Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: In vitro and in situ methods using the in sacco technique have a wide application in ruminant
nutrition as they allow the degradability and quality of forages and ruminant diets to be
determined quicker and at a lower cost than in vivo methods. These trials make use of artificial
fibre bags, made of polyester (dacron) or nylon which are available in variable pore sizes.
Results from such degradability trials are of great value to feed formulation programs such as
AMTS.cattle and CPM Dairy and the more accurate the results are obtained from such trials the
more accurate feed formulation models are enabling the ruminant nutritionist to formulate the
best diet possible to reach the genetic potential of ruminants. The accepted method for in sacco
trials (NRC, 2001) requires that the feed samples are ground through a 2 mm screen. This
usually results in a variety of particle sizes, including a significant amount of extremely fine
particles. Research has, however, shown that these fine particles can potentially be washed out
of the dacron bags that are used in in sacco degradability trials. This would result in an overestimation
of the soluble and rapidly fermentable nutrient fractions. The objective of this study
was to determine the effect of fine particle removal from ground forage samples on the chemical
composition and in vitro dry matter (DM) and neutral detergent fibre (NDF) degradability of
forages. Lucerne hay, oat hay and wheat straw samples were sourced from seven different
locations in the Western Cape. Samples were milled through a 2 mm screen and then sieved
through either 150 μm, 125 μm or 106 μm. All fractions were analysed for DM, crude protein
(CP), NDF, fat and ash. Based on the NDF content of the original samples, four samples from
each forage type were selected for in vitro trials to determine DM and NDF disappearance over
time. Samples were incubated for 0, 6, 24 and 48 hours in an ANKOM Daisy II incubator.
Significant variation occurred within forage types in terms of chemical composition. Fine particle removal had no effect on the NDF content of lucerne hay and wheat straw, but sieved oat hay
fractions had a higher NDF content than the un-sieved samples. The NDF content was on
average 635.9 for the sieved OH fractions, whereas the NDF content of the un-sieved samples
was 606.8. The CP content of sieved oat hay (61.4 on average) and wheat straw fractions (47.7
on average) were lower than the un-sieved fractions (65.7 for OH and 55.4 for WS), whereas for
lucerne hay, sieving had no effect on CP content.
Dry matter and NDF disappearances were significantly higher for the un-sieved samples than
for the sieved fractions for all three forage types at all incubation times, which indicates an overestimation
of the soluble and readily digestible forage fractions. Compared to sieved samples,
DMD values at 0 hours (washing only) of the un-sieved samples were, on average, 13.8%
higher for lucerne hay, 27.3% for oat hay and 44.7% for wheat straw. At 48 h, the overestimation
of lucerne DMD for the un-sieved samples was between 4.0% (compared to 106 μm
sieve) and 7.3% (compared to 150 μm sieve). This over-estimation in the un-sieved samples
was carried over to all four time points. No significant differences between the fractions (150,
125 and 106) were found within a forage type at all incubation times. The estimated degradation
rates and the predicted digested proportions were also significantly higher for the un-sieved
fractions compared to the sieved fractions. It was concluded that fine particle removal from
forage samples would result in more accurate estimations of in sacco nutrient degradability. / AFRIKAANSE OPSOMMING: In sacco in vitro- en in situ-metodes word dikwels toegepas in die studie van herkouervoeding
aangesien hierdie metodes vinniger, meer effektief en meer ekonomies is as in vivo-metodes.
