As a major infectious disease in chickens, Newcastle disease causes considerable economic losses in the poultry industry, especially in developing countries where there is limited access to effective vaccination. Therefore, enhancing resistance to the virus in commercial chickens through breeding is a promising way to promote poultry production. In this study, we investigated gene expression changes at 2 and 6 dpi after infection at day21 with a lentogenic Newcastle disease virus in a commercial egg-laying chicken hybrid using RNA sequencing analysis. By comparing NDV challenged and nonchallenged groups, 526 differentially expressed genes (DEGs) (FDR < 0.05) were identified at 2 dpi, and only 36 at 6 dpi. For the DEGs at 2 dpi, IPA analysis predicted inhibition of multiple signaling pathways in response to NDV that regulate immune cell development and activity, neurogenesis and angiogenesis. Upregulation of Interferon Induced Protein with Tetratricopeptide Repeats 5 (IFIT5) in response to NDV was consistent between the current and most previous studies. Sprouty RTK Signaling Antagonist 1 (SPRY1), a DEG in the current study is located in a significant QTL associated with virus load at 6 dpi in the same population. These identified pathways and DEGs provide potential targets to further study breeding strategy to enhance NDV resistance in chickens.

Heat stress results in significant economic losses to the poultry industry. Genetics plays an important role in chickens adapting to the warming environment. Physiological parameters, including hematochemical parameters, change in response to heat stress in chickens. To explore the genetics of heat stress resilience in chickens, a genome-wide association study (GWAS) was conducted using Hy-Line Brown (HLB) layer chicks treated with either high ambient temperature or combined high temperature and Newcastle disease virus (NDV) infection. Hematochemical parameters were measured during three treatment phases: acute heat stress, chronic heat stress, and chronic heat stress combined with NDV infection. Significant changes in blood parameters were recorded for 11 parameters across the three treatments. The GWAS revealed 39 significant SNPs (P < 0.05) for 7 parameters, located on Gallus gallus chromosomes (GGA) 1, 3, 4, 6, 11, and 12. The significant genomic regions were further investigated to examine if the genes within the regions were associated with the corresponding traits under heat stress. A candidate gene list including genes in the identified genomic regions that were also differentially expressed in chicken tissues under heat stress was generated. Understanding the correlation between genetic variants and resilience to heat stress is an important step in improving heat tolerance in poultry.