Archive for the ‘Ovary’ Category

Medroxyprogesterone Acetate: DISCUSSION(7)

Induction of multiple births has been identified as one of the primary goals in controlled sheep breeding. The results of the present study may provide a basis for devising practical follicle manipulation techniques to increase the ovulation rate in commercial flocks of sheep. However, in cattle, there is evidence, albeit not unequivocal, that oocyte quality […]

Medroxyprogesterone Acetate: DISCUSSION(6)

In the present study, mean serum concentrations of estradiol were significantly higher in ewes that produced as many CL as ovulations compared with animals that had inadequate CL, on Days 1 and 2 after ovulation, but normal CL were observed in both groups of ewes in question. This suggests that luteal insufficiency may be a […]

Medroxyprogesterone Acetate: DISCUSSION(5)

We have now confirmed that ovulations detected in the ewes of the present study during MAP treatment (Figs. 3 and 5) were not preceded by an increase in gonadotropin secretion. The underlying mechanism of these ovulations that occurred during administration of the synthetic progestogen remains to be elucidated. None of the ovulations above were followed […]

Medroxyprogesterone Acetate: DISCUSSION(4)

It is possible that creation of lower than normal luteal phase concentrations of progesterone or progestogen treatment could have direct effects on the ovary. Certainly, the CL can exert local effects on developing follicles in sheep in spite of morphological barriers between the luteal and follicular compartments, and the high concentrations of progesterone in ovine […]

Medroxyprogesterone Acetate: DISCUSSION(3)

In earlier studies, prolongation of follicle lifespan was consistently observed in ewes given PGF2a early in the es-trous cycle (Days 5 or 6 after ovulation), with a subsequent treatment to create low serum concentrations of progesterone or with MAP for 10 or 14 days, respectively. The proposed mechanism when the treatments began early in the […]

Medroxyprogesterone Acetate: DISCUSSION(2)

Submaximal concentrations of progesterone prolonged the lifespan of large antral follicles in cyclic ewes. A similar effect was observed when luteolysis was induced with PGF2a and progesterone was replaced by MAP being released from intravaginal sponges, or when MAP-impregnated sponges were inserted on Day 12 after ovulation and ovaries were exposed to MAP in the […]

Medroxyprogesterone Acetate: DISCUSSION(1)

In the present study, in nonprolific Western white-faced ewes, a 6-day treatment with MAP from midcycle in the absence of luteal progesterone resulted in a significant increase in ovulation rate by approximately 50% when compared with control ewes or the pretreatment cycle of treated ewes. This increase was mainly the result of the ovulation of […]

Medroxyprogesterone Acetate: RESULTS(9)

Following the ovulation after sponge withdrawal, four of eight animals had fewer CL than ovulated follicles. One ewe ovulated two follicles but no CL was detected by Day 5 after ovulation, and serum progesterone concentrations were ± 0.10 ng/ml. In the remaining three ewes, some ovulated follicles failed to form observable CL. One ewe with […]

Medroxyprogesterone Acetate: RESULTS(8)

The last follicular wave before ovulation following MAP treatment contained ovulatory follicles in all ewes; of all follicles reaching >5 mm in diameter in this wave, 86% (12/14) ovulated (Table 2). The penultimate wave before ovulation contained ovulatory follicles in seven of eight ewes. In the penultimate follicular waves, 60% (9/15) of follicles >5 mm […]

Medroxyprogesterone Acetate: RESULTS(7)

The mean day of emergence of the follicles that ovulated during sponging was -3.9 ± 1.5 days before PGF2a (range, from 8 days before to 3 days after PGF2a injection). No ewes were marked by rams and none of the follicles that ovulated during the treatment with MAP formed a CL; however, CH were detected […]

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