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

Abstract

The present investigation aimed to determine 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 the Thermal Accumulation Period (TAP) were the two parameters used for evaluation.

The results showed that a PG extract dose of 4.5 mg/kg was the most effective, producing 1100–1500 g of eggs in fish weighing 4.5–6.75 kg. The lowest TAP value (240°C·h) was recorded using PG doses of 4 and 4.5 mg/kg. HCG doses between 800–900 IU/kg produced 100–140 g of eggs from fish weighing 3.8–4.5 kg. TAP values recorded for HCG treatment varied widely between 265–453°C·h at the 900 IU/kg dose, while higher doses (1100 and 1200 IU/kg) produced similar TAP values ranging between 300–362°C·h. Overall, the response of grass carp females to HCG treatment was not promising despite variations in hormone dose and incubation temperature.

Positive responses were observed in grass carp females treated with Ovaprim doses of 0.4 and 0.5 mL/kg, resulting in egg production ranging from 100–750 g. The best Ovaprim dose was 0.4 mL/kg, which produced the shortest TAP (297°C·h) and shortest ovulation time (11 h) at 27°C. The 0.5 mL/kg dose also produced similar TAP values (300–363°C·h) at incubation temperatures of 24–25°C and ovulation times between 12 and 14.5 h.

The relationships between hormone dose and egg production were calculated as follows:

• 
  

  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 describing the relationships among the 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.