# Avian cecal microbiome response and resilience to Newcastle disease are dictated by breed background

## TL;DR

This study shows that local chicken breeds, like the Naked Neck, are more resistant to Newcastle disease than broilers, likely due to a more stable gut microbiome.

## Contribution

The study identifies breed-specific gut microbiome resilience and immune competence in chickens against Newcastle disease.

## Key findings

- Naked Neck chickens showed the least variation in clinical features and growth during NDV challenge.
- Broiler chickens had lower gut microbial diversity and an unstable core microbiome after NDV infection.
- Shotgun metagenomics revealed higher abundance of AMR and virulence genes in infected broilers.

## Abstract

A wide range of viral infections threaten the long-term sustainability of poultry production. Newcastle disease (ND), caused by Newcastle disease virus (NDV), is endemic in most Asian countries, including Pakistan, causing 50%–100% mortality in young and mature chickens. Some local chicken breeds show resistance to certain diseases and have greater survival probability. The chicken gut microbiome is linked to immune response against infections and to production performance parameters. The present study aims to comprehend disease resistance patterns in multiple chicken breeds with respect to gut microbial communities. Day-old Naked Neck, Black Australorp, Rhode Island Red, white layer, and broiler chicks were raised on an antibiotic-free diet in a semi-controlled setup. Vaccinated and non-vaccinated birds were challenged with NDV. Disease onset was delayed in breeds other than broilers, in which disease symptoms appeared at day 3 post-challenge with maximum severity and mortality. Other breeds, irrespective of vaccination, survived through the challenge period. Naked Neck showed the least variation in clinical features and growth parameters. A lower diversity in broiler groups with a significant decrease after NDV challenge was revealed by 16S rRNA amplicon sequencing of cecal DNA. Furthermore, broiler cecal core microbiome membership was found to be more variable than other breeds. Moreover, differentially abundant genera were observed across treatment groups and breeds with a similar effect on the predicted metabolic pathways, indicating varied energy metabolism responses. Shotgun metagenomics revealed a higher abundance of functional genes, including antimicrobial resistance (AMR) genes, stress genes, virulence genes, and amino acid degradation genes in the broiler NDV-infected group compared to the control group. The gut microbiota in chickens affects immunity to infections, health, and productivity. Compared to broilers, local chicken breeds, specifically Naked Neck, are found to have high immune competence in resisting ND while maintaining most performance metrics. Broilers show lower alpha diversity with an unstable core microbiome. Therefore, stable core microbiome maintenance may help the birds cope with the viral infection. The results support the farming of resistant chicken breeds over broilers to reduce production losses from NDV outbreaks.