Investigation of potential bio-active properties and effects on production performance of aquafeed ingredients derived from fish processing waste by way of enzymatic autolysis

[摘要] ENGLISH ABSTRACT: This study is part of the continuing global research effort dedicated to finding alternativeaquafeed ingredients, which not only replace fish meal and fish oil as sources of essential nutrientsin aquafeeds, but also provide specialist functional properties when included in feeds. Due toconstraints in supply of fish meal and fish oil originating from wild capture fisheries, the continuallygrowing aquafeed industry requires new sources of raw materials for the production of high qualityfeeds.The aim of the study was to investigate the specialist functional properties of feedingredients (with emphasis on immune-stimulation potential) derived from fish processing wasteafter enzymatic hydrolysis by endogenous proteolytic enzymes (autolysis). Further aims were to (i)quantify effects of these feed ingredients on production performance of two species relevant to theSouth African aquaculture industry, namely Mozambique tilapia Oreochromis mossambicus andSouth African abalone Haliotis midae, (ii) compare performance to commercially availableenzymatically produced feed ingredients, and (iii) separate the functional effects of these fishprocessing waste derived feed ingredients from the acid used to preserve them against bacterialspoilage during the autolysis process.Oil recovered after autolysis of rainbow trout viscera proved to be an attractive feedingredient due to favourable effects on the non-specific cellular immune function of bothMozambique tilapia and South African abalone. However, in South African abalone, increasedimmune function due to inclusion of fish oil was accompanied by a significant decrease inproduction performance. The inclusion of hydrolysed proteins, obtained by autolysis of fish waste,in aquaculture feeds also improved non-specific immunity and survival of Mozambique tilapiasignificantly – independently of the preserving acid – although the same was not observed forSouth African abalone. Production performance was dependent on dietary hydrolysed proteininclusion levels in both species; excessive inclusion resulted in decreased production performance.The performance of dietary hydrolysed protein from autolysis and those from commercial production processes were significantly different, possibly as a result of different raw materialorigins and production processes. It is further shown that formic acid can contribute to improvedwater stability in abalone feeds, a novel mode of action not previously described.The study concludes that the simple autolysis process for processing of fish waste canprovide aquafeed ingredients with immune stimulatory potential, which can contribute to improvedproduction performance in the Mozambique tilapia and the South African abalone. The result cancontribute to improved sustainability of the aquafeed industry, through substitution of fish meal andfish oil derived from capture fisheries with processed fish waste components.

[发布机构] Stellenbosch University