Carcass and meat quality characteristics of three halothane genotypes in pigs

Thesis (MScAgric)--Stellenbosch University, 1995.

ENGLISH ABSTRACT: The object of this study was to determine the effect of the halothane gene in pigs on certain production, carcass, meat and processed meat characteristics. Fifty nine (gilts = 25, castrates = 34) Landrace x Large white pigs of three halothane genotypes (NN = 31, Nn = 17, nn = 11) were raised under commercial conditions from 27 kg to 86 kg live weight. Variables measured during this period were days to slaughter and ADG. Upon reaching slaughter weight (86 kg) the pigs were transported to a commercial abattoir and slaughtered and classified according to factory procedures. Variables measured at the classification point were pH i, carcass length, warm carcass weight, fat thickness, meat depth and percentage predicted lean yield. After a 24 h cooling period the carcases were weighed, pH24 measured, cut to factory specifications and samples of the loin removed to determine drip loss. Certain portions (left hand side ham and back) of the carcass were removed, deboned and frozen for further processing. The backs and hams were defrosted after all the pigs were slaughtered. The backs were used to manufacture back bacon according to commercial procedures followed in the factory. This consists of brine injection, immersion in brine for 24 h, smoking and tempering or cooling. Weights of the individual samples (n = 59) were recorded before and after each of the processes mentioned. The deboned hams were grouped according to genotype and minced using a 20 mm mincerplate. Spices, preservatives and ice water were added to the minced meat and tumbled for 30 min to enhance the water binding potential of the meat. The ham mixture of each genotype was canned (20 cans/genotype), weighed and sterilized. After a cooling period the hams were removed from the cans, residual water drained off and the weight of each sample determined. Samples (n = 59) removed from the processed backs were used to determine chemical composition. Moisture content of the samples were determined by method of freeze drying. The dried samples were then analyzed for protein content (Kjeldahl), fat content (ether extraction) and sodium content (chromatography). The variables were analyzed in a two way classification model using the method of least squares to estimate differences between means. Correlations etween variables and multiple linear regression equations for certain dependent variables were also calculated. Interaction between sex and genotype for certain variables (days to slaughter, ADG, carcass length, percentage bacon yield) were discounted due to unalterability of the castrate:gilt ratio (days to slaughter, ADG, carcass length) or due to low significant values for sex in the model (percentage bacon yield). The presence of the halothane gene in homozygous form (nn) caused enhanced growth rate (days to slaughter, ADG). The nn pigs grew significantly (P < 0.05) faster than the NN- and Nn pigs during the growth (days to slaughter) phase (NN = 81.2, Nn = 84.6 and nn = 74.1). No significant differences between the genotypes for ADG were observed (NN = 0.729, Nn = 0.710 and nn = 0.765). Most of the carcass and meat quality characteristics did show statistically significant differences. No differences in the means for percentage chilling loss (NN = 4.4, Nn = 4.7 and nn = 5.2) and pH₂₄ (NN = 5.87, Nn = 5.81 and nn = 5.80) were found. The correlations between pH₁ and pH₂₄ (r = 0.27, P < 0.05) and drip loss (r = -0.39, P < 0.05) were significant. Percentage drip loss differed significantly (P < 0.05) between all three genotypes (NN = 1.69, Nn = 2.39 and nn = 1.06). Fat thickness (NN = 20.0, Nn = 18.8 and nn = 26.1), meat depth (NN = 50.9, Nn = 52.4 and nn = 46.8) and percentage predicted lean yield (NN = 66.1, Nn = 66.7 and nn = 63.0) differed significantly (P < 0.05 for meat depth, P < 0.001 for fat thickness and percentage predicted lean yield) between nn and NN as well as Nn, with no differences between NN and Nn, ruling out the incorporation of this gene and its proposed advantages. Correlations between drip loss and days to slaughter (growth phase) (r = 0.47, P < 0.001) and ADG (r = -0.38, P < 0.05) were significant. The processed meat (back bacon) only showed significant (P < 0.05) differences between Nn and nn for percentage pumped yield (NN = 9.7, Nn = 8.1 and nn = 12.6). Percentage moisture loss differed (P < 0.001) significantly between nn and NN as well as Nn, with no differences between NN and Nn (NN = 2.5, Nn = 1.2 and nn = 7.7). There were no differences in means for percentage bacon yield (NN = 7.2, Nn = 6.9 and nn = 4.8). The chemical composition of the analyzed samples showed significant (P < 0.05) differences between NN and nn for percentage protein (NN = 72.4, Nn = 71.6 and nn = 69.1) and sodium concentration (mg.kg·¹ DM) (NN = 12096, Nn = 12477 and nn = 13446). Percentage moisture differed (P < 0.05) between Nn and NN as well as nn (NN = 50.2, Nn = 44.8 and nn = 49.4). Percentage fat in the samples did not differ significantly (NN = 5.9, Nn = 5.7 and nn = 7.6). None of the multiple regressions . calculated were sufficiently accurate to be of any use as a predictive model. The incorporation of the halothane gene in pig production under South African production and processing conditions seems to have no real benefits for the producer, processor and consumer alike and the exclusion thereof in breeding programs is strongly recommended.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die invloed van die halotaangeen in varke op sekere produksie-, karkas-, vleis- en geprosesseerde vleiseienskappe te bepaal. Nege-en-vyftig (soggies = 25, burgies = 34) Landras x Grootwit varke van die drie halotaangenotipes (NN = 31, Nn = 17, nn = 11) is onder kommersiele produksietoestande gehuisves en grootgemaak vanaf 27 kg tot 86 kg lewendige gewig. Veranderlikes gemeet tydens die groeifase is dae tot slagting en gemiddelde daaglikse toename (GDT). Met voltooiing van die groeifase (86 kg) is die varke na die naaste slagpale geneem, geslag en geklassifiseer volgens fabrieksprosedures. Die volgende veranderlikes is by die klassifikasiepunt gemeet: pH₁, karkaslengte, warm karkasmassa, vetdikte, oogspierdeursnit en die persentasie voorspelde maervleis in die karkas. Na verloop van 'n 24 uur verkoelingsperiode is die karkasse geweeg, pH24 gemeet en opgesny volgens fabriekspesifikasies. Monsters is vanaf die lende verwyder om dripverlies te bepaal. Dele van die karkas (linkerkantse ham en lende) is verwyder, ontbeen en gevries vir verdere verwerking. Nadat al die varke geslag is, is die hamme en lendes ontvries. Die lendes is gebruik vir kommersiele spekvervaardiging volgens fabriekspesifikasies. Hierdie proses sluit in pekelinspuiting, dompeling in 'n pekelbad vir 24 uur, beroking en tempering of afkoeling. Al die lendes (n = 59) is voor en na elke proses geweeg. Die ontbeende hamme is volgens genotipe gegroepeer en deur 'n 20 mm plaat gemaal. Speserye, preserveermiddels en yswater is by die gemaalde vleis gevoeg en vir 30 minute getuimel om die waterbindingsvermoe van die vleis te verbeter. Die hammengsels is volgens genotipe gegroepeer en geblik (20 blikke/genotipe), geweeg en gesteriliseer. Na 'n afkoelingsperiode is die hamme uit die blikke gehaal, oortollige water