrelaxation thus allowing the vaginal bacteria to enterthe uterus. Estrogens may also produce dose relatedbone marrow suppression. Diethyl stilbesterol,oestradiol benzoate and estradiol cypionate havebeen widely used to prevent implantation.But oestrogen preparations are notrecommended in veterinary practice because of theirharmful side effects. Oestrogen is thought topredispose pyometra in bitches by sensitizingprogesterone receptors and enhancing binding ofprogesterone to the endometrium. It has been alsoreported that excess serum estrogens can lead tooestrogen- induced bone marrow destruction.2. PROSTAGLANDINS ANDITS ANALOGUESPregnancy in the bitch depends onprogesterone secretion from corpora lutea. Manystudies indicate that bitches that have corpora luteaare relatively resistant to the luteolytic effects ofprostaglandins during the first 14 to 28 days ofpregnancy. PGF2 (Natural Prostaglandins ieDinoprost) is luteolytic and uterotonic, inducingintense uterine contractions due to the smoothmuscle contraction effects and may lead to adversereactions. Synthetic analogs (cloprostenol sodium)characterized by more specific activity on the corpusluteum and less on smooth muscle stimulationproperties have fewer side effects.A. Natural Prostaglandin: - Prostaglandins arefound to be highly effective for termination ofpregnancy in bitches after 30 days of gestation. Itsuse prior to 30 day is not recommended. Mostpreferred treatment protocol is 0.1 mg/kg s/c every 8hours for 2 days and then 0.2 mg/kg given s/c every 8hours until abortion complete, the average wasJIVA Vol. 10 Issue 1 April 201261