One of the most significant concerns for poultry production is the prevention of infections caused by pathogenic gut microbes. The innate and adaptive immune systems guard the gut mucosal tissues against infection. On day 6 after hatching, B cells were found in the blood of chickens, but endogenous immunoglobulin A was almost never found in the intestine before 14 days of age. As a result, the development of chicken B cells into immunoglobulin-synthesizing cells may take a few weeks after hatching. Within the first 14 days after hatching, maternal IgY undergoes catabolism. The innate immune system utilizes antimicrobial peptides, such as cathelicidins and avian-defensins. Past examinations have revealed that AvBDs are communicated in the digestion tracts of undeveloped and neonatal chicks, and their appearance diminishes from d 4 post-bring forth. As a result, young chicks with immature adaptive immune systems are likely to have a stronger innate immune function in the gut defense system. The proventriculus and gizzard are the two parts of an avian stomach. The luminal contents are mechanically ground and digested by the gastric juice in the gizzard, whereas gastric juice containing gastric acid and pepsin is secreted in the proventriculus. To reduce the pathogenic microbes in the luminal contents before they enter the intestine, germicidal activity in the proventriculus is essential. Although it is known that gastric acid kills germs, little is known about how the innate immune system controls luminal microbes in the proventriculus. Toll-like receptors recognize molecular patterns associated with microbes, which trigger the expression of immune factors, such as cytokines and antimicrobial factors, which are crucial to the immune system's ability to fight infection. The peptidoglycans and lipopolysaccharides of gram-positive and gram-negative bacteria are respectively recognized by TLR2 and TLR4.TLR15, a unique TLR expressed in chickens, recognizes the heat-stable, non-secreted component of bacteria in addition to secreted virulence-associated fungal and bacterial proteases, whereas TLR5 recognizes bacterial flagellin.TLR3 and TLR7 perceive dsRNA and ssRNA infections, individually, though TLR21 perceives unmethylated CpG-DNA of microorganisms. With broad-spectrum antimicrobial activity, fourteen AvBDs and four cathelicidins (CATH1–3 and CATH-B1) have been identified. In the chicken oviduct and other organs, TLR ligands and pathogenic microbes are reported to regulate the expression of proinflammatory cytokines and antimicrobial peptides. Mohammed and other, who looked at how probiotics and LPS affected the gene expression of antimicrobial peptides in the gastrointestinal tract of chicks reported that probiotics increased AvBD6 and 12 expression in the proventriculus when LPS was applied, but CATH expression was unaffected. However, further research, including protein level analysis, is needed to better understand the proventriculus's innate immune system and how it responds to MAMPs. Vaccination alters the adaptive immune response to pathogens through the formation of specific memory lymphocytes. Invertebrates and mammals, as well as other organisms, may also be capable of innate immune training (also known as innate immune memory), according to recent research. Through the activation of macrophages, monocytes, and natural killer cells, vaccination with Bacillus Calmette-Guérin boosts both innate and specific adaptive immune activity. After receiving BCG vaccination, nonspecific innate immune responses to pathogenic agents that are unrelated to the vaccine antigen rise, and this trained immunity results in an increase in the production of cytokines in response to unrelated pathogens. We announced that standard different immunizations, including antibodies for Marek's sickness, avian irresistible bronchitis infection, Newcastle illness and IB infection and irresistible bursal sickness, caused the expansion in the declaration of TLR2 and 21 and the reduction in the AvBDs articulation in the ovary of 21-day-old chicks.