Preslaughter handling of ruminants and meat quality

Considering the above mentioned background, in SA the interest in AW when it comes to production animals has been based more on economic reasons (the loss of quality and quantity of the meat due to mistreatment or loss of access to higher priced markets) rather than just on ethical reasons. Poor AW due structural deficiencies and to bad handling of meat producing animals leads to economical losses by increasing animal deaths, carcass weight losses, trimmings due to injections and bruising, and by negatively affecting meat quality.

Bruises and dark cutting are some of the main problems encountered. A bruise is defined as a tissue injury with rupture of the vascular supply and accumulation of blood and serum (Hoffman et al., Reference Hoffman, Spire, Schwenke and Unruh1998). The presence of bruises on ruminant carcasses directly affects meat quality because bruised tissues need to be trimmed off; it is also used as an indicator of poor welfare during preslaughter operations, because it shows that animals have been hit or handled in an inappropriate way, resulting not only in animal fear but also pain (Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2009, Reference Strappini, Metz, Gallo, Frankena, Vargas, de Freslon and Kemp2012 and Reference Strappini, Metz, Gallo and Kemp2013; Romero et al., Reference Romero, Uribe-Velásquez, Sánchez and Miranda-De La Lama2013). When meat quality alterations are present postmortem it implies that AW was impaired (Gregory, Reference Gregory1998). Meat colour and pH alterations are a reflection of stressful conditions due to inadequate handling of animals during preslaughter operations and long deprivation of food and water (Gallo, Reference Gallo, Tadich, Huertas, César, Paranhos Da Costa and Broom2009; Romero et al., Reference Romero, Uribe-Velásquez, Sánchez and Miranda-De La Lama2013). Stressful conditions during preslaughter handling reduce muscle glycogen content which at the moment of slaughtering results in low production of lactic acid; therefore, meat has a high pH (>5.8), high water holding capacity and an unattractive dark colour; this condition is known as DFD (dark, firm and dry) meat (McVeigh and Tarrant, Reference Mc Veigh and Tarrant1982). The effects of chronic stress on muscle glycogen depletion and the consequent dark cutting condition have been well reviewed (Ferguson and Warner, Reference Ferguson and Warner2008). As colour and pH alterations affect consumer acceptability and shelf life of meat it has economical implications. Therefore, the measurement of muscle pH at 24 h after slaughter is a criterion routinely used at slaughterhouses to determine meat quality and take further processing decisions.

By improving productivity and product quality in livestock production through better AW, the provision of appropriate amounts of good quality food for human consumption can be assured and the welfare of people can be also improved. Therefore, the strategy for most of the research in AW of meat producing livestock in SA has dealt with relating AW to product quality (Gallo, Reference Gallo, Warriss, Knowles, Negrón, Valdés and Mencarini2012; Paranhos Da Costa et al., Reference Paranhos Da Costa, Huertas, Gallo and Dalla Costa2012; Huertas et al., Reference Huertas, Gil, Piaggio and Eerdenburg2014). Complementarily, the dissemination of information about AW topics and relevant research in the subject has been important in order to socialize AW global knowledge and understand practical applications. Since 2004 numerous national and international meetings dealing with AW have been organized in countries such as Argentina, Brazil, Chile, Colombia and Uruguay (Gallo et al., Reference Gallo and Tadich2010). During 2009 the Animal Welfare Programmes of the Universidad Austral de Chile and the Universidad de la República del Uruguay were officially recognized by the OIE as a Collaborating Centre for Animal Welfare Chile-Uruguay. In 2013 the OIE Collaborating Centre for AW and livestock production systems has also incorporated the Animal Welfare Programme of the Faculty of Veterinary Sciences at Universidad Nacional Autónoma of Mexico. Its mission is to promote AW with particular emphasis in production and working animals under SA production systems.

