Relationship between follicular profiles prior to the initiation of superovulation and various types of superovulatory responses in cattle

A field experiment was conducted to determine the influence of follicular profiles over 4 d prior to superovulation on superovulatory responses in terms of the number of large follicles (F; ≥ 7mm) at oestrus and in the number of the corpus luteum (CL) 7 d later. Ultrasonography was performed once daily over 4 d prior to gonadotropin treatment (day 0) and on the day of oestrus during superstimulation. Animals conventionally superovulated (400 mg Folltropin-V) between day 8 to 12 of the oestrous cycles and 88 superovulation cycles were considered in the present experiment. Data were analysed by means of the GLM procedure of the SAS. Each type of superovulatory responses was divided into three classes - low, medium, and high. The profiles of changes in the mean diameter of the largest follicle (F1) and in the mean differences between the diameters of F1 and the second largest (F2) follicle (F1-F2) during the 4 d prior to superovulation did not differ (P>0.1) among the three classes of follicular and ovulatory responses. The proportions of superovulation cycles with high follicular and ovulatory responses were 69% and 52%, respectively. The results of the present experiment suggest that high follicular or ovulatory responses are not associated with follicular profiles prior to the initiation of superovulation.