Abstract
The study was designed to detect fungi and quantify aflatoxins B1 and B2 microbial load levels and toxin binding efficacy of hydrated sodium calcium aluminosilicate (HSCAS) on growth and nutrient utilization of Clarias gariepinus African catfish fingerlings diet formulated with mouldy groundnut cake (MGNC). MGC containing 185.00 ± 7.07 μg/kg and 137.50 ± 10.00 μg/kg of aflatoxins B1 and B2 was incorporated into practical diets. Three practical isoproteinous diets were formulated. Diet 1 contained Groundnut Cake (GNC) with 0.20 ± 0.14 cfu microbial load but no apparent mould contamination. Diet 2 contained MGC 4.38 ± 0.40, 1.99 ± 0.01 μg/kg of aflatoxins B1, B2 and 2.20 ± 0.14 cfu microbial load. Diet 3 contained MGC, HSCAS; 3.49 ± 0.20, 1.34 ± 0.01 μg/kg and 1.35 ± 0.20 cfu of aflatoxins B1, B2 and microbial load, respectively. The diets were fed twice daily to Clarias gariepinus fingerlings mean body weight 1.68 ± 0.01g in triplicate of 20 fish each for 12 weeks. Six fungi; Aspergillus parasiticus, A. flavus, A. niger, A. tamarii, Penicillium citriinum and P. oxalicum were isolated from MGNC diet. Addition of HSCAS reduced fungi present in diet 3 to A. flavus, A. tamarii and P. oxalicum. Also aflatoxins B1, B2 and microbial load in the diet and carcass of Clarias gariepinus were reduced with HSCAS inclusion in diet 3. Feeding African catfish fingerlings with mould contaminated diet (2) significantly (P 0.05) effect on survival of Clarias gariepinus fingerlings. The results of this study show that the inclusion of HSCAS reduced the number of fungi, microbial load and aflatoxins B1 and B2 in the carcass and diet of African catfish formulated with mouldy GNC. But was not effective in alleviating the growth depression induced by mould contamination of the diet. Hence the need for identification of toxins present in mould contaminated feedstuffs in order to design effective toxins management strategies.
Highlights
Feed ingredients contamination with toxins may occur anywhere in the supply chain from the field, manufacturing process, transportation to storage
The co- occurrence of A. flavus, A. niger and Penicillium in the contaminated diet could probably encourage the production of ochratoxins and cyclopiazonic acid (CPA), which have been reported to be commonly found with aflatoxins [1315]
The addition of hydrated sodium calcium aluminosilicate (HSCAS) reduced the number of fungi isolated, potentials exit for the production of all toxins listed against Mouldy Groundnut Cake (MGC) diet, except secalonic acid which is produced by P. oxalicum [18]
Summary
Feed ingredients contamination with toxins may occur anywhere in the supply chain from the field, manufacturing process, transportation to storage. In the tropics conducive environmental condition has majorly been attributed to production and growth of micro-organisms and toxic substances; fungi. This is exacerbated by the cultural practice and lack of adequate regulatory and control system by government for food and feedstuffs contaminant screening in most developing countries in the humid tropics. Aspergillus flavus and A. parasiticus contamination are mostly responsible for the production of aflatoxins in the humid tropics [1]. They are found when environmental temperature is above 27°C, humidity levels greater than 65% and moisture levels in feedstuff is above 14%. Efforts have been focused on reducing the impact of aflatoxin B1 contamination in livestock and fish, with dearth of information on the other aflatoxins
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