Thesis (MScAgric) -- University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Lipids remain one of the most important nutrients required by broilers. The growing awareness that some Western
societies have too high a dietary ratio of n-6/n-3 polyunsaturated fatty acids is of direct relevance to broiler nutrition and
lipid metabolism. Meaningful quantities of n-3 polyunsaturates have been incorporated into major poultry tissues, so that
the production of broiler meat with high n-3 polyunsaturates becomes advantageous for the broiler industry as they are
perceived as having a 'healthier' lipid profile. Unfortunately, such broiler meat is rather susceptible to oxidative
deterioration, and oxidation often determines shelf life of poultry meat products. The addition of a-tocopherol (vitamin E)
to broiler diets is an effective means of improving the oxidative stability of broiler meat. Elevated a-tocopherol levels in
broiler feeds increase tissue concentrations thereof resulting in improved stability of membranal structures which may be
expected to increase the oxidative stability of broiler meat and meat products.
Three investigations were done at Mariendahl Poultry Research Station in Stellenbosch. The broilers were kept in 1 x 0.4
x 0.5 m cages in a broiler rearing house. All the trials started with day-old chicks, except experiment 1 where 3-week old
broilers were used. At the end of trials 2 and 3 the 6-week old broilers were slaughtered and the carcasses prepared for
chemical analysis.
Experiment 1: Metabolisabie energy of Canola acid oil and Famarol acid oil for broiler chickens.
In trials with 21-day-old male broilers the true metabolisabie energy value, corrected for nitrogen retention (TMEn) was
determined by the balance method for Canala acid oil (CAO) and Famarol acid oil (FAO). The trials were duplicated, each
time using different samples of the two oils from the same source (experiment 1 and 2). Each of the two oils were blended
in two ratios with a basal diet to form the test diets, viz. 100% Basal; 96% Basal: 4% Oil; 92% Basal: 8% Oil. In
experiment 3, 50 % bran was added to the maize to form the basal diet. The balance trials lasted for 3 days after an
adaptation period of 4 days. The TMEn values determined by regression for the broilers of CAO did not differ significantly
(P>0.05) between experiments 1 and 2. However, the value for experiment 3 was significantly (P<0.05) higher than those
for experiments 1 and 2. The TMEn values of FAO also did not differ significantly (P>0.05) between experiments 1 and 2,
although the value for experiment 3 was significantly higher than that of experiment 1. The addition of 50 % bran to the
basal diet in experiment 3 could have stimulated the digestive breakdown process and hence increase the secretion of
digestive enzymes. This could lead to an increase in the utilisation of the test lipid and therefore an increase in the TMEn
value. The TMEn values of CAO differed significantly (P<0.05) from those of FAO for all three the experiments (exp.
1:30.6 ± 0.399 MJ/kg for CAO vs. 25.9 ± 0.441 MJ/kg for FAO; expo 2: 31.0 ± 0.633 MJ/kg for CAO vs. 26.1 ± 0.668 MJ/kg
for FAO: expo 3: 32.1 ± 0.867 MJ/kg for CAO vs. 27.1 MJ/kg for FAO).Experiment 2:
of broilers.
The dietary effects of various combinations of Canala acid oil (CAO, a high level of C18:3n-3 and MUFA) and Famarol
Effects of various dietary n-6/n-3 fatty acid ratios on the perfonnance and body composition
acid oil (FAO, a high level of 18:2n-6 and SFA) on tissue fatty acid composition were studied in broiler carcasses and
abdominal fat pads. From day-old to six weeks, chicks were fed one of six diets containing 100% FAO, 80% FAO-20%
CAO, 60% FAO-40% CAO, 40% FAO-60% CAO, 20% FAO-80% CAO, 100% CAO. There were no statistical differences
(P>0.05) in average daily gain (1.71 ± 0.059 g) or feed conversion ratios (1.97 ± 0.051) among dietary groups. No
statistical differences (P>0.05) were found in the chemical proximate composition of the carcasses for the moisture (66.20
± 0.112 %), protein (17.63 ± 0.484 %), lipid (15.92 ± 1.507 %) and ash (0.95 ± 0.115 %) content among dietary groups.
