Fading puppy syndrome (FPS) is a fatal condition in neonatal dogs. Intestinal microbial alterations, although never investigated, may be involved in its pathophysiology. The study examined the occurrence of FPS and its associations with dam, puppy, and husbandry characteristics, compared the intestinal microbial diversity of healthy puppies and those with FPS, and examined whether intestinal microbiomes are predictive of FPS. Day 1 and 8 post-partum (PP) rectal swabs were collected from healthy puppies and puppies which later developed FPS. Microbial compositional structure, including alpha and beta diversities and relative abundance of specific taxa were compared between groups, and microbial data was applied to a machine-learning model to assess the predictive performance of microbial indices of FPS or death. FPS occurred in 22/165 puppies (13%), with a 100% mortality rate. FPS was associated (P < 0.001) with decreased Day 1 PP puppy activity. Day 1 (P = 0.003) and 8 (P = 0.005) PP rectal beta diversities were different in puppies with FPS vs healthy ones. Increased Proteobacteria/Firmicutes ratio, increased relative abundance of Pasteurellaceae, and decreased relative abundance of Clostridia and Enterococcus were associated with FPS. A machine-learning model showed that Day 1 PP rectal microbiome composition accurately predicted FPS-related death. We found that specific rectal microbial phenotypes are associated with FPS, reflecting the significant role of microbiome alterations in this phenomenon. These findings may serve as useful microbial indices for early diagnosis of puppies at risk of FPS and may provide specific therapeutic targets.

褪色幼犬综合症 (FPS) 是新生犬的致命疾病。尽管从未研究过肠道微生物改变，但其病理生理学可能涉及。该研究检查了 FPS 的发生及其与母犬、幼犬和饲养特性的关联，比较了健康幼犬和 FPS 幼犬的肠道微生物多样性，并检查了肠道微生物群是否可以预测 FPS。从健康的幼犬和后来发展为 FPS 的幼犬收集产后 (PP) 第 1 天和第 8 天的直肠拭子。比较各组之间的微生物组成结构，包括 alpha 和 beta 多样性以及特定分类群的相对丰度，并将微生物数据应用于机器学习模型，以评估微生物指数对 FPS 或死亡的预测性能。FPS 发生在 22/165 幼犬 (13%) 中，死亡率为 100%。FPS 已关联 (P  < 0.001)，第 1 天 PP 幼犬活动减少。第 1 天 ( P  = 0.003) 和第 8 天 ( P  = 0.005) 具有 FPS 的幼犬与健康幼犬的 PP 直肠β 多样性不同。Proteobacteria/Firmicutes 比率增加，巴斯德氏菌的相对丰度增加，梭菌和肠球菌的相对丰度减少与 FPS 相关。机器学习模型显示，第 1 天的 PP 直肠微生物组组成准确预测了 FPS 相关的死亡。我们发现特定的直肠微生物表型与 FPS 相关，反映了微生物组改变在这种现象中的重要作用。这些发现可能作为有用的微生物指标，用于早期诊断有 FPS 风险的幼犬，并可能提供特定的治疗目标。