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Effect of cottonseed oilcake meal on ostrich growth performance, meat chemical composition and sensory attributesSchoon, Katryn 12 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This research study consists of three investigations with regard to ostrich (Struthio camelus var.
domesticus) production, meat quality and the processing of ostrich meat into a value added meat
product.
The first study was conducted in order to establish whether the gradual replacement of soybean
oilcake meal with cottonseed oilcake meal (CSOCM) as a protein source in the diet of slaughter
ostriches would affect ostrich growth performance and meat quality. A total of 105 ostriches were
divided into five feeding groups according to the CSOCM inclusion level: Control (0% CSOCM),
3%, 6%, 9% and 12% CSOCM, and fed with experimental diets from 6 to 13 months of age. As a
result of feeding CSOCM, the final live weight and the average daily gain significantly increased in
the 12% CSOCM group compared to the other treatment diets. The proximate composition,
cholesterol content, mineral and fatty acid profile of the meat remained unaffected. Considering all
the results, CSOCM may be used as an alternative protein source to soybean oilcake meal in
ostrich nutrition, resulting in decreased feed costs.
Secondly, a descriptive sensory analysis, together with chemical and physical measurements, was
performed to determine whether the manipulation of the fatty acid composition in the fan fillet
(Iliofibularis muscle) as a result of feeding CSOCM would be detected on a sensory level. Two
levels of CSOCM were investigated; 0% as a control and 9% CSOCM. No significant differences
were found for the physical measurements (cooking loss (%) and shear force) as well as for the pH
and proximate composition of the raw fan fillet. The Control group presented a higher (P<0.05)
mono-unsaturated fatty acid (MUFA) content in the cooked fan fillet whereas the 9% CSOCM
group showed a favourable increased (P<0.05) poly-unsaturated fatty acid (PUFA) content when
compared to the cooked Control samples. As a result, the poly-unsaturated:saturated fatty acid
(PUFA:SFA) ratio in the 9% CSOCM group was also higher (P<0.05). No differences (P>0.05)
were found between the treatments for the n-6:n-3 (omega 6 to omega 3) ratio. The 9% CSOCM
group had a more intense beef aroma, had a higher level of initial and sustained juiciness as well
as increased tenderness (P<0.05). Inclusion of 9% CSOCM resulted in a favourable cooked ostrich
fan fillet.
Finally, the effect of feeding CSOCM on a processed ostrich meat product was investigated. Fan
fillet (Iliofibularis muscle) from 13 month old birds receiving no cottonseed oilcake meal (Control) or
9% cottonseed oilcake meal (9% CSOCM) was used. Olive oil was used as a replacement for
pork fat, and warthog (Phacochoerus africanus) meat was used to replace commercial pork meat
in the production of a semi dry sausage, cabanossi. Olive oil was included at three levels (0%, 1%
and 2%). Six treatments were investigated: Control 0% olive oil, Control 1% olive oil, Control 2%
olive oil, 9% CSOCM 1% olive oil, 9% CSOCM 2% olive oil en 9% CSOCM 2% olive oil. The
Control and 9% CSOCM ostrich meat did not differ significantly in chemical composition nor fatty
acid profile. After smoking and drying the fat content in the cabanossi containing 0%, 1% and 2% olive oil averaged 7.2%, 7.45% and 8.65% respectively. Processed meat products containing less
than 10% fat are classified as a low-fat meat product. Olive oil is a mono-unsaturated vegetable oil
containing mainly Oleic acid (C18:1n9c), and low quantities of saturated fatty acids and
polyunsaturated fatty acids. Total mono unsaturated fatty acids in the cabanossi increased from
47.0% to 73.0% of total fat, whilst total saturated fatty acids and total polyunsaturated fatty acids
decreased from 40.6% to 19.9% and 11.6% to 6.6% respectively as olive oil increased from 0% to
2%. The inclusion of olive oil at 2% resulted in cabanossi with increased (P<0.05) tenderness,
juiciness and cured red meat colour, all factors that appeal greatly to the consumer. Overall flavour
was not adversely affected by the inclusion of olive oil.
