Effects of induced moisture loss in chicken embryos at embryonic day 18 and post-hatch immune response during salmonella enteritidis lipopolysaccharide challenge in broilers

Authors: GREGORICH, JENNA - The Ohio State University; LILBURN, MICHAEL - The Ohio State University; Shanmugasundaram, Revathi

Submitted to: Frontiers in Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2022
Publication Date: 3/7/2022
Citation: Gregorich, J., Lilburn, M., Shanmugasundaram, R. 2022. Effects of induced moisture loss in chicken embryos at embryonic day 18 and post-hatch immune response during salmonella enteritidis lipopolysaccharide challenge in broilers. Frontiers in Physiology. 13:1-12. https://doi.org/10.3389/fphys.2022.820349.
DOI: https://doi.org/10.3389/fphys.2022.820349

Interpretive Summary: Moisture loss in eggs during incubation varies depending on where the eggs are placed within an incubator as well as the relative humidity of incubation. Increased water loss might affect the chicken immune response and negatively affect the chick's immune response against pathogens like Salmonella. The objective of this study was to identify the effects of water loss on embryonic development during incubation and the immune response following an inflammatory challenge immediately post-hatch. Two experiments were conducted to investigate these effects. Embryos from the increased water loss treatment group had a higher inflammatory response and decreased embryo body weight. However, on the day of hatch, chicks hatched from increased water loss treatment group had decreased inflammation. The increased water loss during incubation reprograms gene transcription to enhance cell survival via proliferation and differentiation during an inflammatory challenge. Our study also suggests that osmoregulation is a critical factor during embryogenesis for regulating the immune system. The data in this study indicate that moisture loss during incubation decreased the chick's body weight at the time of hatch and is also critical for the immune system development. Monitoring water loss during incubation is a viable strategy to improve immune response against pathogens and to improve production performance.

Technical Abstract: Two experiments were conducted to investigate the effects of induced moisture loss on embryonic development and the immune response following an inflammatory challenge immediately post-hatch. Fertile leghorn eggs (n=100) and commercial broiler eggs (n=300) were set at 37.5°C and moisture loss was induced in one half of the Leghorn and broiler eggs by drilling two, 1.5 mm diameter holes. The Control eggs had 0 holes. On the day of the hatch, chicks hatched from eggs with 0 holes (control) and 2 holes were randomly distributed into one of four treatments in a 2 (0 and 2 holes) X 2 (0 and 500 µg LPS) factorial set up. Chicks in the LPS groups were injected intraperitoneally with 500 µg/kg BW LPS. At ED18, layer and broiler eggs in the 2-hole treatment had a significant (P < 0.01) increase in moisture loss compared to the control treatments. At ED18, the layer eggs with 2-holes had 10.1% moisture loss compared with 8.2% in control eggs. Similarly, at ED18, the broiler eggs with 2-holes had 9.9% moisture loss compared with 8.4% in control eggs. Thymocytes from both the layer (104%) and broiler (62%) embryos in the 2-holes treatment had significantly increased in vitro proliferation compared with the control embryos. At ED18, layer and broiler embryos in the 2-hole treatment had an approximate 2 fold increase in the thymic and splenic CD8+/CD4+ ratio and CD4+CD25+ cell percentages in both the thymus and spleen. At ED18, layer and broiler embryos from 2-hole treatment both had a significant increase in splenic IL1-ß, IL-6, IL10, and TLR-4 mRNA transcription compared to that in the control group. At 24h and 48h post-hatch, chicks hatched from 2-holes eggs and challenged with LPS treatment group had a significant increase in thymocyte proliferation at 24 h (42%) and 48 hr (37%) when compared with chicks hatched from the control (0-hole; 0 µg LPS) treatments, respectively. Chicks hatched from the 2- hole treatment and challenged with LPS had an approximately 2 fold higher splenic CD8+/CD4+ ratio and 1.5 fold increase in CD4+CD25+ percentage compared to that in the control group. Chicks hatched from 2 hole treatment, MUC2 mRNA transcription had decreased to 1.9 fold and 1.8 fold in response to LPS challenge at 24h and 48h. Our data suggests that the 2-holes treatment reprograms gene transcription to enhance cell survival via proliferation, differentiation during an LPS inflammatory challenge.