The aim of this review is to show the results of research dealing with AW of ruminant livestock for meat production in Chile, although results could be made extensive to many other countries in SA according to earlier published information on the region (Grandin and Gallo, Reference Grandin and Gallo2007; Gallo, Reference Gallo and Gatica2008; Gallo and Tadich, Reference Gallo, Pérez, Sanhueza and Gasic2008).

Stakeholders

According to Gallo and Tadich (Reference Gallo, Pérez, Sanhueza and Gasic2008) the main stakeholders of the meat chain are producers, livestock markets, livestock dealers, livestock transporters, slaughterhouses, supermarkets and butchers. Moreover, cattle producers can be divided in those who breed and fatten beef (complete cycle), those who only produce weaned calves, and those who buy calves and other cattle for fattening and selling. Cattle producers in most SA countries, frequently sell their stock through cattle dealers instead of selling directly to slaughterhouses. Small ruminants like lambs, goats and camelids can go directly to slaughterhouses, to livestock markets and to intermediate dealers; however, the market for goats and camelids is small and scarcely developed, meaning that there is a considerable amount of animals that are slaughtered for home consumption and do not pass through slaughterhouses; moreover, this meat is rarely found for sale in butcher shops or supermarkets.

Handling of animals pre-transport

Animals that are bred extensively usually have few contact with people and are difficult to handle. There are also some structural deficiencies at farm and slaughterhouse level, mainly due to inadequate design and poor maintenance of handling structures (pens, corrals, races, crates, loading ramps and others). In the case of sheep, it is common that the flock, including ewes and lambs, is rounded up and driven for several kilometres to the farm corrals, then the lambs are weaned and immediately afterwards loaded into the transport vehicles. These commercial procedures in lambs destined for slaughter, particularly when transported for 48 h as it is the case of the Chilean Patagonia, are stressful and exhaust body reserves (Tadich et al., Reference Tadich, Gallo, Echeverría and Van Schaik2009). In the case of goats and camelids, there is very little information regarding preslaughter operations in SA; a recent study in llamas (Mamani-Linares and Gallo, Reference Mamani-Linares and Gallo2014) concluded that preslaughter handling of llamas under commercial conditions produces physiological changes similar to those in other species, which fall within acceptable limits for their welfare; however, stress could be reduced and adverse effects like bruises could be minimized by designing proper facilities and following OIE recommendations.

Training of animal handlers

In general, a lack of formal training of animal handlers has been evidenced (Cáraves et al., Reference Cáraves, Gallo, Strappini, Aguayo, Allende, Chacón and Briones2006 and Reference Cáraves, Gallo, Strappini, Barrientos, Allende, Chacón and Briones2007; Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2007), which constitutes a primary problem that affects AW in SA countries. Most of the stockpersons (65%) observed by De Vries (Reference Del Campo, Brito, Soares de Lima, Hernández and Montossi2011) at Chilean livestock markets had a negative human–animal relationship. Moreover, it has been well established that cattle going through markets have more bruises than cattle going directly from farm to slaughterhouse (Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2009, Reference Strappini, Gallo, Cáraves, Barrientos, Allende, Chacón and Briones2010, Reference Strappini, Metz, Gallo, Frankena, Vargas, de Freslon and Kemp2012 and Reference Strappini, Metz, Gallo and Kemp2013).

Bad practices used to get the animals to move, especially when loading and unloading, are observed to be commonplace (Gallo and Tadich, Reference Gallo, Pérez, Sanhueza and Gasic2008); there is a tendency to use aggressive strategies to drive animals and inappropriate aids (sticks, goads, shouting and sometimes even unsuitable handling practices that are described by the OIE, 2013), such as pulling sheep from the fleece or twisting of tails. Training abattoir personnel has been used in intervention studies and its effectiveness has been assessed after the training, using animal behaviour and meat quality measures in slaughterplants (Gallo et al., Reference Gallo2003a and Reference Gallo, Lizondo and Knowles2003c). In 2013 new regulations have been passed in Chile, making it mandatory that there should be at least one trained person in charge of handling animals in each of the premises involved: farms, livestock markets, slaughterhouses, transporters (Chile, 2013a, 2013b and 2013c), getting in line with OIE standards.

