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Wednesday, April 24, 2024

What they don’t tell us: the complexities of pig behavior


UC Davis researcher studies ways to improve pig welfare through personality typing

Kristina Horback, an assistant professor in the Animal Science Department, is researching psychology and communication in swine. She previously studied the behavior of wild species, like elephants and prairie dogs, before coming to UC Davis in September of 2016.

Her interest has always been the psychology of animals, but swine research is her newest project. Previously, Horback worked at the University of Pennsylvania for post-doc research, where she was first introduced to the study of domesticated farm animals.

“The theme of my work is to use noninvasive measurements to understand how the animal is expressing their internal state,” Horback said. “I’m really trying to do my best to guess what the animal is experiencing.”

An animal’s experience can, to some degree, be compared to how humans respond to stimuli in everyday life.

“Essentially, it’s understanding the flight-fright freeze response and how the threshold for each individual is different,” Horback said. “Your threshold when you hear your car backfire could be different than mine. It’s understanding that [response] could accumulate over a lifetime to result in a difference in the strength of the immunity of the animal or their relationship with others in their social group.”

Horback said that emotional states influence how people process information. If a person hears their car backfire while in a positive state, such as happiness or excitement, they will usually react differently than when in a negative state, such as depression or anxiety.

Horback is taking this idea and testing to see if it can also apply to swine.

“That’s what I’m [studying] right now with pigs,” Horback said. “I’ve been looking at different personality traits with pigs — if it’s throughout their lives, if it influences whether or not they get sick or if they are more successful than others. That’s important in the swine industry.”

Internationally, the pork industry is changing drastically from use of individual gestation crates to group pens. Gestation crates stopped sows from getting into fights resulting from the social hierarchy and also provided enough feed for each pig. About 35 years ago, this style of housing was popular and ensured that farmers would have physically healthy livestock. The drawback was that the enclosures were so small that these pigs could not freely move.

“Through today’s lenses, the fact that they chose to put these animals into an enclosure that was two feet by seven looks like a bad decision,” said Dr. Thomas D. Parsons, the director of the swine teaching and research department at University of Pennsylvania’s School of Veterinary Medicine. “At the time, it was actually a welfare breakthrough in improvement, and you could really take care of these animals better. But, of course, what we’ve learned is that when it’s only two [feet] by seven, that precludes the animal from doing a number of natural behaviors, including something as simple as turning around. I think more and more people today would find that not acceptable.”

Parsons also stated the importance of an animal’s psychological welfare, something that was not considered as important as an animal’s physical well being when gestation stalls were first implemented. For him, the biggest changes came within the past five years, as he noticed ordinary citizens’ gradually growing concern about an animal’s mental state. Horback noticed this development as well.

“I think that our country is unique in that we have a lot of public or consumer-raised interests in how our food animals are raised, like Prop 2 in California [also known as “Cage Free California”],” Horback said. “I would think that it would be really helpful for anyone in the public to know my research is trying to address those really difficult questions, like when people ask, ‘Is the chicken happy?’ And many times, we’d say, ‘Oh, we don’t know’. I don’t think I’ll ever be able to say for certain, but just know that UC Davis is trying to answer those types of questions.”

In other countries, including the U.K., Canada, Brazil and Australia, gestation crates are in the process of being banned or are already banned on the basis of animal abuse. However, in America, the federal government is not involved, though some states, including California, have banned use of these stalls. Horback explained that the large pork retailers are the ones who are asking farmers to change the way they house their swine.

“Different pockets of farmers are being asked to renovate all of their farms or housing systems so it’s a challenge, especially because it could be done poorly,” Horback said. “Sows do fight, so there’s a need to understand more about the behavior and natural instincts of the species and how we can work with the species. The issue of personality traits is important because there is a complex environment and social world they need to navigate through.”

Maintaining the social hierarchy of pigs while also ensuring their physical and psychological welfare is the main reason why both Parsons and Horback find these studies to be a crucial step. In comparison to the depth of research in human personality, research of animal personalities is fairly new.

Jason V. Watters is the the vice president of wellness and animal behavior at the San Francisco Zoo and an adjunct professor in UC Davis’ Animal Science Department. He studies a variety of species to understand how animals are similar to create general solutions for their wellbeing.  

“I think we’re learning more about how animals tell us, with their behavior, how they feel, rather than looking at what we’ve given them and deciding that they’re fine,” Watters said. “There’s really interesting stuff coming out about this. Some of it is what Horback’s doing with cognitive bias testing — understanding how the behavior of animals reflects their own inner state. In a sense, how they perceive that they are doing.”

Since researchers cannot directly ask animals how they feel, data has to be collected in more creative approaches tailored to test their personality traits. Researchers have run into problems describing what an animal experiences without making them seem too anthropomorphic.

“A lot of times we end up when we’re looking at animal personalities we try to overlay our experience with humans, and that may or may not be the best way to look at it,” Parsons said. “In other words, what’s behaviorally relevant with humans may not be behaviorally relevant for pigs.”

Horback also stated the importance of swine in relation to people, since they have been a species that has evolved alongside humans, just as horses and dogs have.

“Pigs give a lot more eye contact than other animals I’ve worked with,” Horback said. “I think it’s because they have evolved with us just like dogs. Eye contact is important for all our species because we’re primates, but it’s not important for [pigs]. I spend a lot of hours with pigs, training them to use, for example, a touch screen with their snouts as a pointer. They often will look at me to try to get clues as to what I’m staring at. That was my ‘eureka moment’ — there’s a lot more going on in that mind than we gave them credit for.”

Internationally, the findings are relatively consistent to what Horback observes.

“A lot of the research that I do is also conducted in the U.K. and the rest of Europe, but not very much at all in the U.S.,” Horback said. “There are trends and traits across pigs, tendencies in how they interact with each other, how they interact with humans and how they interact with their environment. That’s what we’re trying to look more into — what are these trends and why do they exist? Does it really mean anything? Or does it not impact health? We don’t know.”

Watters sees this young but growing field as an important milestone in creating better conditions for all animals.

“That’s really the future of animal welfare research: understanding [the animal’s behaviors], rather than looking simply at the resources we’ve given them and deciding based on the checksheet,” Watters said. “Being able to ‘ask’ individual animals how they’re doing is what I see as the big, interesting shift in the way that we’re thinking about animal welfare.”

Since Horback’s work is still in its early stages, there are no definite answers on which personality traits are considered more desirable for raising on a farm.

“I can’t say that aggressive sows are great mothers or nonaggressive sows are better,” Horback said. “I don’t think any small changes in the personality would be strong enough [evidence] because of the way that they’ve been selected for so many years.”

Others at UC Davis and elsewhere are working on similar research, and Horback hopes that her research can aid others in the field.

“I’m planning to continue [this research], and hopefully it’ll be useful to the other animal welfare researchers here in the [animal science] department,” Horback said. “To use the tools I have to understand animals in a certain emotional state with research that is a bit more practical, like understanding the pain that a calf goes through when they are dehorned, or a chicken that has cracks in her main chest bone. Does that hurt her or does that not? Trying to understand pain or fear, I think that’s what, or at least I hope, will come next for me and for the more practical research here.”

Horback has high hopes for her research.

“I’m not trying to reinvent the wheel, and I’m not trying to be controversial against any industry because it’s certainly not my goal at all,” Horback said. “I think it’s possible to change how we raise our animals just a little bit to increase their quality of life on the farm.”


Written by: Jack Carrillo Concordia — science@theaggie.org


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