This investigation indicated that the use of CSOCM had no negative effect on the production
performance of ostriches whilst a 9% CSOCM inclusion level resulted in meat that was found to be
favourable by a trained sensory panel. Furthermore, the use of CSOCM as a feed component also
had no negative effect on a processed product (cabanossi) derived from the meat obtained from
the birds fed this feed component. The CSOCM used in this investigation had low levels of
gossypol (10 to 20ppm) and more research is required on the effect of the use of CSOCM with
higher levels of gossypol on the production performance of ostriches. / AFRIKAANSE OPSOMMING: Die studie het bestaan uit drie ondersoeke met betrekking tot volstruis (Struthio camelus var.
domesticus) -produksie, -vleiskwaliteit en die vervaardiging van waarde-toegevoegde
geprosesseerde volstruis-vleisprodukte.
Die doel van die eerste studie was om vas te stel of die geleidelike vervanging van sojaboonoliekoekmeel
met katoensaad-oliekoekmeel (CSOCM) as ‘n proteïenbron in die voeding van
volstruise, die groeipersentasie en vleiskwaliteit van die Iliofibiularis spier (fan fillet) sal affekteer. ‘n
Totaal van 105 volstruise is verdeel in vyf voedingsgroepe volgens die katoensaad oliekoekmeel
insluitingsvlak: Kontrole (0% CSOCM), 3%, 6%, 9% en 12% CSOCM. Die onderskeie
voedingsgroepe was van ses tot 13 maande ouderdom op die eksperimentele voere geplaas. Die
resultate het aangedui dat die voëls in die 12% CSOCM behandelingsgroep ‘n betekenisvolle
(P<0.05) toename in finale lewende massa asook gemiddelde daaglikse toename gehad het. Die
proksimale samestelling, cholesterol-inhoud, mineraal- en vetsuursamestelling van die vleis was
nie geaffekteer deur die insluiting van CSOCM nie. Die CSOCM kan dus wel as ‘n alternatiewe
proteïenbron in die voeding van volstruise gebruik word. Laasgenoemde bevinding kan ook lei tot
verlaagde voerkostes, aangesien CSOCM heelwat goedkoper is as sojaboon-oliekoekmeel.
Die tweede deel van die studie was van ‘n chemiese asook sensoriese aard. ‘n Beskrywende
sensoriese analiese is uitgevoer om vas te stel of die manipulering van die vetsuursamestelling in
die volstruis fan fillet as gevolg van die CSOCM sensories waargeneem kan word. Die chemiese
en fisiese eienskappe van die vleis is ook ondersoek. Twee vlakke van CSOCM inhoud is
ondersoek; 0% (as kontrole) en 9% CSOCM. Geen betekenisvolle verskille is gevind vir die fisiese
vleiskwaliteit (kookverliespersentasie en taaiheid), asook vir die proksimale samestelling en pH
van die fan fillet nie. Die gekookte fan fillet van die Kontrole behandeling het ‘n betekenisvolle
(P<0.05) toename in mono-onversadigde vetsure (MUFA) getoon en die 9% CSOCM het ‘n
voordelige toename in poli-onversadigde vetsuur-inhoud (PUFA) gehad. Die poli-onversadigde tot
versadigde vetsuurverhouding (PUFA:SFA) was as ‘n gevolg ook betekenisvol hoër. Geen
verskille (P>0.05) is opgemerk in die omega-6 tot omega-3 poli-onversadigde vetsuurverhouding
(n-6:n-3) nie. Met betrekking tot die sensoriese eienskappe het die 9% CSOCM ‘n meer
opvallende beesvleis aroma, hoër vlakke van aanvanklike sappigheid en ook sagter vleis in
vergelyking met die kontrole behandeling gehad (P<0.05). Insluiting van 9% CSOCM het gelei tot
‘n gekookte volstruis fan fillet van voornemende kwaliteit.