Vehicles and roads

The great majority of the animals destined for slaughter are transported by road, in trucks; there are only a few circumstances where a small proportion of animals also have to travel by ferry (Chile) or on boats (some journeys in Amazonian countries). In most SA countries there are paved carriageways in good condition leading to the main cities, but there are also many unpaved or stone roads, often in bad conditions; this is specially the case of side roads serving the farms (Gallo and Tadich, Reference Gallo, Pérez, Sanhueza and Gasic2008). Consequently, travelling is slow because of the geography (including mountainous and winding roads) and the nature of the roads, and there is no close relationship between distance travelled and journey duration (Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2007; Tarumán, Reference Tarumán and Gallo2013).

It is common in Chile and other countries to use trucks with a coupled trailer, making the job of drivers more difficult and adding further risks to livestock transportation. Trucks have no roof and additionally, the use of internal separations in the loading compartment for cattle transport is unfrequent, usually transporting them in big groups (18 to 22 heads/compartment, Gallo et al., Reference Gallo, Teuber, Cartes, Uribe and Grandin2005) instead of smaller groups as recommended (Grandin and Gallo, Reference Grandin and Gallo2007). Vehicles used for the transport of sheep are generally metalic, with two or three floors, also without roof; these have internal separations for transporting the sheep in small groups (Gallo, Reference Gallo, Tadich, Huertas, César, Paranhos Da Costa and Broom2009).

Transport duration and conditions for ruminants during the journey

Bad practices during loading, transport and unloading of cattle are common, as well as overstocking the trucks (Gallo et al., Reference Gallo, Teuber, Cartes, Uribe and Grandin2005). There is no indication that space allowance in longer journeys is higher than in shorter journeys (Aguayo and Gallo, Reference Aguayo and Gallo2005 and Reference Aguayo and Gallo2006). In fact 34.4% of the 413 loads surveyed by Gallo et al. (Reference Gallo, Teuber, Cartes, Uribe and Grandin2005) arrived at the slaughterhouses at estimated stocking densities higher than permitted by the current legislation (500 kg/m²). High stocking densities are commonly observed in SA countries and overloading trucks when transporting cattle has been observed to be a problem in the region, but no precise figures on actual stocking densities used are available, except for the case of Chile (455 kg/m² by Gallo et al., Reference Gallo, Teuber, Cartes, Uribe and Grandin2005; Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2007) and Uruguay (450 kg/m² by Huertas et al., Reference Huertas, Gallo and Galindo2003; Bianchi and Garibotto, Reference Bianchi and Garibotto2004). The effect of stocking densities of 400 v. 500 kg/m² during transportation on the concentration of blood variables indicators of stress was studied in steers transported for 3 and 16 h (Tadich et al., Reference Tadich, Gallo, Brito and Broom2003a); a stocking density of 500 kg/m² produced higher cortisol (P=0.0021), glucose (P=0.039) and CK (P=0.024) at arrival at the slaughterhouse.

With the exception of some countries (Paraguay, Brazil, Uruguay, Argentina), it is not a common practice to separate cattle in smaller groups within the truck (Gallo and Tadich, Reference Gallo, Pérez, Sanhueza and Gasic2008) and there is no provision of water/feed for animals in the vehicle, also it is uncommon that they are unloaded at resting posts (Grandin and Gallo, Reference Grandin and Gallo2007; Gallo, Reference Gallo and Gatica2008).One of the longest journeys would be the one affecting cattle and sheep produced in the Chilean Patagonia Region of Aysén; these animals are frequently transported without water and food, by road and ferry, for distances up to 1700 km and durations up to 72 h (Aguayo and Gallo, Reference Aguayo and Gallo2005; Werner et al., Reference Werner, Hepp, Soto, Gallardo, Bustamante and Gallo2013). Transport durations of 24 and 36 h have been observed to negatively affect cattle welfare, when measured through blood indicators of stress and animal behaviour (Tadich et al., Reference Tadich, Alvarado and Gallo2000).

