Animal welfare and meat quality: Managing pre-slaughter stress

Introduction 

Animal welfare during the pre-slaughter period has gained increasing attention worldwide due to its direct impact on meat quality and consumer perception. Beyond on-farm husbandry, stress linked to transport, handling, and slaughter strongly affects both the animals’ physiological state and the biochemical processes that define meat characteristics.

Poor handling, long transport, food and water deprivation, high temperatures, and overcrowding trigger stress responses that elevate cortisol and lactate levels, deplete muscle glycogen, and disrupt the normal muscle-to-meat conversion process. These changes can produce inferior meat types such as Dark, Firm, and Dry (DFD) (Gallo et al., 2003) or Pale, Soft, and Exudative (PSE) meat (Gonzalez-Rivas et al., 2020).

Minimizing pre-slaughter stress through humane handling, proper facility design, and well-trained personnel is essential for improving carcass quality and ensuring consumer-acceptable meat.

Pre-slaughter stress and meat quality

Public debate increasingly emphasizes animal welfare and the need for more humane livestock farming and meat production systems (Zühlsdorf et al., 2016). Beyond husbandry practices, concerns extend to animal transport and handling in abattoirs (EFSA, 2020). The German Federal Veterinary Chamber also notes that animal welfare issues commonly occur during critical stages between unloading and bleeding, regardless of abattoir size (Tiedemann, 2021).

Stress factors during transport and handling

The transport, handling, and slaughter of livestock are fundamental stages in meat production, exerting significant influence on both animal welfare and meat quality. Research has consistently shown that the journey from farm to slaughter significantly impacts both animal welfare and meat quality. Loading and unloading cattle are particularly stressful moments that cause their heart rates to spike dramatically (Gebresenbet et al., 2012; Costa et al., 2016; Frimpong et al., 2014). During transport, animals face a perfect storm of stressors ranging from no food or water to  poor air circulation, extreme temperatures, aggressive interactions with other animals, and constant physical jolts. All of these factors combine to cause hunger, thirst, pain, and ultimately, lower-quality meat (Adzitey, 2011).

Physiological responses and muscle chemistry changes

Cattle experience high stress; their bodies produce more lactic acid, which drops the pH in their muscles and makes the beef tougher (Benjamin et al., 2001; Hambrecht et al., 2005; Edwards et al., 2010a, 2010b; Rocha et al., 2016; Gruber et al., 2010). If the stress continues long enough, especially in the 24 to 48 hours before slaughter, the animals' glycogen stores become depleted. Without glycogen, there's no lactic acid production, and the muscle pH stays abnormally high. This creates what's known as Dark, Firm, and Dry (DFD) meat (Gallo et al., 2003). Physical exertion and psychological stress prior to slaughter accelerate muscle metabolism, resulting in a rapid drop in pH and further compromising meat quality (Bourguet et al., 2011). Animals exhibit stress through changes in their behavior and physiology, which serve as warning signs that their welfare is compromised (Njisane & Muchenje, 2016). When stressed, their bodies activate the hypothalamic-pituitary-adrenal (HPA) axis, releasing hormones like catecholamines and cortisol. These hormones burn through glycogen reserves, raise the final pH, and interfere with the normal process of muscle converting to meat. As Njisane and Muchenje (2017) and Hemsworth et al. (2011) point out, pre-slaughter stress not only harms the animals but also damages meat quality across all species, affecting aspects such as color, pH, and texture. The problems don't end with transport.

Impact of poor abattoir conditions

Many abattoirs have inadequate facilities and poor hygiene standards, which only exacerbate the animals' distress. Noisy, overcrowded, and unsanitary conditions trigger stress responses like elevated cortisol and further glycogen depletion (Fasanmi et al., 2018; Alimi et al., 2023). Every step of the pre-slaughter process, including handling, transportation, lairage, and stunning, shapes the final meat quality (Sakowski et al., 2022). When these stages are stressful, they disrupt normal muscle metabolism and the biochemical changes that happen after death, leading to undesirable meat characteristics. Excessive stress depletes muscle glycogen, disrupts pH balance, and increases enzyme activity that breaks down proteins. Poor-quality meat like DFD or Pale, Soft, and Exudative (PSE) types that consumers find unappealing and that fetch lower prices at market (Adzitey & Nurul, 2011; Ijaz et al., 2020; Ponnampalam et al., 2017; Terlouw et al., 2021). Without proper lairage areas, ventilation, and slaughter facilities, animals experience prolonged discomfort and physiological imbalance. This disrupts the natural muscle-to-meat conversion process and increases the likelihood of DFD meat, compromising both quality and safety.

