Browsing by Author "North, Megan Kim"

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    The conditioning of springbok (Antidorcas marsupialis) meat : changes in texture and the mechanisms involved
    (2014-12) North, Megan Kim; Hoffman, Louwrens C.; Stellenbosch University. Faculty of AgriSciences. Department of Animal Science.
    ENGLISH ABSTRACT: The purpose of this study was to describe the nature of springbok (Antidorcas marsupialis) muscle and the changes that take place in the longissimus thoracis et lumborum (LTL) and biceps femoris (BF) muscles post-mortem (PM); thereby providing recommendations for the handling of the meat. Springbok muscle contained 64 - 78% type IIX fibres, suggesting that it is considerably more glycolytic than bovine muscle. In males the BF contained more type I and fewer type IIA fibres than the LTL and it appeared that female springbok contained a greater proportion of type IIX fibres than males. The cross-sectional areas (CSA’s) of the fibres were low but within the range reported for domestic species. There was an increase in the CSA with the glycolytic capacity of the fibres in males (I < IIA < IIAX < IIX) but no difference between fibre-types in females. Springbok muscle cooled rapidly and acidified slowly relative to recommended set points for domestic species, with this being most evident in the female LTL. Differences in cathepsin and calpain activity between the genders and muscles were evident, with the higher calpain activity in the BF and male springbok likely a reflection of the fibre-type composition of these samples. The cathepsin BL activity increased PM, possibly due to the degradation of the lysosomal membranes. Calpain and calpastatin activity declined PM, with correlations (r = -0.64; p < 0.01) between the pH decline rate and the change in calpastatin activity indicating that more rapid acidification results in a greater decrease in calpastatin activity. No further improvement in the Warner Bratzler shear force (WBSF) of springbok LTL or BF took place from five to 21 days of ageing. The cathepsin activity increased during the ageing period, with the high activity in the absence of a decline in WBSF suggesting that the cathepsins did not contribute to tenderization. The calpain and calpastatin activity declined to negligible levels by five days PM, suggesting that they were activated in situ and were involved in tenderization. Higher WBSF values were found for the BF throughout the ageing period. Springbok LTL increased in sensorial tenderness and sustained juiciness and decreased in residue from three to eight days PM; however ageing to 28 days increased a number of undesirable aroma and flavour attributes and decreased beef-like aroma. This was most likely due to oxidative and proteolytic changes. The WBSF was low for all ageing periods, with no significant change being found. Gender did not have a large influence on the sensory quality of the meat. The results of this study indicate that springbok meat tenderizes rapidly PM, with ageing periods of five to eight days being recommended to avoid detrimental flavour changes. The chilling rate appears to have a greater effect on the meat than any differences in the fibre-type composition, with the temperature and pH declines PM indicating a risk of cold-shortening. However the WBSF values found question the necessity of specialized handling techniques being used.
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    The conditioning of springbok (Antidorcas marsupialis) meat: changes in texture and the mechanisms involved
    (Stellenbosch : Stellenbosch University, 2015-03) North, Megan Kim; Hoffman, Louwrens C.; Stellenbosch University. Faculty of Science. Dept. of Animal Science.
    ENGLISH SUMMARY: The purpose of this study was to describe the nature of springbok (Antidorcas marsupialis) muscle and the changes that take place in the longissimus thoracis et lumborum (LTL) and biceps femoris (BF) muscles post-mortem (PM); thereby providing recommendations for the handling of the meat. Springbok muscle contained 64 - 78% type IIX fibres, suggesting that it is considerably more glycolytic than bovine muscle. In males the BF contained more type I and fewer type IIA fibres than the LTL and it appeared that female springbok contained a greater proportion of type IIX fibres than males. The cross-sectional areas (CSA’s) of the fibres were low but within the range reported for domestic species. There was an increase in the CSA with the glycolytic capacity of the fibres in males (I < IIA < IIAX < IIX) but no difference between fibre-types in females. Springbok muscle cooled rapidly and acidified slowly relative to recommended set points for domestic species, with this being most evident in the female LTL. Differences in cathepsin and calpain activity between the genders and muscles were evident, with the higher calpain activity in the BF and male springbok likely a reflection of the fibre-type composition of these samples. The cathepsin BL activity increased PM, possibly due to the degradation of the lysosomal membranes. Calpain and calpastatin activity declined PM, with correlations (r = -0.64; p < 0.01) between the pH decline rate and the change in calpastatin activity indicating that more rapid acidification results in a greater decrease in calpastatin activity. No further improvement in the Warner Bratzler shear force (WBSF) of springbok LTL or BF took place from five to 21 days of ageing. The cathepsin activity increased during the ageing period, with the high activity in the absence of a decline in WBSF suggesting that the cathepsins did not contribute to tenderization. The calpain and calpastatin activity declined to negligible levels by five days PM, suggesting that they were activated in situ and were involved in tenderization. Higher WBSF values were found for the BF throughout the ageing period. Springbok LTL increased in sensorial tenderness and sustained juiciness and decreased in residue from three to eight days PM; however ageing to 28 days increased a number of undesirable aroma and flavour attributes and decreased beef-like aroma. This was most likely due to oxidative and proteolytic changes. The WBSF was low for all ageing periods, with no significant change being found. Gender did not have a large influence on the sensory quality of the meat. The results of this study indicate that springbok meat tenderizes rapidly PM, with ageing periods of five to eight days being recommended to avoid detrimental flavour changes. The chilling rate appears to have a greater effect on the meat than any differences in the fibre-type composition, with the temperature and pH declines PM indicating a risk of cold-shortening. However the WBSF values found question the necessity of specialized handling techniques being used.