Very little information on small ruminant transport in SA is available. In Chile most common distances travelled by over 80% of the sheep are short (up to 400 km, Tarumán and Gallo, Reference Tarumán2008). Total transport time for lambs in Chile fluctuates between 0.75 and 75 h (around 5% of the sheep are subjected to the latter which includes maritime ferry crossing) and distances between 5 and 1356 km (Carter and Gallo, Reference Carter and Gallo2008; Gallo, Reference Gallo, Tadich, Huertas, César, Paranhos Da Costa and Broom2009). Owing to the particular characteristics of the roads in the Patagonia (stone roads, very winding and with high slopes), where most Chilean lambs are produced, journeys usually take much longer than expected for the distances travelled (Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2007; Tarumán, Reference Tarumán and Gallo2013).The space availability found by Tarumán and Gallo (Reference Tarumán2008) for lambs was 0.16 to 0.22 m²/lamb (4.55 to 6.14 lambs/m²).

From a welfare point of view as well as from a meat quantity/quality point of view an aspect to be improved is the provision of water and food when transport is prolongued over 24 h. For the case of the ferry crossing in Chile Navarro et al. (Reference Navarro, Gallo and Strappini2007), showed that during the sea crossing and when trucks had stopped, lambs did consume water when available.

Transport of ruminant livestock and meat quality

In relation to the effects of transport duration on bruising, most studies have registered bruises on the carcasses of cattle (Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2009, Reference Strappini, Gallo, Cáraves, Barrientos, Allende, Chacón and Briones2010 and Reference Strappini, Metz, Gallo, Frankena, Vargas, de Freslon and Kemp2012; Huertas et al., Reference Huertas, Gil, Suanes, Cernicchiaro, Zaffaroni, de Freitas and Invernizzi2010; Romero et al., Reference Romero, Uribe-Velásquez, Sánchez and Miranda-De La Lama2013), sheep (Carter and Gallo, Reference Carter and Gallo2008; Tarumán and Gallo, Reference Tarumán2008; Tarumán, Reference Tarumán and Gallo2013) or llamas (Mamani-Linares and Gallo, Reference Mamani-Linares and Gallo2014) at the end of the process (at slaughter), therefore it was not possible to distinguish if bruises had occurred on farm, during transport or at the slaughterhouse. In order to try to distinguish exactly where bruises originate we followed the whole process of loading, transport, unloading, lairage and stunning of culled dairy cows using direct continuous observation and videos (Strappini et al., Reference Strappini, Metz, Gallo and Kemp2013). It was possible to register when and where the potential bruising events occurred. It was remarkable to find out that after a mean of 3 h transport and 19 h lairage, a total of 1792 events occurred; 91% of these were observed during lairage, 5.4% in the stunning box, 2.5% at loading, 0.4% during transport and 0.5% at unloading (Strappini et al., Reference Strappini, Metz, Gallo and Kemp2013). Hence, many events happened very close to slaughter time, whereas few traumatic events happened during short transport. When using the video analysis, it was possible to detect the moment, stage of infliction and the type of event that caused the lesion for 52 bruises (66.7%) out of the total of 78 bruises observed; 38.5% of the bruises occurred within 1 h before slaughter, in the stunning box and were due to impact with a blunt object, this was the case of the sliding doors at the stunning box. Pricking with sticks was commonly observed, usually during loading of the cattle on the farm. All bruises observed by Strappini et al. (Reference Strappini, Metz, Gallo and Kemp2013) were sampled for macro/microscopic and histochemical analyses and a sample of 16 bruises with known origin (and hence known age between <1 and 23 h) was used to find out whether it would be possible to use these techniques for determining age of the lesions. Through macroscopic (colour, diameter, depth, shape and anatomical location) and microscopic (presence of erythrocytes, hemosiderin, inflammatory infiltrate, fibrin, necrosis and fibrosis) characteristics of the bruises it was possible to determine at which stage during preslaughter handling they had been originated; however, within the age range of the bruises studied (up to 23 h) it was not possible to determine actual age by colour nor by immunohistochemical markers (fibronectin, collagen III and IL8) (Vargas, Reference Vargas2014).