Frimpong et al. (2014) found that pre-slaughter stress increases muscle temperature and lactic acid levels, resulting in PSE or dark meat. Gregory (2010) highlighted how various welfare issues, like long transport times, feed deprivation, exhaustion from walking long distances (Apple et al., 2005), rough handling, extended restraint, and isolation, all take their toll on meat quality. Bekuma and Tadesse (2024) also reported that long-distance trekking and poor handling during transport and lairage impose considerable stress on cattle, resulting in reduced welfare and carcass quality. They further noted that improper pre-slaughter handling contributes to a higher occurrence of DFD meat, bruising, and microbial contamination. Gonzalez-Rivas et al. (2020) reported that acute heat stress immediately before slaughter accelerates muscle glycogen breakdown, resulting in pale, soft, and exudative (PSE) meat with low water-holding capacity. In contrast, chronic heat stress reduces muscle glycogen reserves, resulting in dark, firm, and dry (DFD) meat with a high pH and increased water retention. They also stressed that heat stress induces oxidative damage to lipids and proteins, shortening shelf life and compromising food safety due to increased bacterial growth and shedding.

Pre-slaughter handling and animal welfare

In Africa, animals are most commonly transported on foot due to the shortage of vehicles with adequate capacity (Masiga & Munyua, 2005). However, this method often results in significant losses, including injuries, deaths, and thefts. Bulitta et al. (2012) reported that 7.6% of animals died, 6-9% sustained injuries, and 2.8% were stolen during such movements. Common problems include lameness and leg swelling, which also occur during vehicle transport (Masiga & Munyua, 2005), particularly when animals are deprived of rest, water, and feed. Inhumane handling methods commonly reported include whipping (most frequent), tail pulling, stamping on tails, stoning, slapping with bare hands, forcing animals to fall, leg pulling, and horn pulling. Avoiding the use of sticks has been shown to enhance animal welfare and minimize the risk of poor carcass quality (Okeudo & Moss, 2005).

Stress indicators and physiological effects

Cattle are herd animals by nature, so moving them one by one goes against their instincts and often creates handling problems (Frimpong et al., 2014). Interestingly, Zobil (2020) found that while plasma cortisol levels dropped during longer transport times, lactate and creatine kinase shot up after six hours, which are clear signs that the animals' bodies were under stress. Bruising is a massive problem in the livestock industry, costing producers money worldwide. Training employees in low-stress handling techniques can dramatically cut down on these injuries. In cattle, bruises can happen even after stunning but before bleeding, sometimes from something as simple as a stun box door. Fresh bruises look red, while older ones especially those over 48 hours old turn darker or develop a yellowish discharge (Grandin, 2020).

Recognizing behavioral stress signals

Rough handling is a recipe for disaster. Using sticks excessively, forcing animals into contact with facilities or each other all causes bruising, injuries, and sometimes even death. These injuries aren't just signs of poor welfare; they lead to carcasses being condemned, dark meat, and consumers turning away from the product (Zobil, 2020). While pinpointing the exact age of a bruise is tricky, telling fresh from old is fairly straightforward; fresh bruises in cattle are red (Hamdy et al., 1957), while those older than 48 hours darken or show yellowish mucus (McCausland & Dougherty, 1978). When you see cattle vocalizing, jumping, or crashing into fences, those aren't just random behaviors, they're red flags signaling serious physiological stress (Gruber et al., 2010; Hemsworth et al., 2011). According to Adzitey (2011), pre-slaughter stress comes in many forms. There are physical stressors like heat, vibration, sudden acceleration changes, confinement, noise, and crowding. Also, there are psychological ones such as breaking up social groups, mixing unfamiliar animals together, exposing them to strange smells, and forcing them to adapt to new surroundings. All of this takes a toll, resulting in weight loss, poor meat quality, and less profit for producers of which keeping them upright is the best way to restrain animals according to Yardimci et al. (2013). Using panels that block their vision also helps as it reduces struggling and makes the whole process more humane (Grandin, 2003).

