Mass spectrometry-based metabolic profiling for identification of biomarkers related to footpad dermatitis in ducks

1. A new assessment method for duck footpad dermatitis (FPD) evaluation was developed, combining visual and histological characters using the images and sections of 400 ducks’ feet at 340 d of age. All ducks were graded as G0 (healthy), G1 (mild), G2 (moderate) and G3 (severe) according to the degree of FPD.
2. To reveal the potential biomarkers in serum related to duck FPD, non-targeted metabolomics and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were used to explore differential metabolites in each group.
3. There were 57, 91 and 210 annotated differential metabolites in groups G1, G2 and G3 compared with G0, which meant that the severity of FPD increased in line with the number of metabolites. Four metabolites, L-phenylalanine, L-arginine, L-leucine and L-lysine, were considered potential biomarkers related to FPD.
4. KEGG enrichment analysis showed that the FPD was mainly involved in glycolysis, the tricarboxylic acid (TCA) cycle, the pentose phosphate pathway and amino acid metabolism. These are related to production metabolism and can affect the physiological activities of ducks, which might explain the decrease in production performance.

1. 本研究构建了一种针对鸭脚垫皮炎（footpad dermatitis, FPD）的新型评估方法，该方法结合视觉与组织学特征，基于400只340日龄鸭的足部图像与组织切片完成开发。所有试验鸭依据FPD严重程度被划分为G0（健康）、G1（轻度）、G2（中度）与G3（重度）四个等级。
2. 为挖掘与鸭FPD相关的血清潜在生物标志物，本研究采用非靶向代谢组学与京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）富集分析方法，对各组的差异代谢物进行探究。
3. 相较于G0组，G1、G2、G3组分别注释得到57、91和210种差异代谢物，表明FPD的严重程度与差异代谢物数量呈正相关。最终筛选出L-苯丙氨酸、L-精氨酸、L-亮氨酸与L-赖氨酸共4种与FPD相关的潜在生物标志物。
4. KEGG富集分析结果显示，FPD主要涉及糖酵解、三羧酸循环（tricarboxylic acid cycle, TCA）、磷酸戊糖途径以及氨基酸代谢通路。上述通路均与生产代谢相关，可影响鸭的生理活动，这或可解释鸭生产性能下降的现象。