Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Ruminants have a compound stomach system that enables them to utilize forages more efficiently than
monogastric animals. However, forages alone do not contain sufficient nutrients to meet the requirements of
high producing dairy cows. Forages are high in fibre and their nutrient availability depends on the degree of
cell wall degradability. Improvements in forage fermentation would increase energy intake and subsequently
milk production and performance by dairy cows. It is therefore important to find ways to improve forage
degradation and utilization in the rumen.
The use of different non-fibre carbohydrate (NFC) sources has different effects on animal performance.
Supplementing forage based diets with energy sources containing sugar, starch or pectin results in variation
in performance measurements such as milk yield, milk composition and dry matter intake (DMI).
This thesis reports on two studies in which the effect of energy supplementation on forage fermentation and
digestion parameters was investigated. In the first study an in vitro gas production protocol was used to
determine the effect of sugar (molasses), starch (maize meal) and pectin (citrus pulp) on total gas production
and rate of gas production of different forages. The forage substrates included wheat straw (WS), oat hay,
(OH) lucerne hay (LUC), ryegrass (RYE) and kikuyu grass (KIK). The three energy sources, as well as a
control (no energy source) were incubated in vitro with each of the above mentioned forages. Rumen fluid
was collected from two lactating Holstein cows receiving a diet consisting of oat hay, lucerne, wheat straw
and a concentrate mix. Forages alone (0.25 g DM) and/or together (0.125 g DM) with either molasses
(0.1412 g DM), citrus pulp (0.1425 g DM) or maize meal (0.125 g DM) were weighed into glass vials and
incubated for 72 hours. The weights of the energy sources were calculated on an energy equivalent basis.
Blank vials, that contained no substrates, were included to correct for gas production from rumen fluid alone. The substrates were incubated in 40 ml buffered medium, 2 ml of reducing solution and 10 ml rumen fluid.
Gas pressure was recorded automatically every five minutes using a pressure transducer system and the
method based on the Reading Pressure Technique (Mauricio et al., 1999). Gas pressure was converted to
gas volume using a predetermined regression equation. In the first gas production trial, the gas production
included gas produced by the energy sources, while in the second gas production trial, the energy source
gas production was deducted from the total gas production to determine the effect of energy source on gas
production of respective forage substrates per se. Data were fitted to two non-linear models adapted from
Ørskov and McDonald (1979). Significant forage x energy interactions were observed for the non-linear
parameter gas production (b) in Model 1 and for b and lag phase (L) in Model 2 in both trials. In the first gas
production trial, the higher fermentability of the energy sources supplemented to forage substrates,
increased b (Model 1 & 2) of the LUC and WS. The gas production rate was affected in different ways for
different forages, with the most noticeable effect on WS when it was supplemented with energy sources. All
the energy sources increased c of WS irrespective of the model used. Energy sources had no effect on the
L of LUC, OH or RYE, but decreased the L of WS and KIK. In the second trial, maize meal had no effect on
b for any of the forages (Model 1 & 2), while molasses (Model 1 & 2) decreased b for all forage substrates,
and citrus pulp (Model 1 & 2) decreased b of OH and RYE, to lower values than those of the control
treatments. Gas production rate was not affected by molasses for any of the forage substrates, while citrus
pulp (Model 1 & 2) increased c of OH and maize meal increased c of OH and KIK. Lag phase was only
affected by energy sources in WS and KIK, where all the energy sources had lower L values than the control
treatment. It was concluded that forage fermentability is affected differently by different energy sources.
These observations may have important implications, in practice, on rumen health and milk production, and
the data obtained can potentially be used as guidelines in feed formulations.
