Follicle and hormone dynamics in single versus double ovulating heifers

Abstract

Follicles R5 mm were ablated at 4 day post-ovulation in heifers to induce a follicular wave, and prostaglandin F 2a was given at day 6 to increase the incidence of double ovulations. Follicle diameters and plasma hormone concentrations were compared between single ovulators (nZ12) and double ovulators (nZ8). In double ovulators, the interval from follicle deviation to the peak of the pre-ovulatory LH surge was shorter (1.9G0.2 vs 2.5G0.2 days; P!0.02) and diameter of the largest pre-ovulatory follicle was smaller (12.2G0.5 vs 13.3G0.3 mm; P!0.02). The LH concentrations of the pre-ovulatory surge did not differ between single and double ovulators for 24 h on each side of the peak. When data were normalised to LH peak, the peak of the pre-ovulatory FSH and oestradiol (E 2 ) surges occurred in synchrony with the peak of LH surge for both groups. Concentration of FSH for 24 h on each side of the peak showed a group effect (P!0.0001) from lower concentration in the double ovulators. A group-by-hour interaction (P!0.008) for E 2 reflected greater concentration in the double ovulators before and at the peak. Results indicated that two pre-ovulatory follicles resulted in an earlier and greater E 2 increase, leading to lower FSH concentration, an earlier LH surge, and ovulation at a smaller diameter. In conclusion, the difference in hormone concentrations during the pre-ovulatory period was an effect rather than a cause of double ovulations.

Luteal blood flow and concentrations of circulating progesterone and other hormones associated with a simulated pulse of 13,14-dihydro-15-keto-prostaglandin F2α in heifers

“…The intra-and interassay coefficients of variation (CV) and sensitivity were 6.1%, 6.3% and 0.01 ng/ml respectively. Plasma LH and FSH concentrations were assayed by RIAs as described for cattle (Bolt et al 1990) with validations and modifications as reported by our laboratory for LH (Ginther et al 1999) and FSH (Adams et al 1992) and with further recent modifications as reported for both assays (Palhao et al 2009). The intra-and interassay CV and sensitivity respectively were 9.2%, 10.5% and 0.03 ng/ml for LH and 6.5%, 4.8% and 0.07 ng/ml for FSH.…”

Sincronização folicular e vascularização do folículo dominante em novilhas mestiças tratadas com estradiol

“…É importante ter cautela para interpretar esses dados, uma vez que o estradiol utilizado para regredir o FD no início do protocolo também atua como supressor de FSH, que atua no desenvolvimento da nova onda folicular (PALHAO et al, 2009). …”

“…Como o pico de LH causa elevação do fluxo sanguíneo na parede do folículo ovulatório (Acosta, 2007), é possível correlacionar este fato com uma maior sincronia dos animais tratados com BE como indutor ovulatório. Outra evidência da maior sincronia dos animais neste grupo foi o menor diâmetro do folículo ovulatório, uma vez que o crescimento folicular se reduz após o pico de LH (Palhao et al, 2009). …”

Differences between follicular waves 1 and 2 in patterns of emergence of 2-mm follicles, associated FSH surges, and ovarian vascular perfusion in heifers

“…The plasma was decanted and stored (À20 C) until assayed. The RIA for FSH assay has been validated and described for bovine plasma in our laboratory [15]. The intra-assay and interassay coefficients of variation and sensitivity for experiment 1 were 10.2%, 10.9%, and 0.02 ng/mL.…”