Analysis of daily weight gain and GH mRNA expression in juvenile Clarias gariepinu reared at different stocking densities

Juvenile Clarias gariepinus were reared at densities of 35 kg · m^-3, 65 kg · m^-3, 95 kg · m^-3 and 125 kg · m^-3 for 60 d. On 30^th and 60^th day, we measured the daily weight gain (DWG) and assayed the mRNA level of GH in pituitary by semi-quantitative RT-PCR. During 0~30 d breeding, the DWGs showed no significant difference between 35 kg · m^-3 and 65 kg m^-3 treatments as well as between 95 kg · m^-3 and 125 kg m^-3 treatments, but the DWGs were significantly higher at 35 kg · m^-3 and 65 kg · m^-3 treatments than those at 95 kg · m^-3 and 125 kg · m^-3 treatments. While on 30^th day, significant difference was not found in the GH mRNA level of pituitary between any two stocking densities. During 30~60 d breeding, the DWGs of 35 kg · m^-3 and 65 kg · m^-3 treatments were significantly higher than that of 125 kg · m^-3 treatment, there was no significant difference in DWG between the other two treatments. On 60^th day, the expressions of GH gene were significantly higher in 35 kg · m^-3 and 65 kg · m^-3 treatments than those in 95 kg · m^-3 and 125 kg · m^-3 treatments. The results indicate that there was no close correlation between DWG and mRNA level of GH in pituitary of juvenile C.gariepinus.