Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Forages are the main feed components in ruminant production systems for the reason that they are often the major
source of energy available to the animal. However, only 10 to 35% of energy intake is available as net energy because
the digestion of plant cell walls is not complete. This can significantly affect livestock performance and profits in
production systems that use forages as a major source of nutrients of the diet. As a result of low and variable nutritive
values of forage feedstuffs, attempts to improve ruminal fibre degradability have been an ongoing research topic. The use
of exogenous fibrolytic enzymes (EFE) has been proposed as means to improve forage digestibility. Positive results with
regard to rumen forage digestibility and other animal production traits have consequently been obtained due to increased
rumen microbial activity following EFE addition in ruminant diets.
Two EFE (Abo 374 and EFE 2) and one commercial yeast preparation were firstly identified and selected for their
potential to improve the cumulative gas production (GP) at 24 hours of a range of feed substrates using the in vitro GP
system as a screening step to identify the superior EFE products. The different feed substrates were lucerne hay, wheat
straw, wheat straw treated with urea and a commercial concentrate diet. An in vitro experiment was undertaken on these
four different substrates in order to evaluate the two EFE and the yeast preparation. This was to identify the most
promising EFE capable of producing a significant effect on feed digestibility using organic matter digestibility (in vitro true
digestibility) and fermentation characteristics (in vitro GP system). Results from the in vitro evaluation showed that EFE
significantly enhanced in vitro DM degradability and GP profiles (P < 0.05). Abo 374 enzyme showed potential to increase
in vitro microbial protein synthesis (MPS) of GP residues of the concentrate diet. In addition, no correlation was found
between the in vitro MPS and the 48 hours cumulative GP of all the tested substrates (P < 0.05; R2 < 0.30). Treatments
were found to increase in vitro MPS, feed degradability and the cumulative GP of different quality forages and the
concentrate diet, with Abo 374 being the best treatment (P < 0.05). However in vitro responses of EFE were variable
depending on the energy concentration and chemical composition of different substrates. Variation in MPS was mostly
due to the low recovery of purine derivates with the purine laboratory analysis.
On the basis of these results, Abo 374 was selected and consequently further tested in another in vitro and in situ trial
using a mixed substrate of lucerne hay and wheat straw. Abo 374 significantly improved the cumulative GP, in vitro DM
and NDF disappearance of the mixed substrate (P < 0.05). In addition, no correlation was found between the in vitro MPS
and the cumulative GP at 48 hours (P = 0.68; R2 < 0.25). The in situ disappearance of feed nutrients (DM, NDF and CP)
with Abo 374 was similar to the control. The lack of significance of disappearance was probably due to the small number
of sheep used in the study and the relatively high coefficient of variation associated with measuring ruminal digestion. Abo 374 significantly increased the in situ MPS (P = 0.0088) of the mixed substrate of lucerne hay and wheat straw. Evidence
of the increased MPS and both in vitro and in situ disappearance of DM and NDF resulted from the Abo 374 activity
during either the pre-treatment or the digestion process. The addition of Abo 374 to the mixed substrate of lucerne hay
and wheat straw appeared to have been beneficial for microbial colonization of feed particles as a result of the increased
rumen activity. It could be speculated that the primary microbial colonization was thus initiated, leading to the release of
digestion products that attract in return additional bacteria to the site of digestion. This EFE may be efficient to produce
some beneficial depolymerisations of the surface structure of the plant material and the hydrolytic capacity of the rumen
to improve microbial attachment and the feed digestibility thereafter. Therefore, the mechanism of action by which Abo
374 improved the feed digestion can be attributed to the increased microbial attachment, stimulation of the rumen
microbial population and synergistic effects with hydrolases of ruminal micro-organisms. With regard to these findings, the
addition of EFE in ruminant systems can improve the ruminal digestion of DM, NDF and CP to subsequently enhance the
supply of the metabolizable protein to the small intestine.
Key words: crude protein (CP), exogenous fibrolytic enzymes (EFE), dry matter (DM), gas production (GP), neutral
detergent fibre (NDF), microbial protein synthesis (MPS). / AFRIKAANSE OPSOMMING: Ruvoere is die hoof-voerkomponent in herkouer produksiesisteme aangesien dit dikwels die vernaamstebron van energie
aan herkouer is. Slegs 10 tot 35% van die energie-inname is beskikbaar as netto-enrgie, omdat die vertering van
selwande onvolledig is. Dit kan die prestasie en profyt in produksiesisteme drasties beïnvloed waar ruvoere as ’n
hoofbron van nutriënte in die dieet gebruik word. Aangesien die nutriëntwaarde van ruvoere laag is en baie varieer, is
navorsing vir verbeterde ruminale veselvertering steeds ’n voorgesette onderwerp. Dit is voorgestel dat eksogeniese
fibrolitese ensieme (EFE) gebruik kan word vir verbeterde ruvoervertering. Positiewe resultate in ruminale ruvoerverterig
en ander diereproduksie-eienskappe, is verkry as gevolg van toenemende rumen mikrobiese aktiwiteit na EFE aanvulling
in herkouerdiëte.
