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 imaging (MRI) was combined with dual energy X-ray absorptiometry (DXA) to determine cartilage and body tissue characteristics. A total of 127 crossbred pigs (Piétrain x 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 and male castrated pigs. 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) body weight. During the MRI 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], bone mineral area projection [cm²], fat tissue percentage [%], fat tissue [g], and soft lean tissue [g]. In the knee joint, there were no significant differences in cartilage volume in relation to the housing system. In the shoulder and elbow joints, however, there were significant differences in cartilage volume 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 cartilage volume during pig fattening.

猪跛行及软骨、骨骼系统疾病是与高养殖盈利目标紧密相关的重要动物福利议题。本研究旨在探究饲养系统对育肥猪体成分相关软骨组织表达的影响。研究采用磁共振成像（Magnetic Resonance Imaging, MRI）结合双能X线吸收测定法（Dual Energy X-ray Absorptiometry, DXA），以测定软骨与躯体组织特征。共计127头杂交猪（皮特兰×德国兰德瑞斯猪）分3个不同育肥批次开展检测。在活重30kg时完成首次检测后，每批猪只中的半数被随机分配至全漏缝地板饲养系统（多功能舍=MPB）或带有厚垫料的户外气候舍（OCB）。此分组步骤旨在实现母猪与公阉猪的性别比例均衡。试验猪仅在对应饲养系统中饲养至育肥期结束。育肥期内，每头猪共接受3次检测：活重25~30kg（扫描30）、60~70kg（扫描60）以及90~100kg（扫描90）阶段。使用西门子Magnetom Open磁共振扫描仪进行MRI检测时，每个检测时间点均为每头猪采集两组T1加权序列：左肘与肩关节的矢状位序列，以及左右膝关节的冠状位序列。随后，使用GE Lunar iDXA扫描仪对每头猪开展全身扫描，并自动测定以下指标：骨密度[g/cm²]、绝对骨矿物质含量[g]、骨矿物质投影面积[cm²]、脂肪组织占比[%]、脂肪组织重量[g]及瘦软组织重量[g]。膝关节软骨体积未随饲养系统呈现显著差异。但在扫描30阶段，肩关节与肘关节的软骨体积存在无法合理解释的显著差异。与之相对，DXA检测结果显示，自扫描60阶段起，OCB组猪只的骨矿物质含量（BMC）显著高于MPB组。上述差异表明，饲养系统会对猪的骨矿化过程产生影响，但可能不会改变育肥期的软骨体积。