# Dietary Supplementation with Bacillus licheniformis and Bacillus subtilis Modulates Immunity, Serum Metabolome, and Intestinal Homeostasis in Cats

## TL;DR

This study shows that adding two types of probiotics to cat diets improves gut health, immunity, and reduces inflammation.

## Contribution

The novel finding is that Bacillus licheniformis and Bacillus subtilis each uniquely modulate different metabolic pathways in cats.

## Key findings

- Bacillus licheniformis improves fecal quality, modulates amino acid metabolism, and alters gut microbiota composition.
- Bacillus subtilis enhances immune markers, reduces inflammation, and regulates lipid metabolism pathways.
- Both probiotics increase IgA, IgM, and antioxidant levels while decreasing TNF-α in serum.

## Abstract

The health of domestic cats, particularly gastrointestinal well-being, is garnering growing scientific interest, with probiotics recognized for their crucial role in sustaining gut homeostasis. This study investigates the impact of probiotics (Bacillus licheniformis, Bacillus subtilis) on feline immunity, serum metabolomics, and intestinal homeostasis. The results suggest that Bacillus licheniformis and Bacillus subtilis improve fecal quality, mitigate inflammatory responses, enhance immune function, and strengthen the intestinal barrier. Furthermore, Bacillus licheniformis modulates amino acid metabolic pathways, while Bacillus subtilis regulates lipid metabolic pathways. Together, these findings suggest that both strains hold promfecalas feed additives for improving feline gut health.

In recent years, as the number of cats has increased, the intestinal health of cats has receied increasing amounts of attention. Probiotics have positive effects on maintaining intestinal homeostasis. This study was conducted to investigate the effects of probiotics Bacillus licheniformis (B. licheniformis) and Bacillus subtilis (B. subtilis) on cat immunity, inflammation, antioxidants, intestinal barrier and microbiota, and serum metabolites. Thirty-six cats (over one year old, 3.48 ± 0.71 kg) were randomly divided into 3 groups and fed with a basal diet (CON group), a basal diet + B. licheniformis (BL group), and a basal diet + B. subtilis (BS Group). The experiment lasted 35 days. Fecal scoring indicates that B. licheniformis and B. subtilis can improve fecal scores. Serum analysis indicated that the addition of both substances increased levels of IgA, IgM, T-AOC, and SOD, while reducing levels of the pro-inflammatory factor TNF-α. Moreover, 16S rRNA gene sequencing revealed that B. licheniformis and B. subtilis altered the fecal microbiota composition, characterized by the elevated abundance of Bacillus. Adding B. licheniformis to the diet increased the level of Faecalibacterium and decreased the level of Mogibacterium. Serum metabolomics revealed that levels of L-Glycine and Sn-Glycero-3-phosphocholine exhibited marked elevation in both the BL and BS groups, respectively. Furthermore, the study demonstrated that differential metabolites in the BL group were mainly enriched in amino acid metabolism pathways, while those in the BS group were chiefly concentrated in lipid metabolism pathways. However, this study acknowledges the limitations of its exclusive use of Ragdoll cats and its 35-day intervention period. It highlights the need for future research involving diverse breeds and longer durations. Overall, the data highlight B. licheniformis and B. subtilis as cat nutritional supplements that improve immunity and maintain intestinal health.