gedreineer en elke blik se inhoud geweeg om sodoende kookverliese te bepaal. Monsters is van elke lende (n = 59) geneem om die chemiese samestelling daarvan te bepaal. Die monsters is gevriesdroog om voginhoud te bepaal. Ontleding op die gedroogde monsters is gedoen om proteieninhoud (Kjeldahl), vetinhoud (eterekstraksie) en natriumkonsentrasie (chromatografie) te bepaal. Elke veranderlike is ontleed as 'n tweerigtingklassifikasie model en die metode van kleinste kwadrate is gebruik om verskille tussen gemiddeldes te beraam. Korrelasies tussen veranderlikes asook veelvuldige lineere regressies vir sekere afhanklike veranderlikes is bereken. Interaksie tussen geslag en genotipe is vir sekere veranderlikes (dae tot slag, GDT, karkaslengte) ge1gnoreer vanwee die onveranderbaarheid van die burg:sog verhouding of vanwee die lae betekenisvolheid van geslag in die model (persentasie spekopbrengs). Die teenwoordigheid van die halotaangeen in homosigotiese vorm (nn) het aanleiding gegee tot verbeterde produksieprestasies (dae tot slagting, GDT). Die nn varke het minder (P < 0.05) dae geneem om slagmassa te bereik as die NN- en Nn varke (NN = 81.2, Nn = 84.6 en nn = 74.1). Geen betekenisvolle verskille vir GDT is tussen genotipes waargeneem nie (NN = 0.729, Nn = 0.710 en nn = 0.765). Meeste van die vleis- en karkaskwaliteitseienskappe het nie enige betekenisvolle verskille vir persentasie koelverlies (NN = 4.4, Nn = 4.7 en nn = 5.2) en pH₂₄ (NN = 5.87, Nn = 5.81 en nn = 5.80) gehad nie. Die korrelasies tussen pH₁ en pH₂₄ (r = 0.27, P < 0.05) en dripverlies (r = -0.39, P < 0.05) was statisties betekenisvol. Persentasie dripverlies het betekenisvol (P < 0.05) verskil tussen al drie genotipes (NN = 1.69, Nn = 2.39 en nn = 1.06). Vetdikte (NN = 20.0, Nn = 18.8 en nn = 26.1), oogspierdeursnit (NN = 50.9, Nn = 52.4 en nn = 46.8) en persentasie beraamde maervleis in die karkas (NN = 66.1, Nn = 66.7 en nn = 63.0) het betekenisvol verskil (P < 0.05 vir oogspierdeursnit, P < 0.001 vir vetdikte en persentasie beraamde maervleis in die karkas) tussen nn en NN sowel as Nn, met geen verskille tussen NN en Nn. Hierdie resultate wys daarop dat die insluiting van die geen en die voorgestelde voordele daaraan verbonde nie aanbeveel word nie. Korrelasies tussen dripverlies en dae tot slagting (r = 0.47, P < 0.001) asook GDT (r = -0.38, P < 0.05) was statisties betekenisvol. Die verwerkde vleis (rugspek) het slegs betekenisvolle verskille (P < 0.05) tussen Nn en nn gehad vir persentasie gepompde opbrengs (NN = 9.7, Nn = 8.1 en nn = 12.6). Die persentasie vogverlies het betekenisvol verskil (P < 0.001) tussen nn en NN sowel as Nn, met geen verskille tussen NN en Nn (NN = 2.5, Nn = 1.2 en nn = 7.7). Daar was geen verskille tussen genotipes vir persentasie spekopbrengs (NN = 7.2, Nn = 6.9 en nn = 4.8). Die chemiese samestelling van die monsters bet betekenisvol verskil (P < 0.05) tussen NN en nn vir persentasie proteieninhoud (NN = 72.4, Nn = 71.6 en nn = 69.1) en vir natriumkonsentrasie (mg. kg-1) (NN = 12096, Nn = 12477 en nn = 13446). Die persentasie vog het betekenisvol verskil (P < 0.05) tussen Nn en NN sowel as nn (NN = 50.2, Nn = 44.8 en nn = 49.4). Die persentasie vet in die monsters het nie verskil nie (NN = 5.9, Nn = 5.7 en nn = 7.6). Nie een van die berekende veelvuldige linieere regressies was akkuraat genoeg om as voorspellingsmodel te gebruik nie. Dit blyk dat die insluiting van die halotaangeen in varkproduksie onder Suid­ Afrikaanse produksie- en verwerkingstoestande geen werklike voordele vir die produsent, verwerker of verbruiker bet rue en die uitsluiting daarvan m die teelprogram word sterk aanbeveel.

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