No statistical differences (P>0.05) were found in the chemical proximate composition of the abdominal fat pads for the
moisture (28.77 ± 0.112 %), protein (3.03 ± 0.484 %), lipid (63.32 ± 9.789 %) and ash (0.45 ± 0.135 %) content among
dietary groups. With the increase in dietary CAO levels, the percentages of C18:2n-6 and C20:4n-6 in the carcasses
decreased respectively with 1.78 % from 20.88 % and 0.35 % from 1.05 %, whilst C18:3n-3 and longer chain n-3 fatty
acids such as C20:5n-3 and C22:6n-3 increased respectively with 2.25 % from 1 %, 0.1 % from 0.1 % and 0.67 % from
0.2 %. The same tendency was seen in the abdominal fat pads where C18:2n-6 and C20:4n-6 decreased respectively
with 1.55 % from 20.75 % and 0.98 % from 1.2 % with an increase in dietary CAO, whilst C18:3n-3, C20:5n-3 and
C22:6n-3 increased respectively with 2.13 % from 1.15 %, 0.45 % from 0.03 % and 0.95 % from 0.05 %. The n-3/n-6 ratio
in the carcasses and abdominal fat pads increased respectively with 0.16 % from 0.06 % and 0.19 % from 0.06 % with an
increase in dietary CAO. These results clearly indicate that dietary CAO enriched with a-linolenic acid lower saturated
fatty acids respectively in broiler carcasses and abdominal fat pads with 4.88 % from 31.6 % and 10.63% from 31.1 %,
whilst increasing monounsaturated fatty acids with 3.87 % from 44.95 % and 7.25 % from 46.7 % respectively and
polyunsaturated fatty acids with 1.02 % from 23.45 % and 2.38 % from 23.2 % respectively.
Experiment 3: Effect of dietary vitamin E on the performance of broilers and oxidative stability, colour,
microbiological stability, fatty acid composition and pH of broiler meat during refrigerated and frozen storage.
Experiment 1 was carried out with 220 one-day-old broiler chicks to evaluate the effect of eleven concentrations of vitamin
E (0, 20, 40, 60, 80, 100, 120, 140, 160, 180 and 200 mg a-tocopheryl acetate 1 kg diet) on their production performance
and the oxidative stability of their frozen broiler carcasses. The diets with vitamin E levels 0 to 100 mg were fed from
day-old to 42 days of age while the diets with vitamin E levels 120 to 200 mg were fed from 21 to 42 days of age. The
oxidative stability, evaluated by thiobarbituric acid reactive substances (TBARS) values, was determined after 30, 90, 120
and 150 days of storage at -20°C. There were no statistical differences (P>0.05) in average daily gain (1.85 ± 0.111 g) or
feed conversion ratios (2.29 ± 0.397) among dietary groups. TBARS values increased significantly (P<0.05) with
increasing time of storage (basal diet: day 30 = 1.71 ± 0.51; day 150 = 4.89 ± 0.51), but decreased significantly (P<0.05)
with increasing vitamin E levels (day 150: basal = 4.89 ± 0.51; 100 mg / kg = 1.09 ± 0.27). Experiment 2 was carried out
with day-old broiler chicks to evaluate the effect of five concentrations of vitamin E (0, 40, 80, 120 and 160 mg atocopheryl
acetate / diet) on their performance and the oxidative stability of their refrigerated carcasses. The experimental
diets were fed from day-old to 42 days of age. The oxidative stability, evaluated by TBARS values, colour deterioration
and microbiological stability were determined after 0, 4, 8, 10 and 12 days of storage at 4°C. Fatty acid analysis was done
on the samples of days 0 and 12. There were no statistical differences (P>0.05) in average daily gain (1.88 ± 0.117 g) or
feed conversion ratios (2.37 ± 0.467) among dietary groups. TBARS values increased significantly (P<0.05) with
increasing time of storage, but decreased significantly (P<0.05) with increasing vitamin E levels. There were no statistical
