The effect of age and sex on meat quality characteristics of blue wildebeest (Connochaetes taurinus)

Roos, Tenisha (2020-03)

Thesis (MScAgric)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: Selective culling has become a popular practice for intensive to semi-extensive wildlife farms. However, some game farmers remain hesitant to cull surplus, older cows and young heifers and bulls for meat production due to the uncertainties regarding the meat quality of these animals. Therefore, this research aimed to quantify the effect of age and sex on various carcass characteristics and meat quality parameters of blue wildebeest (Connochaetes taurinus) meat to provide baseline data for the Wildlife industry of South Africa. The latter was achieved by collecting data of the carcass characteristics, including muscle-, internal- and external offal yields, as well as the body condition score (BCS) of the dressed carcasses. The physical quality (ultimate pH (pHU), drip- and cooking loss, colour and shear force) and chemical composition (moisture, protein, fat and ash content) of six muscles (Longissimus thoracis et lumborum (LTL), biceps femoris (BF), semimembranosus (SM), semitendinosus (ST), infraspinatus (IS) and supraspinatus (SS)) of blue wildebeest were also determined. The study included a total of 32 blue wildebeest, comprising of two trials. The first trial consisted of 24 blue wildebeest females who were categorised into three age groups (1.5-, 4.5- and >6.5-years old). The trial included eight females of each age group which were culled from a semi-extensive production system in the Central Bushveld region located on the outskirts of the Modimolle region in the Limpopo, South Africa. When the effect of age on carcass yields was investigated, the 4.5-year old cows had the heaviest dead weights (203.63 ± 9.54 kg), total internal- (55.84 ± 2.87 kg) and total offal weights (88.83 ± 5.75 kg). However, no differences were recorded between the cold carcass weights (100.15 ± 10.01 kg >6.5-year old; 105.45 ± 6.82 kg 4.5-year old), dressing percentage (53.10 ± 3.55 % >6.5-year old; 51.78 ± 1.99 % 4.5-years old), total external offal weights (33.29 ± 2.26 kg >6.5-years old; 33.38 ± 2.84 kg 4.5-years old), individual muscle weights, as well as for the BCS of the two older age groups. The 1.5-year old heifers were associated with the lightest carcass yields and lower BCS in comparison to the older age groups. A significant age effect was also observed for the physical parameters measured for the six muscles of blue wildebeest females. The oldest age group was associated with the highest pHU values for all six muscles, and for some muscles (LTL, ST and IS) the pHU was higher than 5.9 which could result in dark-firm-dry (DFD) meat. Many of the muscles of the two older age groups showed tendencies of lower drip loss than the heifers, while the heifers exhibited higher cooking loss for the LTL, BF and ST muscles than the >6.5-year old cows. An age effect was observed for the shear force values of the six muscles. The heifers had significantly lower shear force values for the LTL, IS and SS muscles than the 4.5-year old cows. The muscles of the 4.5-year old cows exhibited more vivid colour (high chroma-, a* and b* values) than the other age groups, while the youngest animals had significantly lighter (high L* values) and less red (high hue-angle) muscles. Furthermore, age had little effect on the basic chemical composition of the muscles investigated. The heifers had higher moisture content in the ST, IS and SS muscles than the older animals, but the differences were less than 1.5 %. Age had a negligible effect on the protein content and the ash content of the muscles of the blue wildebeest females. The oldest cows (>6.5-years old) had higher fat content in the LTL (1.7 ± 0.14 %), BF (1.7 ± 0.09 %) and SS (2.1 ± 0.15 %) muscles than the younger females, however, the differences were negligible (<0.5% differences). The second trial included eight additional 1.5-year old blue wildebeest bulls that were compared to the 1.5-year old heifers from the first trial. Sexual dimorphism was observed for most of the carcass yields (dead-, cold carcass weight, dressing percentage, total offal yields, muscles weights and the BCS) for which the bulls recorded heavier weights than the heifers. Sex also had a significant effect on the physical quality of the six muscles investigated in this trial. The bulls had higher pHU values for four of the muscles than the heifers for which two muscles (LTL and ST) exhibited pHU >5.9 (DFD meat). The heifers had higher drip loss in three muscles (LTL (2.4 ± 0.61 %), SM (3.6 ± 1.05 %) and SS (1.5 ± 0.25 %)) than the bulls, while only two muscles (BF (42.0 ±1.25 %) and ST (42.1 ± 0.91 %)) of the heifers showed higher cooking loss than the bulls. Sex had little effect on the shear force values of the six muscles of the bulls and heifers. Furthermore, the muscles located in the hindquarters of the bulls were darker (low L* values and high myoglobin content (g/100g)) and redder (lower hue-angle values) than that of the heifers. The BF and ST muscles of the bulls were associated with lower metmyoglobin- (MMb) and higher oxymyoglobin (OMb) percentages than the heifers. With regards to the chemical composition of the six muscles of the bulls and heifers, the heifers exhibited higher moisture content and lower protein content in the SM and ST muscles (<1 % difference). Furthermore, sex had a negligible effect on the fat- and ash content of the muscles of bulls and heifers. Therefore, it was concluded that the older surplus blue wildebeest cows and young blue wildebeest bulls can be harvested for meat production due to their high carcass yields and desired physical- and chemical meat quality of the six muscles (excluding those exhibiting DFD characteristics) investigated.