In sheep 7.5% bruised carcasses were found; bruises were mainly small in extension and affected only subcutaneous tissue (Tarumán and Gallo, Reference Tarumán2008). In Chilean studies (Carter and Gallo, Reference Carter and Gallo2008; Tarumán and Gallo, Reference Tarumán2008; Tarumán, Reference Tarumán and Gallo2013) a directly proportional relationship between the incidence of bruises and transport duration (up to 48 h) has been observed; however, in none of the studies a separation was made between transport itself and the handling during loading and unloading of the lambs. In the case of llamas, methods of loading and unloading, as well as the lack of loading ramps on farms and llama slaughterhouses have been observed to increase animal–handler interactions, which could lead to bruising (Mamani-Linares and Gallo, Reference Mamani-Linares and Gallo2014).

Training of transporters

It is crucial that drivers transporting livestock are trained. OIE standards (OIE, 2013) recommend compulsory formal training, evidenced through a certificate given by an institution recognized by the competent authority of each country. Livestock transport drivers as well as animal handlers who help in the process of loading and unloading the animals in general lack training (Cáraves et al., Reference Cáraves, Gallo, Strappini, Aguayo, Allende, Chacón and Briones2006 and Reference Cáraves, Gallo, Strappini, Barrientos, Allende, Chacón and Briones2007; Strappini et al., Reference Strappini, Frankena, Metz, Gallo and Kemp2007; De Vries, Reference Del Campo, Brito, Soares de Lima, Hernández and Montossi2011). Efforts are being made in many SA countries to fulfil AW recommendations provided by the OIE (2013) through the development of national legislation. In Chile, the new regulations approved in 2013 (Chile, 2013a, 2013b and 2013c) state that animal handlers during transport need to be trained and accredit this through a formal certificate given by institutions approved by the Agriculture and Livestock Service of the Ministry of Agriculture.

Lairage

A common problem mentioned in several SA countries is the long waiting time before the animals are unloaded in the stockyards, as well as long lairage times once at the slaughterhouse. In most SA countries there is by law a minimum lairage time between 6 and 24 h (Gallo and Tadich, Reference Gallo, Pérez, Sanhueza and Gasic2008). In Chile there is no minimum lairage time for ruminants (Chile, 2009). Frequently lairage times are extended much longer than the minimum because of operational reasons and/or inadequate planning.

The time animals spend without food and water is important from a welfare point of view, as they suffer from thirst and hunger, as well as from a meat quantity (carcass weight loss) and quality (high pH meat) point of view (Gallo and Gatica, Reference Gallo1995; Gallo et al., Reference Gallo, Altamirano and Uribe2003b). The effect of food deprivation in cattle on blood variable indicators of stress differs according to duration (hours) and whether it occurs together with transport or not. Results of the effects of fasting for 3 and for 16 h, in both cases with and without transport, show that fasting with transport has an additional effect compared with deprivation of food in pens, which reflects more stress (Tadich et al., Reference Tadich, Gallo, Bustamante, Schwerter and Van Schaik2003b). Steers with 24 h of fasting at the slaughterhouse showed 9.4 times a higher probability of having a muscle pH >5.8 in their carcasses than those with 3 h fasting, independently of the previous transport time (Amtmann et al., Reference Amtmann, Gallo, Van Schaik and Tadich2006). During lairage an increase in live and carcass weight can be observed in steers that were previously transported for over 12 h, but not in those with short transport (<6 h) (Gallo et al., Reference Gallo2000 and Reference Gallo, Altamirano and Uribe2003b). This can be attributed to water intake, as it has been also found that steers with over 24 h transport drink water in the lairage pen as soon as they arrive, whereas steers with <6 h transport do not drink (Estrada et al., Reference Estrada, Strappini and Gallo2009).

