The fecal microbiome and metabolome differs between dogs fed Bones and Raw Food (BARF) diets and dogs fed commercial diets

IntroductionFeeding a Bones and Raw Food (BARF) diet has become an increasing trend in canine nutrition. Bones and Raw Food diets contain a high amount of animal components like meat, offal, and raw meaty bones, combined with comparatively small amounts of plant ingredients like vegetables and fruits as well as different sorts of oil and supplements. While many studies have focused on transmission of pathogens via contaminated meat and on nutritional imbalances, only few studies have evaluated the effect of BARF diets on the fecal microbiome and metabolome. The aim of the study was to investigate differences in the fecal microbiome and the metabolome between dogs on a BARF diet and dogs on a commercial diet (canned and dry dog food).MethodsNaturally passed fecal samples were obtained from 27 BARF and 19 commercially fed dogs. Differences in crude protein, fat, fiber, and NFE (Nitrogen-Free Extract) between diets were calculated with a scientific nutrient database. The fecal microbiota was analyzed by 16S rRNA gene sequencing and quantitative PCR assays. The fecal metabolome was analyzed in 10 BARF and 9 commercially fed dogs via untargeted metabolomics approach.ResultsDogs in the BARF group were fed a significantly higher amount of protein and fat and significantly lower amount of NFE and fiber. There was no significant difference in alpha-diversity measures between diet groups. Analysis of similarity (ANOSIM) revealed a significant difference in beta-diversity (p Lactobacillales, Enterobacteriaceae, Fusobacterium and, Clostridium in the BARF group while conventionally fed dogs had a higher abundance of Clostridiaceae, Erysipelotrichaceae, Ruminococcaceae, and Lachnospiraceae. The qPCR assays revealed significantly higher abundance of Escherichia coli (E. coli) and Clostridium (C.). perfringens and an increased Dysbiosis Index in the BARF group. Principal component analysis (PCA) plots of metabolomics data showed clustering between diet groups. Random forest analysis showed differences in the abundance of various components, including increased 4-hydroxybutryric acid (GBH) and 4-aminobutyric acid (GABA) in the BARF group. Based on univariate statistics, several metabolites were significantly different between diet groups, but lost significance after adjusting for multiple comparison. No differences were found in fecal bile acid concentrations, but the BARF group had a higher fecal concentration of cholesterol in their feces compared to conventionally fed dogs.ConclusionMicrobial communities and metabolome vary significantly between BARF and commercially fed dogs.

引言 喂食骨骼生食（BARF，Bones and Raw Food）饮食现已成为犬类营养学领域日益流行的趋势。该类饮食含有大量动物源性成分，如肉类、内脏及带肉生骨，并辅以相对少量的植物性成分（蔬菜、水果）、各类油脂及营养补充剂。尽管已有诸多研究聚焦于受污染肉类引发的病原体传播问题与营养失衡现象，但针对BARF饮食对粪便微生物组与代谢组影响的相关研究仍较为匮乏。本研究旨在探究喂食BARF饮食与喂食商业粮（罐头粮与干粮）的犬只之间，粪便微生物组与代谢组的差异。

方法 本研究从27只喂食BARF饮食的犬只与19只喂食商业粮的犬只处收集自然排出的粪便样本。借助科学营养数据库，计算两种饮食在粗蛋白、粗脂肪、粗纤维与无氮浸出物（NFE，Nitrogen-Free Extract）含量上的差异。通过16S rRNA基因测序与定量PCR（qPCR）检测分析粪便微生物群。针对10只BARF饮食组犬只与9只商业粮组犬只的粪便样本，采用非靶向代谢组学方法分析其粪便代谢组。

结果 BARF饮食组犬只的日粮蛋白质与脂肪含量显著更高，而无氮浸出物与粗纤维含量则显著更低。两组犬只的粪便微生物α多样性无显著差异。相似性分析（ANOSIM，Analysis of Similarity）结果显示，两组β多样性存在显著差异（原文此处存在文本缺失），BARF饮食组犬只粪便中乳杆菌目（Lactobacillales）、肠杆菌科（Enterobacteriaceae）、梭杆菌属（Fusobacterium）与梭菌属（Clostridium）的丰度更高；而常规喂食商业粮的犬只，其粪便中梭菌科（Clostridiaceae）、红蝽杆菌科（Erysipelotrichaceae）、瘤胃球菌科（Ruminococcaceae）与毛螺菌科（Lachnospiraceae）的丰度更高。定量PCR检测结果显示，BARF饮食组犬只粪便中大肠杆菌（E. coli，Escherichia coli）与产气荚膜梭菌（C. perfringens，Clostridium perfringens）的丰度显著更高，且菌群失调指数（Dysbiosis Index）也有所升高。代谢组学数据的主成分分析（PCA，Principal Component Analysis）结果显示，两组犬只的粪便代谢物存在聚类差异。随机森林分析结果显示，多种代谢物的丰度存在组间差异，其中BARF饮食组的4-羟基丁酸（GBH，4-hydroxybutyric acid）与γ-氨基丁酸（GABA，4-aminobutyric acid）丰度更高。基于单变量统计分析，两组间存在多种差异代谢物，但在校正多重比较后，这些差异不再显著。粪便胆汁酸浓度未发现组间差异，但BARF饮食组犬只粪便中的胆固醇浓度显著高于常规喂食商业粮的犬只。

结论 BARF饮食组与商业粮喂食组的犬只，其粪便微生物群落与代谢组均存在显著差异。