Cartilage volume and body composition in fattening pigs in different housing systems using magnetic resonance imaging and dual-energy X-ray absorptiometry

Lameness and diseases of the cartilage and skeletal system in pigs are an important animal welfare issue in connection with the goal of high profitability. The aim of the study is therefore to investigate the influence of the housing system on the expression of cartilage tissue in relation to the body composition of fattening pigs. Magnetic resonance (MR) imaging was combined with dual−energy X-ray absorptiometry (DXA) to determine cartilage and body tissue characteristics. A total of 127 crossbred pigs (Piétrain × German Landrace) were examined in 3 different fattening rounds. After the first test at a live weight of 30 kg, half of the animals in each round were randomly assigned to a fully slatted housing system (multi-purpose barn = MPB) or an outdoor climate barn (OCB) with deep litter. In this step, the aim was to achieve a balanced sex ratio of female (n = 62) and male castrated pigs (n = 65). The animals remained in the respective housing system until the end of the fattening period. Each pig was examined three times during the fattening period: at 25–30 kg (scan 30), at 60–70 kg (scan 60) and at 90–100 kg (scan 90) BW. During the MR imaging examination with a Siemens Magnetom Open, two T1-weighted sequences were created of each pig at each examination time point: a sagittal sequence of the left elbow and shoulder joint and a coronary sequence of the left and right knee joint. Subsequently, a whole-body scan was performed on each pig using the GE Lunar iDXA scanner and the following values were automatically determined: bone mineral density [g/cm²], absolute bone mineral content [g] (BMC), bone mineral area projection [cm²], fat tissue percentage [%] (Fat_PC), fat tissue [g], and soft lean tissue [g]. In the knee joint, there were no significant differences in cartilage volume (CVo) in relation to the housing system. In the elbow joints, however, there were significant differences in CVo at the time of scan 30 that could not be explained. In contrast, the results of the DXA study show that pigs in the OCB have significantly higher BMC values than pigs from the MPB from scan 60 onwards. These differences indicate that the housing system has an effect on bone mineralisation, but possibly not on the CVo during pig fattening.