Ovarian Follicular Dynamics, Ovarian Follicular Growth, Oocyte Yield, In vitro Embryo Production and Repeated Oocyte Pick Up in Thai Native Heifers Undergoing Superstimulation

The objective of this study was to compare the effectiveness of the protocols for superstimulation of follicular growth in Thai native heifers. Heifers (n = 20) were randomly divided into four groups of five heifers/group. Heifers were given a single dose by i.m. administration of 100 mg Follicle Stimulating Hormone dissolved in polyvinylpyrrolidone (FSHp) at 24 h. Ovum pick up (OPU) occurred at 72 h (F(24)O(72) protocol; Group 1) or 96 h (F(24)O(96) protocol; Group 2), and at 36 h and OPU at 72 h (F(36)O(72) protocol; Group 3) or 96 h (F(36)O(96) protocol; Group 4) after follicular ablation. The dynamics of ovarian follicular growth were monitored by twice-daily ultrasonographic examinations. Blood sample collections were performed every 12 h after initiation of treatment for assessment of FSH, E2 and P4 profiles. All heifers were subjected to eight repeated sequential sessions of OPU. The follicular deviation commenced 24±5.32 h after follicular ablation in all groups. The circulatory FSH surged quickly from 24 to 36 h (>0.8 ng/ml) after follicular ablation and circulatory estrogen levels steadily increased from 36 h until OPU in all groups. At the end of the OPU sessions, the mean number of aspirated follicles/heifer/session in F(36)O(72) protocol (Group 3) and F(36)O(96) protocol (Group 4) were higher than in the two other groups (p<0.05). The number of cumulus-oocyte complexes (COCs), cleaved and day 8 blastocysts rates in the F(36)O(72) protocol (Group 3) were higher than in the other groups (p<0.05). It can be concluded that a single dose i.m. administration of 100 mg FSHp at 36 h and OPU at 72 h after follicular ablation (F(36)O(72) protocol; Group 3) was the most effective protocol for superstimulation of follicular growth for repeated OPU and subsequent in vitro embryo production in Thai native heifers.