Facility design and equipment standards

One thing that should never happen is using mechanically powered gates or equipment to knock down or drag animals which is a clear violation of welfare standards (NAMI, 2019). The human element matters enormously in abattoir operations. Most meat handlers are young adults in their twenties with limited education and little to no formal training in meat hygiene and processing.

Few get regular medical checkups, and hygiene standards among workers, animals, and equipment often leave much to be desired (Malachi, 2021). Hultgren et al. (2020) highlighted that animals slaughtered at mobile plants which eliminate the need for long-distance transport showed significantly fewer stress behaviors like backing up, slipping, vocalizing, or violent actions such as kicking and fighting compared to those at stationary facilities. Also, when stockpersons used rough tactics like pushing, hitting with tools, twisting tails, or using electric prods, stress behaviors increased, clearing proving that rough handling makes everything worse.

Other issues plague the system too such as  slaughtering sick animals, delays in processing after slaughter, and careless handling by workers (Alimi et al., 2023). A properly designed abattoir should have all the essentials including lairage areas, slaughter halls, sections for offal and condemned meat, clean water, cold storage, veterinary offices, labs, and waste disposal systems (Gali et al., 2020). When abattoirs are well-designed with adequate space, animals can move calmly in groups, which reduces fear, stress, and the chance of injury. In developing countries, farm animal welfare faces major obstacles including widespread poverty, limited knowledge and skills in animal handling, poor transport and slaughter infrastructure, and deeply rooted cultural beliefs (Bekele et al., 2020; Malena et al., 2006).

Human factors and training needs

Regular training and medical exams for handlers, better infrastructure, and stricter hygiene enforcement are crucial for producing safe, welfare-compliant, high-quality meat. When handlers are properly trained in restraint techniques, calm movement, and hygiene, it promotes humane treatment, reduces pre-slaughter stress, and improves both animal welfare and meat quality. Bulitta et al. (2012) observed that during loading, transport, and marketing, workers often tied ropes around the animals’ necks or horns to pull them toward vehicles. When animals resisted, handlers typically responded by whipping them repeatedly or forcefully twisting their tails. Grandin (2020) emphasized that in European abattoirs, bulls are kept in single-file races between sliding gates to prevent fighting, which can lead to Dark, Firm, and Dry (DFD) beef.

To promote welfare, bulls should be slaughtered on a just-in-time basis, spending minimal time in these races. Raising and transporting them in stable, familiar groups helps reduce stress and improve meat quality. Grandin also recommended staff training, minimizing electric prod use, applying behavioral handling principles, moving animals in small groups, and avoiding dragging. Additionally, lairages should be spacious enough for all animals to lie down and provide access to water to ensure their well-being. Ayuba et al. (2023) identified several welfare concerns for cattle during transport, including lack of feed and water, vehicle overcrowding, inadequate weather protection, and poor handling practices. The authors recommended that stake holders in the meat industry be informed about these welfare issues occurring throughout the supply chain, from transport through lairage to slaughter.

Cycle of poor handling, welfare stress, and meat quality deterioration

Conclusion

Pre-slaughter stress remains a major determinant of both animal welfare and meat quality. Factors such as rough handling, poor transport conditions, inadequate lairage, and insufficient worker training amplify stress and compromise meat safety and value. Conversely, adopting humane handling techniques, ensuring adequate rest, feed, and water, and providing appropriate infrastructure can markedly reduce stress and improve welfare outcomes. Effective management of animals from farm to slaughter supported by training, welfare awareness, and proper facility design not only enhances ethical standards but also ensures the production of high-quality, safe, and marketable meat and meat product. 

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