Influence of genotype and feeding strategy on pig performance, plasma concentrations of micro nutrients, immune responses and fecal microbiota composition of growing-finishing pigs in a forage-based system

Among consumers in Europe and other parts of the world there is an increasing interest in high-value pork positioned with regard to animal welfare (Krystallis et al., 2012). Free-range pork production is considered more animal friendly because the system enables the animals to express their natural behaviour to a large degree. However, outdoor production of growing-finishing pigs on pastures as described by Halberg et al. (2010) has a major drawback in terms of high risk of nitrate leaching (Eriksen et al., 2006ab; Salomon et al., 2007). This is to a large extent related to high stocking densities combined with large input of nutrients from the supplementary feed (Eriksen et al., 2006ab). The use of supplementary feed is often higher in free-range compared to indoor systems for growing pigs due to a poorer feed conversion. This puts additional pressure on land resources (Hermansen et al., 2008)