Anti-inflammatory and intestinal barrier-protective activities of commensal lactobacilli and bifidobacteria in thoroughbreds: Role of probiotics in diarrhea prevention in neonatal Thoroughbreds

We previously isolated the commensal bacteria lactobacilli and bifidobacteria from the Thoroughbred intestine and prepared the horse probiotics LacFi™, consisting of Lactobacillus ruminis KK14, L. equi KK 15, L. reuteri KK18, L. johnsonii KK21, and Bifidobacterium boum HU. Here, we found that the fve LacFi™ constituent strains remarkably suppressed pro-inflammatory interleukin-17 production in mouse splenocytes stimulated with interleukin-6 and transforming growth factor-β. The protective effects of the probiotic on impaired intestinal barrier function were evaluated in Caco-2 cells treated with tumor necrosis factor-α. Evaluation of transepithelial resistance showed that all the strains exhibited intestinal barrier protective activity, with significant suppression of barrier impairment by L. reuteri KK18. The LacFi™ constituent strains were detected in neonatal LacFi™-administered Thoroughbred feces using polymerase chain reaction denaturing gradient gel electrophoresis and culture methods. These fve strains were found to be the predominant lactobacilli and bifidobacteria in the intestinal microbiota of LacFi™-administered Thoroughbreds. Administration of LacFi™ to neonatal Thoroughbreds decreased diarrhea incidence from 75.9% in the control group (n=29 neonatal Thoroughbreds) to 30.7% in the LacFi™-administered group (n=101 neonatal Thoroughbreds) immediately after birth to 20 weeks after birth. LacFi™ treatment also prevented diarrhea especially at and around 4 weeks and from 10 to 16 weeks. The duration of diarrhea was also shorter in the probiotics-administered group (7.4 ± 0.8 days) than in the control group (14.0 ± 3.2 days). These results indicate that the LacFi™ probiotics regulates intestinal function and contributes to diarrhea prevention.