Essential Oils, Chemical Compounds, and Their Effects on the Gut Microorganisms and Broiler Chicken Production: Review

The influence of essential oils (EOs) on gut microorganisms and broiler chicken production was evaluated through the systematic analysis of scientific reports. The present study was focused on the EO antimicrobial activity oriented toward broiler chicken production. There is a great biodiversity of plants, and various compounds with different biological activity have been isolated from them. The EO molecules extracted from plants have been employed recently in livestock feeding. Microbial resistance to antibiotics has led to their reduced use in animal production. To maintain competitive broiler chicken production with reduced antibiotic use, EOs have been explored. In broiler chickens, EOs are supplemented in the diet or drinking water to enhance weight gain and feed efficiency and reduce mortality. EOs are an alternative to antibiotics, and their research is dynamic in poultry production. The present review focused on the antimicrobial activity oriented to broiler chicken production. The search for information in databases used the terms “broiler chicken”, “essential oils” and combined them with the name of the plants. It was detected that the EO of Cinnamon bark or its compound cinnamaldehyde could reduce pathogenic bacteria in the digestive tract and improve intestinal morphology. Essential oils from Cymbopogon spp. and Origanum vulgare had an effect mainly against Gram-negative bacteria, such as Escherichia coli , Klebsiella pneumoniae , Pseudomonas aeruginosa , Salmonella spp., and others, and against some Gram-positive bacteria, such as Staphylococcus spp., or yeasts, such as Candida albicans . Essential oils of Cymbopogon citratus acted against Salmonella . Citrus japonica affected Bacillus subtilis , Escherichia coli , and Salmonella typhimurium . Origanum EO improved the antioxidant status and gut health of chickens, while EO of Eucalyptus with carvacrol, thymol, and Citrus lemon improved the productive performance of broiler chickens; also, Citrus spp. reduced the number of oocysts of Eimeria and showed activity against Listeria monocytogenes , Staphylococcus aureus, and Pseudomonas aeruginosa . It is concluded that EOs are a sustainable alternative to antibiotics in the production of broiler chickens. Future research includes the standardization of EO from different plants and active molecules, as well as the interaction with other feed additives and their impact on the health and production of broiler chickens. In addition, safety for consumers and the environment must be considered.