Development and Radio-Response of the Prenatal Bovine Ovary

Abstract

Qualitative observations of forty-nine bovine foetuses taken at varying stages of gestation revealed the following: (1) the germinal ridge is established at the 32nd day of gestation; (2) due to the formation of the tunica albuginea of the primitive testis, foetal sex is distinguishable by Day 39; (3) meiosis begins in ovaries at 75 to 80 days post coitum; (4) oogonial mitosis is discontinued by 150 to 170 days; (5) the majority of the oocytes have attained their stage of rest (pachytene) and are enveloped in primordial follicles by Day 170; and (6) vesicular follicles appear in ovaries at Day 250 of gestation.Total germ-cell numbers, based on volumetric determinations or direct counts, increased from a low of approximately 16,000 at Day 50 to a high of 2,700,000 at Day 110. From Day 110 numbers declined abruptly to 107,000 at Day 170 and the ovaries of four foetuses at 270 days of gestation (average length of gestation, 283 days) contained an average of 68,000 \m=+-\ 21,000 germ cells.Seventy prenatally irradiated (400 R, whole-body to dam) and twenty-five non-irradiated heifers were slaughtered at either 9 or 23 months of age. Microscopic examinations of their ovaries revealed that irradiation was apparently without effect during the interval of 17 to 59 days of gestation, and of questionable effect during the interval of 59 to 119 days of gestation. Irradiation administered during the 119-to 154-day interval, however, diminished germ-cell numbers by an average of 68%. From Day 154 to term, irradiation was again without effect. The mitotically active oogonium was probably the cell affected during the interval of 59 to 119 days of gestation and the drastic germinal decline during the 119-to 154-day interval was believed to be related to the progression of oocytes from zygotene to pachytene, a transition during which the oocyte under normal conditions is highly susceptible to death.

Appearance and number of follicles and change in the concentration of serum FSH in female bovine fetuses

“…In the present study, fetal ovarian mass increased markedly after day 180 of gestation, as also reported by Erickson (1966). The increase in ovarian mass after day 180 may be associated with the development of follicles.…”

“…Insulin-like growth factor I, growth differentiation factor 9, vasoactive intestinal polypeptide and FSH may affect the development of primordial and primary follicles, although the main initiator responsible for development of primordial follicles to secondary follicles is unknown (George and Ojeda, 1987;Erickson and Danforth, 1995). Erickson (1966) reported that follicles are already present in the bovine fetus during the early stages of gestation. Rüsse (1983) reported that primordial, primary and secondary follicles appeared at day 90, day 140 and day 210 of gestation, respectively, in the bovine fetus.…”

Zebu (Bos indicus) ovarian preantral follicles: morphological characterization and development of an efficient isolation method

“…Other studies, however, reported lower numbers of preantral follicles in goat [4] and sheep [20] ovaries. It is well-known that besides the species differences, preantral follicle populations may be affected by factors such as breed [16], age [18,21], hormone levels and reproductive stage [22], and nutrition [23].…”

Epigenetics and developmental programming of welfare and production traits in farm animals

“…Crucially, in females, the resting reserve of primordial follicles that determines lifetime supply of potentially fertilisable oocytes (eggs) is established before birth and cannot be replenished thereafter (Erickson 1966a(Erickson , 1966bMcNatty et al 1995). In contrast, males continuously produce new spermatozoa after puberty, but the number of Sertoli cells, which are the primary determinant of sperm production and testes size in adulthood, is determined by proliferation during the fetal, neonatal and peripubertal periods (Sharpe et al 2003).…”