Interactions of side (left and right ovary) with the number of follicles per ovary and with the intraovarian relationships between dominant follicle and corpus luteum in heifers

The interactions between side of ovary (left ovary [LO] and right ovary [RO]) and number of follicles per ovary and between side and intraovarian patterns were studied in heifers with two follicular waves (anovulatory wave 1 and ovulatory wave 2). Intraovarian patterns were on the basis of location of the dominant follicle (DF) and corpus luteum (CL) and were termed DF–CL, DF, CL, and devoid. The frequency of the DF–CL intraovarian pattern was greater for the RO than for the LO in wave 1 (80 of 121; P < 0.0004) and in wave 2 (54 of 83; P < 0.006). For each wave, the DF of the DF–CL and DF patterns was more often in the RO for the ipsilateral relationship (e.g., wave 1: 66% vs. 48%; P < 0.01) and in the LO for the contralateral relationship (52% vs. 34%; P < 0.01). An interaction between side and pattern (P < 0.05) for number of follicles in wave 2 that attained 6 mm was from a greater number in RO than in LO when a DF was present (DF–CL and DF patterns). An interaction of side and pattern for the number of wave 2 regressing subordinate follicles that recovered (increased in diameter) and became part of the subsequent wave 1 was greater (P < 0.05) for LO than for RO for the DF pattern but not for the CL pattern. An effect of side or an interaction that involved side was not found for the greater dimensions and blood flow for both the DF and CL of the DF–CL pattern. Results indicated that side interacted with ovarian pattern for number of DF–CL patterns, side of DF, number of follicles per ovary, and recovery of regressing wave 2 follicles. The hypothesis was supported that some aspects of follicle dynamics reflect an interaction of side and intraovarian pattern. Future studies on the effect of side on luteal or follicle dynamics could be incomplete or misleading if intraovarian patterns are ignored.