Volume 12, Number 3 September 24, 2004

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Study to determine best size for hog heaven

Swine researchers look at space allotted for group-housed pigs

By Dale Worobec

Prairie Swine Centre researcher Harold Gonyou and graduate student Brandy Street will study the effects of hog-barn crowding on pigs’ behaviour and health.
Photo by Dale Worobec

Do pigs perform well in large or small herds? And just how many pigs make for a crowded pen?

These are questions U of S researcher Harold Gonyou will study with a $55,000 (US) grant from the U.S. National Pork Checkoff Board. Gonyou will examine the performance, physiology and behavior of pigs in commercial barns.

“ From a production standpoint, if you crowd the animals, it’s more profitable. But looking at the animal’s welfare, there is the issue of how much space pigs should have, or how many pigs should be in a pen,” says Gonyou, an adjunct professor and researcher at the Prairie Swine Centre, a non-profit centre affiliated with the U of S.

In previous research efforts, Gonyou has worked to develop a method of assessing when crowding begins to affect animal welfare in pig barns. That background is the reason the producer-funded U.S. board decided to fund a Canadian researcher, says Anna Johnson, director of animal welfare for the Pork Checkoff.

“ Dr. Gonyou is very well known in this research area,” says Johnson.

Gonyou says research shows that pigs are adaptable animals, but when stressed by crowded conditions they show definite changes in behaviour. Increased injury rates and self-inflicted tail biting are two examples.

He explains that in pig pens, space is needed for eating and sleeping. But pigs also require a certain amount of space for movement and social behaviour – which means that larger groups may be beneficial.

“ Envision it this way – a pig may want to make a sudden run for 20 feet, but that 20-foot space is pretty difficult to find if you have a pen designed for 20 pigs,” says Gonyou. But in a larger pen of 300 or more – assuming the same amount of space per pig as the smaller pen – those vacant spaces are easier to find.

In 2003, Gonyou led a workshop for the Pork Checkoff Board in which experts from around the world spent three days reviewing the latest scientific literature on space allowance for pigs. The attending scientists endorsed Gonyou’s research on using a mathematical formula – called the “k” concept – to calculate exactly where crowding begins in hog barns.

The Pork Checkoff grant will let Gonyou and graduate student Brandy Street study the weekly changes – in growth, behaviour, physiology and health – of pigs in large versus small groups and within two levels of space allocation. The funding is in addition to previously announced grants from Canada’s Natural Sciences and Engineering Research Council (NSERC) and SaskPork.

Gonyou’s research into space allocation for pigs could eventually find its way into producer handbooks, guidelines and programs. He hopes to have results from the study within the next year.

For more information, contact communications.office@usask.ca

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