Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2008
Publication Date: 12/1/2008
Citation: Purswell, J.L., Fritz, B.K., Branton, S.L., Leigh, S.A. 2008. Effects of System Pressure and Nozzle Type on Spray Application of Avian Vaccines. Applied Engineering in Agriculture 24(6):785-789.
Interpretive Summary: The efficacy of vaccination programs for commercial poultry is of prime concern within the poultry industry because improper management of vaccination programs can reduce productivity and profitability of poultry flocks. Optimizing vaccination delivery systems can improve seroconversion rates and uniformity and reduce vaccine wastage by applying only the amount necessary for proper inoculation. Spray characteristics of commercially available nozzle applicators were assessed to determine their “as-applied” performance by measuring droplet spectra, application rate, and deposition. Vaccine viability was also measured to determine how it is affected by the spray application process. Three nozzle types (coarse, medium, and fine) were tested at two differing system pressures (40 and 60 psi). Results show that very few defined respirable droplets were generated and in general, droplet sizes were relatively consistent between nozzles, illustrating that delivery rate and subsequent deposition rate are of greater concern than droplet size. This is anecdotally corroborated by field use which shows an improvement in seroconversion rate when application rate is more uniformly controlled. Also, in the present study, vaccine viability appears to be unaffected by the treatments tested.
Technical Abstract: Optimization of vaccine delivery via spray application of live Mycoplasma gallisepticum (MG) vaccine to commercial caged layer chickens is impacted by many factors. One of these factors is the pressure utilized to dispense the vaccine, which affects both delivery rate and droplet size. MG vaccine was applied using a self-propelled, constant speed vaccinator operated at two different pressures and using three different nozzle types, designated “coarse”, “medium”, and “fine” by the supplier. Droplet size and “as-applied” coverage and deposition were measured to determine the effects of system pressure and nozzle type on spray characteristics. Vaccine viability was also assessed to determine how viability is affected by the spray application process. Volume median diameter (VMD) varied with nozzle type and pressure, with the “fine” nozzle at 310.2 kPa yielding the largest mean VMD of 192.9 'm. However, the lowest mean VMD observed was 154.2'm for the “coarse” nozzle at 448.1 kPa; while statistically different, this represents a narrow range in VMD of 38.7 'm. Very few respirable droplets (< 10 'm) were observed for any treatment. Coverage and deposition were greatest for the “coarse” nozzle, followed by the “medium” and “fine” nozzles. Vaccine viability appears to be unaffected by any of the treatments tested. The relative similarity of droplet sizes coupled with the disparity of coverage and deposition between nozzle types indicated that delivery rate is of greater concern than droplet size, especially given the negligible amount of respirable droplets observed.