Mitigating airborne bacteria generations from cage-free layer litter by spraying acidic electrolysed water

Cage-free (CF) hen housing has an inherent air quality challenge of high airborne bacteria (AB) concentrations arising from hens' activities (e.g., scratching, dustbathing, and social interactions) on the litter floor. Acidic electrolysed water (AEW) is an effective disinfectant that has been widely used in the food industry. Information on AEW application to mitigate AB and litter bacteria (LB) in CF housing is lacking. This lab-scale study evaluated reduction of AB and LB by spraying AEW at three dosages (25, 50, and 75 mL [kg dry litter]−1 d−1, or designated as D25, D50, and D75, respectively), three pH values (3, 5, and 7) and two free-chlorine (FC) concentrations (100 and 200 mg L−1, or FC100 and FC200). Treatment combinations were compared with control (no spray). Three replicates were conducted for testing the effect of spray dosage and pH and four replicates for testing the effect of FC on AB and LB reduction. The results showed that a lower pH AEW yielded a greater AB and LB reduction efficiency. Spraying a lower-dosage AEW (e.g., D25) at pH of 3, 5, or 7 significantly reduced airborne total bacteria (P < 0.001) as compared to control; however, D75 resulted in higher airborne total bacteria due to litter moisture accumulation that promoted bacteria growth (P < 0.001). Under the D25-pH3 regimen, FC200 resulted in 45.2% lower AB emissions from the hen litter as compared to FC100. This study provides a foundation for conducting the subsequent field test to verify the efficacy of this promising mitigation technique (AEW spray) to improve the indoor air quality and air emissions of CF hen houses.