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How pig pre-slaughter welfare affects pork quality and the pig industry

By Voster Muchenje and Saymore Petros Ndou, Department of Livestock and Pasture Science, University of Fort Hare
South Africa contributes about 0.2% of the world pig population with about 1.6 million pigs, which are kept for pork production. The demand for animal-protein is necessitated by the ever increasing human population. Most of the pigs are slaughtered in commercial abattoirs. Slaughterhouses are located some distance from pig farms, hence, pigs are inevitably exposed to pre-slaughter handling procedures that may affect the quality of pork. Pre-slaughter welfare procedures that stress the pigs may not only influence the conversion of muscle to pork, but may also compromise pig health and well-being. Handling procedures, which are harsh, result in on-farm or transport mortalities, cause skin and carcass damage due to bruising and injury, thereby increasing the economic losses to the pork industry.
The pre-slaughter welfare of a pig refers to the influence of the various internal challenges or conditions on the physiological or biochemical state of the pig at the time of observation, during the growth phase and handling before slaughter. Producer and consumer concerns of pig pre-slaughter welfare are major issues in most developed countries and are based on the fact that animals can suffer, eventually leading to low pork eating quality, especially when the five familiar freedoms that define the animal’s fundamental needs and freedoms are not met.
These are freedom from thirst; hunger and malnutrition; discomfort; pain, injury and disease; fear and distress. Pre-slaughter stress influences pork attributes such as acidity, PSE, dark firm dry (DFD), aroma, bruising, toughness, sogginess, cooking loss, meat dryness, colour, water holding capacity, texture and rancidity in stored products.
The PSE pork is characterised by pale colour (photo top), soft texture and low water-holding capacity. The PSE is a meat quality defect, which is caused by a combination of factors, such as stress-susceptible genes, rough handling shortly after slaughter and poor carcass chilling. The PSE conditions result in reduced shelf life due to increased chances of growth of microorganisms. PSE is common in November and December when abattoirs handle high numbers of pigs in preparation for Christmas. Conversely, DFD pork (photo top) has a dark, unattractive appearance and a firm, dry and sticky texture due to enhanced water binding capability. Pork that is dark in colour represents a major problem to the pork industry due to its poor processing characteristics and unacceptable appearance to both processors and consumers.
Different vehicles
Most pigs are transported to markets and/or slaughterhouses in different forms of vehicles. As pigs are transported, several human-animal interactions and environmental factors that affect pig welfare are at play. These factors include handling, genotype, nutrition, feed withdrawal, loading, transportation to the slaughterhouse, off-loading, lairage waiting, and finally the slaughtering process. These conditions influence pig behaviour, welfare, productivity and subsequently pork quality.
Animal handlers are faced with challenges of improving physical post mortem pork attributes which are concerned with both consumer acceptance and technological aspects.
Other pork characteristics that are affected by pre-slaughter stress include shelf life, cooking loss and tenderness. All these are important in the meat science and technology industry and they also influence consumers’ purchasing decisions, preferences and eating behaviours.  Producers and abattoir operators need to improve the way pigs are handled if they are to benefit from improved pork products. This should be supported by research on the perception of farmers, butcheries and consumers on pig handling, transportation and slaughterhouse practices and their effects on pig injuries, bruising and pork quality.
Developed countries
Animal welfare issues are a major consideration in most developed countries; and this has led to government interventions and the formation of non-profit organisations, which are responsible for raising animal welfare awareness issues. Developing countries such as South Africa are becoming conscious of animal welfare issues and some regulations such as the “Code of practice for the handling and transport of livestock,” are being implemented.
Poor handling facilities, lack of education on animal handling and welfare awareness issues, to some extent, social customs and beliefs are major impediments to proper animal welfare amongst most farmers in the developing world. Pigs respond to handling procedures through behavioural expressions. Stockpersons should understand the behaviour of pigs so that stress can be reduced. Welfare audits or assessment records, currently used in countries such as the USA and Canada, can potentially improve animal handling of commercial pigs in South Africa. Assessment records of pig welfare status should accompany traceable records about the history of the animals from rearing at the farm until the time of slaughter at the abattoir.