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    The potential of quercetin to improve growth performance and meat quality in rabbits
    (Stellenbosch : Stellenbosch University, 2019-04) North, Megan Kim; Hoffman, Louwrens C.; Zotte, Dalle A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science.
    ENGLISH ABSTRACT: Flavonoids are naturally-occurring bioactive compounds that may improve livestock production and product quality. Unfortunately, while their antioxidant, antimicrobial and other activities have been demonstrated, there has been limited research on their practical use as a livestock dietary supplement. This study investigated the effects of quercetin dihydrate (0 or 2 g/kg feed) on the growth performance and meat quality of growing New Zealand White rabbits. Sixty-six rabbits (31 males, 35 females) were fed control (Ctrl, 34 rabbits) or quercetin-supplemented (Qrc, 32 rabbits) feeds from weaning (5 weeks) until slaughter. The growth, feed intake and feed conversion ratio (FCR) were measured, and serum hormone levels were determined at 11 weeks old. Sixteen males and 16 females were slaughtered at 12 weeks old; carcass and meat quality traits were measured and the fatty acid composition of the caecotrophes, dissectible fat, loin meat and hindleg meat were determined using GC-FID. Fifteen males and 19 females were slaughtered at 13 weeks old; caecal contents were collected from 12 rabbits for the 16STM metagenome sequencing of the microbiome, and the loins were minced and stored for 1, 3 or 5 days at 3.2 C under oxygen-permeable wrapping to test the shelf-life. Quercetin-supplementation did not improve live performance, with Qrc rabbits only tending (P ≤ 0.10) to have higher overall FCRs, smaller sex-differences in growth and FCR, and higher free triiodothyronine levels. Quercetin-supplemented rabbits also only had higher proportions of some Firmicutes families and Anaerofustis and lower proportions of Roseburia, Oscillibacter and Ruminococcus albus in the caecal microbiome. This limited effect may have been due to the aglycone being absorbed prior to the caecum. Strong correlations between the composition of the microbiome and live performance traits were found, supporting further research on this topic. Quercetin-supplemented rabbits had higher hindleg meat:bone ratios due to lighter bones, which could increase meat yields but could also cause bone-breakage problems. This was contrary to previous findings that flavonoids decrease bone demineralisation, but may have been due to its effects on the connective tissue, which could have also caused the higher skin weight found. The largest effect of supplementation was on the loin fatty acid (FA) composition, increasing C18:3n-6, C20:3n-6, C20:3n-3 and C20:4n-6, and decreasing C20:2n-6, among others, thereby decreasing the n-6:n-3 ratio and improving the nutritional quality of the meat. This suggested an interaction between quercetin and endogenous lipid metabolism, which may have been influenced by the FA composition of the diet. The caecotrophes, dissectible fat and hindleg FAs were unchanged by quercetin. Quercetin-supplemented rabbits’ meat samples had lower day one concentrations of hexanal (an oxidation indicator), but no difference in oxidation (TBARS and FRAP) or microbial status during the shelf-life study. Dietary quercetin therefore did not improve the shelf-life of rabbit meat. Further research on the effects of quercetin on lipid metabolism should be done, particularly testing different inclusion levels and dietary FA compositions. The effects on bone-integrity, whole-carcass meat:bone ratio and pelt/skin quality should also be looked into. While some sex differences were found in these studies, they did not meaningfully affect production or product quality.