In total, a team of researchers analyzed 7,414 audio recordings of pigs in different situations. “The idea was to collect acoustic data from every stage of a pig’s life, from birth to slaughter,” says Elodie Briefer, an assistant professor at the University of Copenhagen who specializes in animal behavior studies.
Most of the recordings come from farms or slaughterhouses, and some are from experimental installations. We then analyzed this data on the basis of various criteria such as frequency or length, and then examined how all that grunting, growling, and squeaking changed depending on whether the pig was facing a positive or negative situation.
The study builds on known insights into pig vocalization, but provides much more detail than previous research, a brief explains. Something we found in our data is that sounds with higher frequencies – screeching and screeching – are more common in a pig’s passive context. Grunts and murmurs, sounds with low frequencies, we see in both positive and negative situations. Our analysis showed that both pigs’ sounds at high and low frequencies become shorter as the animal experiences a particular condition more positively.
AI understands pigs
Based on all that data, Briefer and her team developed an algorithm that associates pig’s grunts, growls, and squeaks with positive or negative emotions with 92% accuracy. In addition, their AI was able to associate a sound with a specific state in 82 percent of cases. In all, we identified 19 types of context, both positive, such as suckling a piglet, or negative, such as transportation or slaughter. Insight into small fluctuations in the length and frequency of sounds also makes it possible to measure differences in pigs’ emotional state in the same context.
Funding for the study came from ERA-Net ANIHWA, an organization that promotes scientific research in animal welfare. Prevere said the findings are an important step in the quest for better care for pigs in agriculture. The aim of this study was to develop a method for better recognition of pigs’ emotions. The next step is to find practical solutions that benefit animal welfare in pig farming, and to test what works and what doesn’t. Constant and automatic monitoring of pigs in the stables, for example, will allow the farmer to quickly intervene if the AI detects negative emotions.
Better measure well-being
Professor Frank Tweetens finds Prevere and her team’s study interesting and hopeful. Tuyttens, who was not involved in the research, is professor of animal care at Ghent University and works at ILVO, the Institute for Agricultural, Fisheries and Food Research. In livestock farming, the pursuit of a positive animal experience is becoming increasingly central. Only, it is difficult to measure their emotional state.
Previous research had already shown that animals’ vocalizations lend themselves well to documenting their emotions, Tweetins says. It was already known that pig sounds with lower frequencies are more likely to be associated with a positive emotional state, while higher frequency indicates negative emotions. In research on the effect of castration of pigs, for example, loud and noisy sounds indicate the degree of pain experienced by the piglet.
However, this research goes further than that. About twenty different contexts have been identified and an algorithm has been developed that accurately matches pig sounds to the correct context. This is much more complicated than simply distinguishing between high and low frequencies. However, the major advantage of the study lies in the fact that it was possible to detect differences in vocalization such as snoring, growling or screaming, and changes in vocal parameters that indicate whether the pig is facing a particular situation more or less favorably. This makes it possible to measure in detail what the pig feels in a situation within a type of articulation.
Tuyttens also sees opportunities to improve pig welfare through the study results. But this study is of particular value for research in animal welfare. ‘It allows us to better evaluate specific treatments or interventions to increase animal welfare. It gives us a deeper look into the emotional world of pigs, a very welcome insight. Current approaches to interventions to improve animal welfare depend on external characteristics, such as behaviour, injuries, … However, these have their limitations.† One A deeper understanding of pigs growling, snoring, and screaming opens up their environment a little more, and allows us to create an environment in which the animals feel good.
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