Thesis (MScAgric (Animal Sciences))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The production and especially the export of game meat from Southern African are steadily increasing and
with this growth, it is inevitable that more emphasis is being placed on the quality of game meat. Research
regarding the effect of different cropping methods on ante-mortem stress, and as a result, on meat quality in
wild ungulates, is lacking and thus the purpose of this study was to investigate the effect of some of the
commonly used cropping methods on the meat quality of red hartebeest, impala, gemsbok and kudu. Antemortem
stress was measured using serum cortisol levels (nmol/L), a subjective stress score allocated to
each animal as well as the rate and extent of pH decline in the M. longissimus dorsi. Special emphasis was
also placed on the meat quality parameters drip loss, cooking loss, colour and Warner-Bratzler shear force
(kg/1.27 cm diameter).
The effect of day and night cropping on the meat quality of red hartebeest, gemsbok and kudu was
investigated. An exponential decay model, y = a + b-ct, was fitted to the pH data of the gemsbok and red
hartebeest, and pHu measurements taken at 24 hours post-mortem. Only pHu readings taken at 48 hours
post-mortem were analysed in the kudu. Day-cropped kudu had a lower mean pHu (5.40 ± 0.030) than nightcropped
kudu (5.48 ± 0.041). No differences in pHu were found for the red hartebeest although night-cropped
gemsbok had a higher mean pHu (5.54 ± 0.013) than day-cropped gemsbok (5.49 ± 0.014). None of the
constants of the exponential decay model differed for the red hartebeest although day-cropped gemsbok
produced a lower constant than night-cropped gemsbok. Mean stress scores and cortisol levels were found
to be higher in day-cropped animals for both the gemsbok and kudu while only cortisol levels were higher in
die day-cropped red hartebeest. Stress score and cortisol levels were found to be correlated in all three
species (red hartebeest: r = 0.51; gemsbok: r = 0.786; kudu: r = 0.823). No treatment differences in drip loss
or cooking loss were found for either the red hartebeest or gemsbok, while day-cropped kudu had a higher
mean drip loss % (2.76 ± 0.261%) than night-cropped kudu (1.36 ± 0.361%). Night-cropped gemsbok and
kudu produced higher mean shear force values (gemsbok = 4.19 ± 0.138; kudu = 4.06 ± 0.237 kg/1.27 cm
diameter) than day-cropped animals (gemsbok = 3.57 ± 0.154; kudu = 3.45 ± 0.171 kg/1.27 cm diameter).
Colour differences indicated that day-cropped gemsbok and kudu produced lighter meat than night-cropped
animals. The results indicate no difference in the effects of day and night cropping in red hartebeest although
day-cropped gemsbok and kudu experienced more ante-mortem stress than their night-cropped
counterparts.
The effect of conventional hunting during the day and night cropping on impala meat was also investigated. No differences were found in pH45 or pHu (taken at 45 minutes and 24 hours post-mortem respectively)
although the exponential decay model, y = a + b-ct, fitted to the pH data revealed differences in all the
constants (day: a = 5.424 ± 0.039, b = 1.405 ± 0.034, c = -0.385 ± 0.022; night: a = 5.295 ± 0.033, b = 1.556
± 0.029, c = -0.184 ± 0.019). No differences were found for drip loss, cooking loss or shear force although
day-cropped animals produced higher a* and chroma values. The results indicate that, although
conventional hunting caused a faster and more severe post-mortem pH decline, both treatments produced
meat of similar quality. / AFRIKAANSE OPSOMMING: Die produksie en veral die uitvoer van wildsvleis vanuit Suidelike Afrika is gedurig aan die toeneem en met
hierdie groei is dit onvermydelik dat meer klem op die gehalte van wildsvleis gelê word. Daar is ’n tekort aan
navorsing oor die uitwerking van verskillende oesmetodes op ante mortem stres en gevolglik ook
vleisgehalte van verskillende wildspesies en dus was die doel van dié studie om die uitwerking van sommige
van die gewildste oesmetodes op die vleisgehalte van rooihartebees, gemsbok, koedoe en rooibok te
ondersoek. Ante mortem stres is gemeet deur die gebruik van serum-kortisolvlakke (nmol/L), ʼn subjektiewe
strestelling wat aan elke dier gegee is asook die tempo en vlak van pH-daling in die M. longissimus dorsi.
