This study was conducted to determine the minimum dose of ovaprim (contains 20μg synthetic salmon gonadotropin releasing hormone analogue (sGnRHa) and 10 mg domperidone per
ml), human chorionic gonadotrophin (HCG), and silver carp pituitary (SCP) to induce ovulation in Japanese catfish,
Silurus asotus. The minimum dose was defined as the dose that induces ovulation of all injected fish, an egg somatic index (ESI) >6%, fertilization rate (FR) >60%, and hatching rate (HR) >50%. Broodstock with vitellogenic oocytes of at least 1, 300μm in diameter were injected by using various doses of ovaprim: 0.02, 0.05, 0.1, 0.2, 0.3, or 0.5
ml/kg, HCG: 2, 500, 5, 000, 7, 500, or 10, 000IU/kg, or SCP: 0.5, 1, 3, or 5mg/kg. The hormone was given as a single intraperitoneal injection. Each treatment was performed in triplicate broodstock, with saline as a control. The results showed that the minimum dose of ovaprim, HCG, and SCP was 0.05
ml/kg, 5, 000IU/kg, and 1mg/kg respectively. These treatments produced relatively high percentage of ESI (>6.9%), FR (83.8-91.9%), and HR (74.4-95.2%) . The fertilization rate was relatively high and did not differ significantly (
P>0.05) among the doses of three hormones that induced ovulation. The results indicate that the currently used doses of hormones in Japanese catfish could be reduced by 2-10 times that of previously reported levels.
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