Thesis (PhDAgric)--Stellenbosch University, 2006. / ENGLISH ABSTRACT: The South African pork industry is characterised by low slaughter weights
when compared to the rest of the world. This inevitably leads to a smaller
number of kilograms produced per unit fixed cost and subsequently the
efficiency of production is reduced. A study was conducted with 189 pigs
representing three sex types (boar, gilt and castrate) and five commercial
genotypes. Pigs entered into the trial at an age of 10 weeks and an average
live weight of 27.5±2.5kg. Treatments were according to slaughter weight
ranging between 62 and 146kg. Production and carcass characteristics, meat
quality and processing characteristics and sensory attributes were assessed.
Production characteristics assessed included live weight gains, intake, P2
backfat thickness and feed conversion ratio. Main observed effects were
associated with slaughter weight and its interaction with sex type. Rates of
change in parameters measured were described. Growth and feed
conversion ratio were described using linear models while cumulative feed
intake was described using 2nd order polynomials. Carcass characteristics
assessed included carcass weight, dressing percentage, carcass length, ham
length, ham circumference, chest depth, backfat thickness measurements,
muscle depth, eye muscle area, subcutaneous fat area, intramuscular fat area
as well as ratios of eye muscle to subcutaneous and intramuscular fat area.
The main statistical differences observed were for slaughter weight.
Significant sex type differences were observed for dressing percentage and
some fat and muscle depth measurements. Meat quality characteristics
assessed included colour measurements, tenderness, drip loss and water
holding capacity. Main differences observed were for slaughter weight.
Carcass yields were assessed in terms of absolute and percentage yields of
commercial cuts as well as yield of processable lean meat. In terms of the
absolute and percentage yields of the commercial cuts, the main statistical
differences observed were for slaughter weight. Changes in cut yield with increased slaughter weight are described using regression analysis. In terms
of yields obtained for processable lean meat, the main statistical differences
observed were for slaughter weight.
Sex type differences were only observed for percentage belly and topside
processable lean meat and percentage brine uptake of belly bacon, whole
gammon ham and topside gammon. Genotypic differences were observed for
percentage yield of processable lean meat of the neck and whole gammon
and percentage fresh to smoke losses of back bacon and whole gammon
ham. Sensory attributes were assessed using gammon ham, belly bacon and
fresh loin. Observed slaughter weight differences were inconsistent and did
not appear to change with an increase in slaughter weight. Once meat was
processed, most sensory differences were no longer observed. Increased
slaughter weight generally led to increased juiciness and decreased
tenderness.
It is therefore concluded that the current South African pig genotypes have the
ability to maintain high growth rates for a much longer time and therefore can
be slaughtered at a higher weight without detrimental effect on production
efficiency, carcass and meat quality characteristics, yields of commercial and
processable lean meat, processing characteristics and ultimately sensory
characteristics of the meat produced. / AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse varkbedryf word gekenmerk deur relatiewe lae
slagmassas in vergelyking met die res van die wêreld. Dit lei onvermydelik tot
‘n kleiner aantal kilogramme vleis geproduseer per eenheid vaste koste. ’n
Studie is gevolglik gedoen met die doel om die tempo’s van verandering van
sekere produksie-, karkas-, vleis- en proseseringseienskappe te kwantifiseer
ten einde die optimale slagmassa te bepaal wat vir alle rolspelers in die bedryf
tot voordeel sal wees. Die studie is gedoen met 189 diere wat vyf
kommersiële genotipes en drie geslagstipes (beer, sog en kastraat)
verteenwoordig het. Varke is op ’n ouderdom van 10 weke met ’n gemiddelde
lewende massa van 27.5±2.5kg in die proef opgeneem. Behandelings was
volgens slagmassa en het gevariëer van 62 tot 146kg. Produksieparameters
en karkas-, vleiskwaliteits-, en proseseringseienskappe sowel as sensoriese
eienskappe, is ëvalueer.
Produksieeienskappe wat ëvalueer is sluit in: groei, inname, P2 rugvetdikte en
voeromset-verhoudings. Hoofeffekte wat waargeneem is, was vir slagmassa
en interaksies van slagmassa met geslag. Tempo van verandering in die
parameters gemeet, is beskryf. Groei en voeromsette is beskryf deur die
passing van ‘n linieêre model terwyl kumulatiewe voerinname beskryf is deur
‘n 2de orde polinoom. Karkaseienskappe wat ëvalueer is, sluit in:
karkasmassa, uitslagpersentasie, karkaslengte, hamlengte, hamomtrek,
borsdiepte, rugvetdikte, spierdiepte, oogspieroppervlak, onderhuidse vet-,
binnespierse vetoppervlak en verhoudings van oogspier- tot-vetoppervlakke.
Die hoof statistiese effekte wat waargeneem is, was vir slagmassa.
Betekenisvolle geslagsverskille is waargeneem vir uitslagpersentasie en
sommige, vet- en spierdieptemetings. Genotipiese verskille is waargeneem
vir sommige vetmetings. Vleiskwaliteiteienskappe wat beoordeel is, het kleur,
drupverlies, waterbindingsvermoë en sagtheid ingesluit. Hoofeffekte
waargeneem was vir slagmassa. Karkasopbrengste is ëvalueer in terme van absolute en persentasie opbrengste van kommersiële snitte sowel as
prosesseerbare maer vleis. In terme van absolute en persentasie opbrengste
van kommersiële snitte, was meeste van die variasie beskryf deur slagmassa.
Tempo van verandering in die persentasie opbrengste van die snitte word
beskryf. In terme van opbrengste vir proseseerbare maer vleis is die hoof
statistiese verskille waargeneem vir slagmassa. Geslagverskille is
waargeneem vir persentasie streepspek en binneboud maer vleis opbrengs
vir prosesering en persentasie pekelopname van streepspek, heel varkboud
ham en binneboud ham. Genotipe verskille is waargeneem vir persentasie
opbrengs van maer vleis vir prosesering van die nek en heelboud en
persentasie vars-tot-klaar-gerook verliese van rugspek en heelboud hamme.
Sensoriese eienskappe is ëvalueer vir twee geprosesseerde en een vars snit.
Slagmassa-effekte was nie konstant nie en parameters het klaarblyklik nie
verander soos slagmassa verander het nie. Sodra vleis geprosesseer is, het
die meeste sensoriese verskille verdwyn. Beide sappigheid en taaiheid het
toegeneem met ‘n toename in slagmassa.
Dit kan dus aanvaar word dat, gegewe die huidige Suid Afrikaanse genotipes,
dit moontlik is om swaarder karkasse te produseer sonder noemenswaardige
nadelige effekte op karkas-, vleis-, opbrengste-, prosesering- en sensoriese
eienskappe van varkvleis.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17329 |
| Date | 04 1900 |
| Creators | Pieterse, Elsje |
| Contributors | Hoffman, L. C., Siebrits, F. K., 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 | xviii, 180 leaves : ill. |
| Rights | Stellenbosch University |
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