AFRIKAANSE OPSOMMING: Intensiewe en semi-ekstensiewe wildplase beskou selektiewe uitskot as 'n waardevolle hulpmiddel om optimale opberengste van ‘n kudde te verseker. Wildboere huiwer egter om surplus, ouer koeie en jong bulle vir vleisproduksie te oes weens die onsekerhede met betrekking to die vleiskwaliteit van hierdie diere. Die doelwit van hierdie navorsing was om die invloed van ouderdom en geslag op verskillende karkaseienskappe en die vleiskwaliteit van blouwildebees (Connochaetes taurinus) te kwantifiseer om data vir die wildbedryf van Suid-Afrika te voorsien. Hierdie doel was bewerkstellig deur data van die karkaseienskappe te versamel, insluitend spier-, interne- en eksterne afvalopbrengste, sowel as die liggaamskondisie (BCS) van die karkasse. Die fisiese (finale pH (pHU), drup- en kookverlies, kleur en skeurkrag) en chemiese samestelling (vog, proteïen, intramuskulêre vet (IMF) en asinhoud) van ses spiere (Longissimus thoracis et lumborum (LTL), biceps femoris (BF) ), semimembranosus (SM), semitendinosus (ST), infraspinatus (IS) en supraspinatus (SS)) van blouwildebeeste is ook bepaal. Die studie het 32 blouwildebeeste ingesluit, wat in twee proewe verdeel is. Die eerste proef het 24 vroulike blouwildebeeste bevat, wat uit drie ouderdomsgroepe (1.5, 4.5 en >6.5 jaar oud) bestaan het. Elke ouderdomsgroep het agt vroulike diere bevat wat vanuit 'n semi-ekstensiewe produksiestelsel in die Sentraal-Bosveldstreek, aan die buitewyke van die Modimolle-streek in Limpopo, Suid-Afrika, geoes is. Die 4.5 jarige koeie het die swaarste dooiegwig (203.63 ± 9.54 kg), totale interne afval- (55.84 ± 2.87 kg) en totale afvalgewigte (88.83 ± 5.75 kg) gehad. Geen verskille is egter aangeteken tussen die koue karkasgewig (100.15 ± 10.01 kg > 6.5 jaar oud; 105.45 ± 6.82 kg 4.5-jaar oud), uitslagpersentasie (53.10 ± 3.55 % >6.5 jaar oud; 51.78 ± 1.99 % 4.5 jaar oud), totale eksterne afvalgewigte (33.29 ± 2.26 kg >6.5 jaar oud; 33.38 ± 2.84 kg 4.5 jaar oud), individuele spiergewigte, sowel as vir die BCS van die twee ouer ouderdomsgroepe nie. Die 1.5 jarige verse het die ligste karkasopbrengste en laagste BCS gehad in vergelyking met die twee ouer ouderdomsgroepe. 'n Beduidende ouderdomseffek was ook waargeneem vir die fisiese vleiskwaliteitskenmerke van die ses spiere van die vroulike blouwildebeeste. Die koeie van die oudste ouderdomsgroep het die hoogste pHU waardes vir al ses spiere gehad, en vir sommige spiere (LTL, ST en IS) was die pHU hoër as 5.9, wat kan lei tot donker, ferm, droë vleis (DFD-kenmerke). Die meerderheid van die spiere van die twee ouer ouderdomsgroepe het 'n neiging tot laer drupverliespersentasies as die verse getoon, terwyl die verse hoër kookverliespersentasies vir die LTL, BF en ST spiere as die >6.5 jarige koeie gehad het. Ouderdom het ‘n klein effek op die skeurkragwaardes van die ses spiere van die