Characterization and comparison of fecal microbiota in horses with pituitary pars intermedia dysfunction and age‐matched controls

Abstract Background Altered gut microbiota has been associated with dopaminergic degenerative diseases in people, but studies on horses with pituitary pars intermedia dysfunction (PPID) are lacking. Hypothesis/Objectives Investigate the effect of PPID on fecal microbiota in horses. Animals Nine horses with PPID and 13 age‐matched control horses. Methods Prospective control study. Fecal samples were collected bimonthly. Microbial analysis used 16S rRNA sequencing to determine the relative abundance at genus and phylum levels, assess alpha and beta diversity and identify core microbiota. Results Horses with PPID had decreased relative abundances of Christensenellaceae R‐7 group (median; 95% confidence interval [CI]: PPID, 2.04; 1.82‐2.35 vs control, 2.54; 2.37‐2.76; P = .02) and NK4A214 group (PPID, 2.21; 2.02‐2.56 vs control, 2.62; 2.44‐2.85; P = .05), and significant lower abundances of Romboutsia (log2FoldChange = −3.54; P = .04) and Peptococcaceae uncultured (log2FoldChange = −0.89; P = .04) by differential abundance analysis. However, the abundance of Fibrobacter (log2FoldChange = 0.74; P = .04) was significantly higher in the PPID group. A significant effect of PPID on beta diversity was observed (P = .004), whereas alpha diversity varied with months (P = .001). Seven unique genera were identified in horses with PPID and 12 in control horses. Conclusions and Clinical Importance The fecal microbial composition is altered in horses with PPID. These findings support the potential role of the microbiota‐gut‐brain axis in the pathogenesis of PPID.