differences (P>0.05) in colour measurements for L* (44.97 ± 0.662), a* (5.23 ± 0.315) or b* (12.76 ± 0.321) values
between treatments. Microbiological counts increased significantly (P<0.05) over time with vitamin E concentration
showing no effect. There were no statistical differences (P>0.05) for any of the fatty acid groups measured (SFA: Day 0 =
26.1 ± 1.13%, Day 12 = 26.1 ± 1.17%; MUFA: Day 0 = 41.4 ± 1.46%, Day 12 = 40.2 ± 2.28%; PUFA: Day 0 = 32.4 ± 1.95%, Day 12 = 33.8 ± 2.52%) among dietary groups. Similarly, none of the fatty acids showed statistical significant
(P>0.05) concentration changes over time. There were no statistical differences (P>0.05) in pH (6.01 ± 0.206) among
dietary groups. / AFRIKAANSE OPSOMMING: Lipiede is steeds een van die mees belangrike voedingstowwe wat deur braakuikens benodig word. Die groeiende
bewuswording dat sekere Westerse gemeenskappe 'n te hoë verhouding van n-6/n-3 poli-onversadigde vetsure in hul
dieet het, is direk relevant vir braaikuikenvoeding en lipiedmetabolisme. Betekenisvolle hoeveelhede n-3 polionversadigde
vetsure is geïnkorporeer in die belangrikste hoendersnitte, met die gevolg dat die produksie van
braaikuikenvleis met hoë n-3 poli-onversadigde vetsure voordelig is vir die braaikuikenindustrie en geag word 'n meer
"gesonde" beeld te hê. Ongelukkig is sodanige braaikuikenvleis redelik vatbaar vir oksidatiewe bederf, en oksidasie
bepaal dikwels die rakleeftyd van hoendervleisprodukte. Die byvoeging van a-tokoferol (vitamine E) by braaikuikendiëte
is 'n effektiewe manier om die oksidatiewe stabiliteit van braaikuikenvleis te verbeter. Verhoogde a-tokoferol vlakke in
braakuikenvoere verhoog die weefselkonsentrasie wat verhoogde stabiliteit van die membraanstrukture en derhalwe
moontlike verhoogde oksidatiewe stabiliteit van braakuikenvleis en -produkte tot gevolg het.
Drie ondersoeke is onderneem by Mariendahl Pluimvee Navorsingstasie te Stellenbosch. Die braakuikens is aangehou in
1 x 0.4 x 0.5m hokke in braaikuikenhuise. In al die proewe is dagoud kuikens gebruik, behalwe eksperiment 1 waar drieweek
oue kuikens gebruik is. Aan die einde van proewe 2 en 3 is die ses-week oue braaikuikens geslag en die karkasse
voorberei vir analise.
Eksperiment 1:
braaikuikens.
Die ware metaboliseerbare energie waarde van Canola voergraadolie (CAO) en Famarol voergraadolie (FAO),
Metaboliseerbare energie van Canola voergraadolie en Famarol voergraadolie vir
gekorregeer vir stikstof retensie (WMEn), is by wyse van proewe op 21 dae oue braaikuikenhaantjies bepaal deur van die
balansrnetode gebruik te maak. Die proewe is tweemaal herhaal vir verhoogde akkuraatheid, met die gebruik van
verskillende monsters van die twee olies vanaf dieselfde bron. Die olies is in twee verhoudings met 'n basale diëet
gemeng om die proef dieet te vorm, nl. 100% Basaal; 96% Basaal: 4% Olie en 92% Basaal: 8% Olie. Die balans proewe
het 3 dae geduur na afloop van 'n aanpassingsperiode van 4 dae. Die WMEn waardes van CAO, bepaal deur middel van
regressie analise, het nie betekenisvol verskil (P>0.05) tussen eksperimente 1 en 2 nie. Die waarde van eksperiment 3
was betekenisvol hoër (P<0.05) as die van die eerste twee eksperimente. Die WMEn waardes van FAO het ook nie
betekenisvol verskil (P>0.05) tussen eksperimente 1 en 2 nie, maar die waarde vir eksperiment 3 was betekenisvol hoër
as dié van eksperiment 1. Die WMEn waardes van COA het betekenisvol verskil (P< 0.05) van dié van FAO vir al die
eksperimente (exp. 1: 30.6 ± 0.399 MJ/kg vir CAO vs. 25.9 ± 0.441 MJ/kg vir FAO; expo 2: 31.0 ± 0.633 MJ/kg vir CAO vs.
