الكاتب: Multiple References

Prior to tirst ovulation, heifers exhibit a wave-like pattem of follicular growth similar to that seen in adult cyclic animals. In these heifers, prior to the establishment of regular esirous cycles, one or mom 3 to 5 d periods of progesterone secretion are seen. Progesterone treatment prior to the East ovulation synchronises or induces ovulation. We wanted to see if exposing heifers to progesterone for 4 d during the growth of a dominant follicle shortly prior to tirst ovulation would alter follicular dynamics and result in early ovulation. Seventeen age-matched (rt 10 days) spring-born heifers were examined daily by transrectal ultrasonography Ram 44 to 54wks ofage (mean tirst ovulation 56.5 f 1.2 wks), the position and diameter of CL and follicles t 3mm diame& were recorded, and a blood sample was collected. Further blood samples were collected 3 times per wk until heifers had a luteal phase of 12 d or more in duration.