In the second study, in vitro digestibility trials were undertaken to determine the effect of sugar (molasses
and sucrose), starch (maize meal and maize starch) and pectin (citrus pulp and citrus pectin) on neutral
detergent fibre (NDF) and dry matter (DM) degradability of forages. Forage substrates used included wheat
straw, oat hay, lucerne hay, ryegrass and kikuyu grass. Rumen fluid was collected from two lactating
Holstein cows receiving a diet consisting of oat hay, wheat straw and a concentrate mix. In vitro
degradability was done with an ANKOM Daisy II incubator and forage substrates were incubated with or
without the respective energy sources for 24, 48 and 72 hours. The substrates were incubated in 1076 ml
buffered medium, 54 ml of reducing solution and 270 ml rumen fluid. The residues were washed, dried and
analyzed for NDF. In the study with the applied energy sources (molasses, maize meal and citrus pulp)
there were a forage x energy source interactions. Supplementation with the applied energy sources all
improved dry matter degradability (DMD) of forages (24 and 72 hours), when compared to the control
treatment, except for RYE supplemented with maize meal and citrus pulp at 24 hours. Molasses seemed to
have had the biggest effect on DMD in all forage substrates. Supplementation with maize meal had no effect
on neutral detergent fibre degradability (NDFD) of any forage substrate, except for an improvement in NDFD
of LUC at 72 hours. Molasses improved NDFD of LUC at 24h, but had no effect on the other forage
substrates. Citrus pulp improved NDFD of OH (72 hours), as well as LUC and WS (24 and 72 hours). It is
postulated that the NDF of the energy sources was more digestible than that of the respective forages, and
that the improved NDFD values could be ascribed to the contribution of the energy source NDFD. Overall,
pasture grasses had a higher NDFD than the hays and straw, and appear to be more readily fermentable by rumen microbes than the low quality hays and straw explaining the higher NDFD. In the study involving the
purified energy sources (sucrose, maize starch and citrus pectin), forage x energy source interactions were
observed. In general, supplementation with these energy sources improved DMD at 24 and 72 hours except
for RYE and KIK (72 hours). Pasture grasses (RYE and KIK) had a higher NDFD than LUC, OH and WS. At
72 hours, NDFD was 37.1% for LUC, 42.5% for OH and 40.3% for WS, compared to 70.5% for KIK and
64.9% for RYE. A possible explanation is that KIK and RYE samples came from freshly cut material,
harvested after a 28d re-growth period. In general, sucrose (24 and 72 hours) and citrus pectin (72 hours)
had no effect on NDFD of forage substrates. However, supplementing oat hay (24 hours) with starch and
citrus pectin, and wheat straw (24 and 72 hours) with starch lowered NDFD, when compared to the control
treatment. It is hypothesized that microbes fermented the easily fermentable energy sources first, before
attacking forage NDF. The study suggested that forage NDFD values are not fixed, and may be altered by
type of energy supplementation. / AFRIKAANSE OPSOMMING: Die meervoudige maagsisteem van herkouers stel hulle in staat om ruvoer meer effektief te benut as
enkelmaagdiere. Ruvoere alleen bevat egter nie genoeg voedingstowwe om die behoeftes van hoogproduserende
melkbeeste te bevredig nie. Ruvoere is ryk aan vesel en hul voedingstofbeskikbaarheid word
bepaal deur die graad van selwand degradeerbaarheid. ‘n Verhoging in ruvoerfermentasie sal energieinname
verhoog en gevolglik ook melkproduksie en prestasie. Dit is dus belangrik om maniere te vind om
ruvoerdegradeerbaarheid en -verbruik in die rumen te verbeter.
Die gebruik van verskillende nie-vesel koolhidraat (NFC) bronne het verskillende uitwerkings op die prestasie
van diere. Energie-aanvullings soos suiker, stysel en pektien tot ruvoer-gebasseerde diëte, beïnvloed
prestasiemaatstawwe soos melkproduksie, melksamestelling en droëmateriaalinname (DMI) op verskillende
maniere.
