Bathing in Oils and Acids: how combining natural antimicrobials demonstrate synergy in combating Aflatoxin contamination

Authors: Pokoo-Aikins, Anthony; Satterlee, Tim; McDonough, Callie; CHEN, CHONGXIAO - University Of Georgia; Gold, Scott; Glenn, Anthony - Tony

Submitted to: Poultry Science Association Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/24/2023
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Organic acids and essential oils are commonly used in the poultry industry as antimicrobials and for their beneficial effects on gut health, growth performance, and meat quality. A common postharvest storage fungal colonist, Aspergillus flavus, contaminates poultry feed with the highly toxic aflatoxin mycotoxin. Aflatoxin adversely affects poultry feed intake, feed conversion efficiency, weight gain, egg production, fertility, hatchability, and poultry meat yield. Organic acids such as acetic acid have been reported to inhibit the growth of Aspergillus spp. isolated from poultry feed. Essential oils have also been shown to suppress A. flavus growth. With this in mind, we decided to evaluate if synergy between combined essential oils (cinnamon and lemongrass) and organic acids (acetic, butyric, and propionic acids) could further decrease aflatoxin contamination in poultry feed. To determine the Minimum inhibitory concentration (MIC) of each acid, 24 well plates were used. The respective organic acid concentration was added to each well along with PDA to a volume of 1 mL. 5 µL of 106 spores/mL of A. flavus were added to the plates and stored in the dark at 28°C for 5 days. Concentrations of each acid were done in replicates of four. For the essential oils, 25 mL of PDA was added to a 100 mm petri dish and seeded with A. flavus in the four cardinal points and center of the dish. The essential oils were added to Whatman filter discs and placed on the lid of the petri dish. Dishes were done in replicates of four and stored upside down at 28°C in the dark for five days. On day 5, plates were examined for growth. No growth was considered effective, while growth was considered ineffective. After determining the (MIC) of both acids (butyric= 0.10%; acetic= 0.25%, propionic= 0.15%) and essential oils (Lemongrass= 250 µL/L air; Cinnamon= 1000 µL/L air), combinations of ½, 1/4/, 1/8, and 1/16 of both the acids and essential oils were examined. For the synergy study, the method for essential oil MIC was repeated with the addition of the respective acid added to the PDA. Under in vitro settings, combinations at or below 50% of each MIC were shown to completely inhibit the growth of A. flavus. The lowest effective concentrations of all organic acids were at 1/16 MIC (Acetic acid= 0.015625%; butyric acid= 0.00625%; propionic acid= 0.009375%) when combined with either essential oil at their respective ½ MIC (Lemongrass= 125 µL/L air; Cinnamon= 500 µL/L air). With the evident strong synergism demonstrated, combining essential oils and organic acids creates an effective natural method for controlling postharvest aflatoxin contamination in poultry feed. This strategy has a potential application in poultry feed.