Laastens is daar ondersoek ingestel op die vervanging van varkvet met olyfolie in die
vervaardiging van ‘n volstruis cabanossi. Chemiese asook sensoriese analises is uitgevoer op die
gedroogde en gerookte volstruis cabanossi. Vir die vervaardiging van laasgenoemde produkte is
die fan fillet van 13 maande oue voëls van die Kontrole (0% CSOCM) en 9% CSOCM
behandelings gebruik. Addisioneel tot die volstruisvleis is daar ook vlakvarkvleis (Phacochoerus
africanus) gebruik om die kommersiële varkvleis te vervang. Olyfolie was ingesluit teen drie vlakke (0%, 1% en 2% van die totale mengsel). Ses behandelings was ondersoek: Kontrole 0% olyfolie,
Kontrole 1% olyfolie, Kontrole 2% olyfolie, 9% CSOCM 1% olyfolie, 9% CSOCM 2% olyfolie en 9%
CSOCM 2% olyfolie. Daar was geen verskille (P>0.05) in die chemiese en vetsuursamestellings
van die Kontrole en 9% CSOCM volstruisvleis nie. Na die droging en rooksiklus was die
gemiddelde vet-inhoud van die 0%, 1% en 2% olyfolie cabanossi monsters onderskeidelik 7.2%,
7.45% en 8.65%. Geprosesseerde vleisprodukte met ‘n vet-inhoud van minder as 10% word in die
kommersiële vleisindustrie na lae vet vleisprodukte verwys. Olyfolie is baie ryk aan MUFA, veral
Oleïensuur (C18:1n9c) en dit bevat ook lae hoeveelhede SFA en PUFA. Die totale MUFA inhoud
in die cabanossi het toegeneem van 47.0% tot 73.0% terwyl die totale SFA en PUFA
onderskeidelik afgeneem het van 40.6% tot 19.9% en 11.6% tot 6.6%, met ‘n olyfolie toename van
0% tot 2%. Die insluiting van olyfolie teen 2% het gelei tot ‘n sagter cabanossi wat meer sappig
was met ‘n meer opvallende rooi gekuurde vleiskleur, wat almal eienskappe is wat dié produk
meer aantreklik maak vir die verbruiker.
Hierdie studie het aangedui dat CSOCM geen negatiewe effek gehad het op die produksie van
volstruise nie. Volstruisvleis van die behandelingsgroep wat CSOCM teen 9% van die dieet
ontvang het, het wel vleis geproduseer wat as aanvaarbaar aanskou was deur ‘n opgeleide
sensoriese paneel. Die gebruik van CSOCM as ‘n voerbestandeel het ook geen negatiewe effek
gehad op ‘n geprosesseerde produk (cabanossi) gemaak van die volstruisvleis nie. Die CSOCM
wat in die huidige studie gebruik is, het baie lae vlakke van gossypol (10 – 20dpm) gehad en
verdere ondersoek is noodsaaklik om die effek van CSOCM met hoër vlakke van gossypol op die
produksie van volstruise te bevestig.
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The manipulation of ostrich meat quality, composition and shelf lifeJoubert, Marisa 12 1900 (has links)
Thesis (MScVoedselwet)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Two experiments were conducted in order to manipulate the physical and chemical
properties and shelf life of ostrich meat.
Experiment 1: The effect of dietary fish oil rich in n-3 fatty acids on the organoleptic,
fatty acid and physicochemical characteristics of ostrich meat.
The diet of four ostrich groups (15 birds per group), approximately 3 months of age (ca. 41
kg live weight) grazing a predominantly oats pasture, was supplemented with a diet
containing 6.7% fish oil. The birds received a supplement of either 0 (diet 1), 800 (diet 2),
1600 (diet 3) or 2400 g (diet 4) DM/day resulting in the consumption of 0 (diet 1), 14.5 (diet
2), 29 (diet 3) and 43.5 (diet 4) g fish oil per day. The ostriches were slaughtered at 10
months of age (ca. 70 kg live weight).
An increase in the amount of fish oil consumed was found to have had statistically no
significant effect on the sensory characteristics of the M. iliofibularis, although there was a
tendency towards an increase in ‘fishiness’, for both aroma and flavour. However,
increased concentrations of fish oil had a significant effect on the aroma and flavour of the
abdominal fat pads. The muscle pHf and muscle lightness (L*) reflected a significant
reduction with increased fish oil levels. The increased feed intake, on the other hand, had
no effect on the chemical composition (moisture, protein, fat and ash content) of the meat.
The fatty acid profile of both fat and meat was affected by the consumption of fish oil. The
SFA concentration increased, while the PUFA concentration decreased, with an increase
in feed intake. The MUFA concentration remained constant for all four groups.
