Abstract

Three present investigations aimed at determining the optimum doses of three hormones used for induced spawning of Grass Carp. PG extract, HCG, and Ovaprim Preparation). Egg production by females and acceleration of thermal accumulation period (TAP) are the two parameters used for evaluation. Results showed that the PG dose of 4.5 mg/kg was the best as it produced 1100 - 1500 g of eggs in fish of 4.5-6.75 kg in weight. The lowest TAP value (240°C.h) was recorded upon the use of 4 and 4.5 mg/kg doses of PG. Doses of HCG between 800–900 IU/kg produced 100-140 g of eggs form fish of 3.8-4.5 kg. TAP recorded for HCG hormone varied extensively between 265-453°C.h at the dose 900 IU/kg. Higher doses (1100 and 1200 IU/kg) produced similar TAP values (300- 362°C.h). Response of grass carp females to HCG treatment was not promising despite changing the dose or incubation temperature. Positive response was recorded in grass carp females receiving doses of 0.4 and 0.5 mL/kg ovaprim preparation leading to the production of 100- 750 g of eggs weight. The best dose which produces the shortest TAP (297°C. h) and the shortest ovulation time (11 h) at 27°C was 0.4 mL/kg. The other dose 0.5 mL/kg also gave close values of (300-363°C. h) at incubation temperature of 24-25°C and ovulation time between 12 and 14.5 h. Relationship between Dose and egg production were calculated as: Egg wt.=377.04-53.89 ×Dose level (PG), Egg wt.=32.796–0.255×Dose level (HCG), Egg wt.=-81.90+270.59×Dose level (Ovaprim ). Regression polynomial equations for relationships between the three parameters were calculated as: TAP(°C.h)= 282.1457+9.4933 Dose-0.1847 Egg wt. for PG, TAP (°C.h) = 256.4199+0.0744 Dose+ 1.2113 Egg wt. for HCG, TAP (°C.h)=142.3494+384.1948 Dose-0.1372 Egg wt. for Ovaprim.

Keywords: Hormone dose, Egg production, Thermal period, Grass carp