The Effects of the Rearing System, Genotype at the RYR1 Locus and Sex of Fattening Pigs on Selected Biochemical Blood Parameters and Concentrations of Cortisol and β-Endorphin

There has been a growing interest in alternative rearing systems, including free-range rearing. This is particularly important in the case of indigenous pig breeds, which are prized for the high quality of their meat and traditional products, and whose importance in the production of high-quality food is steadily increasing. The aim of this study was to assess the effect of the rearing system (pen/free-range), genotype at the RYR1 locus and sex of fattening pigs on cortisol and β-endorphin concentrations, as well as the parameters of protein, lipid and electrolyte metabolism, and indicators of liver and kidney function. This study was carried out on 120 Złotnicka Spotted breed fattening pigs raised under two rearing systems: pen housing (n = 60) and free-range (n = 60). The rearing system had the greatest impact on the biochemical indicators analysed in relation to the assessment of pig welfare. In free-range pigs, the observed changes included increases in total protein (8.04%%), albumin (4.7%), Ca (3.4%), total cholesterol (11.7%), and triglycerides (107%), but lower urea (44.4%) and glucose (10.7%) concentrations compared with pen-reared pigs. The effect of the rearing system on the selected biochemical parameters was dependent on the RYR1 genotype, sex or body weight of the animals, while for cortisol and β-endorphin, no significant interactive effects were demonstrated. By contrast, the effect of sex on the biochemical parameters analysed was minor.