Scielo RSS <![CDATA[South African Journal of Animal Science]]> vol. 45 num. 3 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Relevance of the South African Carcass Classification System</b>]]> <![CDATA[<b>Description of carcass classification goals and the current situation in South Africa</b>]]> Carcass classification is an essential part of efficient animal production, price fixing and meeting consumer demands. Carcass classification (or grading) is based on the description of carcasses by means of clearly defined characteristics that are of prime importance to the meat industry, retailers and consumers. Significant variation exists in carcass composition and quality due to the effects of species, age, maturity type, sex and interaction effects with animal production systems. A number of extrinsic and intrinsic factors affects carcass and meat quality and the purpose of carcass classification in South Africa is to classify carcasses to ensure more consistent meat quality, composition and consumer satisfaction. Although carcass inspection is compulsory in South Africa, carcass classification is not a requisite at all South African abattoirs. South Africa employed a carcass grading system from 1944 to 1992, which was replaced by a carcass classification system in 1992. Carcass classification differs fundamentally from carcass grading. In carcass classification there is a shift of emphasis to classifying carcasses in order to provide the meat industry and consumers with a choice of different types of carcasses in terms of carcass composition and physical attributes, while there is no indication of perceived quality as is provided in a grading system. In a carcass grading system, an indication is provided of standard, prime and superior carcass grades which relate to standard, prime and superior meat quality. The conceptual basis of the carcass classification system is therefore based on the principle that producers, retailers and consumers differ in terms of their perceptions and expectations of carcass and meat quality, and subsequent eating experience. More recently it has become apparent that the current classification system is being used as a grading system due to the use of preferred classes, which defeats the original purpose of a classification system. Furthermore, recent research suggests that the variation within carcass classification categories has increased considerably due to differences between livestock breeds and types, animal production systems and the use of modern feedstuffs and growth enhancing technologies. The purpose of this paper is to review the characteristics and goals of the current South African carcass classification system, grading systems in other countries and the implications for effective marketing, price fixing and consumer satisfaction based on the complex cycle from 'farm to fork'. <![CDATA[<b>The beef tenderness model</b>]]> In Phase1 of this study, three breed types (Simmentaler-, Brahman- and Nguni bulls; n = 60 each) were grain-fed and slaughtered at 12 months of age (A-age, fat-class 2). Feed was withdrawn for either three hours or 24 hours pre-slaughter. Within each feed withdrawal group, three electrical stimulation (ES) treatments were applied, viz. ES for 15 seconds, 120 seconds or no stimulation. In Phase 2, the effects of animal age and feeding regime were investigated using of A-age (feedlot and pasture), AB-age (feedlot and pasture) and B-age (pasture) animals. All carcasses were electrically stimulated for 15 seconds. Longer feed withdrawal increased dark-firm-dry (DFD) meat occurrence (pHu &gt;6) in the Nguni and Simmentaler-cross. Brahman-cross longissimus (LL) tended to be more tender with paler colour and higher drip loss when 120 ES was applied. Longer feed withdrawal recorded higher Warner Bratzler shear force (WBSF) than three hour feed withdrawal. However, ES neutralized the effect of stress on tenderness. On average the AB-age feedlot animals produced the most tender LL followed by the B-age pasture and A-age feedlot which was similar to the AB-age pasture. A-age pasture animals produced the least tender LL steaks. The calpain proteolytic system played a pivotal role in determining the ultimate meat tenderness and although connective tissue becomes less soluble in older animals it did not play the determinant role in tenderness in this study. The intramuscular fat (< 3%) played an important role in the tenderness outcome of Nguni LL which marbled well at AB-age. <![CDATA[<b>Proteomics approach as a new way to predict tenderness as compared to the classical South African Beef Carcass Classification System</b>]]> The current South African Beef Carcass Classification System classifies carcasses using physical attributes such as age, fatness code and the conformation of the carcass as the only indicator of tenderness, implying that optimal tender meat is obtained from carcasses from animals with no permanent teeth. Research shows that if we take modern technologies (use of beta-agonists, growth hormones and electrical stimulation amongst others) into account, this is not necessarily true. In this study m. longissimus lumborum samples were collected from Nguni breed animals, snap frozen and stored at -80 °C for further use in search of protein markers that can be used to predict tenderness in a non-invasive manner. Proteins were extracted in 1 mL TES buffer, isoelectrically focused on strips (pH 5 - 7) and separated by 2D SDS PAGE, stained with coomassie brilliant blue G250) and imaged by a Chemi-doc Mp imager. The results showed differences in protein expression, e.g. some proteins are present at 1 hour post mortem (Day 0) but absent at 3 days post mortem (Day 3). Other proteins showed an increase in expression as ageing progresses. These proteins correlated with myofibril fragments and Warner Bratzler changes which were measured. There are several factors that may be responsible for these changes in differential expression during ageing such as proteolytic action (i.e. calpains and calpastatin system, cathepsins) or maybe apoptosis. The proteins in the profiles of Nguni breed animals which showed differential expression in response to ageing are still to be determined. <![CDATA[<b>Visual evaluation of beef tenderness by using surface structural observations and its relationship to meat colour</b>]]> The study describes the relationship between visual and