The poultry industry evolved and reached high production performance, with several zootechnical techniques that contributed to the current scenario, including ambience, genetics and diet - all contributing and optimizing the digestive system of the birds. The gastrointestinal tract is a system with several functions and attributions within the organism, among them, digestion of the host, immunity and proper functioning of the system. The gut microbiota has direct effects on metabolic processes and subsequently on the performance of birds. Issues related to microbiota have acquired relevance both for the maintenance and modulation of these microorganisms. One of the maneuvers used to manipulate the intestinal microflora was the use of antibiotics, acting as growth promoters; however, this type of additive, due to sanitary pressure, should be abolished in the coming years, which makes other options appear on the scene, among them, phytogenic additives. Among the latter, essential oils have gained prominence for their beneficial activity in the microbiota as well as their natural composition and non-residual impacts on the process. Based on this, the aim was to review the guidelines that affect the intestinal microbiota in poultry.

Phytogenic additives have been shown to act as a substitute for antibiotics because of their functionality in breaking up bacterial membranes, being effective in combating microorganisms and acting as antioxidants. Used in a strategic way, in promoting action, it will mainly favor the intestinal condition, increasing the zootechnical gains and increasing the prevention of pathologies associated with bacteria or fungi. Therefore, the aim of this review was to seek scientific information on what are the phytogenic additives, their compositions and mode of action and the applicability with the results obtained through their use in broiler feed. For this review an analysis was made of scientific studies that studied which are the main additives and their active principles, as well as their mode of action of essential oils and which plants have potential to be used as phytogenic additives, evidencing their effects on food. of broiler chickens. It is concluded that the use of phytogenic actives in the form of essential oils can be used in chicken feed, providing improvements in the intestinal health of birds and consequently improvement in their productive performance. Even if its positive points are shown, some conditions still need to be elucidated, such as dose / action relationship and association of the various active principles belonging to the phytogenic additives, which may provide several new studies.

O trato gastrointestinal da ave possui uma diversidade microbiológica, as bactérias de caráter benéfico desempenham papel na digestão e absorção, contribui com o sistema imunológico e na competição contra patógenos que compõe aproximadamente 10% da microbiota intestinal. Os filos mais abundantes são Actinobacteria, Firmicutes, Fusobacteria e Bacteriodetes, tais microrganismos são essenciais para a saúde da ave. Os microrganismos patogênicos são Proteobacteria, Protozoa, Apicomplexa, Tenericutes e Firmicutes, colonizam o lúmen do trato gastrointestinal da ave sem ocasionar danos, entretanto, quando há disbiose os agentes patogênicos se multiplicam provocando lesões na mucosa intestinal podendo causar distúrbios entéricos, por vezes irreversíveis. A microbiota benéfica é capaz de estimular o sistema imune com a produção de células T, diminuindo o processo inflamatório e a produção de imunoglobulina A, G e M. As Bifidobacterium influenciam a proliferação de macrófagos potencializando o sistema imunológico do animal, além de produzir bacteriocinas que inibe a multiplicação de patógenos (Salmonella spp. e Clostridium perfringens). Os Lactobacillus spp. estimulam a secreção de imunoglobulinas, lactato e acetato e inibem a adesão de patógenos ao epitélio intestinal. Os Bacteroides spp. e Bifidobacterium spp. instituem ácidos graxos voláteis e suprimem a toxicidade da Salmonella spp., Escherichia coli e Campylobacter spp.. A espécie Bacteroides fragilis estimula a produção de células T com o objetivo de diminuir a inflamação. O objetivo principal é revisar as informações científicas disponíveis sobre o o microbioma intestinal das aves e sua importância, detalhando sua composição e correlação com o sistema imunológico.