Thesis (PhD) -- tellenbosch University, 2014. / ENGLISH ABSTRACT: This study is part of the continuing global research effort dedicated to finding alternative
aquafeed ingredients, which not only replace fish meal and fish oil as sources of essential nutrients
in aquafeeds, but also provide specialist functional properties when included in feeds. Due to
constraints in supply of fish meal and fish oil originating from wild capture fisheries, the continually
growing aquafeed industry requires new sources of raw materials for the production of high quality
feeds.
The aim of the study was to investigate the specialist functional properties of feed
ingredients (with emphasis on immune-stimulation potential) derived from fish processing waste
after 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 the
South African aquaculture industry, namely Mozambique tilapia Oreochromis mossambicus and
South African abalone Haliotis midae, (ii) compare performance to commercially available
enzymatically produced feed ingredients, and (iii) separate the functional effects of these fish
processing waste derived feed ingredients from the acid used to preserve them against bacterial
spoilage during the autolysis process.
Oil recovered after autolysis of rainbow trout viscera proved to be an attractive feed
ingredient due to favourable effects on the non-specific cellular immune function of both
Mozambique tilapia and South African abalone. However, in South African abalone, increased
immune function due to inclusion of fish oil was accompanied by a significant decrease in
production performance. The inclusion of hydrolysed proteins, obtained by autolysis of fish waste,
in aquaculture feeds also improved non-specific immunity and survival of Mozambique tilapia
significantly – independently of the preserving acid – although the same was not observed for
South African abalone. Production performance was dependent on dietary hydrolysed protein
inclusion 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 material
origins and production processes. It is further shown that formic acid can contribute to improved
water 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 can
provide aquafeed ingredients with immune stimulatory potential, which can contribute to improved
production performance in the Mozambique tilapia and the South African abalone. The result can
contribute to improved sustainability of the aquafeed industry, through substitution of fish meal and
fish oil derived from capture fisheries with processed fish waste components. / AFRIKAANSE OPSOMMING: Hierdie studie vorm deel van die voortdurende en wêreldwye soeke na nuwe akwakultuur
voerbestanddele wat nie net vismeel en –olie kan vervang as bron van noodsaaklike
voedingstowwe nie, maar wat ook gespesialiseerde funksionele eienskappe openbaar wanneer dit
in akwavoere ingesluit word. As gevolg van beperkings in die voorsiening van vismeel en –olie
afkomstig vanaf wilde visserye, word die voortdurend groeiende akwavoer bedryf genoodsaak om
nuwe grondstowwe te benut vir die vervaardiging van hoë kwaliteit voere.
Die doelwit van die studie was om moontlike gespesialiseerde funksionele eienskappe (met
spesifieke klem op potensiële immuun-stimulasie) van voerbestanddele te ondersoek wat herwin is
vanaf reënboogforel proseseringsafval, na ensiematiese hidrolise d.m.v. endogene ensieme
teenwoordig in die afval (outolise). Verdere doelwitte was om (i) effekte op produksie prestasie
van hierdie bestanddele te kwantifiseer in twee akwakultuur spesies relevant tot die Suid-
Afrikaanse bedryf (naamlik die Mosambiekse kurper Oreochromis mossambicus en die Suid-
Afrikaanse perlemoen Haliotis midae), (ii) om produksie prestasie te vergelyk met kommersieel
beskikbare voerbestanddele voorberei d.m.v. ensiemtegnologie, en (iii) om die moontlike effekte
van die voerbestanddele te skei van die van die sure gebruik om die bestanddele te preserveer
tydens die outolitiese proses. Daar is bevind dat olie herwin na outolise van reënboogforel ingewande ‘n goeie
voerbestanddeel is wat gunstige effekte op die nie-spesifieke, sellulêre immuniteit van beide
Mosambiekse kurper en Suid-Afrikaanse perlemoen gehad het. In die Suid-Afrikaanse perlemoen
het verbeterde immuunfunksie gepaard gegaan met ‘n verswakking in produksie prestasie. Die
gehidroliseerde proteïen komponent van ge-outoliseerde prosesseringsafval het ook beduidende
verbetering in nie spesifieke immuniteit en oorlewing van Mosambiekse kurper tot gevolg gehad -
onafhanklik van die preserverende suur - maar dieselfde is nie in die Suid-Afrikaanse perlemoen
waargeneem nie. Produksie prestasie was afhanklik van die insluitingsvlakke van gehidroliseerde
proteïen in beide spesies en dit is bevind dat oormatige insluiting produksie nadelig beïnvloed.
Prestasie van proteïen afkomstig van outolise en die van ‘n kommersiële produksieproses het
beduidend verskil, moontlik as gevolg van verskillende grondstowwe en prosesseringstegnieke.
Daar is verder vir die eerste keer getoon dat mieresuur ‘n beduidende verbetering in waterstabiliteit
in sekere perlemoenvoere teweeg kan bring.
Die studie kom tot die slotsom dat die eenvoudige outolise proses funksionele
akwavoerbestanddele kan produseer wat kan bydra tot ‘n verbetering in produksie prestasie in die
Mosambiekse kurper en Suid-Afrikaanse perlemoen. Die resultaat kan bydra tot verbeterde
volhoubaarheid van die akwavoer bedryf, deur vismeel en –olie afkomstig van wilde visserye, te vervang.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/95907 |
| Date | 12 1900 |
| Creators | Goosen, Neill Jurgens |
| Contributors | Gorgens, Johann F., De Wet, Lourens, Stellenbosch University. Faculty of Engineering. Department of Process Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xv, 172 p. : ill. |
| Rights | Stellenbosch University |
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