Twee EFE’s (Abo 374 en EFE 2) en `n gisproduk is geïdentifiseer en geselekteer vir hul potensiaal om die kumulatiewe
gasproduksie (GP) na 24 uur met ’n reeks voersubstrate te verbeter met die gebruik van die in vitro GP sisteem as
seleksiemetode om die superieure EFE produkte te identifiseer. Die verskillende ruvoersubstrate was lusernhooi,
koringstrooi, ureumbehandelde koringstrooi en ’n kommersiële konsentraatdieet. ’n In vitro eksperiment was onderneem
om die vier verskillende substrate te gebruik om die twee EFE’s en gisproduk te evalueer. Hierdeur sou die belowendste
EFE’s identifiseer kon word wat ’n betekenisvolle effek op ruvoervertering het. Die vertering van ruvoer sal bepaal word
deur organiese materiaal vertering (in vitro ware vertering), asook fermentasie-eienskappe (in vitro GP sisteem).
Resultate van die in vitro evaluering het getoon dat EFE’s in vitro DM degradering en GP profiele verbeter. Dit blyk dat
die Abo 374 ensiem ’n potensiële toemame in in vitro mikrobiese proteïensintese (MPS), soos bepaal deur die GP
oorblyfsels van konsentraat diëte, tot gevolg gehad het. Daar was geen korrelasie tussen die in vitro GP en MPS van al
die proefsubstrate nie. Dit blyk dat die behandelings ’n toename in in vitro GP, MPS en ruvoerdegradeerbaarheid van lae
kwaliteit ruvoer- en konsentraatdiëte gehad het, waar Abo 374 die beste behandeling was. Die in vitro reaksies van die
EFE’s was egter wisselend, afhangende van die energiekonsentrasie en die chemiese samestelling van die verskillende
substrate. Variasie van MPS was meestal as gevolg van die lae herwinning van purienderivate tydens die purienanalise.
Op grond van dié resultate, is Abo 374 geselekteer om verdere toetse in ander in vitro en in situ proewe te doen. Die
substraat wat gebruik is, was ’n 1:1 mengsel van lusernhooi en koringstrooi. Abo 374 het die kumulatiewe RP, in vitro DM
en NBV verdwyning van die gemengde substraat verbeter. Boonop is geen korrelasie tussen die MPS en in vitro GP
gevind nie. In situ verdwyning van DM, NBV en RP was hoër vir Abo 374, maar nie betekenisvol nie. Die gebrek aan
betekenisvolle verdwynings mag die gevolg wees van die klein hoeveelheid skape wat in die proef gebruik is, asook die
relatiewe hoë koëffisient van variasie wat gepaard gaan met die bepaling van ruminale vertering. Abo 374 het die in situ MPS betekenisvol verhoog. Verhoogde MPS en in vitro en in situ verdwyning van DM en NBV is waargeneemwaarskynlik
as gevolg van die aktiwiteit van Abo 374 gedurende die voorafbehandeling óf die verterings proses. Die byvoeging van
Abo 374 tot die gemengde substraat van lusernhooi en koringstrooi blyk om voordelig te wees vir mikrobiese kolonisering
van voerpartikels as gevolg van ’n toename in rumenaktiwiteit. Die primêre mikrobiese kolonisering het waaarskynlik gelei
tot die vrystelling van verteringsprodukte wat addisionele bakterieë na die plek van vertering lok. Die EFE mag geskik
wees vir voordelige depolimerisasie op die oppervlakstruktuur van die plantmateriaal, asook verbeterde hidrolitiese
kapasiteit van die rumen om sodoende mikrobiese aanhegting, asook ruvoervertering te verbeter. Dus, Abo 374 se
meganisme van aksie wat verbeterde ruvoervertering tot gevolg het, kan toegeskryf word aan `n verhoogde mikrobiese
aanhegting, stimulering van die rumen mikrobiese populasie en die sinergistiese effek met hidrolases van rumen
mikroörganismes. Ten opsigte van die bevindings, kan die byvoeging van EFE in herkouersisteme ruminale vertering van
DM, NBV en RP verbeter, wat dan daaropvolgend die dunderm met meer metaboliseerbare proteïn sal voorsien.
Sleutelwoorde: eksogene fibrolitiese ensieme (EFE), droëmaterial (DM), ruproteïen (RP), neutraal bestande vesel (NBV),
mikrobiese proteïensintese (MPS), gasproduksie (GP).
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6744 |
| Date | 03 1900 |
| Creators | Useni, Bilungi Alain |
| Contributors | Van de Vyver, W. F. J., University of Stellenbosch. Faculty of AgriSciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 105 p. : ill. |
| Rights | University of Stellenbosch |
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