Plant extracts have attracted more and more attention because of their antimicrobial activity and not causing drug resistance and residues in livestock products.

Many components of essential oils such as carvacrol, thymol, eugenol, perillaldehyde, cinnamaldehyde and cinnamic acid have antimicrobial activity (Table 1). It was found that anise oil could significantly inhibit the growth of Gram-positive and Gram-negative bacteria, and it also showed it had antifungal effects. Plant extracts can kill spoilage bacteria in carcass muscle and improve carcass quality. It has been reported that essential oils extracted from oregano can kill harmful microorganisms in carcass of broiler chickens. At present, clove oil and cinnamon oil are also used to preserve meat and prevent its decay. They are not only beneficial to human health, but also have inhibitory or killing effects on Gram-positive bacteria and Gram-negative bacteria. They are widely used in feed and food industry.

Zhijie Zhanget al. studied the effect of plant essential oil (the main component is 15% thymol and 5% cinnamaldehyde) on chickens infected with coccidiosis. The results showed that plant essential oil can improve the production performance of chickens infected with coccidiosis, which is related to the enhancement of immune cell function and bactericidal ability of essential oil.

Table I Major components of selected essential oils (Eos) that exhibit antibacterial properties