vroulike diere gehad. Die verse het egter laer skeurkragwaardes vir die LTL, IS en SS spiere as die 4.5 jarige koeie getoon. Die spiere van die 4.5 jarige koeie het ‘n meer helder kleur (hoë chroma-, a*- en b* waardes) gehad as die ander ouderdomsgroepe, terwyl die spiere van jongste diere aansienlik ligter (hoë L* waardes), en minder rooi (hoë kleurtoon) was. Weining ouderdoms invloed was waargeneem vir die basiese chemiese samestelling van die ses spiere. Die verse het 'n hoër voginhoud in die ST, IS en SS spiere as die ouer diere gehad, nietemin, die verskille was minder as 1.5 %. Ouderdom het ‘n weglaatbare invloed op die proteïeninhoud en die asinhoud van die spiere van die vroulike blouwildebeeste gehad. Die oudste koeie (>6.5 jaar oud) het 'n hoër vetinhoud in die LTL (1.7 ± 0.14 %), BF (1.7 ± 0.09 %) en SS (2.1 ± 0.15 %) spiere as jonger ouderdomsgroepe gehad, die verskille was egter weglaatbaar (<0.5 % verskille). Die tweede proef het agt bykoomende 1.5 jarige blouwildebees bulle ingesluit wat met die 1.5 jarige verse van die eerste proef vergelyk was. Seksuele dimorfisme was waargeneem vir meeste van karkasopbrengste (dooie, kouekarkasgewig, uitslagpersentasie, totale afvalopbrengste, spiergewigte en die BCS) waarvoor die bulle swaarder gewigte as die verse getoon het. Geslag het ook 'n beduidende invloed op die fisiese vleiskwaliteit van die ses spiere gehad. Die bulle het hoër pHU waardes as die verse getoon in vier van die spiere, waarvoor twee spiere (LTL en ST) pHU >5.9 (DFD-kenmerke) gehad het. Die verse het hoër drupverliespersentasies vir drie spiere (LTL (2.4 ± 0.61 %), SM (3.6 ± 1.05 %) en SS (1.5 ± 0.25 %)) as die bulle gehad, terwyl slegs twee spiere (BF (42.0 ± 1.25 %)) en ST (42.1 ± 0.91 %) van die verse hoër kookverliespersentasies as die bulle getoon het. ‘n Weglaatbare geslagseffek was opgemerk vir die skeurkragwaardes van die ses spiere van bulle en verse. Verder was die spiere in die agterkwartte van die bulle donkerder (lae L* waardes en hoë mioglobieninhoud (g/100 g)) en rooier (laer kleurtoon) as dié van die verse. Die BF en ST spiere van die bulle het laer metmioglobien (MMb) en hoër oksimioglobien (OMb) persentasies as die verse gehad. Met betrekking tot die chemiese samestelling van die ses speiere van die bulle en verse, het die verse hoër voginhoudpersentasies en laer proteïeninhoudpersentasies vir die SM en ST spiere (<1 % verskil) getoon. Verder het geslag 'n weglaatbare effek op die vet- en asinhoud van die spiere van die bulle en verse gehad. Die navorsing het bevestig dat die ouer, surplus blouwildebees koeie en jong bulle geskik is vir vleisproduksie as gevolg van die hoë karkasopbrengste en die gewenste fisiese- en chemiesevleiskwaliteit van die ses spiere (uitgesonderd die wat DFD-kenmerke toon) wat in die studie ondersoek is.

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