Browsing by Author "Patience, Ashley O'Brian"

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    Evaluating silage oil from rainbow trout (Oncorhynchus mykiss) viscera as a substitute for dietary fish oil on production parameters of juvenile African catfish (Clarias gariepinus)
    (Stellenbosch : Stellenbosch University, 2020-03) Patience, Ashley O'Brian; Salie, Khalid; De Wet, Lourens; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences.
    ENGLISH ABSTRACT: Fresh rainbow trout (Oncorhynchus mykiss) viscera was used to extract fish silage oil by acid and fermentation ensiling methods. Organic acid mixtures (lactic acid x formic acid, lactic acid x propionic acid, and a commercial bacterial inoculum x molasses) were added to about 900 L of minced viscera in three airtight 1000 L, respectively. The silage oils were assessed for their volume, quality and fatty acid composition with the view to being used as feed oil in African catfish (Clarias gariepinus) diets. After 30 days, across the treatments, an average volume of 291 L of silage oil was produced, with a quality deemed favourable by food grade standards. The silage oils were very similar in their fatty acid fatty acid composition and compared favourably to a regular marine-based feed oil in their percentage of polyunsaturated fatty acids. However, the silage oils had a low percentage of omega-3 fatty acids and a high percentage of omega-6 fatty acids, resulting in a high omega-6:omega-3 fatty acid ratio. A 90-day feeding trial was conducted to investigate the effects of replacing fish oil with rainbow trout (O. mykiss) silage oil in the diets of juvenile African catfish (C. gariepinus), on their growth, survival and feed conversion. The three silage oils (derived from a lactic acid x formic acid silage, lactic acid x propionic acid silage, and a commercial bacterial inoculum x molasses silage) and a marine fish oil (control) were evaluated as the feed oils in four treatment diets. The diets were fed to juvenile African catfish (1.36 ± 0.14 g) in six replicate tanks per treatment, over a period of 92 days in a temperature-controlled recirculating aquaculture system. Overall there was no significant difference (p>0.05) between the four treatments on growth, survival and feed conversion ratio. The results indicate that the total dietary replacement of marine fish oil with Rainbow trout silage oil does not significantly affect the growth, survival or feed conversion of juvenile African catfish after a 92-day feeding trial, and that Rainbow trout silage oil could prove to be a viable alternative to fish oil for juvenile African catfish in the 1.36 – 53.33 g size range. This bodes well for the sustainable utilisation of Rainbow trout visceral waste as an aquafeed ingredient.