Successful Induction of Sterilization and Growth Improvement in Common Carp Cyprinus carpio Through Dietary Administration of the Androgen Norethindrone
Six-d-old fry of the carp, Cyprinus carpio (Linn.) were fed diets incorporated with 5, 25 and 50 mg•kg-1 diet of norethindrone (NE) for 50 d in fiberglass tanks; this was followed by 180 d rearing in fertilized cement cisterns where hormone-free diet was given.
NE at 5 mg•kg-1 diet produced 40.00% male, 31.40% female and 28.60% sterile fish. While 25 mg•kg-1 NE induced 96.30% sterile carp and 3.70% males, 50 mg•kg-1 produced 100% sterile carp. The sex ratio of the untreated control group was almost 1:1.
Administration of NE at 5 mg•kg-1 slightly suppressed the gonads (both ovaries and testes). At higher doses, the steroid produced sterile carp which lacked any visible ovarian/testicular portions. After 180 d post-treatment grow-out, the increase in mean final weights of hormone-treated fish was 19.80, 11.30 and 216.32%, respectively, when compared with the control. Loss of weight due to evisceration was 16.40-17.50% in normal fish, and only 8.4-8.90% in steroid-treated groups, suggesting the availability of 8% more edible meat per unit weight from sterile fish compared to normal fish. Results of biochemical analysis revealed that the hormone treatment had a positive effect on fat deposition, and significantly increased RNA/DNA ratio.
The results suggest that it is possible to produce a 100% sterile progeny of common carp, and to improve growth and dressing weight of NE-treated fish. This is the first report on the successful induction of sterilization with NE treatment in this carp. The benefits of stocking grow-out ponds with sterile carp fry are also discussed.
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