Özet:

Feed and feed ingredients in the tropics are prone to attacks of mycotoxigenic fungi (myco-fungi) infestation during storage or from the field. The heat applied in feed production destroys only the myco-fungi leaving mycotoxins that eventually end up in the fish. Mycotoxins have negative effects on the growth of fish. It is plausible to reduce or totally eliminate the mycotoxins and myco-fungi by the inclusion of special African bentonite supplement called `Uro`. Five iso nitrogenous and iso energetic feed were made with soybean meal of 12% moisture stored at relative humidity of 78% and temperature 29.45±0.87oC for 30 days. The feed was labelled as F1 to F5 and varied in inclusion levels of bentonite supplement as follows, F1, 34%, F2, 25%, F3, 15%, F4, 5% and F5, 0%. The protein supplement and basal ingredients in the diets were same. Feed ingredients were weighed, mixed, conditioned and pelleted. The feed was dried at 40oC for 24 hours and subjected to mycological analysis. African catfish fingerlings of average weight 6.5±0.36 g were stocked at 15 fish per three replicate aquaria per feed type. Fish were fed to satiation twice daily for 140 days. The catfish fed with F1(35% bentonite) had the best food conversion ratio, 1.63±0.15, highest SGR 5.7±0.05% day-1, weight gain 45.7±3.65g, protein efficiency ratio 1.19±0.10 and highest gut weight 3.46±0.45g. All growth and nutritional parameters were increasing with increasing inclusion of bentonite. Mycological analyses showed that three myco-fungi, namely Aspergilus flavus, Mucor mucedo and Cladosporium cladosporioides were prevalent in the feed. However, feed 1 to feed 3, were completely free from myco-fungi, while feed 4 had traces of M. mucedo and C. Cladosporioides but all myco-fungi were prevalent in F5. African bentonite is calcinated and sequestered feed ANF, myco-fungi and mycotoxins. Bentonite increased digesta viscosity which enabled better digestion of feed, lower FCR, enhanced alkaline intestine for protein and fatty acid absorption. Bentonite increased catfish total glycerides and cholesterol but reduced AST and ALT of the catfish

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