Research Shows Pigs Raised in Large Groups Less Aggressive than in Small Groups

CANADA - Research conducted at the Prairie Swine Centre shows pigs raised in very large groups tend to be far less aggressive than those raised in small groups, writes Bruce Cochrane.
calendar icon 5 April 2007
clock icon 3 minute read

Over the past decade the Prairie Swine Centre has conducted a wide range of research looking at the dynamics of group housing including such things as the impact of group size on social behavior and aggression.

Dr. Harold Gonyou, a research scientist in animal behavior, says pigs seem to learn from their social environment how they should react socially.

Dr. Harold Gonyou-Prairie Swine Centre

When you have pigs coming from small groups, they've been in a system where it was possible to for them to dominate every other pig in the pen or they at least had some pigs there where it was worth their while to fight for resources etceteras.

When you get to a large group it just isn't worth your while and we certainly see a difference by the time we get to 100 pigs in a pen.

So I would say it's somewhere between 50 and 100 pigs where we start seeing a difference in the social behavior of the pig.

They become more socially tolerant, less willing to fight.

Now, when you go to market those pig, if you have small pens of 20 pigs, then you're taking three or four pigs from a pen, they're taken down and they're loaded together or they're held in the loading area with pigs from several other small pens and they fight.

The pigs from the large groups, first of all, if they're put into a pen of 25 pigs in all likelihood all those 25 pigs came from the same group but even if they were mixed with pigs from multiple groups they're not prepared to fight.

They're much more socially tolerant.

You won't see the scratches on them as much as you do from pigs in small groups.

We also find that they load easier.

You can get pigs from large groups onto the truck easier than you do from small groups.

Dr. Gonyou notes another consideration, as the industry considers group housing for sows, is what type of sow do you want?

He asks Do you want a glt that comes from a small pen and is interested in fighting or one that's grown up in a large group where it has become socially tolerant and doesn't see the need to fight.

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