**6. Genes that govern gut health and immunity**

Genes present in the body will regulate all the activities in the body including gut, but in gut, genes do not have any role without the microbiota [78]. It is considered that microbiota will regulate the activity of genes in the gut. The microbiota present in the gut mainly defines the gut condition whether it is in good condition or not [79].

The main target of Nutrients to alter the activity of genes and results in more activation of good genes and suppresses the activity of bad ones. Through nutrigenomics careful selection of nutrients for fine-tuning genes and DNA present in every cell and every tissue of an animal is possible stated in the review [80]. In **Table 2** results of some the researches were presented regarding influence of nutrients on gene expression.

Jiang et al. [86] reported variations in expression pattern of hepatic genes apolipoprotein A-I (ApoA-I) and apolipoprotein B (Apo B) with varying amount of nicotinic acid in feed indicates the lipid metbalosim. Addition of prebiotics likes mannan oligosaccharides (MOS) to broiler diets increases the expression of mucin, and down-regulates selected genes involved in cell turnover and proliferation [78]. Delay in feeding immediately after hatch alters the hepatic gene expression [87]. Nutrigenomics provides a way to identify precisely which nutrient or nutrient combinations that is optimal to elicit maximum benefits [79].


#### **Table 2.**

*Gene expression related to nutrition in chicken.*

Nutragenomics is an emerging science which would reveals the diseases induced by nutrient availability or alteration in diets [88]. For sustainable poultry production there is an emerging need to trace the relationship between economic traits and dietary regimen [57].

Among the different diseases occurring in poultry, those caused by the genus Salmonella is the most common, causing serious economic losses to the poultry industry in terms of mortality, reduced growth and loss of egg production [89].

Some of the works [29] inferred that MHC-B haplotypes reactions were different towards genetic resistance against salmonellosis. Resistance to salmonella was linked to ILs, IFNγ, TLRs, iNO and apoptosis genes, and expression of IL-2, IL-6, IL-8 and IFNγ genes was higher, microsatellite analysis inferred [90] that MHC-1class was linked to colonisation to salmonella. Ocak et al. [91] noticed salmonella at gensus level by PCR-RV, and ST at serovar level.

### **7. Bio markers**

Determination of biomarkers to know the intestinal health is important breakthrough. Inflammation is the first sign of infection or injury to the system [92].

Baxter et al., [46] reported serum citrulline and IFN-È, cloacal IgA, are the potential biomarkers to identify the inflammation in intestine due to dysbacteriosis, and impaired gut permeability.

Alterations in gene expression of claudin-1 and occludin indicate mitochondrial respiration and ATP production variations which indicate the state of intestinal permeability at tight junctions and celluar energy status [89].

Whereas oxidative stress is measured [93] by superoxide dismutase enzyme activity Thiobarbituric acid reactive substances produces during peroxidation and damage of the cells, break down of nitrite and nitrate produces nitricoxide which can be noted by griess assay to identify the concentration of nitric oxide in the cell [74].Pathogens like coccidian directly damages the epithlieal cells and loss of villous epithelia, results in decreased absorption [94]. Simple techniques like measuring the villi length, crypt depth and ratio are helpful standards to know the gut health. Villus height at duodenum, jejunum and ileum are 1400,900 and 700 mm and crypt

**109**

*Gut Health and Immunity in Improving Poultry Production*

were reported by Verdal et al. [95] in broilers at 23 days of age.

depth of 190,170,160 mm with villus height to crypt depth ratio were 8, 6 and 5

The gut represents a continuously evolving ecosystem where a dynamic interaction between host immune, neuroendocrine and entero-endocrine cells. The gut micro biota of the birds has influence on normal physiological development and homeostasis. Ban on AGPs make the evaluation of precision feeding as well as availability of various additives, phytobiotics, nutraceuitical…etc. are forcing the nutritionist to formulate the least cost rations for better production. Change in dietary regimen to boost immune system, minimise stress, good management and bio security practices are needed. Identification of genes/bio markers that regulates health and immune system is essential. Relationship among economic traits, dietary regimen and gene expression are the gaps. This review reveals that nutrition, immunity and stress are factors that influences the gut integrity in birds and production

• Introduction of new technologies that unveil the underlying transcriptional

• Technologies that aid in identification of disease resistant genes include next generation sequencing, microarray analysis, RNA sequencing and high density

• Exploring of genes related to degradation and digestion of complex NSP for better utilisation of alternative feedstuffs to incorporate in large-scale indus-

• Development of biomarkers of gut health is for understanding the pathophysiological events which influence the intestinal barrier, its functionality and the

• Quantification of *Enterobacteriaceae* using Q-PCR or other means may be of

and other molecular mechanisms for disease resistance in chicken.

*DOI: http://dx.doi.org/10.5772/intechopen.95989*

**8. Conclusion**

output.

**9. Future research**

SNP genotyping.

trial production.

ecology of the GIT microbiota.

use to measure dysbiosis in poultry.

depth of 190,170,160 mm with villus height to crypt depth ratio were 8, 6 and 5 were reported by Verdal et al. [95] in broilers at 23 days of age.
