Context: Drinking water vaccination of young meat chickens with Infectious Laryngotracheitis (ILT) vaccine is problematic. Vaccine failure and adverse vaccine reactions are frequently reported. Variations in the technique of applying ILT vaccines by this mass vaccination method need to be understood to contribute to improving the success of vaccination. Aims: This study aimed to examine variations in the techniques of application of Infectious Laryngotracheitis vaccines via drinking water for young meat chickens. Methods: Drinking water vaccination techniques were observed and recorded across 52 broiler flocks during ILT outbreaks in three geographic areas of Australia. Descriptive statistics for all variables were computed and variations between integrator company procedures were statistically compared. Key results: Despite rigorous standard operating procedures, wide variations were observed in time of water deprivation prior to vaccination (3–15 min), time drinking water was stabilised prior to addition of vaccine and the type of stabiliser product used, time to activate the flock following filling of the water lines with vaccine (10–127 min), time for the vaccine to be consumed (36–226 min) and the volume of drinking water per bird used to provide the vaccine (11–48 mL/bird). Conclusions: Variation in vaccination technique can affect the success of drinking water vaccination against ILT in young meat chickens. Implications: Understanding the importance of the variable factors in vaccine application method can improve the success of water vaccination against ILT
