How does the pig feel can one measure emotions?

The emotional public debate concerning animal welfare has led to the necessity of an objective measurement tool. Animal welfare comprises different aspects, amongst others the emotional state. Thus, to measure animal welfare as a whole, also the emotional state must be included, which is, however, up to date still a great challenge. Therefore, the present study analyses the structure of the emotional state of growing pigs and aims to detect potential objective indicators for its measurement. Over the time period of two growing periods, on three German farms with different housing systems, a variety of indicators is tested: the play behaviour and body language are observed, a Novel Object Test and Human Approach Test are carried out repeatedly, the concentration of Immunoglobulin A is measured in the saliva and the protein composition of the saliva is analyzed. Additionally, the Welfare Quality (R) protocol is carried out as measurement tool for different aspects of welfare. After culling, adrenal glands and brains, especially the hippocampi are further analyzed patho-histologically. In particular, number and volume of astroglial cells are evaluated. By structural equation modelling, these empirical data are used in order to estimate the influences of each indicator on the latent variable of emotionality. Thus, also valuable information about the general structure of the emotional state of pigs will be gained. In the end, potentially useful indicators for the assessment of emotions will be extracted.