Meat quality parameters of the impala (Aepyceros melampus)

Kritzinger, Brian (2002-12)

Thesis (MSc)--Stellenbosch University, 2002.

Thesis

ENGLISH ABSTRACT: The purpose of this study was to evaluate the effects of age, sex, region and cropping methodology on the meat quality of impala. Forty impala were cropped during separate day and night operations at the Mara Agricultural Development Centre. Carcass pH45 (measured in M. longissimus dorsi 45 minutes post mortem) was higher in night cropped animals (6.67 ± 0.111; P<0.05) compared to the day cropped animals (6.55 ± 0.236). The ultimate carcass pH (pHu) of animals cropped at night was lower (5.39 ± 0.081; P<0.05) compared to those cropped in the day (5.45 ± 0.108). Non-linear regression analysis showed that the rate of pH decline of the night cropped animals was slower than that of the day cropped animals (P<0.05). The cooling rate of the M. longissimus dorsi was twice as fast in the night cropped group (P<0.05). Shear force values and drip losses of the night cropped animals were both lower (19.11 ± 5.675 g/mm2 and 2.93 ± 1.597% respectively; PO.OS) compared to those of day cropped animals (23.42 ± 8.128 g/mm2 and 4.15 ± 2.339%). The results indicate that nighttime cropping has a beneficial effect on certain meat quality parameters compared to daytime cropping. A second group of impala was sampled at the Musina Experimental Farm in the Limpopo Province of South Africa. Live weights of the Mara animals (50.23 ± 9.32 kg) were higher (P<0.05) than the Musina animals (44.25 ± 10.81 kg). Impala sampled at Mara had significantly higher dressing percentages than those at Musina (P<0.05). Impala ewes from both regions had a higher lipid content (P<0.05), but the sex of the animal had no effect on the remaining chemical parameters. The crude protein content of impala at Musina (24.88 ± 1.044%) was higher (P<0.05) than the Mara animals (23.80 ± 0.840%). Regional differences (P<0.05) were found in the amounts of phosphorous and calcium in the meat. Female animals at Mara showed higher proportions (P<0.05) of saturated (SFA), and mono-unsaturated fatty acids than the male animals. Males from both regions showed higher proportions (P<0.05) of poly-unsaturated fatty acids. Myristic, palmitic and stearic acid formed the greatest proportion of the SFA component for males and females from both regions. Samples of the M. semi-membranosus (SM), M. deltoideus (D), M. longissimus dorsi et laborum (LO), and M. psoas major (PS) were analysed for citrate synthase (CS) and phosphofructo-kinase activities. MHC distribution varied significantly between 0, SM and LD (P<O.05). D expressed more MHC I, and less MHC lIa than the other three muscle groups. Positive correlations were found between age and MHC I in 0 (r=O.93; P<O.05) and CS and weight of the animal in D (r=O.76; P<O.05). The enzyme activities and MHC distribution indicate that energy in the impala is produced to a large extent via oxidative pathways.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die invloed van ouderdom, geslag, area, en uitdunmetodes op die vleiskwalitiet van rooibokke te evalueer. Veertig rooibokke is gedurende afsonderlike dag en nag uitdunningsoperasies by die Mara Landboukundige Ontwikkelings Sentrum geoes. Karkas pH45 (gemeet in die M. longissimus dorsi 45 minute post mortem) was hoër (P<0.05) in nag-geoesde diere (6.67 ± 0.11) in vergelyking met die dag-geoesde diere (6.55 ± 0.23). Die finale pH (pHu) van diere wat in die nag geoes is (5.39 ± 0.08) was laer (P<0.05) in vergelyking met die wat in die dag geoes is (5.45 ± 0.11). Nie-lineêre regressie analise toon dat die tempo van pH-daling van die nag-geoesde diere merkbaar stadiger was as die dag-geoesde diere (P<0.05). Die afkoelings tempo van die M. longissimus dorsi et lumborum was twee keer vinniger in die nag geoesde groep (P<0.05). Die gemiddelde skeurkragwaarde en drupverlies was beide laer (P<0.05) vir nag geoesde diere (respektiewelik 19.11 ± 5.67 g/mm2 en 2.93 ± 1.59%) in vergelyking met diere wat in die dag geoes is (23.42 ± 8.12 g/mm2 en 4.15 ± 2.33%). Die resultate toon dat nag-uitdunning 'n voordelige effek op vleiskwaliteit gehad het, in vergelyking met dag-uitdunning. 'n Tweede groep van rooibokke is gemonster by die Musina Eksperimentele plaas in die Limpopo Provinsie in Suid-Afrika. Die gewigte van die Mara diere (50.23 ± 9.32 kg) was hoër (P<0.05) as die van die Musina diere (44.25 ± 10.81 kg). Die Mara groep het hoër uitslag persentasies (P<0.05) gehad. Vroulike diere in beide areas het 'n hoër vet inhoud (P>O.05) gehad. Die ru-proteien inhoud van die Musina diere (24.88 ± 1.04%) was hoër (P<0.05) as die van die Mara diere (23.80 ± 0.84%). Area verskille (P<0.05) is gevind in die fosfaat en kalsium inhoud in die vleis. Vroulike diere by Mara het 'n hoër proporsie (P<0.05) van versadigde en mono-onversadige vetsure in die weefsel as manlike diere gehad. Manlike diere van beide areas het 'n hoër proporsie (P<0.05) van poli-onversadige vetsure (P<0.05) as die vroulike diere getoon. Miristien, palmitien en stearien suur was kwantitatief die belangrikste vetsure in manlike en vroulike diere van beide areas. Monsters van die M. semi-membranosus (SM), M. deltoideus (D), M. longissimus dorsi et laborum (LO), en M. psoas major (PS), van die rooibokkarkasse is ontleed vir sitraatsintase (SS) en fosfofruktokinase aktiwiteite (FFK). MSK verspreiding het merkbaar varieer tussen 0, SM en LO (P<O.05). 0 toon meer MSK I en minder MSKlia as die ander drie spiergroepe (P<O.05). Postiewe korrelasies is bevind tussen ouderdom en MSK I in 0 (r=O.93; P<O.05), asook tussen SS en die gewig van die dier in o (r=O.76; P<O.05). Die ensiemaktiwiteite en MSK verspreiding toon dat energie in die rooibok tot 'n groot mate deur die oksidatiewe paaie geproduseer word.

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