**4. Stress**

*Advances in Poultry Nutrition Research*

*3.1.11 Polyunsaturated fatty acids*

*3.1.12 Mycotoxin mitigation*

schedules.

application in the gut health arena.

*organs: mainly GALT*

**3.2 Immune system in relation to gut health**

and process of mucin synthesis in chicks [67].

Fish oil and corn oil are the main source of n-3 fatty acids and n-6 fatty acids, respectively in poultry diets and improves the body's function and immunity [56].

This limits intestinal damage and suppression of immune responses for

Genetically superior birds are in immunologically stress full condition which creating pressure in the producers due to ban of antibiotic growth promoters. This creates tremendous pressure on immune system of the birds by various vaccination

Feed deprivation at early stage of life delays the development of mucosallayers

*3.2.1 Position of lymphoid tissues associated with mucosa and spread in different* 

(Intestinal wall), Oesophagus –proventriculus junction, caecal tonsils.

role in protection and immune competence in birds [67].

cell types that needed for initiate and mediate immunity.

*3.2.2 Interrelationship between nutrition and immunity*

the nutrient utilisation during challenge period [72].

c.Production of immunologically active substances.

a.Development of lymphoid tissues.

d.Cellular proliferation and activation

e.Intracellular killing of pathogens.

b.Mucus Secretion by goblet cells.

(Gut associated Lymphoid Tissue): Meckels diverticulum, Payers patches

Additionally, gallbladder, liver, pancreas, kidney and oviduct are also having some

Gut is the key immunoclogical organ comprises of myeloid and lymphoid cells [68] with its associated structures it forms a site for production of many immune

Immune system in gut depends on microbiota and maturation of the system eliciting by antigen-specific responses mainly influenced by dendritic cells [69]. The non invasive microbes initiates the production of IgA, which controls the host commensal interaction by both impacting commensal gene expression in the lumen and preventing adhesion of commensal bacteria to the epithelial surfaces [70].

Poultry encounter numerous stressors during their lives. Alterations in feed intake, poor FCR, varied nutrient metabolism, suppressed immune system are the consequences due to stress [71]. To overcome stress birds defence system prioritise

Birds immune system get affected by nutrition in several ways [73] like.

**106**

Another important factor influences the suppression of immunity as well as production is stress [48]. It may be due to environment (other than comfort zone), diet, vaccination- and medication, microflora imbalance, as well as a result of pathogen or parasitic load [74]. Disruption of gut function may occur and imbalance between production and elimination of ROS is a common phenomenon during stress [48]. Excess ROS in intestine causes destruction of PUFA in the cell membrane and leads to production of peroxides (malondialdehyde) which ruin the intestinal integrity [40]. A compromised epithelium creates a good opportunity for opportunistic pathogens, in addition to this dietary deficiencies in certain nutrients can increase the stress-induced susceptibility of poultry to oxidative stress [48, 49, 75, 76]. The outcome of this is an economic loss to the producer. Improper management makes the poultry exposure to disease causing agents, stress, and Meagre immunity, birds prone to less production or even death [76]. Increased feed efficiency and gut integrity was noticed [77] during in vitro experiments by addition of *Lactobacillus* species which produced bacteriocin Reuterin that might inhibit the growth of *Salmonella, Shigella, Clostridium* and *Listeria*.
