Estimate of the population of preantral follicles in the ovaries of Bos taurus indicus and Bos taurus taurus cattle

Abstract

The number of oocytes recovered from Bos taurus indicus females subjected to ovum pick-up averaged two to four times greater compared to Bos taurus taurus females. The objective of the present study was to test the hypothesis that this difference in oocyte yield was due to more preantral follicles in the ovaries of Bos indicus females. Ovaries (n = 64) from Nelore (Bos indicus) fetuses (n = 10), heifers (n = 12), and cows (n = 10), and Aberdeen Angus (Bos taurus) fetuses (n = 10), heifers (n = 12), and cows (n = 10) were cut longitudinally into halves, fixed, and processed for histological evaluation. The number of preantral follicles was estimated by counting them in each histological section, using the oocyte nucleus as a marker and employing a correction factor. The average number of preantral follicles in the ovaries of Bos indicus vs Bos taurus was (mean ± SD) 143,929 ± 64,028 vs 285,155 ± 325,195 for fetuses, 76,851 ± 78,605 vs 109,673 ± 86,078 for heifers, and 39,438 ± 31,017 vs 89,577 ± 86,315 for cows (P > 0.05). The number of preantral follicles varied greatly among individual animals within the same category, as well as between breeds. In conclusion, we inferred that the higher oocyte yield from Bos indicus females was not due to a greater ovarian reserve of preantral follicles. Therefore, mechanisms controlling follicle development after the preantral stage likely accounted for differences between Bos indicus and Bos taurus females in number of oocytes retrieved at ovum pick-up.

Characterization of folliculogenesis and the occurrence of apoptosis in the development of the bovine fetal ovary

“…Although we did not directly compare cattle and buffalo ovaries, the number of follicles isolated in this study at 3 to 7 months of fetal age was similar to that previously reported in cattle [19], but higher than in buffalo fetuses of the same age [34]. Conversely, the results obtained in regard to in situ follicular quantification in this study were similar not only to those previously reported for Bos indicus [23], but also to buffalo [22] fetuses. Moreover, in agreement with previous studies, there was large variation in follicle population among animals of the same age and among various fetal ages [3,19,20].…”

“…In the adult bovine ovary, TUNEL and caspase assays have also been used to demonstrate the role of apoptosis in follicles undergoing atresia [18]. Although the ovarian follicular population has been described [19][20][21][22][23], the incidence of apoptosis in the bovine fetal ovary has apparently not been reported.…”

Population estimate of the preantral follicles and frequency of multioocyte follicles in prepubertal and adult bitches

“…The ovaries were dehydrated in increasing concentrations of alcohol, diaphonized in xylol, embedded in paraffin, and serially sectioned at 5 mm [17] with a rotating microtome (Leica RM2255; Leica Biosystems Melbourne Pty Ltd., Wetzlar, Germany). In all ovaries, one of each 70 histologic sections was mounted and stained with periodic acid-Schiff and hematoxylin [18]. All procedures were performed by the same operator.…”

Antral follicle count in cattle: advantages, challenges, and controversy

“…This reproducibility of AFC in the same individual becomes a strategic resource for classifying an animal by the AFC with a single ultrasound examination. For taurus animals, AFC is directly correlated with the size of the ovarian follicular reserve (Ireland et al, 2011), which was not proven in indicus females when examining fetuses, heifers, and cows (Silva- Santos et al, 2011). However, other factors, such as genetics (Walsh et al, 2014), maternal environment, nutritional status, and healthiness (Ireland et al, 2011;Evans et al, 2012) also appear to influence the AFC.…”