Experiment 2: The effect of dietary vitamin E and the type of packaging on the
sensory quality, physicochemical composition and shelf life of ostrich meat.
Two groups of ostriches (35 birds per group; ca. 3 months old) were fed diets containing
either 40 mg/kg feed vitamin E (control) or 150 mg/kg feed Vitamin E for nine months. The
birds were slaughtered at 12 months of age.
The effect of different the levels of vitamin E and heat shrink treatment of vacuum
packaging material on the shelf life of refrigerated (0°C) ostrich M. flexor cruris lateralis,
was evaluated over 81 days. Vitamin E and heat shrink treatments were found to have
had no significant effect on the sensory characteristics; off-meat aroma, sourness,
juiciness and mealiness. Rancidity was found to be slightly more pronounced (although not statistical significant) in the vitamin E and heat shrink groups than in the feed control
and vacuum-packed groups. A significant decrease in the organoleptic quality of the
meat, over a 40 day shelf life period, was observed. The pH and muscle tenderness
showed a significant reduction with increased storage time. The purge loss in the package
increased over time with no change in muscle drip loss. The colour, conjugated dienoic
acid and fatty acid content showed no significant changes over time or with regards to
treatment. The total viable counts and coliform numbers in the muscle increased over
time, with the coliforms being slightly suppressed by the inclusion of vitamin E in the diet.
A microbiological safe shelf life of 40 days at 0°C was obtained. / AFRIKAANSE OPSOMMING: Twee eksperimente is uitgevoer om die fisiese en chemiese eienskappe, asook die
rakleeftyd van volstruisvleis, te manipuleer.
Eksperiment 1: Die effek van visolie, ryk aan n-3 vetsure, op die organoleptiese,
vetsuur- en fisies-chemiese eienskappe van volstruisvleis.
Die dieet van vier groepe volstruise (15 voëls per groep), ongeveer 3 maande oud (ca. 41
kg lewende massa) wat ‘n hawer weiding bewei het, is aangevul met ‘n
byvoedingsmengsel wat 6.7% visolie bevat en in toenemende hoeveelhede vir die groepe
volstruise gevoer is. Die voëls het ‘n aanvulling van 0 (dieet 1), 800 (dieet 2), 1600 (dieet
3) of 2400 g (dieet 4) DM/dag ontvang wat gelei het tot ‘n inname van 0 (dieet 1), 14.5
(dieet 2), 29 (dieet 3) en 43.5 (dieet 4) g visolie per dag. Die volstruise is op ‘n ouderdom
van 10 maande geslag (ca. 70 kg lewende massa).
‘n Toename in die hoeveelheid visolie ingeneem, het geen statisties betekenisvolle
effek op die sensoriese eienskappe van die M. ilifibularis gehad nie, alhoewel daar ‘n
tendens was vir ‘n toename tot ‘n ‘visagtige’ aroma en smaak. ‘n Toename in die
konsentrasie visolie het egter ‘n betekenisvolle effek op die ‘visagtige’ aroma en smaak
van die abdominale vet neerslae gehad. Die spier pHf en spier ligtheid (L*) het ‘n
betekenisvolle afname met toename in voer inname getoon. Die verhoogde olie inname
het egter geen effek op die chemiese samestelling (vog-, proteïen-, vet- en asinhoud) van
die vleis gehad nie. Die vetsuurprofiel van beide die abdominale vet neerslae en die vleis
is deur die inname van visolie verander. Die versadigde vetsuurkonsentrasie het verhoog
terwyl die poli-onversadigde vetsuurkonsentrasie verlaag het met ‘n toename in
rantsoenvlakke. Die mono-onversadigde vetsuurkonsentrasie het egter konstant gebly vir
al vier groepe.
Eksperiment 2: Die effek van vitamien E en die tipe verpakking op die sensoriese
kwaliteit, fisies-chemiese samestelling en rakleeftyd van volstruisvleis.
Twee groepe volstruise (35 voëls per groep, ongeveer 3 maande oud) het voere oor ‘n
tydperk van nege maande ontvang wat 40 mg vitamien E/kg voer (kontrole) of 150 mg
vitamien E/kg voer bevat het. Die voëls is op 12 maande ouderdom geslag.
