Abstract
This study was conducted to determine the effect of selection for functional ovarian structures on follicular development, oestradiol concentration and conception rate in 160 Boer goats aged between 6 and 7 months. The ovaries of the does were examined using trans-rectal ultrasonography. Based on the follicle size (≥ 3 mm in diameter) and presence of corpus luteum (CL), each goat was placed into one of 4 groups of 40 does each. Group A were does with clearly visible ovaries and presence of a CL or ≥ 6-mm diameter follicle(s). Group B: Same as group A but without CL and with follicles that were 3- 5 mm in diameter. Group C: Same as Group B but with follicles that were 3 mm in diameter only. Group D (Control) were not examined with ultrasound. All the does were oestrus synchronised with flugestone acetate (FGA) and the sponges (Ovakron™ Johannesburg) were inserted intravaginally and left in place for 14 days. An intramuscular injection of 125µg (0.5ml) of cloprostenol (Estrumate™, Schering-Plough, Australia) was administered on the day of sponge removal (day 14). Follicular development was monitored via daily ultrasonographic screening from end of oestrus synchronisation treatment until artificial insemination with fresh extended semen using FTAI at 60th h after cloprostenol injection. Goats with CL or ≥ 6-mm diameter follicle had highest mean oestradiol concentration as well as conception rate compared with the other groups and control. It was concluded that selection of goats with ultrasound influenced the plasma oestradiol concentration, and conception rates.

Key words: Goat, ultrasonography, follicular development, oestradiol, conception rate