Proteomics and the search for welfare and stress biomarkers in animal production in the one-health context.

Stress and welfare are important factors in animal production in the context of growing production optimization and scrutiny by the general public. In a context in which animal and human health are intertwined aspects of the one-health concept it is of utmost importance to define the markers of stress and welfare. These are important tools for producers, retailers, regulatory agents and ultimately consumers to effectively monitor and assess the welfare state of production animals. Proteomics is the science that studies the proteins existing in a given tissue or fluid. In this review we address this topic by showing clear examples where proteomics has been used to study stress-induced changes at various levels. We adopt a multi-species (cattle, swine, small ruminants, poultry, fish and shellfish) approach under the effect of various stress inducers (handling, transport, management, nutritional, thermal and exposure to pollutants) clearly demonstrating how proteomics and systems biology are key elements to the study of stress and welfare in farm animals and powerful tools for animal welfare, health and productivity.

Identification of serum stress biomarkers in pigs housed at different stocking densities.

Eight Duroc×(Landrace×Large White) male pigs housed at a stocking rate of 0.50m(2)/pig were subjected to a higher stocking rate of 0.25m(2)/pig (higher density, HD) for two 4-day periods over 26 days. Using biochemical and proteomic techniques serum and plasma samples were examined to identify potential biomarkers for monitoring stress due to HD housing. HD housed pigs showed significant differences (P<0.001) in total cholesterol and low density lipoprotein-associated cholesterol, as well as in concentrations of the pig-major acute phase protein (Pig-MAP) (P=0.002). No differences were observed in serum cortisol or other acute phase proteins such as haptoglobin, C-reactive protein or apolipoprotein A-I. HD-individuals also showed an imbalance in redox homeostasis, detected as an increase in the level of oxidized proteins measured as the total plasma carbonyl protein content (P<0.001) with a compensatory increase in the activity of the antioxidant enzyme glutathione peroxidase (P=0.012). Comparison of the serum proteome yielded a new potential stress biomarker, identified as actin by mass spectrometry. Cluster analysis of the results indicated that individuals segregated into two groups, with different response patterns, suggesting that the stress response depended on individual susceptibility.