Hierdie tesis lewer verslag oor twee studies waar die invloed van energie-aanvullings op ruvoerfermentasie
en verteringsmaatstawwe ondersoek is. In die eerste studie is ‘n in vitro gasproduksieprotokol gebruik om
die invloed van suiker (melasse), stysel (mieliemeel) en pektien (sitruspulp) op totale gasproduksie (b) en
tempo van gasproduksie (c) van verskillende ruvoersubstrate te bepaal. Ruvoersubstrate wat gebruik is,
was koringstrooi (WS), hawerhooi (OH), lusernhooi (LUC), raaigras (RYE) en kikuyugras (KIK). Die drie
energiebronne, sowel as ‘n kontrole (geen energiebron), is in vitro geïnkubeer saam met elk van die
genoemde ruvoere. Rumenvloeistof is verkry van twee lakterende Holsteinkoeie, wat ‘n dieet ontvang het
bestaande uit hawerhooi, koringstrooi en ‘n kragvoermengsel. Ruvoere is alleen en/of in kombinasie met
melasse (0.1412 g DM), sitruspulp (0.1425 g DM) of mieliemeel (0.125 g DM) in glasbottels afgeweeg en vir
72 uur geïnkubeer. Die massas van die energiebronne is op ‘n energie-ekwivalente basis bereken. Leë
bottels wat geen substraat bevat het nie, is ingesluit om te korrigeer vir gasproduksie afkomstig vanaf
rumenvloeistof alleen. Substrate is in 40 ml van ‘n buffermedium, 2 ml reduserende oplossing en 10ml
rumenvloeistof geïnkubeer. Gasdruk is elke vyf minute outomaties aangeteken deur gebruik te maak van ‘n
drukmetersisteem en die metode is gebasseer op die Reading gasdruktegniek. Gasdruk is omgeskakel na
gasvolume deur gebruik te maak van ‘n voorafbepaalde regressievergelyking. In die eerste proef het totale
gasproduksie die gas wat deur die onderskeie energiebronne geproduseer is, ingesluit. In die tweede proef
is gasproduksie afkomstig van die energiebronne afgetrek van totale gasproduksie, om sodoende die invloed
van die energiebronne per se op die gasproduksie van die onderskeie ruvoersubstrate, te bepaal. Data is
met behulp van twee nie-liniëre modelle gepas. Betekenisvolle ruvoer x energie-interaksies is in albei
proewe waargeneem vir die nie-liniëre parameter b (gasproduksie) in Model 1, en vir b en L (sloerfase) in
Model 2. In die eerste proef het die energiebronne se hoë fermentasie gelei to ‘n verhoging in b (Model 1 &
2) van LUC en WS. Energie-aanvullings het die c-waarde van die onderskeie ruvoere verskillend beïnvloed,
met WS wat die mees opvallende effek gehad het. Al die energiebronne het die c-waarde van WS verhoog,
ongeag watter model gebruik is. Energiebronne het geen invloed op die L-waarde van LUC, OH of RYE
gehad nie, maar het wel die L-waarde van WS en KIK verlaag. In die tweede proef het mieliemeel geen
invloed op die b-waarde van enige van die ruvoere gehad nie (Model 1 & 2), terwyl melasse (Model 1 & 2)
die b-waarde van alle ruvoere verlaag het, en sitruspulp (Model 1 & 2) OH en RYE se b waardes verlaag het
tot laer as die kontroles. Melasse het geen invloed op die c-waarde van die onderskeie ruvoersubstrate
gehad nie, terwyl sitruspulp (Model 1 & 2) die c-waarde van OH, en mieliemeel die c-waarde van OH en KIK,
verhoog het. Energiebronne het slegs ‘n invloed op die sloerfase in WS en KIK gehad, waar dit L verlaag
het tot laer waardes as dié van die kontroles. Daar is gevind dat ruvoer-fermenteerbaarheid verskillend
beïnvloed word deur verskillende energiebronne. Bogenoemde resultate kan in die praktyk betekenisvolle
invloede hê op rumengesondheid en melkproduksie en die data wat verkry is, kan potensieël gebruik word
as riglyne in voerformulerings.
