Pd/a Crsp Eighteenth Annual Technical Report

Proximate analyses of broodstock and grow-out feeds for gamitana (Colossoma macropomum) and paco (Piaractus brachypomus) and their constituent feedstuffs were conducted. Literature values for specific nutrients known to affect fish reproduction were calculated from published sources for the broodstock diet. Broodstock eggs have not yet been obtained for proximate analysis. However, similar analyses conducted previously on eggs of similar species in Brazil have been described. Analytical information on the feedstuffs and diets currently being used in Iquitos, Peru, together with published information on the natural diets of colossomids and broodstock nutrition of other species were combined to formulate preliminary recommendations for the nutrition and feeding of gamitana and paco broodstock. EIGHTEENTH ANNUAL TECHNICAL REPORT 66 Cite as: [Author(s), 2001. Title.] In: A. Gupta, K. McElwee, D. Burke, J. Burright, X. Cummings, and H. Egna (Editors), Eighteenth Annual Technical Report. Pond Dynamics/Aquaculture CRSP, Oregon State University, Corvallis, Oregon, [pp. ___.] of other fish species for weight gain and prevention of deficiency signs (National Research Council, 1993). The stability of vitamin C is poor under conditions of high heat and humidity, as found in Iquitos. Therefore, the form of vitamin C is critical—a stabilized form should be used. If this is not the case currently, a different form can be used and/or other antioxidants (e.g., ethoxyquin or equivalent) can be added to the diet to ensure stability. The swine vitamin/mineral premix currently used in the broodstock diet supplies about 100 mg kg-1 of vitamin E, and the feedstuffs supply another 20 to 30 mg kg-1. One hundred mg kg-1 meets or exceeds the vitamin E requirements of most fish species for weight gain and absence of deficiency signs (National Research Council, 1993). However, only alphatocopherol has high biological activity. The form of vitamin E in the premix is not specified. The form should be verified since the supplement supplies most of the dietary vitamin E. Also, a stabilized form of vitamin E should be used (e.g., alpha-tocopherol-acetate). Vitamin E is very prone to oxidation under conditions of high heat and humidity. In addition, vitamin E is quickly used up in the presence of unsaturated lipids (as from fish oil) because it is a powerful antioxidant. The amount of vitamin E should be increased proportionately if unsaturated lipids (especially those found in fish oil) are increased in the diet. Furthermore, there are studies showing that broodstock diets containing large amounts of vitamin E have positive effects when given to broodstock just prior to spawning (Kanazawa, 1988). In carp, vitamin E increases gonadosomatic index, facilitates vitellogenesis, and protects essential fatty acids in the oocytes. The specific amount of vitamin E needed to optimize these activities is not known, but vitamin E nutriture has not been investigated in gamitana or paco. Of pigments reported to have beneficial effects in fish or other animals, only xanthophylls (about 17 mg kg-1 from the corn flour) are present in the broodstock diet. Other carotenoids such as beta-carotene are important for egg viability in some fish and are prevalent in the natural diets of colossomid species. Therefore, carotenoid supplementation of the broodstock diet may be beneficial for spawning success of gamitana or paco. Further research is necessary to identify inexpensive, available sources of carotenoids (e.g., fruits, vegetables, and/or flowers) that could be used in Iquitos. The combination of fish meal (25%) and soybean meal (30%) should meet all of the essential amino acid requirements of the fish, as well as the available phosphorus requirement (National Research Council, 1993). However, reduction of the fish meal in the diet should be considered for environmental and/or economic reasons. Most studies indicate that there is little or no benefit to using fish meal in vegetarian or omnivorous colossomid species diets. The fish meal in the broodstock diet could be reduced to 10% (with a concomitant increase in soybean meal) without creating any amino acid deficiencies. If fish meal is reduced, available phosphorus may become limiting and a supplement should be considered (there is no phosphorus in the swine premix). Large juvenile Piaractus brachypomus are now at the aquaculture research facility in Pine Bluff, Arkansas. Preliminary feeding trials to bracket the dietary vitamin C and vitamin E requirements of this species are underway. ANTICIPATED BENEFITS Improving the nutritional status of colossomid broodstock should increase spawning success and possibly the quality of resulting fry. These changes would enhance the economic viability of commercial colossomid farming in Peru.