Gold¢sh (Carassius auratus) are in demand in world markets due to their attractive golden colour. Carotenoids are the primary source of colour in the skin of ¢sh. To optimize the colour in captivity, ¢sh must obtain an adequate level of carotenoids in their feed. With this objective, four natural colour enhancers were tested. A common batch of feed was divided into ¢ve equal portions and colour ingredients, spirulina (D-S), china rose petals (D-C), marigold petals (D-M) and Lactobacil, a commercial probiotic (D-L), were added at 5 mg kg À1 to four portions of feed; one portion (D-O) was kept as a control without any additive. A feeding trial was conducted for 8 weeks. Each 70 L aquarium was stocked with 10 ¢sh (average weight 1.6 g) and feed was given at 5% of the body weight. Growth rate, survival, biochemical composition and pigmentation in the skin of ¢sh were measured. Histological studies of gonads were also conducted. Growth of ¢sh in di¡erent treatments was signi¢cantly di¡erent. There was no di¡erence in the proximate composition of the ¢sh at the start of the experiment but after 8 weeks of feeding, ¢sh fed the diet supplemented with china rose petals had a lower moisture content (70.48%) and higher protein (17.7%) and lipid (5.25%) levels than the group fed the control diet. Pigmentation was the highest (4.01 mg g À1 ) in D-C, followed by D-M (3.16 mg g À1 ), D-S (2.92 mg g À1 ) and D-L (2.84 mg g À1 ) and the lowest (0.24 mg g À1 ) in D-O. Gonad development of ¢sh fed with the D-C diet was better compared with the gonads of control (D-O) ¢sh, followed by D-M-, D-Land D-S-fed ¢sh. Gonads of ¢sh, fed D-C, showed well-marked changes in the testis where a large number of seminiferous tubules bound together by means of a thin layer of connective tissue were observed. These tubules were highly convoluted and were separated from each other by thin connective tissue stroma. The intra space contained connective tissue, blood capillaries and interstitial cells. The spermatogonia could be seen as a large spherical cell containing a large central nucleus with a distinct nucleolus. The study shows that the china rose (Hibiscus rosasinensis) petal is a potent natural carotenoid source for gold¢sh to enhance its colour and also accelerate gonadal development.
The main constraint presently is the availability of sufficient/ required quantity of cost effective quality feed. At present one of the main fish feed ingredient (fishmeal) is procured from outside the state due to which the cost of production is very high. In order to make available sufficient quantity of cost effective feed and cater to the demand of various rearing units for feed in the State, it is high time to replace fishmeal with alternate source of protein. Kashmir valley produces good quantities of feed materials derived from crops and other sources. These include a wide variety of oil-seed cakes and meals, pulses, and mill by-products of seeds and grains. Also available are appreciable quantities of by-products from the meat, fish, fruit processing industries and particularly silkworm pupae. Keeping in view the nutritional value of silkworm pupae and its profuse availability in the state, cost effective feed could be formulated and feeding trails in coldwater aquaculture could be conducted. Lot of research has been done on the replacement of fishmeal throughout the world.
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