Intraovarian spatial and vascular harmony between follicles and corpus luteum in monovulatory heifers, mares, and women.

The research explored the intraovarian spatial and vascular relationships between follicles and corpus luteum (CL) in heifers, mares, and women, and has noted that follicle selection and ovulation occur more frequently from the right ovary in heifers and women, while in mares, it occurs with equal frequency between ovaries.

Follicle Development and Deviation

• The study observed that during each interovulatory interval, heifers develop two or three primary follicle waves, while mares and women generally have only one major wave (about 75% of the time).
• The onset of follicle size deviation during the future selection of the dominant follicle (DF) is followed by continued growth of the DF and reduced growth of future subordinate follicles.
• The deviation in size in heifers, mares, and women typically begins when the future DF is about 8.5mm, 22.5mm, and 10.5mm respectively.

Ovary Predilection and Follicle Count

• In terms of ovary preference, the selection of the ovulatory follicle more often happens in the right ovary (RO) in heifers and women, and in the left ovary (LO) in nulliparous mares. However, there is no observable ovary preference in parous mares.
• In heifers and women, there were more pre-deviation follicles in the right ovary than in the left ovary. In mares, the number of pre-deviation follicles is roughly equal between the two ovaries.

Impact of Corpus Luteum (CL)

• In heifers, ovulation from the right ovary tends to occur more often when a regressed CL is also in the right ovary – this is owing to a positive intraovarian effect of the CL on pre-deviation follicles that are adjacent to the CL.
• The research notes that greater dimensions and vascular perfusion of CL and DF express the positive interaction between the CL and future DF when they are adjacent. This relationship should be studied further in mares and women.

Vascular Perfusion and Asymmetrical Ovarian Function

• The study revealed a preovulatory contralateral relationship (DF and CL in opposite ovaries) during the last follicle wave of an IOI in heifers, which usually turns into an ipsilateral relationship in the first wave of the next IOI. This is in association with the continuity of vascular perfusion and the number of pre-deviation follicles per ovary.
• The presence of alternating relationships between consecutive ovulations was not found in mares and remains controversial in women.
• The applied potential of ovarian asymmetry is illustrated by a higher blastocyst rate for right ovary oocytes in cattle and a higher pregnancy rate for right ovary ovulation in women.