Essential oils (EOs) are plant-derived natural bioactive compounds that have been shown to have positive effects on animal growth and health due to their antimicrobial and antioxidative properties, University of Manitoba researchers noted in an accepted manuscript posted to Translational Animal Science.

However, EOs are volatile, can evaporate quickly and may be rapidly absorbed in the upper gastrointestinal tract. Also, due to their labile nature, the stability of EOs during feed processing is often questionable, leading to variations in the final concentration in feed, according to researchers Janghan Choi, Lucy Wang, Emily Ammeter, Ludovic Lahaye, Song Liu, Martin Nyachoti, Chengbo Yang of the University of Manitoba.

Choi et al. said encapsulation has become one of the most popular methods of stabilizing EOs during feed processing, storage and delivery into the lower gut, so they conducted a study to:

1. Evaluate the stability of thymol microencapsulated in combination with organic acids in commercially available lipid matrix microparticles during the feed pelleting process and storage;

2. Validate and demonstrate the slow release of thymol from the lipid matrix microparticles in a simulated pig gastric fluid (SGF) and simulated pig intestinal fluid (SIF), and

3. Evaluate the in vivo release of thymol from the lipid matrix microparticles along the pig gut.

According to Choi et al., the thymol concentration was not significantly different in the mash and pelleted feeds (P > 0.05).

In the in vitro experiment, 26.04% thymol was released in SGF, and the rest of the thymol was progressively released in SIF until completion, which was achieved by 24 hours, the researchers reported.

The in vivo experiment showed that 15.5% of thymol was released in the stomach, and 41.85% of thymol was delivered in the mid-jejunum section, Choi et al. reported, adding that only 2.21% of thymol was recovered in feces.

Choi et al. concluded that lipid matrix microparticles were able to maintain the stability of thymol during a feed pelleting process and storage and allow a slow and progressive intestinal release of thymol in weaned pigs.