Die effek van die verskillende vlakke van vitamien E en hitte-behandeling van die
verpakkings materiaal op die rakleeftyd van verkoelde (0°C) volstruis M. flexor cruris lateralis, is oor 81 dae geëvalueer. Vitamien E en die hitte-behandeling het geen
betekenisvolle effek op die organoleptiese eienskappe (af-vleis aroma, suurheid,
sappigheid en melerigheid) gehad nie. Galsterigheid was ‘n bietjie meer gedefinieerd
(anie-betekenisvol) in die vitamien E en hitte behandelde groepe as in die rantsoen
kontrole en vakuum verpakte vleis. ‘n Betekenisvolle afname is waargeneem in die
organoleptiese kwaliteit van die vleis oor ‘n 40 dae rakleeftyd periode. Die pH en taaiheid
van die spier het betekenisvol afgeneem met ‘n toename in bergingsperiode. Die drup
verlies tydens verpakking het ook oor tyd toegeneem, terwyl geen verandering in die
analitiese drup verlies van die spier verkry is nie. Die kleur, gekonjugeerde dieensuur en
vetsuursamestelling het geen verandering oor tyd of ten opsigte van behandeling getoon
nie. Die Totale Lewendig Seltelling en coliforme het toegeneem oor tyd, terwyl die
coliforme deur die byvoeging van vitamien E tot ‘n mate onderdruk is. ‘n Mikrobiologies
veilige rakleeftyd van 40 dae is verkry.
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The effect of different levels of supplementary feed on the production of finisher ostriches (Struthio camelus) grazing irrigated lucerne (Medicago sativa) pasturesStrydom, Marline 12 1900 (has links)
Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of this study was to evaluate the production of slaughter ostriches in a grazing environment at
different levels of supplementary feed.
Two grazing trials were conducted. In the first trial, one group of finisher ostriches (six months old) was put into
a feedlot and received a complete finisher diet. The other four groups were allowed to graze lucerne pasture
(stocking rate of 15 birds/ha) with 1500, 1000, 500, and 0g supplementary feed/bird/day. Pasture production
and intake were measured. There was no difference (P >0.05) between the end mean live weights of the feedlot
ostriches and those two grazing groups receiving 1500 or 1000g supplementation. The average daily gain
(ADG) of the group receiving 1000g supplementation was lower (P <0.05) than the ADG of the group receiving
1500g supplementation, but all three groups reached a mean target slaughter weight of 95kg within the 154 days
of the study. Therefore, pastures together with the correct supplementation (at least 1000g/bird/day) can
replace complete feeds in the finishing phase of slaughter ostriches and can play an important role in the
production of these birds. For lucerne intake, a quadratic relationship (P <0.01) was found between pasture dry
matter (DM) intake (g/bird/day) and supplementary feed intake (g/bird/day). The maximum lucerne intake level
(1692.8g/bird/day) was achieved at 619.6g supplementary feed/bird/day.
In the second grazing trial, finisher ostriches were allowed to graze lucerne pastures at two different stocking
rates (10 and 15 birds/ha) while receiving either 0 or 800g supplementary feed/bird/day. Ostriches receiving
supplementation had higher (P <0.05) mean end live weights than ostriches receiving no supplementation.
Ostriches receiving supplementation reached a mean target slaughter weight of 95kg within the timespan of the
trial, but ostriches receiving no supplementation did not. Stocking rate had no influence on mean end live weight
of the birds. An interaction (P <0.05) was found between the level of supplementation and stocking rate for ADG
of the birds. Stocking rate influenced ADG only for birds receiving no supplementation. As stocking rate
increased, ADG of birds receiving no supplementation declined. Results of the pasture data indicated an
increasing level of replacement of grazed lucerne DM by supplementary feed as the trial progressed and this
was more pronounced at the higher stocking rate of 15 birds per hectare. A high stocking rate seems to have
had a gradual depressing effect on lucerne DM production, while the less severe levels of defoliation at a lower
stocking rate promoted lucerne DM production.
