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Abstract
Over time, vaccination and management practices have adjusted to meet the demands imposed by the changing structure of the poultry industry. Vaccination programs typically involve serial administration of multiple vaccines, including infectious bronchitis virus (IBV), Newcastle disease virus (NDV), and infectious laryngotracheitis virus (ILTV). Often the interval between immunizations is short, sometimes a week or less, and it is unknown whether the short interval between immunizations interferes with the development of immunity and protection against challenge. Additionally, birds are commonly exposed to ambient ammonia (NH3), which has been linked to disease susceptibility. Our research aimed to determine the effects of vaccination schedule and ambient NH3 on the immune response to vaccination and protection from homologous challenge in chickens. Specific-pathogen-free white leghorns were administered multiple live attenuated vaccines against IBV, NDV, and ILTV until 16 weeks-of-age (WOA), after which certain groups were challenged with IBV, NDV, or ILTV at 20, 24, 28, 32, and 36 WOA. Five days post-challenge, viral load, clinical signs, ciliostasis, tracheal histopathology, and antibody titers in serum and tears were evaluated. One-day-old broiler chicks were administered IBV vaccine and exposed to NH3 until challenge with a homologous strain at 28 DOA. Protection was measured by viral detection, clinical signs, ciliostasis, presence of airsacculitis, IBV-specific serum IgG and lacrimal fluid IgA titers, and Harderian gland immune cell phenotypes. Leghorns serially administered live attenuated vaccines against IBV, NDV, and ILTV were protected against homologous challenge with IBV, NDV, or ILTV until they were at least 36 WOA. Additionally, the timing of these vaccines and intervals between each vaccine did not interfere with the development of immunity to each virus and consequently protection against homologous challenge. Our data also indicated that ambient NH3 exposure had no clear impact on the broiler immune response to IBV vaccination and also did not impact vaccine or challenge virus replication and clearance, ciliostasis, or tracheal histopathology scores. Collectively, our data promote poultry health and performance by contributing valuable information to the development of poultry vaccination and management programs.