New doctoral thesis on animal welfare at slaughter

Every year, millions of pigs and cattle are raised and slaughtered for human consumption. Although the time an animal spends in the slaughterhouse is short compared with its life on the farm, it represents one of the most critical and sensitive stages for its welfare. During this time, the animal is handled by unfamiliar humans, stunned, and bled - processes that, if not performed properly, can cause unnecessary suffering. However, aspects of improving animal welfare during slaughter are often considered an additional cost to the slaughterhouse business. Is that actually the case, or is it possible that better welfare at slaughter also could have economic value for the slaughterhouses? 

Stunning

Animal welfare at slaughter depends on many factors, including how animals are handled, the design of the slaughterhouse, the quality of the stunning process, and the skills of the personnel. Within the European Union, animals must be rendered unconscious before bleeding, usually by mechanical stunning in cattle and carbon dioxide (CO2) stunning in pigs. In Sweden, this requirement is stricter than in most countries, as no exceptions are permitted. However, stunning is a technically demanding procedure and ensuring that each animal is rendered fully unconscious until death requires not only functional equipment but also skilled and attentive workers. Failures in this process can cause unnecessary suffering and interrupt the slaughter process, which leads to higher labour costs and reduced operational efficiency. This thesis, therefore, examined both animal welfare outcomes and their economic relevance in commercial slaughterhouses through five studies, primarily focusing on Sweden but also relevant to other countries. 

First study - interviews

In order to explain how investments in animal welfare may influence profitability, the first study of this thesis introduced an economic model that viewed animal welfare as an intangible asset within the slaughterhouse production system. More traditional factors such as labour, capital, and materials were also included in the model. Focus group interviews with slaughterhouse personnel validated the outcomes of the model - investments in animal welfare can affect profitability in several ways: by improving workflow, reducing labour demands, and enhancing the quality of carcasses and by-products. Thereto, they emphasised that by-products played a significant role in profitability. Many facilities had already made, or were planning to make, welfare-related investments such as redesigned drive- 108 races, improved lairage areas, or new stunning boxes. This made handling calmer for animals, improved the working environment for employees, reduced noise, and increased overall production efficiency. However, the representatives from the slaughterhouses also highlighted challenges in measuring the financial return on such investments and noted that consumer awareness of slaughter practices is low, which makes it difficult to communicate the benefits of improvements to the public. 

Second study

The second study assessed stunning efficiency in pigs and cattle under commercial conditions at eleven Swedish slaughterhouses. Most animals were adequately stunned, but there was notable variation between slaughterhouses. Around 96% of pigs and 93% of cattle were effectively stunned, while the rest showed signs of inadequate stunning. In total, 4% of the pigs were re-stunned and nearly 6 % of the cattle. The likelihood of initially poor stun quality, or inefficient stunning between stunning and bleeding, increased when the stun-to-stick-interval, known as the time between stunning and bleeding, increased. The likelihood for re-stunning also increased with longer stun-to-stick intervals. For pigs, the risk increased after about one minute, while for cattle the critical point was around one and a half minutes. In pigs, differences were also linked to the type of CO2 stunning system: dip-lift systems produced more consistent stunning results than paternoster systems. In cattle, about a quarter of the stunning shots missed the ideal position on the skull, often due to short bolt lengths or poor maintenance of the equipment. The study showed that proper training, careful equipment maintenance, and short stun-to-stick intervals are essential to ensure that animals remain unconscious until death and that the slaughter process runs smoothly.

Follow-up of injuries

The third and fourth studies examined traumatic injuries in pigs and cattle using Swedish slaughter inspection data from over seven million pigs slaughtered between 2019 and 2021, and three hundred thousand cattle slaughtered between 2020 and 2022. These injuries, such as bruises, skin lesions, and fractures, indicate compromised welfare before or during slaughter and lead to meat losses and economic costs. Chronic injuries were more common than acute ones in both species, affecting around 9% of cattle and less than 1% of pigs. Seasonal patterns suggested that injury rates increased in colder months, likely due to handling procedures and environmental challenges. Carcases with injuries lost significant amounts of saleable meat, on average more than twenty kilograms per injured cattle 109 carcase. In pigs, condemnations linked to injuries accounted for about 16% of all condemned meat during the studied period, and for cattle, the corresponding figure was 34%. Overall, these studies showed that injuries not only affect animal welfare but also reduce product value and increase food waste. This link between welfare at slaughter and conditions on farms and during transport demonstrates that animal welfare at slaughter is influenced by events that occur earlier in the animals’ lives; injuries sustained on farms or during transport can cause pain and distress during slaughter. Overall, these studies showed that injuries not only affect animal welfare but also reduce product value, while increasing food waste. This link between welfare at slaughter and conditions on farms and during transport demonstrates that animal welfare at slaughter depends on what happens earlier in the animals’ lives; injuries on farms or during transport can cause pain and distress at slaughter. 

Effect on economy

The final study used economic simulations to estimate the financial effects of reducing stunning failures. By modelling different scenarios for pigs and cattle, the study showed that investing in new stunning equipment and improving equipment maintenance and standard operating procedures could be economically justified. Under most conditions, the benefits slightly outweighed the costs. For pigs, the annual net benefit of upgrading the stunning system was estimated at nearly 90,000 SEK, while for cattle it was around 37,000 SEK. The most important factors driving these positive outcomes were lower labour costs, smoother workflow, and fewer equipment breakdowns. Although the financial gains were relatively modest, they demonstrated that improving welfare does not necessarily reduce profitability and can in fact support a more efficient and sustainable production process. 

Conclusions

Overall, the results of this thesis show that animal welfare at slaughter is both an ethical and an economic concern. Humane handling and effective stunning not only reduce suffering for animals but also improve product quality, reduce waste, and enhance worker safety and morale. The findings also underline the importance of management commitment and regular training for slaughterhouse personnel, as well as the need for wellfunctioning equipment. However, welfare improvements are not always easy to measure in monetary terms, and the benefits are often long-term or indirect. For this reason, economic incentives or policy measures may be 110 needed to encourage slaughterhouses to invest in welfare-enhancing technologies and training. Since slaughterhouses operate under strict legal and ethical obligations, these investments also strengthen public trust and the social legitimacy of meat production.

This thesis demonstrates that animal welfare and economic outcomes are not mutually exclusive. On the contrary, they often move hand in hand. When animals are treated calmly, equipment works as intended, and when personnel are properly trained, the slaughter process becomes safer, more efficient, and more humane. Achieving this balance requires continuous effort, since failures, such as an animal showing signs of consciousness after stunning or injuries caused by rough handling, have welfare and economic implications. Humane slaughter is therefore not only a legal requirement but also a matter of professional pride and ethical responsibility. It reflects the values of the people who produce meat and the society that consumes it. 

This research contributes new knowledge about how animal welfare at slaughter can be improved and its economic relevance. By integrating animal science with production economics, it provides practical tools for decisionmaking within the slaughter industry and insights that can guide future policy. The findings show that investments in animal welfare, whether through improved stunning systems, better facility design, enhanced training, or a combination of the above, can bring benefits that extend beyond the slaughterhouse. Ultimately, they help ensure that animals are treated with respect in their final moments while supporting efficient, responsible, and economically sustainable food production. 

Learn more

Read the doctoral thesis:

Killing them softly. Pig and cattle welfare at slaughter and its economic relevance.