Monitoring Pig Stress Through Observing Behaviour

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Pigs can’t tell you how they’re feeling, so the best way of assessing how they’re reacting to transport is watching them with a trained eye.

That was what Dr. Stephanie Torrey and her colleagues with Agriculture Canada in Guelph, Ont. did as part of a national study. They studied the behaviour of pigs during loading, transport, unloading and holding.

“Behaviour is a non-invasive way to assess welfare under a number of conditions,” Torrey told a recent seminar here. “It tells us a lot about pig comfort and stress levels.”

Torrey’s research was conducted during the Western trials of the hog transport study. Pigs were segregated into groups of four or five to facilitate the loading process. Observations during the loading process were conducted by two trained observers who noted durations of behaviours, slips, balks and vocalizations of the animals, and the number of times pigs were prodded with electric prods. The observers also tracked the time it took to load and unload each group of pigs.

On the truck, behaviour was monitored by digital cameras mounted in various compartments. A still camera shot the activities of the pigs in five-minute intervals. During holding time, pigs in four pens were monitored by a live observer.

Researchers noted the number of pigs lying, standing and sitting in the truck. Pigs that were standing and sitting were thought to be calmer and more relaxed.

THEY DON’T LIKE RAMPS

Unloading took longest when pigs had to turn or climb ramps, regardless of the season.

“It appears that both ramps and turns present problem with moving pigs onto and off of trucks,” said Torrey. Ramp climbing often engages pigs in behaviour that might lead to injuries.

Researchers found a difference in prod use during the seasons. Groups of four or five pigs were generally prodded about five times in summer to encourage them to move to their compartments, and needed about eight prods to encourage them to do so in winter. Researchers noted that it took more time for the pigs to be unloaded from the various compartments in winter.

When pigs are unloaded too quickly, they seemed to have more slips and overlaps depending on which compartment they were held in.

“It appears that the speed of unloading could actually be a liability and could result in some behaviour problems that could lead to injuries,” said Torrey.

When pigs were transported in the summer, 15 minutes passed before the pigs were able to rest and relax in holding areas. In the winter, the pigs took about half an hour before they assumed resting postures, said Torrey. The researchers found that pigs had a much higher heart rate in winter, which contributed to the increase in time before they were able to relax once off the truck. “Perhaps they needed some time to let their heart rate stabilize before resting,” she said.

The researchers found that loading took longer in summer, which led researchers to believe that climbing the ramps was a significant physical effort for pigs in the heat. In winter, pigs going down into the pot belly took the longest, possibly due to the cooler temperatures in this compartment.

About the author

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Alexis Kienlen

Alexis Kienlen lives in Edmonton and has been writing for Alberta Farmer since 2008. Originally from Saskatoon, Alexis is also the author of two collections of poetry, a biography, and a novel called "Mad Cow."

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