Effects of Twice-Weekly Follicular Punctures of Ovaries With or Without the Corpus Luteum on Follicular and Luteal Dynamics

We investigated the effects of twice-weekly follicular punctures of ovaries with or without corpus luteum (CL) on follicular and luteal dynamics. A cross-over design was used, with each cow (seven Japanese Black beef cows) being assigned to one of the three groups at 2-month intervals. Follicular punctures were performed twice weekly for three consecutive weeks until day 20 (oestrus = day 0). All visible follicles (diameter >3 mm) in the ovaries bearing CL (ipsilateral group) or those in the contralateral ovaries (contralateral group) were aspirated. As a control, all visible follicles in both ovaries were aspirated (bilateral group). Follicular development, CL formation and progesterone concentrations in each cow were monitored from days 0 to 30. Follicular growth profiles in the punctured ovaries during/after puncture treatment were similar, irrespective of the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries. After puncture, two cows (28.6%) each in the ipsilateral and bilateral groups did not exhibit behavioural oestrus until day 30, whereas all cows in the contralateral group exhibited oestrus. CL growth and increase in progesterone concentrations after the last follicular puncture in the bilateral group were delayed when compared with those in the ipsilateral group. Our results indicate that the presence of follicles in the unpunctured ovary and the CL in the punctured or unpunctured ovaries does not significantly influence follicular growth in punctured ovaries during/after puncture treatment. However, follicular puncture in ovaries bearing CL may disturb or delay oestrus occurrence after treatment.