**7. Metagenomics and metaproteomics in poultry**

The gut microbiota of birds plays a pivotal role in various aspects of their health and performance. Advances in metagenomic and metaproteomic techniques have enabled scientists to delve deeper into the complex microbial communities residing within the avian gut. Metagenomics involves analyzing the genetic material present in a sample to identify and characterize the diversity of microorganisms. On the other

### *Advances on Probiotics Utilization in Poultry Health and Nutrition DOI: http://dx.doi.org/10.5772/intechopen.113738*

hand, metaproteomic focuses on the proteins expressed by these microorganisms, providing insights into their functional roles [50].

In a study, the fecal microbiota of broiler growers with varying FCR was analyzed using shotgun sequencing. The analysis revealed distinct microbial compositions between low and high FCR birds, with differences in phylum-level abundances and gene proportions related to metabolism, stress response, and virulence. Notably, certain genes associated with improved feed efficiency were found to be overrepresented in low FCR birds, providing insights for enhancing poultry feed efficiency and formulation strategies [51]. Yet another study, investigated the influence of heat stress on the gut microbiota of caged laying hens using metagenomics sequencing. Firmicutes, Bacteroidetes, and Proteobacteria were dominant phyla. Heat stress reduced Firmicutes and increased Bacteroidetes, leading to altered metabolic pathways like cysteine and methionine metabolism. The findings provide insights into potential interventions for mitigating heat stress effects in poultry [52]. Moreover, a study explored how diet affects the protein content of chicken gastrointestinal tract (GIT) using label-free metaproteomics. The crop section showed Lactobacillaceae dominance, irrespective of diet, while Veillonellaceae increased with phosphorus supplementation. In the ceca, Bacteroidaceae proteins rose with phosphorus, and Eubacteriaceae decreased; protein patterns indicated thriving communities with supplementation, highlighting GIT dynamics [53].

Thus, metagenomic and metaproteomic analyses can assist in the selection of probiotic strains with specific functional attributes. By identifying strains that promote beneficial metabolic pathways or produce bioactive compounds, researchers can tailor probiotic formulations to address particular challenges, such as enhancing nutrient absorption or modulating immune system.
