Science - January 29, 2004

Pig’s character says little about its immune system

Since they worked out how to measure the character of pigs, Wageningen animal researchers have been busy trying to work out how they can use character to predict behaviour types in adult animals. The research is fruitful, but in one area they have found no relation. When they examined the immune system of pigs, they found out it had little to do with character.

“How a piglet reacts to being turned over on its back, tells us something about how it deals with stress,” says Dr Nicoline Geverink. “Some piglets will struggle with all their might to get back on their feet, but others just lie there passively. On the basis of their reactions you can divide some animals up into ‘high resisting’ and ‘low resisting’.” Research on rats and mice has shown that high-resisting animals perform well in a predictable environment. In a fast changing environment it is the low-resisting animals that have the best survival odds.

Geverink published the results of her research on the effect of pig character on the immune system in Physiology & Behavior this month. She injected low- and high-resisting pigs with a substance which the body recognised as an intruder. She then measured how vigorously the immune system responded to fight the intruders. The pigs she used were divided into two groups: half were housed in a group, the rest were housed in individual stalls.

Neither the type of housing nor the character of the pigs had any effect on the pigs’ immunity. “The tests were carried out under stable conditions. Maybe we would have seen more differences if we had simulated transport conditions,” suggests Geverink. She adds that in research on other parameters, differences do emerge: “High-resisting animals behave more abnormally if they have no contact with other pigs. They chew more often on their chains for example.”

Research on pig character, their coping strategies if you will, serves two purposes according to Geverink: “You can look at what type of pig is best for a farmer. That would appear to be the low-resisting type, because it needs less food. On the other hand, you can also examine in more detail the effect of the surroundings on pigs, and as a result improve their living conditions.” Geverink concludes that she is more interested in the latter approach. | Willem Koert