Lairage times have been in general reduced in Chilean slaughterhouses in the last few years, and also regulations do not state a minimum duration for ruminant lairage. However, still the most common situation is that cattle and sheep arrive the night before slaughter, reaching 12 h lairage as a mean (Herrera and Gallo, Reference Herrera and Gallo2009); it is not mandatory for ruminants to receive feed during this time, only if they stay over 24 h.

If feed deprivation due to transport is added to fasting during lairage, it is not uncommon that cattle and sheep proceeding from the Patagonia (over 1000 km transport) reach up to 60±19 h fasting due to transport plus lairage (Aguayo and Gallo, Reference Aguayo and Gallo2005; Carter and Gallo, Reference Carter and Gallo2008). Considering this fasting duration, Gallo and Gatica (Reference Gallo1995) found a significant decrease in carcass and liver weight. Carcass muscular pH has also been shown to be higher as lairage time increases, being more evident if previous transport has also been prolonged (Gallo et al., 2003Reference Gallo, Altamirano and Uribeb). The effects of lairage duration need to be studied in each country according to their own production and transport conditions, as well as type of cattle. In Colombia, it has been observed that cattle remain in lairage for up to 5 days in some cases, with water but no food available (Ramírez and Gallo, Reference Ramírez and Gallo2012).

Experiments observing the behaviour of steers (Estrada et al., Reference Estrada, Strappini and Gallo2009) and cows (Opitz et al., Reference Opitz, Strappini, Vargas and Gallo2012) during lairage show that during this period many animal–animal interactions occur, that can produce bruises and also use glycogen reserves favouring high pH presentation in the carcasses. Estrada et al. (Reference Estrada, Strappini and Gallo2009) found that during lairage steers that underwent a long previous transport journey (>24 h) lie down sooner and more and drank water immediately after arrival, whereas those with short transport journeys (up to 3 h) remained standing and did not drink. On the other hand agonistic behaviours were more frequent in the steers with short transport journeys.

In Chile a direct relationship between cattle transport duration and lairage duration has been established with high pH. After a transport of 16 h, carcass weight of steers of the same origin and similar live weights have been observed to be lower than after a transport of 3 h (Gallo et al., Reference Gallo, Altamirano and Uribe2003b); steers transported for 16 or 24 h present 3.6 and 5.4 times a higher probability of having carcasses with pH >5,8, respectively, compared with those transported for 3 h, independently of the lairage time (Amtmann et al., Reference Amtmann, Gallo, Van Schaik and Tadich2006). In general from an AW point of view, prolonging lairage duration from 3 to 24 h in order to recover basal blood indicators from transport stress, does not help much in cattle because basal levels are not recovered before 24 h and negative effects on meat quality such as dark cutting do not justify it, particularly if animals are not fed (Tadich et al., Reference Tadich, Gallo, Knowles, Uribe and Aranis2005).

In sheep, feed deprivation times due to transport and lairage are also prolonged in Chile. The mean lairage time for sheep has been found to be 15 h, fluctuating between 5 and 26 h (Gallo, Reference Gallo, Tadich, Huertas, César, Paranhos Da Costa and Broom2009). It needs to be considered that in lambs slaughter age is proportionately shorter than in cattle and in most cases lambs are also weaned immediately before loading and transporting them for slaughter, with a consequently additional stress. The concentration of β-hydroxybutyrate, an indicator of prolonged feed deprivation, increases significantly in lambs with 68 h fasting; this time includes collection from the paddocks, a 48 h transportation time and lairage afterwards, indicating that body reserves are being used for maintenance (Tadich et al., Reference Tadich, Gallo, Echeverría and Van Schaik2009). In fact it coincides with the BW losses and almost no reserves of glycogen found in the carcasses of the same animals (Carter and Gallo, Reference Carter and Gallo2008).