A digestibility trial was conducted with mature ostriches (12 months old) to investigate the effect of
supplementation on intake and digestibility of nutrients, as well as to investigate the substitution effect that
ostriches may display when they receive supplementary feed in addition to grazing. The same dietary
treatments as in the first grazing study were given to ostriches while they were kept in metabolism crates. These
diets were also fed to 20-week old roosters to obtain energy values for these diets for roosters. These energy
values would be used to predict ostrich energy values for the same diets by means of a regression equation. For the roosters, each diet treatment was mixed with 50% maize to prevent digestive disorders and ensure
maximum feed intake. Ostriches started to substitute supplementary feed for pasture when supplementation
was supplied at levels higher than 62% (i.e. 1000g supplementary feed/bird/day) of total feed intake. For each
increase of 100g in supplementary feed intake, pasture was replaced at a rate of 4.9%. Higher (P <0.05) total
feed intakes were reached by ostriches if they grazed lucerne pastures and received supplementation than if
they grazed pasture alone. Pasture grazing alone had lower (P <0.05) dry matter digestibility (DMD) and
apparent metabolizable energy (AME) values for both ostriches and roosters than if pastures were supplied with
a supplement. A significant stepwise regression could not be computed for the prediction of ostrich AME values
from rooster AME values.
The economics of different feeding systems (extensive versus intensive) were evaluated with an economic
analysis, which was based on the same materials and methods and results of the first grazing trial. A margin
above feed cost (MAFC) analysis was performed to evaluate the economic viability of the different feeding
systems. The present value (PV) of the MAFC for the pasture-based system with 1000g/bird/day
supplementation was only 8.3% lower than that of the feedlot system over a period of six years, while the PV of
the cost of the same pasture-based system was 78.4% lower than that of the feedlot system. Birds finished on
lucerne pasture with 1000g supplementation led to a saving of 57% in feeding costs if compared to a feedlot
system. A sensitivity analysis of the MAFC revealed that the pasture-based system was less sensitive to
changes in feeding costs than the feedlot system. Therefore, the unique circumstances of each ostrich producer
will play a role in the decision whether to raise ostriches in a feedlot or on pastures. / AFRIKAANSE OPSOMMING: Die produksie van slagvolstruise in ‘n ekstensiewe weidingsstelsel met verskillende vlakke van aanvullende
voeding is gedurende hierdie studie ge-evalueer.
Twee weidingsstudies is uitgevoer. In die eerste studie is een groep afrondingsvolstruise (ses maande oud) in
‘n voerkraal geplaas en ‘n volledige afrondingsdieet gevoer. Die ander vier groepe is op besproeide
lusernweiding geplaas (teen ‘n weidigtheid van 15 voëls/ha) en het onderskeidelik 1500, 1000, 500 en 0g
aanvullende voeding/voël/dag ontvang. Weidingproduksie en -inname is gemeet. Daar was geen verskil (P
>0.05) tussen die eindgewigte van die voerkraal volstruise en dié van die weidende voëls wat onderskeidelik
1500 en 1000g aanvullende voeding ontvang het nie. Die gemiddelde daaglikse toename (GDT) van die groep
weidende voëls wat 1000g aanvullende voeding ontvang het was laer (P <0.05) as die GDT van die groep
weidende voëls wat 1500g aanvullende voeding ontvang het, maar al drie hierdie groepe het ‘n gemiddelde
teiken slaggewig van 95kg bereik binne die 154 dae van die studie. Weiding, tesame met die korrekte
aanvullende voeding (van ten minste 1000g/voël/dag) kan volvoer rantsoene in die afrondingsfase van
slagvolstruise vervang en kan dus ‘n belangrike rol speel ten opsigte van die produksie van hierdie voëls. Vir
lusern inname is ‘n kwadratiese passing (P <0.01) tussen weiding droë materiaal (DM) inname (g/voël/dag) en
aanvullende voeding inname (g/voël/dag) gevind. Die maksimum lusern inname (1692.8g/voël/dag) is bereik
wanneer voëls 619.6g aanvullende voeding/voël/dag ingeneem het.
In die tweede weidingsstudie, is afrondingsvolstruise (6 maande oud) toegelaat om lusern te bewei teen twee
verskillende weidigthede (10 en 15 voëls/ha) en het ook 0 of 800g aanvullende voeding/voël/dag ontvang.
