Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this study was to investigate the variation that exists between maize samples regarding
particle size separation, in vitro fermentation kinetics and in vitro dry matter (DM) disappearance. A second
objective was to quantify possible relationships between the Roff Milling Index (RMI) of maize and any of the
measured in vitro parameters. Three trials were conducted: a particle size distribution trial, a gas production
trial and an in vitro DM degradability and starch disappearance trial.
Overall, nine maize samples, which differed in terms of cultivar and endosperm type, were collected from
different origins for the study. The samples were selected in terms of their Milling Index (MI). Three of the
nine samples had a high MI that ranged between 109 and 118, three had a low MI that ranged between 67
and 71 and the other three samples had a medium MI that ranged between 85 and 92. Although the MI is not
a direct indication of the hardness or softness of the endosperm, it was believed to be indirectly associated
with vitreousness.
In the first trial, the different maize samples were milled through a 1 mm screen and sieved through a series
of three sieves 150, 125 and 106 μm, respectively. It was found that RMI was not a reliable indicator to
predict particle size distribution, especially in terms of the coarse (>150 μm) and very fine (<106 μm)
particles.
In the gas production trial, the nine different maize samples were subjected to a gas production system for a
duration of 48 hours. Here gas production and rate of gas production of the different maize types in buffered
rumen liquor were measured during incubation. After fitting the gas volume data to the respective models,
the non-linear parameters b, c and L were subjected to a main effects ANOVA with the aid of Statistica,
version 9 (2009). Main effects were treatment and repetition. Means were separated by means of a Scheffé
test and significance was declared at P < 0.05. The results were compared to the RMI of the different maize
types and it was concluded that RMI was not a reliable predictor of gas production or rate of gas production
of different maize types.
In the third trial, in vitro DM degradability and starch disappearance of the different maize types were
measured. In vitro DM degradability was conducted in the Ankom DAISYII incubator apparatus and the incubation times were 0, 2, 4, 8, 12 and 24 hours. Starch disappearance was measured on residues of the
samples incubated for 0, 2 and 4 hours. After fitting the DM disappearance data to the respective models,
the non-linear parameters a, b, c and L were subjected to a main effects ANOVA with the aid of Statistica,
version 9 (2009). Main effects were treatment and repetition. Means were separated by means of a Scheffé
test and significance was declared at P<0.05. The results indicated variation between maize samples,
especially in terms of the a-, b- and L-values. The RMI did not appear to be a reliable predictor of digestibility
parameters. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die variasie tussen mieliemonsters te ondersoek ten opsigte van die
skeiding van partikelgroottes, in vitro-fermentasiekinetika en in vitro-droëmateriaalverdwyning. ‘n Tweede
doel was om te bepaal of daar moontlike verwantskappe tussen die Roff Milling Index (RMI) van mielies en
enige van die ander in vitro-parameters bestaan. Drie proewe is gedoen: verspreiding van partikelgrootte, ‘n
gasproduksieproef en ‘n droëmateriaal degradeerbaarheid- en stysel verdwyningsproef.
Nege mieliemonsters, wat van mekaar verskil ten opsigte van kultivar en endospermtipe, is van verskillende
lokaliteite versamel. Die monsters is gekies in terme van hul maal-indeks (MI). Drie van die nege monsters
het ‘n hoë MI gehad wat gewissel het tussen 109 en 118, drie het ‘n lae MI gehad wat gewissel het tussen
67 en 71 en die ander drie monsters het ‘n medium MI gehad wat gewissel het tussen 85 en 92. Alhoewel
die MI waardes nie ‘n direkte indikasie van ‘n endosperm se hardheid- of sagtheidsgraad is nie, is dit
aanvaar dat daar ‘n indirekte verwantskap tussen MI en glasagtigheid van die mielie bestaan.
In die eerste proef is die nege verskillende mieliemonsters deur ‘n 1 mm sif gemaal en daarna deur ‘n reeks
van drie siwwe met groottes van onderskeidelik 150, 125 en 106 μm gesif. Daar is bevind dat die RMI nie ‘n
betroubare voorspeller is om partikelgrootte-verspreiding aan te dui nie, veral nie ten opsigte van growwe (>
150 μm) en baie fyn (< 106 μm) patikels nie.
Tydens die gasproduksieproef is die nege mieliemonsters vir 48 ure blootgestel aan ‘n gasproduksiesisteem,
waar gasdruk outomaties aangeteken is. Gasproduksie en tempo van gasproduksie van die verskillende
mieliemonsters is gemeet en aangeteken gedurende inkubasie met ‘n gebufferde rumenvloeistofmedium.
Nadat die gasvolumedata met behulp van relevante modelle gepas is, is die nie-linêre parameters b, c en L
onderwerp aan ‘n hoof-effek ANOVA met die gebruik van Statistica weergawe 9 (2009). Hoof-effekte was
behandeling en herhaling. Gemiddeldes is deur ‘n Scheffé-toets geskei en betekenisvolheid is verklaar by
P<0.05. Die resultate verkry is vergelyk met die RMI van die verskillende mielietipes. Die gevolgtrekking is
gemaak dat Roff MI nie ‘n betroubare voorspeller van totale gasproduksie of gasproduksietempo is nie.
Tydens die derde proef is droëmateriaaldegradeerbaarheid en styselverdwyning van die verskillende
mielietipes bepaal. In vitro droëmateriaal (DM) degradeerbaarheid is gedoen in die Ankom DAISYII inkubator
met inkubasietye van 0, 2, 4, 8, 12 en 24 ure. Styselverdwyning is bepaal deur styselanalises op die residue van die monsters wat geïnkubeer is vir 0, 2 en 4 ure. Nadat die DM-degradeerbaarheid met behulp van
relevante modelle gepas is, is die nie-lineêre parameters a, b, c en L onderwerp aan ‘n hoof-effek ANOVA
met die gebruik van Statistica weergawe 9 (2009). Hoof-effekte was behandeling en herhaling. Gemiddeldes
is deur ‘n Scheffé toets geskei en die betekenisvolheid is verklaar by P<0.05. Die resultate het aangedui dat
daar groot variasie tussen mielies bestaan, veral ten opsigte van die a-, b- en L-waardes. Dit het verder
geblyk dat die RMI van die verskillende mielietipes nie ‘n betroubare voorspeller van DM-degradeerbaarheid
was nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5408 |
| Date | 12 1900 |
| Creators | Burden, Petro Trudene |
| 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 | 74 p. : ill. |
| Rights | University of Stellenbosch |
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