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n Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie - Die Suid-Afrikaanse varkkarkas-klassifikasiestelsel : oorspronklike navorsing

Volume 31, Issue 1
  • ISSN : 0254-3486
  • E-ISSN: 2222-4173

Abstract

Die regressievergelyking waarmee varkkarkasvleispersentasie in Suid-Afrika beraam word, is in 1992 opgestel en sedertdien nog nie weer opgedateer nie. Intussen het varke aansienlik maerder geword. Die regressievergelyking is opgestel met karkasse waarvan die massa nie 90 kg oorskry het nie, terwyl dit al meer in die praktyk gebeur. Dit het dus nodig geword om die huidige klassifikasieregressies weer krities te ondersoek om te bepaal of die verbetering in genetiese potensiaal 'n wesentlike uitwerking op die vleisvoorspelling sou hê en of die vergelyking gebruik kan word om te ekstrapoleer. Uiteindelik moet bepaal word of die vergoeding wat die produsent ontvang, regverdig bepaal word. 'n Totaal van 81 varke, bestaande uit 5 verteenwoordigende genotipes en 3 geslagte (soggies, bere en burge) met 'n lewende massa van tussen 20 kg en 30 kg, is in agt slaggroepe verdeel, op 'n standaarddieet gevoer en tussen 74 kg en 160 kg lewende massa geslag. Vetmate is met die Hennessy® graderingspeilstif en die Intraskoop® op die karkasse geneem waarna die linkersye in die groothandelsnitte gesny en in been, vet, vel en vleis gedissekteer is. Vetmate is ook met die Renco Lean Meater® op die lewendige varke geneem. Regressies is tussen vleispersentasies en vetdiktemate en oogspierdeursnit beraam met stapsgewyse regressieanalise. Hoewel die oorpronklike (1992) regressievergelykings nog geldig is - ook vir swaarder karkasse - is die afwyking van die voorspelde klassifikasie vanaf die klassifikasie gebaseer op die waargenome vleispersentasie, kommerwekkend. Dit beteken dat Suid-Afrikaanse varkprodusente te min vergoed word, of die vleishandel en die verbruiker moet te veel betaal. Die prysverskille tussen die maerste twee klasse en die vetste twee klasse is egter so klein dat dit nie 'n noemenswaardige invloed op die vleisprys het nie.


The current regression equations for the prediction of pig carcass lean content in South Africa were calculated in 1992 and had not been updated since, whilst pig carcasses became much leaner and often heavier than the 90 kg originally used. It therefore became necessary to critically evaluate the classification regressions to establish whether the genetic improvement had a substantial effect on lean prediction and whether the same regression may be extrapolated to heavier carcasses. Ultimately, it must be established whether the producer is fairly remunerated. Eighty-one pigs, consisting of five representative genotypes and three sexes (gilts, boars and barrows) at a live mass between 20 kg and 30 kg, were allocated to eight slaughter groups, fed a standard diet and slaughtered at live masses ranging from 74 kg to 160 kg. Fat measurements were taken on the carcasses using a Hennessy Grading Probe® and an Intrascope®, whereafter the left sides were divided into wholesale cuts and dissected into lean, fat, skin and bone. Fat measurements were also taken on the live animals prior to slaughter using a Renco Lean Meater®. Stepwise linear regression analysis was used to calculate regression equations between lean percentage and fat measurements as well as eye muscle diameter. Although the original equations still hold, even for heavier carcasses, alarming deviations from frequencies of observed carcass classifications were observed. This implies that either the producers are paid less than what they deserve, or the meat trade and consumer pay more than what they should. However, the price differences between both the two leanest classes and the two fattest classes are too small to have a significant effect on the price of pork.

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/content/aknat/31/1/EJC128705
2012-01-01
2019-08-21

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