The World Organisation for Animal Health (OIE) provides a definition of animal welfare that is now used as a reference. It is based on the 5 fundamental freedoms. At the European level, directives translate the respect of these 5 freedoms into obligations of means for each spieces of livestock.
For pig production, it is the directive 2008/120/EC which defines the minimum standards to be respected by pig farmers. However, despite the strict application of these standards, it turns out that pigs remain stressed by so-called unavoidable events that are detrimental to their well-being! We then become aware that these obligations of means can only target external factors to the animal (feed, surface, atmosphere…) and do not cover the management of the well-being which can only be based on an obligation of results.
Psychosocial stress: the first obstacle to pig welfare
Before talking about stress, it is important to define it. Stress defines the state of an individual, which is the response to a stressful event that is described as a stressor.
The main stressors inherent in the pig’s life are :
- Weaning of piglets,
- Farrowing of the sow,
- The change of building or the departure to the slaughterhouse.
All these events are known to be stressful for the animal. Indeed, since pigs are gregarious animals, they need to form stable groups in which a hierarchical social relationship is established. Any change that would destabilize this balance is therefore stressful. What all these stressors have in common is that they are psychosocial in nature, so we will talk about psychosocial stress!
Controlling psycho-social stress to control pigs’ well-being
“Psychosocial stress” is defined by two dimensions:
- a social dimension: stress comes from social interactions
- a psychological dimension: stress is integrated by the animal at the cerebral level.
The social dimension requires a good animal-animal relationship. New husbandry practices such as the early socialisation of piglets under the mother allows a better management of weaning stress (less fighting in post-weaning). As a result, the zootechnical performance of fattening animals is improved. The relationship between man and animal is also important. Habituation and learning skills exist to improve this relationship.
The psychological dimension is more complex to apprehend because it is more cerebral. It can nevertheless be divided into two parts: the integration of the stress message by the animal and then the response it will give (what behaviour will it adopt?).
How to reduce psychosocial stress?
Psychosocial stress being the first stress inherent to the pig’s life, controlling it is the key lever for success in managing its well-being. 3 solutions exist:
- To reduce or eliminate stressors
- To block the integration of the message at the brain level
- To improve the animal’s response to stress