26.1 ± 0.668 MJ/kg vir FAO: expo 3: 32.1 ± 0.867 MJ/kg vir CAO vs. 27.1 MJ/kg vir FAO). Eksperiment 2: Die invloed van verskeie rantsoen n-6/n3 vetsuurverhoudings op die produksie en
liggaamsamestelling van braaikuikens.
Die rantsoeneffek van verskeie kombinasies Canola voergraadolie (CAO, 'n hoë vlak van C18:3n-3 en monoonversadigde
vetsure) en Famarol voergraadolie (FAO, 'n hoë vlak van 18:2n-6 en versadigde vetsure) op die
weefselvetsuursamestelling is bestudeer in braaikuikenkarkasse en abdominale vetneerlegging. Die kuikens is van dagoud
to op ses-weke ouderdom een van ses diëte gevoer met die volgende samestellings: 100% FAO, 80% FAO-20%
CAO, 60% FAO - 40%CAO, 40% FAO - 60% CAO, 20% FAO - 80% CAO, 100% CAO. Daar was geen statistiese verskil
tussen die rantsoengroepe (P>0.05) in die gemiddelde daaglikse toename (1.71 ± 0.059 g) of die voeromsetverhoudings
(1.97 ± 0.051) nie. Geen statistiese verskil (P>0.05) is gevind in die chemiese samestelling van die karkasse vir vog
(66.20 ± 0.112 %), proteïn (17.63 ± 0.484 %), lipied (15.92 ± 1.507 %) en as (0.95 ± 0.115 %) inhoud tussen die rantsoen
groepe nie. Geen statistiese verskille (P>0.05) is gevind in die chemiese samestelling van die abdominale vetneerlegging
vir vog (28.77 ± 0.112 %), proteien (3.03 ± 0.484 %), lipied (63.32 ± 9.789 %) en as (0.45 ± 0.135 %) inhoud onder die
rantsoengroepe nie. Met die verhoging in die rantsoen CAO vlakke het die persentasie van C18:2n-6 en C20:4n-6 in die
karkasse verminder met 1.78 % en 0.35 % respektiewelik, terwyl C18:3n-3 en langer ketting n-3 vetsure soos C20:5n-3
en C22:6n-3 respektiewelik met 2.25 %, 0.1 % en 0.67 % verhoog het. Dieselfde tendens is opgemerk in die abdominale
vetneerlegging waar C18:2n-6 en C20:4n-6 afgeneem het met 1.55 % en 0.98 % respektiewelik met die verhoging van
rantsoen CAO, terwyl C18:3n-3, C20:5n-3 en C22:6n-3 verhoog het met 2.13 %, 0.45 % en 0.95 % respektiewelik. Die n-
3/n-6 verhouding in die karkasse en abdominale vetneerlegging het verhoog met 0.16 % en 0.19 % respektiewelik met die
verhoging van die rantsoen CAO. Die resultate toon onomwonde aan dat rantsoen CAO verryk met c-Iinoletensuur,
verlaag versadigde vetsure in braaikuikenkarkasse en -adbdominale vetneerleggings met 4.88 % en 10.63%
respektiewelik, terwyl die mono-onversadigde vetsure met 3.87 % en 7.25 % respektiewelik verhoog word en polionversadigde
vetsure met 1.02 % en 2.38 % respektiewelik verhoog word.
