BLOOD PROGESTERONE LEVEL DURING ESTROUS CYCLE IN GAROLE EWES AND THE LUTEOLYTIC EFFECT OF OXYTOCIN ADMINISTERED ON DIFFERENT DAYS OF ESTRUS CYCLE, PREGNANCY AND DICLOFENAC SODIUM MEDIATED EXTENDED LUTEAL PHASE

The effect of exogenous oxytocin injected on different days of estrus cycle and pregnancy on uterine PGF2a mediated luteal regression in Garole ewes and compared it with physiological pattern of luteal growth and regression was investigated. Three consecutive days progesterone concentration was measured after intravenous injection of oxytocin to non-mated ewes on day 5 (n=5), on day 8 (n=5), on day 13 (n=4), on day 18 to pregnant ewes (n=4) and diclofenac treated ewes (days 11 to 15) with extended luteal phase. All ewes were detected for heat twice daily by a vasectomized ram. In Garole ewes blood progesterone level starts increasing from day 3, reaches a maximum level on day 9, stays steady till day 12 and thereafter starts declining from day 13 onwards. Oxytocin injection on day 5, on day 8 and on day 18 (pregnant) had non-significant (P>0.05) effect on estrus cycle length as well as two successive day progesterone concentration compared to control unlike in ewes injected with oxytocin on day 13 and on day 18 (diclofenac treated). The results indicated that the endometrium of Garole ewes was insensitive to a luteolytic dose of oxytocin during the diestrous period but as the sensitivity was regained on day 13 of estrous, it persisted thereafter. The presence of conceptus rendered the endometrium insensitive to oxytocin during and after the time of normal luteolysis.