Ovarian and hormonal responses of cows to treatment with an analogue of gonadotrophin releasing hormone and prostaglandin F_2α

Abstract

Blood samples were taken from 11 cows and their ovaries were scanned by ultrasound at least daily. Around day 5 of an induced cycle, they were injected with 10 micrograms buserelin, an analogue of gonadotrophin releasing hormone, and on day 12 they received 0.5 mg cloprostenol, an analogue of prostaglandin F2 alpha (PGF2 alpha). Two days later six of the cows (the treated group) received a second injection of 10 micrograms buserelin, but the remaining five received no further treatment (control group). The dominant, that is, the largest follicle in each cow disappeared after the first buserelin injection and was replaced by a new one which grew synchronously in all the cows until after the treatment with PGF2 alpha. Ovulation occurred significantly earlier after PGF2 alpha in the treated group than in the control group (72 to 96 hours v 96 to 120 hours; P < 0.05). Plasma progesterone concentrations then increased more rapidly in the treated group than in the control group and were significantly higher on days 3 and 4 after ovulation (P < 0.05).

Changes in endocrine profiles during ovsynch and ovsynch plus norprolac treatment in Murrah buffalo heifers at hot summer season

“…The results of this investigation are in agreement with Paul and Prakash (2005), Chenault et al (1990), Peters et al (1999), Sarkar and Prakash (2005), for only ovsynch treatment and with Schallenberger et al (1978) who also observed that inhibition of prolactin secretion with bromocriptine did not affect LH concentration in Brown Swiss cows. Other researchers also reported that administration of bromocriptine in postpartum beef heifers reduced circulatory concentrations of prolactin without having any significant effect on LH, progesterone, estradiol and ovarian activity (Williams 1979;Williams and Ray 1980).…”

Efficacy of Ovsynch Protocol with Antiprolactin Treatment for Timed Artificial Insemination During Non‐breeding Seasons in Yaks (Poephagus grunniens L.)

“…The circulatory levels of plasma progesterone were basal (≤0.2 ng/ml) at the time of second GnRH injection in all the treated yaks, and continued to stay low up to 24 h. A similar decline in plasma progesterone concentration to basal levels (< 0.1 ng/ml) within 24 h after the PGF 2α administration was observed in Ovsynch‐treated cows (Peters et al. 1999), in Murrah buffaloes (Paul and Prakash 2005) and in yaks (Sarkar and Prakash 2005a,b).…”

Effects of GnRH, a progesterone‐releasing device, and energy balance on an oestrus synchronisation program in anoestrous dairy cows

“…The overall range of diameters of DFs on day 7 (13.4 ± 1.1–15.7 ± 0.6 mm) was slightly greater than the 12.2 mm previously reported by Peters et al at 7 days after giving GnRH alone to cyclic cows. The size and maturity of the DF on day 7 (i.e.…”