A Study on Spawning Induction in Grass Carp (Ctenopharyngodon Idellus Valenciennes, 1844) by Using Different Combinations of Lhrha ([d-Ser(but)6,pro9< and Domperidon

Abstract

In this study, the effects of single administration of [D-Ser(But)(6),Pro(9)-NEt]-LHRHa at high dose alone (50 mu g kg(-1)), and at different doses (10, 20 mu g kg-1) combined with constant dose of the dopamine receptor antagonist, Domperidon (10 mg kg(-1)), for induction of spawning in the grass carp broodstocks were determined under local hatchery conditions, and compared with classic Carp Pituitary Extract (CPE, double injection) application (Water temperature; 25 degrees C). Physiological salina (0.7% NaCl) injected fish were used as control group. No spawning was observed in the control group. Spawning ratio was low in LHRHa at high dose alone treatment group (50 mu g kg(-1)), and in 10 mu g kg(-1) dose of LHRHa at combined with 10 mg kg(-1) dose of DOM treatment group. Spawning ratio was high in 20 mu g kg(-1) dose of LHRHa combined with 10 mg kg(-1) dose of DOM treatment group, and in CPE treatment group. Latency period was shorter approximately two times in LHRHa+DOM treatment groups than CPE treatment groups (9-10 h, 17 h respectively). There was no differences between all spawning groups in respect of spawning index of broodstocks, and fertilisation rates of eggs (P>0.05). As a result, spawning was induced successfully in grass carp broodstocks by 20 mu g kg(-1) [D-Ser(But)(6),Pro(9)-NEt]-LHRHa+10 mg kg(-1) DOM treatment, in a single injection, in a shorter latency period and without decreasing in egg quality, comparing to CPE treatment. Application of this combination can be useful for healthy broodstock and hatchery management in grass carp culture.