The pot belly trailer is the most popular vehicle for transporting hogs in North America, but it is not the best way.
About 16,000 pigs die in transport each year in Canada.
To reduce deaths and enhance animal welfare, the Prairie Swine Centre in Saskatoon, in collaboration with scientists from across Canada, is studying why the trailer is stressful for hogs.
To gather information, the researchers have transported hogs in belly trailers for two-hour runs in Quebec, and from Saskatoon to Maple Leaf Foods’ processing plant in Brandon.
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“Transportation is the most critical phase (of processing hogs),” said Luigi Faucitano, a research scientist with Agriculture Canada in Lennoxville, Que., who is part of the team studying the pot belly.
“It’s the phase where pigs are predisposed to die or to suffer.”
The trailer is named the pot belly after the lower deck between the tires. The trailer, which can transport about 200 hogs, has 10 animal compartments and two complete decks, said Harold Gonyou, a research scientist in ethology at the swine centre and the study’s team leader.
“Four (compartments) in the top level, four in the middle and two in the pot.”
Certain compartments can get hotter than others, which can kill the pigs.
“We run fewer deaths than they do within the U.S., but most of our deaths occur during the summer,” Gonyou said.
“So we feel there are some heat related problems … that would also suggest why you see more of it in the U.S.”
In Canada, the hog mortality rate resulting from transport is around .08 percent, said Faucitano, which equals $2.5 million in losses per year. In comparison, the U.S. mortality rate is .22 percent.
Researchers have installed sensors in the compartments to measure temperature variations.
They found that it gets hotter in the belly, in part because it has less ceiling space. The top deck gets warmer when the summer sun beats down on the trailer’s roof.
To monitor hog body temperature during transport, the researchers use a sensor the size of a nickel. Before departure, the hogs swallow the sensor as part of their food. It is then recovered from the hog’s intestines at the slaughter plant.
The study also looks at how hogs get in and out of the trailer.
“Pigs have lots of difficulties in negotiating ramps, and the pot bellied model can have up to five ramps inside,” said Faucitano, who has studied hog welfare for 15 years and edited the book The Welfare of Pigs: from birth to slaughter.
Because pigs don’t like ramps, the truck driver may have to use an electrical prod to get them moving, Faucitano said, which is another source of stress.
“In Quebec, we compared it (the pot belly) with a truck that is equipped with a hydraulic deck. In that case, pigs that go to the upper deck don’t have to climb the ramp,” Faucitano said.
The scientists are also interested in how transport stress affects meat quality.
“We know that stress prior to slaughter can change the metabolism of the meat when the animal is slaughtered,” said Gonyou, who attributed the change to the buildup of lactic acid in the muscles.
“The result is that you have pale meat, and you have a very watery meat.”
The study will continue for the next two years, at which time scientists will recommend modifications to the pot belly trailer, Faucitano said.
“(We want to) identify the best design of a vehicle, more adapted to the climate and road conditions in Canada.”