instrumental measurements for colour and tenderness between five South African beef breeds: Bos indicus (Brahman), Sanga type (Nguni), British Bos taurus (Angus), European Bos taurus (Charolais) and the composite (Bonsmara). Ten animals per genotype were used (total = 50). The carcasses were split and the right sides were electrically stimulated, while the left sides were not stimulated. Steaks were aged until three days post mortem on polystyrene plates and until 9, 14 and 20 days post mortem in vacuum bags. The steaks were evaluated by visual analysis for colour, marbling, fibre separation, surface texture and structure integrity by a 10-member trained panel. Colour was also measured by the CIE L*, a*, b* system using a Minolta meter, and tenderness was measured by means of Warner-Bratzler shear force. High negative correlations were observed between the visual colour and L* (r = -0.809), b* (r = -0.698) and high positive correlations were observed between the visual colour and hue (r = 0.797). There were also negative correlations between shear force and structure integrity (r = -0.410) and fibre separation (r = -0.401). Very low negative correlations were observed between colour and shear force (r = -0.242). Therefore, although it may be possible to judge meat colour by visual analysis, it does not appear possible to predict tenderness by colour judgment. There is potential for an experienced eye to predict tenderness by observing visual structural properties such as fibre separation and structural integrity. <![CDATA[<b>Relevance of the formal red meat classification system to the South African informal livestock sector</b>]]> In 1992 the South African meat industry was deregulated and this led to the formation of the new Marketing of Agricultural Products Act, Act no. 47 of 1996. The Act made provisions for producers to sell animals to customers of their own choice at mutually agreed prices. Thus, producers in the informal sector took advantage of the free marketing system. The result was a substantial increase in the number of animals slaughtered in the informal sector. Unfortunately the requirements for animal identification are not always observed in this sector. Challenges faced by communal farmers which include the multipurpose roles of livestock, lack of slaughter facilities within reasonable distance and lack of access to market information make them less willing to sell their animals through the formal market. The formal market is characterised by meat inspection and carcass classification which scare away the communal farmers for fear of income loss through animal condemnation. The informal sector might not recognise the importance of formal carcass classification. There is need to direct research and development efforts to address marketing constraints faced by communal farmers, and to promote formal marketing of livestock for meat quality assurance and a fair return to the farmers. This review seeks to assess the relevance of formal classification of red meat carcasses to the informal sector, make recommendations on ways to ameliorate the undesirable effect of the classification system on the informal sector, and identify possible areas which need further research to develop the classification system in South Africa. <![CDATA[<b>Associations between animal traits, carcass traits and carcass classification in a selected abattoir in the Eastern Cape Province, South Africa</b>]]> In this study the associations between animal traits, carcass traits and carcass classification within cattle, sheep and pigs slaughtered in a high throughput abattoir were determined. Classes of carcasses from cattle, sheep and pigs delivered for slaughter at this abattoir were recorded and analysed. Significant associations were found between carcass classes and breeds of all livestock species. Of all the cattle delivered to the abattoir, the non-descript ones dominated the AB2 category while the Bonsmara and Brahman dominated the C categories. Almost 70% of carcasses of the cattle delivered to the abattoir were in the C classes. In the sheep, the dominant category was A2 with a percentage of 77%, and the Dorper was the most dominant in this category. In pigs, the P class was the most dominant with about 50%, and the Duroc X Landrace cross dominated this category. However, significant associations between sex and carcass classes were only found in cattle. Warm carcass mass had significant associations with carcass classes of cattle and sheep only. It can be concluded that while associations between carcass classes and breeds were found in all species, associations between sex and carcasses were dependent on species. <![CDATA[<b>Sources of variation in quality of South African beef: Case studies in relation to the red meat classification system</b>]]> The South African classification system describes beef carcasses in regard to visual fat cover, conformation and age by dentition. Animal age provides a fairly accurate description of expected eating quality in regard to tenderness in an industry where other sources of variation in tenderness are limited. Since deregulation in the beef industry in the 90s many changes have occurred in all parts of the value chain. This paper presents a number of case studies that focussed on the sources of variation in meat quality, but in particular on sources of changes in meat tenderness over the past two decades. These sources include feeding regime, the use of beta agonists, post mortem ageing and electrical stimulation. In some studies these factors are integrated with age or interactions among two or more of these factors are investigated. <![CDATA[<b>Fat quality of South African pigs with different carcass classification characteristics</b>]]> The carcasses of South African pigs are classified into six groups (PORCUS) according to their calculated lean meat content and measured backfat thickness. Pigs with the highest lean meat content and lowest backfat thickness belong to the P group. Fat quality of backfat from 2107 pig carcasses, sampled within the different pork classification groups at a major South African pig abattoir, was evaluated to determine the relationship between carcass classification and backfat quality. Extracted fat was used to determine the iodine value of these samples. Significant differences in carcass characteristics and iodine value were observed between the classification