Evidence for and implications of follicular heterogeneity in pigs.

Follicular heterogeneity has been demonstrated in both naturally cyclic and PMSG-stimulated immature gilts in that follicles in the selected ovulatory population differ in size by up to 2 mm and show marked variability in steriod content and gonadotrophin binding ability. This biochemical and morphological asychrony continued into the immediate preovulatory phase and changes in response to the LH surge did not always occur simultaneously even in the same follicle or in all follicles within an ovary. It is suggested that these differences in follicular maturation immediately before ovulation may result in heterogeneity in the population of corpora lutea. Following oestrus or hCG administration, oocyte maturation was again not completely synchronous in all follicles within an animal. It is proposed that follicular heterogeneity has implications for oocyte maturation and early embryonic development.