Environmental assessment of three egg production systems – Part III: Airborne bacteria concentrations and emissions

Abstract

Airborne microorganism level is an important indoor air quality indicator, yet it has not been well documented for laying-hen houses in the United States. As a part of the Coalition for Sustainable Egg Supply (CSES) environmental monitoring project, this study comparatively monitored the concentrations and emissions of airborne total and Gram-negative (Gram(-)) bacteria in three types of commercial laying-hen houses, i.e., conventional cage (CC), aviary (AV), and enriched colony (EC) houses, over a period of eight months covering the mid and late stages of the flock cycle. It also delineated the relationship between airborne total bacteria and particulate matter smaller than 10 μm in aerodynamic diameter (PM10). The results showed airborne total bacteria concentrations (log CFU/m(3)) of 4.7 ± 0.3 in CC, 6.0 ± 0.8 in AV, and 4.8 ± 0.3 in EC, all being higher than the level recommended for human environment (3.0 log CFU/m(3)). The much higher concentrations in AV arose from the presence of floor litter and hen activities on it, as evidenced by the higher concentrations in the afternoon (with litter access) than in the morning (without litter access). The overall means and standard deviation of airborne total bacteria emission rates, in log CFU/[h-hen] (or log CFU/[h-AU], AU = animal unit or 500 kg live weight) were 4.8 ± 0.4 (or 7.3 ± 0.4) for CC, 6.1 ± 0.7 (or 8.6 ± 0.7) for AV, and 4.8 ± 0.5 (or 7.3 ± 0.5) for EC. Both concentration and emission rate of airborne total bacteria were positively related to PM10 Gram(-) bacteria were present at low concentrations in all houses; and only 2 samples (6%) in CC, 7 (22%) samples in AV, and 2 (6%) samples in EC out of 32 air samples collected in each house were found positive with Gram(-) bacteria. The concentration of airborne Gram(-) bacteria was estimated to be <2% of the total bacteria. Total bacteria counts in manure on belt (in all houses) and floor litter (only in AV) were similar; however, the manure had much more Gram(-) bacteria than the litter. The results point out the need to mitigate airborne total bacteria in laying-hen houses, especially in AV houses.

Concentrations of Aerosol Numbers and Airborne Bacteria, and Temperature and Relative Humidity, and Their Interrelationships in a Tie-Stall Dairy Barn

“…After inoculation into the medium sheets, media were incubated 48 h for the airborne total aerobic bacteria and 24 h for the airborne S. aureus and E. coli at 35 • C. After incubation, characteristic colonies were immediately counted by the colony counter. Among the dilutions, culture medium sheets showing 30-300 colonies were used for calculating the concentrations of various types of airborne bacteria using Equation (1) [32,36]. The principle detection limit of the culture medium sheet method is one colony on each of the two culture medium sheets among three culture medium sheets with 0.1 M diluted sample after incubation.…”

Reduction of Particulate Matter and Ammonia by Spraying Acidic Electrolyzed Water onto Litter of Aviary Hen Houses: A Lab-Scale Study

“…The PM 10 level was higher than the 24 h concentration threshold of 150 μg m -3 set by the U.S. Environmental Protection Agency to protect public welfare (USEPA, 2015). PM can also serve as a carrier of airborne microorganisms and endotoxins that, once inhaled, may cause infection or trigger respiratory diseases in animals and their caretakers (Zhao et al, 2016). Therefore, mitigating PM generation and emissions is critical to protecting the health and well-being of the laying hens and their caretakers, as well as improving the environmental stewardship of the cage-free egg production operation.…”

A tracing method of airborne bacteria transmission across built environments

“…On a broader scale, microorganism could be shed via/from activity (coughing, sneezing, talking, or breathing), skin and excrement of individuals and aerosolized into airborne microorganism [41,[58][59][60][61]. Large amount of particulate matter and microorganism, including pathogens, were emitted from animal houses by the ventilation system [62][63][64][65], which resulted in higher concentration of particulate matter and airborne microorganism in their vicinity [66,67]. An airborne transmission model, which obtained from Gaussian Plume Model by incorporating the dust deposition process, pathogen decay, and a model for the infection process on exposed farms, revealed that wind-borne route alone was insufficient when compare transmission risk pattern predicted by the model with the pattern observed during the 2003 epidemic [68].…”