Hierdie studies maak gebruik van kunsveselsakkies, gemaak van poliëster (dacron) of nylon wat
beskikbaar is in verskeie poriegroottes. Resultate van sulke verteringsproewe is belangrik vir
toepassing in voerformuleringsprogramme soos AMTS.cattle en CPM Dairy. Die resultate wat
deur hierdie studies verkry word, is belangrik vir akkurate voerformulering deur formuleringsmodelle
en stel die herkouervoedingkundige in staat om die ideale voer te formuleer vir die
manifestering van die dier se genetiese potensieaal. Die aanvaarde in sacco-metode (NRC,
2001) vereis dat voermonsters deur ‘n 2 mm sif gemaal word wat ‘n groot verskeidenheid
partikelgroottes tot gevolg het met ‘n beduidende hoeveelheid baie fyn materiaal. Navorsing het
getoon dat hierdie baie fyn partikels uit die dacronsakkies gewas kan word tydens in sacco
verteringstudies, met die gevolg dat die oplosbare en vinnig-verteerbare fraksie oorskat kan
word. Die doel van die huidige studie was om die invloed van die verwydering van fyn partikels
op die chemiese samestelling van ruvoermonsters te bepaal, asook die in vitro droë materiaal
(DM) en neutraal-onoplosbaare vesel (NDF) verteerbaarheid daarvan. Monsters van lusernhooi,
hawerhooi en koringstrooi, afkomstig van sewe verskillende lokaliteite in die Wes-Kaap, is deur
'n 2 mm sif gemaal en sub-monsters is deur ‘n reeks siwwe met poriegroottes van 150 μm, 125
μm of 106 μm gesif. Al die fraksies is geanaliseer vir DM, ruproteïen (RP), NDF, vet en as. Vier
monsters van elke voertipe is op grond van die NDF-inhoud geselekteer vir in vitro-studies om
die DM- en NDF- verteerbaarheid oor tyd te bepaal. Monsters is vir 0, 6, 24 of 48 uur
geïnkubeer. Die resultate het getoon dat daar betekenisvolle variasie in chemiese samestelling
binne ruvoertipes voorgekom het. Die verwydering van die fyn partikels het geen invloed die NDF-inhoud van lusernhooi en koringstrooi gehad nie. Wat hawerhooi betref, was die NDFinhoud
van die gesifte monsters egter betekenisvol hoër in vergelyking met die ongesifte
monsters. Die NDF inhoud was gemiddeld 635.9 vir die gesifte monsters en vir die ongesifte
monsters 606.8. Sifting het geen invloed op die RP-inhoud van lusernhooi gehad nie, maar vir
hawerhooi (61.4 gemiddeld) en koringstrooi (47.7 gemiddeld) was die RP-inhoud van die gesifte
monsters betekenisvol laer as dié van die ongesifte monsters (65.7 vir hawerhooi en 55.4 vir
koringstrooi).
In vergelyking met die gesifte monsters, was die in vitro DM- en NDF-verteerbaarhede
betekenisvol hoër vir die ongesifte monsters vir al drie ruvoertipes by alle inkubasietye. Hierdie
resultate bevestig ‘n oorskatting van oplosbare en maklik verteerbare fraksies in gemaalde
voermonsters. In vergelyking met die gesifte monsters, was die DMV-waardes van die ongesifte
monsters by 0 ure (slegs gewas) gemiddeld 13.8% hoër vir lusernhooi, 27.3% vir hawerhooi en
44.7% vir koringstrooi. Na 48 h inkubasie was die oorskatting van lusern DMV vir die ongesifte
monsters tussen 4.0% (vergeleke met die 106 μm sif) en 7.3% (vergeleke met 150 μm sif). Die
oorskatting is oorgedra na al vier inkubasietye. Die resultate het geen noemenswaardige
verskille tussen die fraksies (150 μm, 125 μm en 106 μm poriegroottes) van ‘n ruvoertipe by
enige inkubasietyd aangedui nie. Die beraamde verteringstempo’s en verteerde fraksies was
ook aansienlik hoër vir die ongesifte monsters in vergelyking met die gesifte monsters. Die
gevolgtrekking is gemaak dat die verwydering van fyn partikels uit gemaalde ruvoermonsters
die akkurate bepaling van in sacco verteerbaarheidswaardes verhoog.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6609 |
| Date | 03 1900 |
| Creators | Mack, Claudia Isabell |
| Contributors | Cruywagen, C. W., 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 | 69 p. : ill. |
| Rights | University of Stellenbosch |
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