In die tweede studie is in vitro verteerbaarheidsproewe gedoen om die effek van suiker (molasse en
sukrose), stysel (mieliemeel en mieliestysel) en pektien (sitruspulp en sitrus-pektien) op neutraalonoplosbare
vesel (NDF) en droë materiaal (DM) degradeerbaarheid van ruvoere, te bepaal.
Ruvoersubstrate wat gebruik is, was WS, OH, LUC, RYE en KIK. Rumen vloeistof is verkry van twee
lakterende Holstein koeie, wat ‘n dieet ontvang het bestaande uit hawerhooi, koringstrooi en ‘n konsentraat
mengsel. Die in vitro degradeerbaarheidsproef is gedoen met ‘n ANKOM Daisy II inkubator.
Ruvoersubstrate is geïnkubeer met of sonder die onderskeie energiebronne vir 24, 48 en 72 uur. Die
substrate is geïnkubeer in 1076 ml buffer medium, 54 ml reduserende oplossing en 270 ml rumen vloeistof.
Residue is gewas, gedroog en geanaliseer vir NDF. In die proef met toegepaste energiebronne (molasse,
mieliemeel en sitruspulp), was daar ruvoer x energiebron interaksies. Toegepaste energiebron aanvullings
het almal DMD van ruvoersubstrate (24 en 72 uur) verbeter, uitsluitend vir RYE wat aangevul is met
mieliemeel (24 uur) en sitruspulp (24 uur). Van al die ruvoersubstrate het molasse die grootste effek gehad
op DMD. Mieliemeel aanvullings het geen effek gehad op neutraal-onoplosbare vesel degradeerbaarheid
(NDFD) van ruvoersubstrate nie, behalwe vir ‘n verbetering in NDFD van LUC by 72 uur. Molasse het NDFD
van lucern by 24 uur verbeter, maar geen effek gehad op ander ruvoersubstrate nie. Sitruspulp het NDFD
van OH (72 uur), asook LUC en WS (24 & 72 uur) verbeter. Daar word beweer dat die NDF van
energiebronne meer verteerbaar is as die van ruvoersubstrate, en dat die verbetering in NDFD waardes
toegeskryf kan word aan die bydraes van energiebronne se NDFD. Weidingsgrasse (RYE & KIK) het oor die
algemeen ‘n hoër NDFD as hooie en strooi gehad. Rumen mikrobes blyk ook om dié grasse vinniger te
verteer as lae kwaliteit hooie en strooi, wat gevolglik die hoër NDFD verduidelik. In die proef met suiwer
energiebronne (sukrose, mieliestysel en sitrus-pektien) is ruvoer x energiebron interaksies waargeneem.
Energiebronaanvullings het DMD by 24 en 72 uur verbeter, buiten vir RYE en KIK (72 uur). Weidingsgrasse
het hoër NDFD as LUC, OH en WS. By 72 uur was die NDFD van LUC 37.1%, OH 42.5%, WS 40.3%, in
vergelyking met 70.5% vir KIK en 64.9% vir RYE. ‘n Moontlike verklaring vir die hoër NDFD van KIK en
RYE, is omdat dit vars gesnyde material is, geoes na slegs 28 dae hergroei. Oor die algemeen het sukrose
(24 & 72 uur) en sitrus-pektien (72 uur) geen effek gehad op NDFD van ruvoersubstrate nie, terwyl stysel en
pektien aanvullings tot OH (24 uur), en stysel aanvullings tot WS (24 & 72 uur) NDFD verlaag het. Daar
word hipotetieseer dat mikrobes eers die vinnig fermenteerbare energiebronne fermenteer, voordat hulle
ruvoer NDF aanval. Hierdie studie beweer dat ruvoer NDFD waardes nie vas is nie, en dat dié waardes
beïnvloed mag word deur energiebron aanvullings.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4028 |
| Date | 03 1900 |
| Creators | Malan, Marcia |
| 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 | English |
| Type | Thesis |
| Format | 72 p. :ill. |
| Rights | University of Stellenbosch |
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