groups. Improved fat quality, indicated by a lower iodine value, was associated with increased backfat thickness and decreased lean meat content. The P and O classification groups (with backfat thickness <17 mm) could not conform to international standards proposed for good technological quality backfat. The C, U and S groups (with backfat between 23 and &gt;32 mm) possessed good technological quality backfat. Backfat from the R group had borderline fat quality. Correlation analyses were employed to acquire equations to describe relationships between iodine value and carcass classification data. The French classification system predicts fat quality by utilizing backfat thickness and lean meat content. It was proposed, through modification of the French system, that South African pig carcasses with a backfat thickness &gt;17 mm and a lean meat content <67% would potentialy deliver good quality backfat. Results from this study indicate that carcass classification data may be used to improve the probability of selecting pig carcasses with good quality fat. <![CDATA[<b>Nutrient content of South African red meat and the effect of age and production system</b>]]> Feeding systems, slaughter age and other production techniques notably influence the nutrient content of red meat. The modernization of the different South African production systems since the previous nutrient composition studies, justifies the necessity to update existing knowledge on the nutritional profile of South African produced beef. In addition, a need was identified to extrapolate the effect of the two different feeding systems (extensive and intensive) on this nutritional profile. Results indicate that the total lipid content of marketable young carcasses (age A, fat code 2) has decreased over time, in line with global health and nutrition trends for leaner foods. With the majority of beef from these young carcasses being produced on intensive grain-based feeding systems, South Africa has a unique advantage in terms of total lipid content of such grain-fed produce. Internationally, grain-fed red meat is in most cases higher in total and saturated fat content compared to grass-fed counterparts, while in South African the opposite was observed. In addition to total fat content, the role of various lipid fractions in human health has often been associated with specific produce positioning and marketing. South African grass-fed beef is significantly higher in healthy omega 3 fatty acids and conjugated linoleic acid, irrespective of degree of fat trimming. From a human nutrition perspective, it should be kept in mind that the total amount of omega 3 fatty acids per edible portion of beef produced in either production system is low in comparison to human dietary recommendations. <![CDATA[<b>Changes in the composition of South African red meat</b>]]> Red meat often evokes a wide array of complex and contradictory arguments. It is viewed as the most expensive component of any diet, supplying many essential nutrients as part of a healthy, prudent eating plan. Yet, red meat is non-homogenous, unique to each country, and continually changing in composition. It is observed that the amount of fat on carcasses has reduced over time, simultaneously improving nutrient density through feed efficiency. The objective of this paper is to present composition data on South African lamb, mutton and beef, and report on the changes observed between local data and international data (for lamb and mutton), as well as changes in the composition of South African beef over time. South African lamb and mutton contain notably less fat and more nutrients per 100 g product than international sheep meat produced, rendering a lean product with a higher nutrient density. Compared to previous studies on South African beef, the current data indicate notable changes in the composition over time, specifically related to a reduction in fat content. This reduction together with changes in carcass weight has resulted in changes in carcass composition and thus changes in nutrient density. The data attest that in order to align industry processes, as well as legislation and marketing strategies, continued research on composition needs to be performed for the baseline information to remain relevant and accurate. <![CDATA[<b>A consumer perspective of the South African red meat classification system</b>]]> The South African consumer market is characterised by socio-economic and cultural diversity. Food expenditure patterns, behaviour and preferences differ significantly between the various socio-economic subgroups. Packaging information, including red meat classification information, could be an important tangible resource used by consumers to gauge product quality. The first objective of the research reported in this paper is to investigate the red meat knowledge, usage and perceptions regarding beef and sheep meat classification and related quality parameters among South African consumers. Consumer perceptions of red meat classification were extracted from a comprehensive consumer survey among stratified representative samples of South African low-, middle- and high-income consumers (n = 165, n = 171 and n = 249). The paper also briefly reports on an in-store 'observational' research project that was conducted to develop an understanding of the communication of carcass classification to consumers through fresh red meat product labels at independent butchers and large retailers across South Africa (n = 60). Low-income consumers had very limited understanding and gave little attention to red meat classification. Even though middle-class and wealthy consumers also have a limited understanding of red meat classification, about half of these consumers check for a classification mark. Red meat classification was not mentioned by consumers as a major concern regarding red meat, but related aspects were important such as quality, fattiness, tenderness, juiciness, taste, freshness, smell and appearance. Purchase considerations for beef and mutton/lamb focussed largely on safety, appearance, price and eating quality. Labelling information observed at retail outlets gave very little attention to classification. There is a definite need for consumer education relating to the red meat classification system and for the development of an appropriate front-of-pack labelling system to communicate red meat classification.