Identification of biological characteristics that predict adaptation (and maladaptation) in pigs

Health and/or behavioural problems in pigs may be a consequence of maladaptive responses by the animals to their environment. Those responses may include tail biting and other manipulative behaviour or poor growth. The occurrence of such maladaptive responses is influenced not only by housing environments in which the pigs have 'too little to do'; the biological susceptibility of the pig is also an important factor. The objective of this project is the identification of biological characteristics that could predict maladaptive responses in pigs.

Three steps were followed in the project:
  1. The measurement of behavioural, immunological and endocrine/neuroendocrine responses of pigs in a diverse range of experimental tests. It will be tested if these measurements are related to maladaptive responses of the pigs throughout life. The behaviour in the home pens was also observed.
  2. Testing whether these measurements of the pig are interrelated in multivariate clusters such as coping strategies or fearfulness.
  3. Testing simple measurements in practice that could predict the susceptibility of a pig or group of pigs to developing maladaptive responses such as tail biting.

A total of four experiments were carried out:

  1. A trial involving 32 pigs, examining the relationship between the neurotransmitter serotonin in the brain and in the blood, and the behaviour during a test.
  2. 480 pigs were monitored, from piglet (starting with 1000 piglets) to slaughter. These pigs underwent a variety of behavioural tests, and were categorised in terms of various neuroendocrine and immunological characteristics. Relationships between behaviour, physiology and maladaptation can be defined, and tail biting throughout life can be described.
  3. In a commercial setting, various measurements were performed on 440 pigs in order to investigate whether there are any predictors of maladaptation that could be used in practice. Here too, the occurence of tail biting and other manipulative behaviour was monitored over time.
  4. At another commercial farm we, again, examined possible predictors of maladaptation in practice (in 480 piglets), and the development and expression of manipulative behaviour was monitored over time. In addition, half of the pigs kept at this farm were given stall enrichment to test its effect on manipulative behaviour later in life.