On-farm handling procedures begin at the time of birth up to the time of loading onto vehicles. On-farm handling and welfare practices are influenced by factors such as loading, use of sticks or electrical goads, appropriateness of handling facilities, previous experience and the skill of the handler. Poor handling may lead to serious injuries and bruising, especially to pigs that are not familiar with new confinements and handling. The situation can be worsened if stockpersons are not familiar with the principles of pig behaviour, such as flight zones, visual fields and social instincts. Implementation of such principles protects pigs from forceful physical disturbances leading to reduced cases of carcass devaluation. Carcass devaluation leads to huge losses to farmers and the pig industry because consumers do not accept poor meat quality, while trimming imposes additional expenses in terms of labour.
Harsh handling
Any occurrence of bruises indicates that some handling aspect was harsh because skin damage from an injury is inevitably painful to the animal. Age and position of the bruises indicate when and where the welfare between the farmer, the transporter and the abattoir owner needs to be improved. Incidences of bruises can be reduced through the use of opaque passages, shades, uniform colours of handling facilities, flipping flags, proper loading facilities and formulating pig groups according to age, sex, size or herd.
Transportation of animals to slaughterhouses is inevitable, but can be potentially harmful. The process is characterised by threatening and novel events that can physically or physiologically hinder pig wellness depending on the mode of transportation and road type used. Vehicles used for transportation should be suitable and not overloaded. Unfamiliarity of pigs to novel transport conditions, different social groups, weather conditions, loading density, duration of trip and loading or unloading and associated handling during transportation influence the welfare status of pigs.
Long journeys without resting periods result in huge economic losses to the pig industry, especially when the pigs are loaded at high stocking densities. By regulation, all pigs should at least be able to stand or lie down in their natural position, requiring a stocking density of 0.30 m2/100 kg pig. For example, a typical vehicle compartment with a space of 6 m2 can accommodate twenty 90kg pigs. The vehicle should be partitioned to reduce physical interaction between pigs, and the duration of the journey should not be longer than eight hours. Moreover, laws and ordinances governing animal transportation in the developing world are either not explicitly enforced, lax or absent.
Transport regulations in effect in South Africa can be obtained from the Red Meat Abattoir Association and Department of Agriculture (http://www.rmaa.co.za/legislationsummary.htm). However, information to confirm the implementation of these guidelines in the local meat industry is scarce.
Handling in the resting pens at the slaughterhouse (photo below) is important to allow recovery and acclimatisation from trauma and novelty of the transport, and to produce pork of high quality. The welfare status of the animal at the slaughterhouse is influenced by how animals are unloaded from the vehicle, duration of resting, stocking density, weather conditions and ventilation in the resting pens. Welfare procedures associated with pre-slaughter conditions at the abattoir begin during unloading of animals up to the time when the animals are stunned in the slaughterhouse. During unloading, proper handling facilities and knowledge of behavioural aspects, such as pig comfort zone and visual fields prevent detrimental effects which may occur. These include bruises, injuries and broken limbs which induce negative effects on animal well-being, carcass grading or classification and subsequently consumer acceptability.
Inferior quality
Handling methods that result in high carcass temperatures during slaughter may lead to inferior pork quality. However, allowing the pigs to shower will reduce body temperature which should remain within the normal range of 38.7 to 39.8 oC at slaughter. Management should consult climate and weather forecasting information before transporting pigs, to reduce pork defects associated with thermoregulation because, by nature, pigs are heat susceptible. Pigs that are easily agitated by nature, difficult to drive and handle for short periods (< 2 hours) are at a greater risk of producing inferior pork which appears pale, lacking firmness and with fluid dripping from its cut surfaces. This pork quality is commonly referred to as pale, soft, exudative (PSE) and is difficult to use when preparing pork by-products such as ham, polony and sausages. Pork which has high fluid loss can reduce profitability due to reductions in weight. There is a need to ascertain or quantify actual optimum resting time for optimisation of desired pork quality.
Although the method of stunning affects pork eating quality, CO2 stunning systems improve carcass and meat quality attributes of pork to a greater extent than electrical stunning. In Denmark, researchers have developed excellent CO2 stunning chambers and handling systems which allow pigs to be stunned in a group of four or five without the use of electrical goads for moving the animals. Although this system has not been introduced in South Africa, the use of gases during stunning imposes economic advantages such as reduced blood splashing, reduced PSE incidences and enhanced worker safety.
Pre-slaughter welfare procedures which are stressful will subsequently influence the process of transformation of pig to pork. Pre-slaughter pig handling management is important in improving pork quality because failure to improve pig pre-slaughter management affects consumers’ decisions to buy pork products. This signifies a major problem for the pig industry.
A detailed review on this topic by the authors is available on the SAPPO website: http://www.sapork.com/

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