Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The use of fungal enzymes as ruminant feed digestibility enhancers was investigated. Currently,
ruminants may not digest 38 to 80 % of fibrous forages' content. A renewed interest in the potential
of feed enzymes for ruminants was prompted by the high costs of livestock production, together
with the availability of newer enzyme preparations. Direct application of enzyme preparations can
improve in vitro dry matter (DM) and neutral detergent fibre (NDF) degradation, indicating that
direct-fed fibrolytic enzymes may be effective in enhancing in vivo digestion of forages.
Two commercial enzyme products, Fibrozyme and Celluclast, and fungal extracellular
enzyme extracts from Aureobasidium pullulans, Trichoderma reesei, Aspergillus aculeatus, and
Thermomyces lanuginosus were evaluated for enhancing in vitro feed digestibility. Fibrozyme
addition to both wheat straw and lucerne hay did not improve their in vitro digestibilities, even after
a two hour pre-incubation period. The four fungal enzyme extracts did not enhance wheat straw's
digestibility, but marginal increases were evident for lucerne hay. Celluclast addition resulted in
marginal increases in the digestibility of both oat hay and oat silage, with no enhanced effect on
lucerne hay and NaOH-treated wheat straw. No relationship could be found between the level of
enzyme activity and the degree of feed digestion in the in vitro assay.
Enzyme hydrolysis with Celluclast, in the absence of rumen fluid, gave more conclusive
results. All the feed samples tested showed a positive response to Celluclast addition, even the less
digestible feeds, namely sugarcane bagasse and wheat straw.
In vitro results show that the assays were unsuccessful, because almost all of the
experiments conducted showed inconclusive results. Alternative feed evaluation assays, which
include the in vivo, in sacco and in situ methods of analysis, as well as gas production measurement
and in vitro analysis with the DAISyII system, should be evaluated. A more detailed study of feed
digestibility should be motivated by determining which feeds are hydrolysable, their chemical
composition, i.e. how accessible the feeds are, and also evaluation of feed mixtures. The enzyme
supplements also need to be evaluated for optimum temperature and pH, as well as the compilation
of enzyme cocktails. / AFRIKAANSE OPSOMMING: Die gebruik van swamensieme om die verteerbaarheid van herkouervoere te verhoog, is ondersoek.
Tussen 38 en 80 % van veselagtige voere se inhoud is tans onverteerbaar. 'n Hernieude
belangstelling in die potensiaal van voerensieme vir herkouers word deur die hoë koste van
veeproduksie, asook die beskikbaarheid van nuwe ensiempreparate gedryf Direkte byvoeging van
ensiempreparate kan die in vitro droëmateriaal (DM) en neutrale onoplosbare vesel (NOV)
vertering verbeter, wat daarop dui dat fibrolitiese ensieme wat direk gevoer word, effektief mag
wees tydens die in vivo vertering van voer.
Twee kommersiële ensiemprodukte, Fibrozyme en Celluclast, en die vier ekstrasellulêre
ensieme van vier swamme, naamlik Aureobasidium pullulans, Trichoderma reesei, Aspergillus
aculeatus, en Thermomyces lanuginosus is vir hul vermoë om die in vitro verteerbaarheid van voere
te verbeter getoets. Byvoeging van Fibrozyme by beide koringstrooi en lusernhooi het geen
verbetering in hulonderskeie in vitro verteerbaarheid tot gevolg gehad nie, selfs nie eens na 'n twee
uur vooraf inkubasieperiode nie. Koringstrooi se verteerbaarheid is nie verbeter deur die byvoeging
van die vier swam-ensiempreparate nie, maar 'n minimale verbetering is wel waargeneem in die
verteerbaarheid van lusernhooi. Byvoeging van Celluclast het 'n minimale verbetering in beide
hawerhooi en hawerkuilvoer se verteerbaarheid tot gevolg gehad, maar geen effek op lusernhooi of
NaOH-behandelde koringstrooi se verteerbaarheid nie. Geen verwantskap is tussen die vlak van
ensiemaktiwiteit en die mate van vertering tydens die in vitro toets gevind nie.
Ensiematiese afbraak met Celluclast, in die afwesigheid van rumenvloeistof, het meer
konkrete resultate gelewer. Al die voermonsters het 'n positiewe respons op die byvoeging van
Celluclast getoon, selfs ook die minder verteerbare voere, nl. suikerrietbagasse en koringstrooi.
In die wyer konteks was die resulate van die in vitro verteringstoetse egter onbeduidend as
gevolg van groot variasie in die metings. Alternatiewe voerontledingstoetse, wat moontlik beter
resultate mag lewer, sluit in in vivo, in sacco en in situ analises, asook die meting van gasproduksie
en in vitro analise met die DAISyII sisteem. 'n Meer uitgebreide studie van voerverteerbaarheid wat
die bepaling van die afbraak van voere, hul chemiese samestelling, met ander woorde
toeganklikheid van voere, en die ondersoek van voermengsels behels, behoort aandag te geniet. Die
ensiemmengsels behoort ook ten opsigte van samestelling, optimum temperatuur en pH ondersoek
teword.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52280 |
| Date | 03 1900 |
| Creators | Lakay, Francisco Martin |
| Contributors | Prior, B. A., Van Zyl, W. H., Stellenbosch University. Faculty of Science. Dept. of Microbiology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 86 p. : ill. |
| Rights | Stellenbosch University |
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