Influence of drinking water quality on immune responses to viral vaccines in layer chickens.

Drinking water quality is a critical factor in poultry production, and suboptimal drinking water can negatively influence immune functions leading to reduced vaccine efficacy. In the field study, we assessed drinking water quality on Alberta layer farms and evaluated its impact on vaccine-induced immune responses. Chemical, physical and microbiological analyses were performed on 26 water samples collected from Alberta layer farms and serological response for poultry viral vaccines were evaluated at the same time. The water hardness, pH, bicarbonates, and dissolved sodium exceeded acceptable limits in 34 %, 50 %, 46 %, and 27 % of the farms, respectively. Farm-level data revealed no significant direct correlation between water quality scores and vaccine induced serological response. For the controlled experiment, specific pathogen-free White Leghorn chicks were assigned to 4 groups: tap water control (TW-control), field water control (FW-control), tap water vaccinated (TW-vaccinated), and field water (FW-vaccinated), two of the groups were vaccinated against infectious bronchitis while maintaining unvaccinated controls and all 4 groups were maintained on their respective water sources for ∼8 weeks. Controlled experiments showed that vaccinated birds receiving FW had 600 units lower mean antibody titers compared to those given TW, which is statistically not significant. The vaccinated FW group also showed reduced CD4⁺ and CD8⁺ T-cell populations in the spleen and lungs, along with altered IFN-γ and significantly increased IL-10 transcription. In conclusion, although the field data showed a lack of correlation between water quality and vaccine induced serological response, the control experiment revealed that poor water quality might influence the infectious bronchitis vaccine effectiveness in layers.