Effect of dose level of three hormones on egg production and thermal accumulated period during induced spawning of grass carp (Ctenopharyngodon idella)

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 ۴.۵ mg/kg was the best as it produced ۱۱۰۰ - ۱۵۰۰ g of eggs in fish of ۴.۵-۶.۷۵ kg in weight. The lowest TAP value (۲۴۰°C.h) was recorded upon the use of ۴ and ۴.۵ mg/kg doses of PG. Doses of HCG between ۸۰۰–۹۰۰ IU/kg produced ۱۰۰-۱۴۰ g of eggs form fish of ۳.۸-۴.۵ kg. TAP recorded for HCG hormone varied extensively between ۲۶۵-۴۵۳°C.h at the dose ۹۰۰ IU/kg. Higher doses (۱۱۰۰ and ۱۲۰۰ IU/kg) produced similar TAP values (۳۰۰-۳۶۲°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 ۰.۴ and ۰.۵ mL/kg ovaprim  preparation leading to the production of ۱۰۰- ۷۵۰ g of eggs weight. The best dose which produces the shortest TAP (۲۹۷°C. h) and the shortest ovulation time (۱۱ h) at ۲۷°C was ۰.۴ mL/kg. The other dose ۰.۵ mL/kg also gave close values of (۳۰۰-۳۶۳°C. h) at incubation temperature of ۲۴-۲۵°C and ovulation time between ۱۲ and ۱۴.۵ h. Relationship between Dose and egg production were calculated as: Egg wt.=۳۷۷.۰۴-۵۳.۸۹ ×Dose level (PG), Egg wt.=۳۲.۷۹۶–۰.۲۵۵×Dose level (HCG), Egg wt.=-۸۱.۹۰+۲۷۰.۵۹×Dose level (Ovaprim ). Regression polynomial equations for relationships between the three parameters were calculated as: TAP(°C.h)= ۲۸۲.۱۴۵۷+۹.۴۹۳۳ Dose-۰.۱۸۴۷ Egg wt. for PG, TAP (°C.h) = ۲۵۶.۴۱۹۹+۰.۰۷۴۴ Dose+ ۱.۲۱۱۳ Egg wt. for HCG, TAP (°C.h)=۱۴۲.۳۴۹۴+۳۸۴.۱۹۴۸ Dose-۰.۱۳۷۲ Egg wt. for Ovaprim .

Keywords:

Hormone dose , Egg production , Thermal period , Grass carp