| dc.description.abstract | The major aim of aquaculture (farming and husbandry of fish and shellfishes) is to boost the production of fish in ~the attempt <...to satisfy human need for food and protein. qne of the most important challenges in any aquacultural enterpri 't> is the need for cost-effective fish feeds; t~is item being the mos( e~ensive item in fish farming. As a result, the search for suitable feeds (economically and nutritionally effective; based on locally available ingredients) for culture fisheries continues in many laboratories throughout the world.
A number of materials have been subjected to investigations and tests to find out their suitability as possible food source for fish. These include, several species of plants, animals, domestic refuse (especially kitchen refuse) and by-products from manufacturing and food processing industries. The materials that have attracted attention in these regard include grains, oil Seed cakes, plants (seeds, fruits and vegetative parts i-Ie aves ), insects (and other invertebrates including earthworms, Achantina), housefly larvae, silkworm larvae, slaughter-house byproducts, brewery wastes, and poultry by, products.
In the present study, the effect of three terrestrial plants (Amaranthus caudatus, Bi dens pilosa, and Galins og a p aviflor ay and two invertebrates (termites, Hodotermes sp. and. the giant African snail, Ach antino fulica) on growth in the cichlid fish, Oreochromis niloticus L. have been investigated, by the following steps; analyses of the nutrient contents of each of the test feed mate-rial; diet formulation; digestibility studies; and, effects on growth.
The nutrient contents determined by the method of the Weende Proximate Analyses (the Method of the Association of Official Analytical Chemists, 1984) reveals that these feeds are high in crude protein contents ranging from 27.5 % in Amaranthus, 29.6 % in Galins oga, 30.5 % in Bi dens , 48.3 % in Hodotermes to 74.2%
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in the Achantina (exluding shell). The amino acid profile (by the method of gas-liquid chromatography) show that the Hodotermes and the Achantina can be good sources of essential amino acids in formulated diets especially for supplementation to plant p':r2teins.
Digestibilities of the nutrients investigated by the indirect method using the inert chromium oxide (Cr203) as a marker, and casein as reference diet reveal high apparent digestibilities in both the animal and plant matter, (except Amaranthus), with significant differences at PO.05 level noted between diets and nutrients. During digestibility trials, it was observed that the Am ar anthus diet was generally rejected resulting in negative growth values.
Apparent digestibility coefficients (%) for protein, fat and energy in the test diets were: Amaranthus 72.97, 80.87 and 72.69; Bidens 84.30,83.17, and 78.03; Galinsoga 83.90,87.82, and 76.31; Termite 82.19, 96.19, and 85.01; and Achantina 93.49, 97.19. and 93.96 respectively.
From the analyses of the nutrient contents and their .digestibilities in the plant and animal materials of the present experiments, it has been concluded that the H odotermes and Achantina may be selected for inclusion in the supplementary diet for b. nil oticus on the primary basis of amino acid composition rather than the crude protein content. Because of the general rejection of Amaranthus during digestibility trials, its further investigations were regarded unnecessary and thus it had to be eliminated by the end of the digestibility-trial-stage.
In growth studies, feeding experiments were designed to examine the effects of Bi dens, Galinsoga termite and Achantina on weight gain, feed conversion, ichthyornass productivity in Oreochromis. niloticus. O. niloticus weighing 15.3 g to 18.9 g average weights were used to stock 24 holding cages (80 fish per cage) placed in a pond. The fish were fed to seven experimental diets; each diet given to three replicated groups. One group, also in
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triplicate, were held without any supplementary feeding to serve as control. The feeding experiments lasted ninety-one days, during which period, the growth parameters (lengths and weights) were measured fortnightly. '-'
The average weights at the end of the feeding period ranged from 48.5 g in the control; 53.7 g in Galinsoga; 56.3 gin Galinsogaltermite; 57.7 g in Bi dens; 59.3 g in Bidensltermite 66.8 g in Galinsogalsnail; 67.8 g in BidenslGalinsogaltermite/snail to 75.5 g in the Bidens/snail based diets. Bidens-meallsnail-meal based diets resulted in the best growth performance (weight gain, mean daily growth rate, specific growth rate) and biomass productivity. No significant differences (P > 0.05) were observed in feed conversion ratios and conversion efficiencies.
Details of the methods and results are presented and discussed. It has been concluded that Bi dens pilosa, Achantina and Hodotermes can be effectively used as supplementary feeds, to the Nile tilapia Oreochromis niloticus. It was further concluded that Amaranthus caudatus is not a suitable material as feed ingredient in . the diets for O. niloticus. | en_US |
