Thesis (MPhil)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: trout was conducted at the Jonkershoek trout research station of the Division of Aquaculture,
University of Stellenbosch. Treatments consisted of ten experimental diets containing increasing
levels of Spirulina (0%, 0.05%, 0.1%, 0.15%, 0.3%, 0.6%, 1.25%, 2.5%, 5% and 10%). The data
was analyzed through means of a one-way ANOVA and Tukey’s pair wise comparison test for
significant differences between treatments for the various parameters of flesh pigmentation and
growth.
The results indicates that the inclusion of Spirulina in the diets of rainbow trout will cause a
undesirable yellowing of fillets, particularly at levels of inclusion at 5 percent and above, which
may limit its use in diets for rainbow trout. There was an inconsistent increase in b* (yellowblue)
and Chroma values with increasing levels of Spirulina inclusion, which may indicate the
deposition of carotenoids (yellow-orange colour range) instead of the desired deposition of
xanthophylls (pink-red colour range) in the flesh of the rainbow trout. This increase in b*
(yellow-blue) values was significantly higher (P<0.05) at inclusion levels above 5 percent.
Spirulina had no significant effect on weight gain of rainbow trout at any level of inclusion. No
significant differences (P>0.05) were observed in any of the other production performance
parameters (growth rate, feed intake, feed conversion ratio, viscerosomatic index, hepatosomatic
index, and liver lipid content) that were evaluated. Low mortality rates were observed with no
significant differences between treatments. A trend of decreased feed intake with increased levels
of Spirulina inclusion became significant at the 2.5 percent level of inclusion, caused by
deterioration in the palatability of the feed. A significantly higher dress-out percentage was
observed at levels of Spirulina inclusion above 5 percent. A trend of decreased liver lipid content
with increased Spirulina inclusion was observed, though not significant at any level of Spirulina
inclusion. This observation justifies further investigation because of its potential to improved
carbohydrate metabolism in carnivorous fish
Results confirm that up to 10% Spirulina can effectively replaced soybean meal in the control
diets for rainbow trout while simultaneously improving carcass dress-out at high inclusion levels. / AFRIKAANSE OPSOMMING: rantsoen van reënboog forel te evalueer. Die eksperiment is opgestel by die Akwakultuur Divisie,
van die Universiteit van Stellenbosch, se navorsingstelsel in Jonkershoek, buite Stellenbosch.
Reënboog forel (Oncorhynchus mykiss) vingerlinge van gemiddeld 20 gram is gebruik en
ingedeel in 20 ronde tenks volgens kommersieële digthede (250 per tenk).
Die rantsoene is gemeng met verskeie vlakke van Spirulina insluiting (0%, 0.05%, 0.1%, 0.15%,
0.3%, 0.6%, 1.25%, 2.5%, 5% en 10%). Twee herhalings van elke rantsoen is gevolg vir ‘n
periode van 3 maande. Die vis is ad lib (volgens behoefte) gevoer, drie maal per dag.
Daar was ‘n neiging tot ‘n verhoging in b* (geel-blou) en Chroma waardes met verhoogde
insluitingsvlakke van Spirulina. Hierdie is wel ‘n aanduiding van die deponeering van karoteen,
maar val in die geel-oranje kleur reeks en is nie die verlangde pienk-rooi (xantofil) kleur in die
spier weefsel van die vis nie. Die verhoging in b* (geel-blou) waardes was statisties betekenisvol
(P<0.05) bo die 5% insluitings vlak.
In vergelyking met die kontrole (0%) rantsoen, was daar geen betekenisvolle massa toename na
afloop van die proef tussen die verskeie behandelings nie. Behalwe vir ‘n verskil in voer inname,
was daar geen statisties betekenisvolle verskil (P>0.05) waarneembaar tussen die verskillende
behandelings ten opsigte van die verskeie produksie prestasie parameters nie. Daar was wel ‘n
afnemende neiging in voer inname met verhoogde vlakke van Spirulina wat betekenisvol geraak
het bo 2.5% insluitingsvlak. Smaaklikheid kan die moontlike rede hiervoor wees. Baie lae
mortaliteite is ervaar by al die insluitings vlakke. Daar was ook ‘n neiging in hoër uitslag
persentasie by verhoogde insluitingsvlakke van Spirulina wat betekenisvol geraak het bo 5 %
insluiting. ‘n Afnemende vlak van lewer lipied inhoud is waargeneem maar was nie betekenisvol
by enige van die insluitingsvlakke nie.
Resultate van die proef dui daarop dat 10% Spirulina insluiting effektief kan dien as ‘n
gedeeltelike plaasvervanger vir soyaboon meel in forel rantsoene. Die hoër uitslag persentasies
hou belofte in. Die onverlangde vergeeling van die filette mag die gebruik van Spirulina beperk
by reënboog forel rantsoene veral bo 5 % insluitings vlakke. Die verlaging in lewer lipied vlakke
by ‘n verhoging van Spirulina insluiting regverdig vêrdere navorsing oor die potensiaal van
Spirulina om die metabolisme van koolhidrate te verbeter by karnivoor visspesies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20905 |
| Date | 04 1900 |
| Creators | Stander, Hendrik Barend |
| Contributors | De Wet, L.F., Brink, D., Stellenbosch University. Faculty of Agrisciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 45 leaves : ill. |
| Rights | Stellenbosch University |
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