Effect of GnRHa, pimozide and Ovaprim on ovulation and plasma sex steroid hormones in African catfish Clarias gariepinus

Nine groups each of four fish were injected with a single intramuscular dose of the following preparations: Physiological saline (0.9% NaCl) as a control group, 0.5 ml kg−1 Ovaprim, 20 and 40 μg kg−1 BW of GnRHa, 8 and 16 mL kg−1 pimozide tablets and the following combination of GnRHa with pimozide (GP): 20 μg + 4 mg, 30 μg + 8 mg and 40 μg + 16 mg kg−1 BW. The primary oocyte diameter (POD) before hormone administration ranged from 943.3 to 1071.0 μm. The latency periods (LP) were in the range of 9.0 to 12.0 h after injection. The highest ovulation ratio (OR) was observed in groups Ovaprim, GP(30 + 8) and GP(40 + 16). Other treatments were effective for ovulation, the ovulation ratio in Groups G(40) and GP(20 + 4) were significantly higher than G(20) treatment. The ovulation index (OI) was in the range 62 to 77% and showed significant differences among groups. There was no significant difference in fertilization ratio (FR) among Ovaprim, GP(30 + 8) and GP(40 + 16) groups, while there were significant difference between the previous group and G(20) and G(40) groups. Control, P8, P16 showed negative results in all the parameters LP, OED, OR, OI and FR. Levels of sex steroids were analyzed on 6 and 12 h after initiation of treatments. A significant increase in plasma E2 with GP(30 + 8) injection was observed 6 and 12 h after injection, while there were no significant increase between all the other groups 6 h after injection. Treatments with GP(20 + 4) resulted in a significant increase in plasma T concentration in females compared with control after 6 h. In contrast, plasma T and E2 concentrations were lower during the combined GP(20 + 4), GP(30 + 8) and GP(40 + 16) after 12 h than after 16 h of injection. The combined treatments (GnRHa + PIM) are better compared with Ovaprim which gave the same results, they have some advantages, such as reliable response and low cost. Ovaprim is more than 3 to 5-fold of the cost of (GnRH + PIM). Therefore, this method could be useful tool for commercial catfish breeders to ensure spawning success.