Relationship between two morphological types of ovaries and their follicular microscopic population before puberty and their ensuing follicular development and ovulation rates at puberty in gilts.

A population of ovarian follicles was studied in 32 gilts with two morphological types at four physiological stages. Left ovaries were serially sectioned (10 microns), and follicles (greater than .19 mm) were counted and measured by histological technique. In Exp. 1, prepuberal gilts that maintained the grape-type (GT) or other-type (OT) of ovaries at 140 and 160 d of age as determined by laparoscopy had their population of follicles studied at 165 d of age and compared with that on d 3 of the first puberal estrus in gilts that maintained the same ovarian type (GT or OT) at 140, 160 and 180 d of age. In Exp. 2, gilts that maintained the same ovarian types at 140, 160 and 180 d of age were compared at d 19 and 3 of the first and second puberal estrus, respectively. At 165 d of age, OT ovaries contained a greater number of classes 3 (.63 to 1.12 mm) and 4 (1.13 to 2.00 mm) nonatretic (less than 4 pycnotic bodies) follicles than GT (P less than .01), whereas at d 3 of the first puberal estrus, their mean number became comparable between the two ovarian types (P greater than .1) and similar to 165-d GT ovaries. At 165 d of age, atretic follicles formed 19.6% and 10.7% of the population of antral follicles in OT and GT ovaries (P less than .05) whereas at puberty 17.5% and 19.6% atresia was observed in the same two groups, respectively (P greater than .10).(ABSTRACT TRUNCATED AT 250 WORDS)