# Rosemary Extract Reduces Odor in Cats Through Nitrogen and Sulfur Metabolism by Gut Microbiota–Host Co-Modulation

## TL;DR

Rosemary extract, especially its small molecule fractions, reduces cat odor by improving gut health and reducing ammonia and hydrogen sulfide emissions.

## Contribution

Rosemary extract fractions below 100 Da are shown to effectively reduce cat odor through gut microbiota and host co-modulation.

## Key findings

- Rosemary extract reduced ammonia and hydrogen sulfide emissions by 46.84% and 41.64%, respectively.
- Fractions below 100 Da achieved even greater reductions of 55.62% and 53.87%.
- The extract increased Bifidobacterium abundance and improved immune function in cats.

## Abstract

Odorous emissions from pet cats are an important contributor to the quality of life of cat owners. Plant extracts rich in bioactive compounds offer a potentially effective solution to this problem. This study evaluated twelve plant extracts via in vitro fermentation, identifying rosemary and licorice as the most effective. Further analysis revealed that rosemary fractions below 100 Da (Dalton) had the best deodorizing effect. Building on these findings, feeding trials were conducted to evaluate the practical effectiveness of rosemary extract in reducing odor emissions and to explore its underlying mechanisms. In feeding trials with British Shorthair cats, rosemary extract, particularly its fractions below 100 Da, significantly reduced ammonia and hydrogen sulfide emissions. It reduced odor emissions by decreasing urease and uricase activity, inhibiting sulfur-containing protein degradation and sulfate reduction, while increasing the relative abundance of the intestinal probiotic (Bifidobacterium) and enhancing immune function. These results suggest that rosemary extract, particularly its fractions below 100 Da, is a promising natural pet deodorizer.

Odors from pet cats can negatively affect the quality of life of cat owners. The diverse bioactive compounds in plant extracts make them a promising candidate for effective odor reduction. This study evaluated twelve plant extracts for deodorizing efficacy via in vitro fermentation tests. Rosemary extract and licorice extract exhibited better deodorizing effects, with fractions of rosemary extract below 100 Da demonstrating the most effective deodorizing performance. Based on these findings, subsequent feeding trials were conducted using rosemary extract and its fractions below 100 Da. In the feeding trial, adult British Shorthair cats were divided into three groups (Control Check, RE, and RE100) and housed in a controlled-environment respiration chamber for 30 days. Measurements included odor emissions, fecal and blood physicochemical parameters, immune parameters, microbiota composition based on 16S rRNA sequencing, and metabolome analysis. The results of the feeding trial indicated that rosemary extract significantly reduced ammonia and hydrogen sulfide emissions (46.84%, 41.64%), while fractions below 100 Da of rosemary extract achieved even greater reductions (55.62%, 53.87%). Rosemary extract regulated the intestinal microbial community, significantly increasing the relative abundance of the intestinal probiotic Bifidobacterium (p < 0.05) and reducing the population of sulfate-reducing bacteria (p < 0.05). It also significantly reduced urease and uricase activities (p < 0.05) to reduce ammonia production and inhibited the degradation of sulfur-containing proteins and sulfate reduction to reduce hydrogen sulfide emissions. Furthermore, rosemary extract significantly enhanced the immune function of British Shorthair cats (p < 0.05). This study suggests that rosemary extract, particularly its fractions below 100 Da, is a highly promising pet deodorizer.