Why some pigs fight and kill each other

Pigs normally appear to be very docile animals. Clean, well-nourished pigs also look graceful and intelligent. For sure pigs are very intelligent animals. They are able to craft, understand and follow a routine.

They define how to keep their pens hygienic by choosing the defaecation and urination areas while keeping their feeding and sleeping areas clean and dry. However, when conditions change and irritate these animals, they can be very vicious; so vicious that they fight each other to death. 

Even though domestic pigs have their canine teeth clipped early in life and never grow back, pigs still retain teeth that are sharp enough to injure each other fatally. They will bite straight with the incisors or even bite on the side.

Three weeks ago, Betty called me and said her pig farm had become a serious battleground. She had increased the population of her pigs hoping for good business but in two pens, the animals were fighting non-stop. Betty said three pigs had already been killed by the others. She was surprised that pigs could fight each other to death. 

She had thought they just inflicted cuts on the skin. The problem had started when she expanded her pens and grouped many pigs together. I enquired from Betty the production stages of the pigs and how they were grouped. It turned out the animals were properly grouped, according to their ages, sizes and stage of production. However, the fighting problem occurred in three pens which had growing and finishing pigs. She had initially thought the problem was too much heat but it did not abate when she opened up some of the walls to increase ventilation and lower the temperature.

Causes of pig fights
Betty noticed that the pigs would identify one and all would beat it and chase it around the pens until it stopped, lowered its head and appeared to succumb to its fate. The attackers would then bite it around the ears, neck and tail. They would also hit it with their snouts. The snout of a pig is very tough and can even break a bone in humans or cut through the flesh if adequate force is applied. The pig’s snout is a weapon driven by the head and the rest of the body to exert brute force and damage on a target. Betty said she often isolated the pigs that were fought by the others. She would then find some dead in the morning with a lot of skin cuts and bruises.

“Have my pigs gone mad?” she wondered. Pigs normally fight for many reasons. I considered the various possibilities. I ruled out inadequate or poor quality feed. Betty’s pigs always hit the market weight at the desired six months of age. Second, Betty had over time perfected the production of good quality feed and adhered to the feed requirements for each pig at different stages of production. She affirmed that nothing had changed in the feed and the growth rates were good.

Another cause of fighting in pigs is introduction of new animals. She had not introduced new animals into the herds that were fighting. The pigs had been very calm until she expanded the pens to hold more animals than before. Betty had moved the pigs into the new pens.
I asked her the dimensions of the pens and the number of pigs in each pen. I calculated the space available per pig and found it was less than the required one square metre. Betty’s pigs were overcrowded.

Stressed pigs
In the absence of any other factor being inadequate, I diagnosed congestion as the cause of the fighting. I agreed with Betty she would ventilate the pig pens well and also decongest them to ensure at least each animal had about a square metre of space to itself. That was its “me space”.
Having followed my advice, Betty called to say the pig war on her farm was over. Every pig was happy with its space. She regretted she had lost three baconer pigs just because of congestion.

When pigs are congested, they generate a lot of heat. They also annoy each other due to their close proximity. The question, however, still arises that when pigs have sufficient space, they lie close to each other when resting but do not fight. I believe it is the issue of getting into contact for affection but missing the individual space when they need it.

The heat generated by congestion and the continuous interaction causes stress to the pigs. The stress builds up to annoyance and they try to reduce their numbers by fighting to increase individual space.
It is usually the commanding or alpha pigs that will start the fight. Once one pig is injured, the others all direct their anger to the poor animal and may fight it to death.

The injuries on the pig being beaten may look shallow. However, death may occur due to bleeding when a major skin blood vessel is severed. The ear veins in pigs are large and vulnerable to injury. Pigs may also die due to damage caused to internal organs by the heavy blunt force of the snouts of attacking pigs.

Fighting 
The major cause of fighting in pigs is introduction of new animals. She had not introduced new animals into the herds that were fighting. The pigs had been very calm until she expanded the pens to hold more animals than before. Betty had moved the pigs into the new pens.