Volstruise wat aanvullende voeding ontvang het, het hoër (P <0.05) gemiddelde eindgewigte bereik as volstruise
wat geen aanvullende voeding ontvang het nie. Volstruise wat aanvullende voeding ontvang het, het ook die
teiken slaggewig van 95kg bereik binne die tydsduur van die studie, terwyl die volstruise wat geen aanvullende
voeding ontvang het nie, nie daarin kon slag nie. Weidigtheid het nie ‘n invloed (P >0.05) gehad op die
eindgewigte van die voëls nie, maar ‘n interaksie (P <0.05) is gevind tussen vlak van aanvullende voeding en
weidigtheid wat GDT van die voëls betref. Weidigtheid het GDT beïnvloed slegs vir volstruise wat geen
aanvullende voeding ontvang het nie. Soos die weidigtheid van die voëls wat geen aanvullende voeding
ontvang het nie, toegeneem het, het die GDT van hierdie voëls afgeneem. Ontleding van die weidingsdata het
‘n toenemende vlak van verplasing van die weiding met aanvullende voeding getoon soos die studie gevorder
het en dit was meer merkbaar by die hoër weidigtheid. Die hoër weidighteid het ook gelei tot ‘n geleidelike
afname in lusern DM produksie, terwyl die minder aggressiewe vlakke van ontblaring by die laer weidigtheid
lusern DM produksie bevorder het.
‘n Verteringsstudie is gedoen met volwasse volstruise (12 maande oud) om die invloed van aanvullende voeding
op inname en verteerbaarheid van nutriente te toets, asook om die substitusie effek wat volstruise mag toon wanneer hulle aanvullende voeding ontvang op weiding, te ondersoek. Dieselfde dieet behandelings as in die
eerste weidingsstudie is vir die volstruise gegee terwyl hulle in metabolisme kratte aangehou is. Hierdie diëte is
ook aan 20-week oue hane gevoer om die energie waardes van die diete vir hane te verkry. Hierdie
energiewaardes sal dan gebruik word om volstruis energiewaardes te voorspel vir dieselfde diëte met behulp
van ‘n regressie vergelyking. Vir die hane is elke dieet gemeng met 50% mielies om inname te handhaaf en
spysverteringsstoornisse te voorkom. Volstruise het weiding begin verplaas met aanvullende voeding sodra die
vlak van aanvullende voeding hoër as 62% (d.i. meer as 1000g aanvullende voeding/voël/dag) van die totale
inname van die voëls was. Vir elke 100g toename in aanvullende voeding, word weiding verplaas teen ‘n tempo
van 4.9%. Weiding, tesame met aanvullende voeding, het gelei tot hoër totale droë material (DM) voerinnames
by volstruise as wanneer weiding alleen beskikbaar was. Wanneer weiding alleen voorsien was, was daar laer
(P <0.05) verteerbaarhede van DM en waarskynlike metaboliseerbare energie (WME) waardes vir beide
volstruise en hane as wanneer die weiding voorsien word met aanvullende voeding. Geen betekenisvolle
stapsgewyse regressie kon gevind word om volstruis energie waardes uit hoender energie waardes te voorspel
nie.
Die ekonomie van verskillende sisteme (ekstensief versus intensief) is in hierdie studie vergelyk en is gebaseer
op dieselfde materiaal en metodes en resultate van die eerste weidingsstudie. ‘n Marge bo voerkoste analise is
gebruik om die ekonomiese lewensvatbaarheid van die sisteme met mekaar te vergelyk. Die huidige waarde
van die marge bo voerkoste van die weidingssisteem waar 1000g aanvullende voeding gevoer word was 8.3%
laer as dié van die voerkraal sisteem oor ‘n periode van ses jaar. Daarteenoor was die huidige waarde van die
koste van dieselfde weidingssisteem 78.4% laer as dié van die voerkraal sisteem. Die weidingssisteem waar
volstruise 1000g aanvullende voeding ontvang het, het ‘n besparing van 57% in voerkoste getoon wanneer dit
met die voerkraal volstruise vergelyk is. ‘n Sensitiwiteitsanalise van die marge bo voerkoste het getoon dat die
weidingssisteem minder sensitief is vir wisselende voerkoste as die voerkraal sisteem. Die unieke
omstandighede van elke produsent sal ‘n rol speel in sy keuse om volstruise op weiding of in ‘n voerkraal af te
rond.
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