In lamb carcasses, muscle pH is not measured routinely at slaughterhouses in SA because conservation technologies such as vacuum packaging are less developed than for beef. Tarumán (Reference Tarumán and Gallo2013) found 51% of lamb carcasses with pH >5.8<6.3, and only a 0.1% of carcasses with pH >6.3. In the same study a positive association was also found between the presence of bruises and high pH.

More research within and between countries in SA is necessary to improve AW during lairage, as situations may vary largely due to type of animals, climate, farming, transport and slaughterhouse facilities and handling (Del Campo et al., Reference De Vries2010).

Stunning

The purpose of stunning animals before slaughter is to avoid unnecessary suffering and pain when they are slaughtered through bleeding and it is mandatory according to OIE (2013) AW standards and also Chilean regulations (Chile, 2013a). Out of all preslaughter handling operations, stunning is an overlooked aspect in many SA countries; there has been little awareness to avoid animal suffering during this stage, probably by assuming that the animal will die anyway within a short time (Gallo, Reference Gallo, Tadich, Huertas, César, Paranhos Da Costa and Broom2009). A survey in 2006 (Gallo, Reference Gallo and Cartes2007) showed that the whole process of stunning is not well understood among slaughterhouse operators and even professionals in many SA countries. Most countries have regulations covering this stage, however, it is still possible to find small and municipal slaughterhouses where the Spanish knife or just bleeding is performed, demonstrating that there is not much enforcement of the regulations. The evaluation of the actual efficiency (efficacy) of the process, meaning if methods are accomplished accordingly to OIE recommendations (OIE, 2013) or national regulations for each species, if they are applied correctly and if actual checking of unconsciousness is assured, has started only recently (Gallo et al., Reference Gallo2003a and 2003Reference Gallo, Lizondo and Knowlesc; Romero et al., Reference Romero, Uribe and Sánchez2012).

Stunning is usually performed according to OIE recommendations in all export and bigger slaughterhouses. A low efficacy of the stunning process, as well as the use of unacceptable methods is still a common situation in some SA countries (Gallo, Reference Gallo and Cartes2007). A study performed in a sample of Chilean slaughterhouses in 2000 (Gallo and Cartes, Reference Gallo2000), showed that only a mean of <85% of cattle slaughtered fell with the first shot when using captive bolt stunning; moreover, there was a high percentage of cattle showing signs of recovery after stunning. These results would be considered unacceptable according to Grandin (Reference Grandin1998). The same study showed that the time between stunning and bleeding was longer than a minute. A study performed after these findings (Gallo et al., Reference Gallo, Lizondo and Knowles2003c) showed that improvements could be made through implementing a headholder in the stunning box, using a new penetrating captive bolt pneumatic stunner and through the training of personnel. A frequent problem observed in sheep stunning is the placing of electronarcosis electrodes in the wrong anatomical sites (for instance neck); the problem is due to lack of training (Cáraves et al., Reference Cáraves, Gallo, Strappini, Barrientos, Allende, Chacón and Briones2007). More recent intervention studies in 14 of the largest cattle and sheep slaughterplants in Chile, showed that the efficacy of stunning was being further improved (Cáraves et al., Reference Cáraves, Gallo, Strappini, Aguayo, Allende, Chacón and Briones2006 and Reference Cáraves, Gallo, Strappini, Barrientos, Allende, Chacón and Briones2007). Devices for the restriction of body movement are required by law in Chile since 2009 (Chile, 2009a and 2013a); these devices need to be carefully designed and animals have to be immobilized for as short time as possible, otherwise they can end up being more stressful for the animals rather than an advantage (Muñoz et al., Reference Muñoz, Strappini and Gallo2012).

At present training of people handling animals at the slaughterhouses and particularly during stunning has been given a main focus; most SA countries that export meat evaluate the process periodically and train their personnel in order to reach acceptable standards of AW during slaughter (Gallo et al., Reference Gallo and Tadich2010).