# From Bench to Piglet: A Comparison of In Vivo and In Vitro Effects of Phytogenics on Post-Weaning Diarrhea, Growth Performance, and Bacterial Behavior

## TL;DR

This study compares how plant-based compounds affect piglet health in lab and real-world settings, finding that certain combinations improve growth and reduce diarrhea.

## Contribution

The study demonstrates the effectiveness of combining specific phytogenic compounds in feed additives to improve piglet health and performance.

## Key findings

- Prototype two, containing carvacrol, eugenol, and star anise oil, showed stronger antimicrobial activity and inhibited biofilm formation better than prototype one.
- PFA Core 2 improved piglet body weight, daily gain, feed efficiency, and fecal scores compared to the control group.
- The study shows that in vitro assays can guide the development of effective phytogenic feed additives for livestock.

## Abstract

The post-weaning period in piglet production is associated with bacterial disorders and challenges such as diarrhea. Bioactive plant compounds are promising alternatives to traditional antimicrobial growth promoters, although translating lab studies to field conditions remains challenging. This study investigates the antimicrobial properties of bioactive plant compounds to tackle these issues. Carvacrol, eugenol, garlic oil, star anise oil, and tea tree oil were screened for their antimicrobial activities, effects on biofilm formation, bacterial communication, and adhesion to piglet intestinal mucus. Based on the results, two prototypes were created. Prototype two, containing carvacrol, eugenol, and star anise oil, showed stronger antimicrobial activity and better inhibition of biofilm formation and bacterial communication than prototype one, which contained garlic oil and tea tree oil. In part two of the study, 1000 post-weaning piglets were divided into four groups: the control group and three treatment groups receiving diets with prototype one, prototype two, or zinc oxide. Prototype two and zinc oxide improved body weight, daily gain, feed efficiency, and fecal scores compared to the control. The results of this study suggest that the compounds in prototype two can support piglets by likely influencing intestinal bacteria and demonstrate the potential of combining lab tests to develop effective feed additives.

Finding effective alternatives to antibiotics and zinc oxide in livestock feed remains challenging, but phytogenic compounds show promising potential. In the first part of the present study, the in vitro antimicrobial activities of carvacrol, eugenol, garlic oil, star anise oil, and tea tree oil as well as their effects on the biofilm formation of two Escherichia coli field isolates, quorum sensing of Chromobacterium violaceum, and the adhesion of an E. coli field isolate to piglets’ small intestinal mucus were determined. Based on these results, two prototypes were formulated. Phytogenic feed additive (PFA) Core 2, containing carvacrol, eugenol, and star anise oil, showed stronger in vitro antimicrobial activity, inhibition of biofilm formation, and quorum sensing than PFA Core 1, which was mainly composed of garlic oil and tea tree oil. In the second part of the present study, 1000 post-weaning piglets were divided into four groups receiving a control or diets with either PFA Core 1, PFA Core 2, or zinc oxide. Only PFA Core 2 and zinc oxide significantly improved body weight, daily gain, feed efficiency, and fecal scores compared with the control, while PFA Core 1 increased the feed efficiency and fecal scores. The results show that feed additives based on carvacrol and eugenol can improve the growth performance of post-weaning piglets and reduce the incidence of diarrhea, possibly by influencing detrimental bacteria. Furthermore, the present study demonstrates the potential of combinations of in vitro assays to support the development of effective feed additives.