Eksperiment 3: Die invloed van vitamine E op die produksie van braaikuikens en die oksidatiewe stabiliteit,
kleur, mikrobiologiese stabilitiet, vetsuursamestelling en pH van braaikuikenvleis gedurende verkoelde en
bevrore berging.
Eksperiment 1 is uitgevoer met 220 dagoud braaikuikens ten einde die effek van elf konsentrasies van vitamine E (0, 20,
40, 60, 80, 100, 120, 140, 160, 180 en 200 mg a-tokoferyl acetaat / kg voer) op hul produksieprestasie en die oksidatiewe
stabiliteit van hul gevriesde braakuikenkarkasse te evalueer. Die diëte met vitamine E vlakke 0 tot 100 mg is vanaf
dagoud tot 42-dae-ouderdom gevoer, terwyl die diëte met vitamine E vlakke van 120 tot 200mg gevoer is vanaf 21 tot 42-
dae-ouderdom. Die oksidatiewe stabiliteit, soos geëvalueer deur tiobarbituriese suur reaktiewe stowwe (TBARS) waardes,
is bepaal na 30, 90, 120 en 150 dae van berging teen -20°C. Daar was geen statistiese verskille (P>0.05) in die
gemiddelde daaglikse toename (1.85 ± 0.111 g) of voeromsetverhoudings (2.29 ± 0.397) tussen die rantsoengroepe nie.
TBARS waardes het betekenisvol toegeneem (P<0.05) met die verhoging in bergingsperiode, maar het betekenisvol
afgeneem (P<0.05) met verhoogde vitamine E vlakke. Eksperiment 2 is uitgevoer met dagoud braaikuikens ten einde die
effek van vyf konsentrasies van vitamine E (0, 40, 80, 120 and 160 mg a-tokoferyl acetaat / kg voer) op hul prestasie en
die oksidatiewe stabiliteit van hul verkoelde karkasse te evalueer. Die eksperimentele diëte is gevoer vanaf dagoud tot 42-
dae-ouderdom. Die oksidatiewe stabiliteit, geëvalueer deur middel van TBARS waardes, kleur afname en mikrobiologiese
stabiliteit is bepaal na 0, 4, 8, 10 en 12 dae van berging teen 4°C. Vetsuuranalises is gedoen op die monsters van dae 0
en 12. Daar was geen statistiese verskille (P>0.05) in die gemiddelde daaglikse toename (1.88 ± 0.117 g) of
voeromsetverhoudings (2.37 ± 0.467) tussen die rantsoengroepe nie. TBARS waardes het betekenisvol verhoog (P<0.05)
met die verlengde bergingsperiode, maar het betekenisvol afgeneem (P<0.05) met verhoogde viatmine E vlakke. Daar
was geen statistiese verskille (P>0.05) in kleur metings vir L* (44.97 ± 0.662), a* (5.23 ± 0.315) of b* (12.76 ± 0.321)
waardes tussen behandelings nie. Mikrobiologiese tellings het betekenisvol verhoog (P<0.05) oor tyd met die vitamine E konsentrasie wat geen effek getoon het nie. Daar was geen statisties betekenisvolle verskille (P>0.05) vir enige van die
vetsuurgroepe tussen die behandelings nie. Soortgelyks het geen van die vetsure statisties betekenisvolle (P>0.05)
konsentrasieveranderings oor tyd aangetoon nie. Daar was geen statistiese verskil (P>0.05) in die pH (6.01 ± 0.206)
tussen die rantsoengroepe nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51736 |
| Date | 04 1900 |
| Creators | Coetzee, Gerna (Gertruida Johanna Maria) |
| Contributors | Hoffman, L. C., Hayes, J. P., Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Sciences. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 1 v. (various pagings) |
| Rights | Stellenbosch University |
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