Characterization of the periovulatory period in superovulated heifers.

Heifers (n=31) were superovulated with an FSH-P/cloprostenol regimen, and at 12 and 24 hours after the onset of estrus they were inseminated. Blood sampling for LH analyses and ultrasound scanning of the ovaries were performed at 4-hours intervals. The scanning, at which the first and last ovulations were recorded, was performed at 22.7 +/- 1.5 (mean +/- SD) and 31.0 +/- 1.5 hours after the LH peak, respectively. An average of 7.8 +/- 1.0 ovulations was monitored when the first ovulations were detected, while 2.8 +/- 0.7 ovulations occurred later. At 16 hours after detection of the first ovulations the oviducts were flushed and 5.6 +/- 0.5 fertilized and 2.3 +/- 0.3 unfertilized ova were isolated per animal. The fertilized ova displayed spherical pronuclei of synchronous development, and polyspermic penetration was not seen. At 24 hours after detection of the first ovulations the content of the remaining 3.3 +/- 0.5 nonovulatory follicles > 8 mm per animal was aspirated. Expanded cumulus investment was found in 69.4% of the oocytes, while 22.4% had abstricted the first polar body.

[Characteristics of the cumulus-oocyte complex during the preovulatory period in superovulated heifers]. / Charakteristika cumulus-oocytárnych komplexov superovulovaných jalovíc v preovulacnom období.

The nature of cumulus--oocyte complexes was examined in PMSG (group 1, n = 18) and FSH (group 2, n = 30) stimulated heifers. Laparoscopy was performed 65 h after cloprostenol application. The number of follicles was 13.67 +/- 0.75 and 12.67 +/- 0.81 (P greater than 0.05) in group 1 and 2, respectively (Tab. I). The recovery rate of oocytes was 56% in the first and 67% in the second group (Tab. I). The cumulus oophorus was divided into three groups: compact, expanded and partial (Tab. II). Most oocytes (65 and 75% in the first and second group, respectively) exhibited an expanded cumulus (P greater than 0.05). In the first and second group 11 and 26% (P less than 0.01) of oocytes with the extruded first polar body were aspirated (Tab. III). As judged from the pool of visible follicles, the superovulation response to stimulatory treatment and recovery rate of oocytes in the present experiment were not different from the results published earlier. The degree of the cumulus oophorus expansion is an indicator for the evaluation of cumulus--oocyte complexes. After the preovulatory LH peak the disintegration of cumulus oophorus proceeds from glycosaminoglycan accumulation. In our experiment this effect resulted in a significantly higher number of oocytes with expanded cumulus in both treatments. The enlargement of perivitelline space is related to a subsequent release of the first polar body in the preovulatory period. It can be seen from our results that after FSH treatment it is possible to reach the high number of oocytes with the extruded polar body.(ABSTRACT TRUNCATED AT 250 WORDS)

Timing of laparoscopic aspiration of preovulatory oocytes in heifers.

Twenty-one heifers were synchronized with PGF(2) alpha and 22 heifers were stimulated with FSH-P in decreasing doses and synchronized with PGF(2) alpha. The beginning of LH rise was observed to be 47.6+/-14.0 h and 35.9+/-1.3 h (P < 0.05) and the peak of LH rise was observed at 53.8 +/- 13.4 h and 40.14+/-1.4 h (P < 0.05) after the luteolyticum administration in the synchronized and superovulated group respectively. The beginning of LH rise was observed 6.9+/-6.7 h and 4.8+/-2.6 h (P < 0.05) and the LH peak was observed 11.8+/-7.7 h and 8.3+/-3.2 h (P < 0.05) after the frist symptoms of oestrus in the synchronized and superovulated group respectively. Ovulation was not observed in stimulated heifers in the period of 23-25 h after the preovulatory LH rise. Compact cumulus oophorus was seen at 30.5%, expanded at 67.0 and partial at 2.5% during this interval of 23-25h. Within this same interval 26.9%, 51.3% and 21.8% oocytes without perivitelline space, with perivitelline space and with extruded first polar body were aspirated respectively. It may be concluded from the reported results that to recover fully mature oocytes for in vitro fertilization, it will be necessary to monitor the preovulatory period of the donor cow in great detail.