Spesiale klem is gelê op die vleisgehalteparameters drupverlies, kookverlies, kleur en Warner-Bratzlerskeurwaarde
(kg/1.27 cm deursnee).
Die uitwerking van dag- en nag-oes op die vleisgehalte van rooihartebees, gemsbok en koedoe is
ondersoek. ’n Eksponensiële vervalkurwe, y = a + b-ct, is aan die pH-data van die gemsbokke en
rooihartebeeste gepas en pHu-metings is op 24 uur ná dood geneem. Net pHu-lesings op 48 uur ná dood in
die koedoe is geanaliseer. Koedoes wat in die dag geoes is, het ’n laer pHu (5.40 ± 0.030) gehad as koedoes
wat in die nag geoes is (5.48 ± 0.041). Daar was geen verskille in pHu vir die rooihartebeeste nie, alhoewel
die gemsbokke wat in die nag geoes is, ’n hoër pHu (5.54 ± 0.013) gehad het as gemsbokke wat in die dag
geoes is (5.49 ± 0.014) . Geeneen van die konstantes van die eksponensiële vervalkurwe het verskil in die
geval van rooihartebeeste nie terwyl gemsbokke wat in die dag geoes is ʼn hoër konstante a en ʼn laer
konstante c getoon het as gemsbokke wat in die nag geoes is. Gemiddelde strestellings en kortisolvlakke
was hoër in die geval van gemsbokke en koedoes wat in die dag geoes is terwyl net die kortisolvlakke hoër
was in die rooihartebeeste wat in die dag geoes is. Daar is ook bevind dat die strestelling en kortisolvlakke
gekorreleer was in al drie spesies (hartebees: r = 0.51; gemsbok: r = 0.786; koedoe: r = 0.823). Geen
verskille in drupverlies of kookverlies is aangetref vir die rooihartebeeste of gemsbokke nie, alhoewel
koedoes wat in die dag geoes is ʼn hoër gemiddelde drupverlies % (2.76 ± 0.261%) getoon het in vergelyking
met koedoes wat in die nag geoes is (1.36 ± 0.361%). Gemsbokke en koedoes wat in die nag geoes is, het
’n hoër gemiddelde skeurwaarde gehad (gemsbokke = 4.19 ± 0.138; koedoes = 4.06 ± 0.237 kg/1.27 cm
deursnee) as diere wat in die dag geoes is (gemsbokke = 3.57 ± 0.154; koedoes = 3.45 ± 0.171 kg/1.27 cm
deursnee). Kleurverskille het aangedui dat gemsbokke en koedoes wat in die dag geoes is, ligter gekleurde
vleis geproduseer het as diere wat in die nag geoes is. Die resultate dui aan dat daar by rooihartebeeste
geen verskil is tussen die uitwerking van dag-oes en nag-oes nie, maar dat die dag-oes van gemsbokke en
koedoes meer voordoodse stres veroorsaak het as nag-oes.
Die uitwerking van konvensionele jag gedurende die dag- en nag-oes op die vleisgehalte van rooibokke is
ook ondersoek. Geen verskille is aangetref in pH45 of pHu (geneem op 45 minute en 24 uur ná dood
onderskeidelik) nie, alhoewel die eksponensiële vervalkurwe, y = a + b-ct, wat gepas is aan die pH-data
verskille getoon het in al die konstantes (dag: a = 5.424 ± 0.039, b = 1.405 ± 0.034, c = -0.385 ± 0.022; nag:
a = 5.295 ± 0.033, b = 1.556 ± 0.029, c = -0.184 ± 0.019). Geen verskille is aangetref ten opsigte van
drupverlies, kookverlies of skeurkrag nie. Diere volgens die konvensionele maniere geoes het wel hoër a*-en chroma-waardes getoon. Die resultate dui daarop dat, alhoewel konvensionele jag ʼn vinniger en meer
ekstreme pH-daling veroorsaak het, albei behandelinge tot dieselfde vleisgehalte gelei het.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4055 |
| Date | 03 1900 |
| Creators | Laubscher, Liesel L. |
| Contributors | Hoffman, L. C., 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 | 134 p. : ill. |
| Rights | University of Stellenbosch |
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