Intertwining of the IGF system and animal welfare

To date, husbandry categories are defined based on the human concept of animal needs, however, to objectively assess animal welfare in defined husbandry systems, animal-related indicators must be evaluated. Here, we studied the impact of differential housing conditions on factors of the insulin-like growth factor system (IGF-system) in mother sows either housed in a conventional husbandry system corresponding to the regulations of the German husbandry form 1, or in the associated ecological facility, corresponding to the German husbandry form 4/5. Utilizing a proprietary bioassay that determines the activity of the IGF system at the level of intracellular signal transduction, we revealed altered serum IGF bioactivities in differentially housed sows. Moreover, we present a comprehensive analysis of the individual factors of the IGF system in serum of pregnant and lactating sows to elucidate which of these are modified depending on the housing conditions. An unsupervised principal component analysis suggests that IGF system factors might distinguish sows based on their housing environment. These results imply that the IGF system provides a solid basis for the documentation and objective assessment of animal health and welfare. However, a robust biomarker system for animal welfare assessment will likely require a multifactorial and integrative approach.