Application of neutral electrolyzed water spray for reducing dust levels in a layer breeding house

Abstract

Reducing airborne dust is an essential process for improving hen housing environment. Dust reduction effects of neutral electrolyzed water (pH 8.2) spray were investigated in a commercial tunnel-ventilated layer breeding house during production in northern China. A multipoint sampler was used to measure airborne dust concentration to study the dust reduction effects and distribution in the house. Compared with the control treatment (without spray), airborne dust level was reduced 34% in the 3 hr after spraying 216 mL m⁻² neutral electrolyzed water in the breeding house. The dust concentration was significantly higher during the periods of feed distribution (1.13 ± 0.13 mg m⁻³) and artificial insemination (0.72 ± 0.13 mg m⁻³) compared with after spray (0.47 ± 0.09 mg m⁻³) and during lights-off period (0.29 ± 0.08 mg m⁻³) in the three consecutive testing days (P < 0.05). The experimental cage area was divided into four zones along the length of the house, with zone 1 nearest to the evaporative cooling pad and zone 4 nearest to the fans. The air temperature, relative humidity, airflow rate, and dust concentration were measured at the sampling points of the four zones in 3 consecutive days and mortality of the birds for the duration of a month were investigated. The results showed that the air temperature, airflow rate, dust concentration, and number of dead birds increase from zone 1 to zone 4 in the tunnel-ventilated layer breeding house.

Implications:

It is difficult to effectively reduce hen house airborne dust levels and limited information is available on airborne dust distribution in tunnel-ventilated hen houses. This work investigates (i) the application of neutral electrolyzed water spray for reducing dust in a layer breeding houses; (ii) dust concentration variations in 24-hr house operation; as well as (iii) the effects of location on dust concentrations. It was demonstrated that neutral electrolyzed water spray can be efficiently used for dust reduction in poultry houses. Further, a better understanding of the dust concentration variations in 24-hr house operation and in different spatial zones can contribute to bird housing environment management and poultry house design so as to improve bird health.

Introduction

Over the past decades, egg production has developed toward large and intensive operations and the health of birds has been an increasing concern in China. Airborne dust is a potential carrier for noxious gas and pathogens (Gustafsson, 1999; Homes et al., 1996), which can cause bird diseases and be harmful to the health of workers. Reducing airborne dust is an essential process to improve hen housing environment.

Dust in animal housing may originate from several sources, including the skin, hair, feathers, feed, manure, and bedding material, as well as from external sources such as ambient aerosols from incoming ventilation air (Aarnink et al., 1999). Dust concentration can be affected by many factors, such as air temperature, relative humidity, ventilation rates, building design, animal age, bird activity, bird density, feed type, and manure management (Just et al., 2009). Bird activity is a major cause of dust concentration changes in modern hen houses with cages (Heber et al., 2006). Ventilation is also critical and influences the concentrations and distribution of the dust in a layer breeding house (Lim et al., 2003; Ikeguchi, 2000).

Several approaches can be used to reduce dust in an animal house, including vacuum cleaning, adding fat to feed, fogging water, sprinkling with vegetable oil, spraying a mixture of plant oil and water, ionization, purge ventilation, filtering system, recirculation, and electrostatic methods (Mitchell et al., 2004). Spraying is a common and effective approach among these methods. Takai and Pedersen (2000) compared several different dust control methods in pig houses, including adding animal fat in feed, liquid feeding, spraying with water, and spraying with a mixture of rapeseed oil and water. The results showed that spraying water and liquid feeding were not effective enough to reduce dust. The most effective method was a combined approach of spraying an oil-water mixture controlled by an animal activity sensor and adding animal fat to the dry feed. The mean reduction rate of total dust was approximately 24% for spraying 60 mL m⁻² water, compared with the initial level before spraying additives (Kim et al., 2006). Neutral electrolyzed water (NEW) is generated by the electrolysis of a diluted sodium chloride solution. It is considered to be a novel, pH-neutral, highly effective, and environmentally friendly disinfect in the food industry (Deza et al., 2005; Abadias et al., 2008). NEW with a neutral pH and a high oxidation-reduction potential contains hypochlorous acid, sodium ions, hypochlorite ions, and chloride ions. They have potential capacities of dust adsorption and reducing living organisms. It has been used for spray disinfection in hen houses during production (Zheng et al., 2010). NEW spray also has potential effects on airborne dust reduction. It may be considered as a novel approach for airborne dust reduction in hen houses. However, limited information is available on the application of NEW for dust reduction in hen houses. An investigation of NEW spray effects on airborne dust level reduction during production will contribute to the development of dust reduction approaches.

Airborne dust plays an important role in the level of bacteria in the air of animal houses (Murch, 2001; Lai et al., 2009). Dust is correlated with airborne microorganisms of which some can cause bird diseases and even deaths (Verreault et al., 2010). A tunnel ventilation system is widely used in hen house ventilation, but little is known regarding the dust distribution at different times and in different spatial zones in a tunnel-ventilated hen house. A better understanding of the dust concentration and dust distribution at different hours of operation and in different zones may contribute to bird housing environment management and facilities design so as to improve bird health in a tunnel-ventilated hen house.

The objective of this research was to

i.	examine the use of neutral electrolyzed water spray on dust reduction;
ii.	evaluate airborne dust concentration variations for a period of 24 hr;
iii.	evaluate airborne dust concentration in different spatial locations in a typical tunnel-ventilated layer breeding house in China.

Materials and Methods

Experimental house and spraying system

Experiments were conducted in a 10 m × 77 m hen house located at a poultry farm in Hebei Province, northern China. The study was carried out in the summer of 2010. Eight thousand laying hens of 1 year old were confined in stair-step cages with three rows and three tiers in a layer breeding house (as shown in Figure 1) ventilated with a negative-pressure fan system. Two gable walls located at each end of the building held four axial flow fans (model 9FJ12.7; Shanghai Zhengcheng Electrical and Mechanical Manufacturing Co., Ltd., Beijing, China; air volume: 41750 m³ hr⁻¹ per fan) on one end and an evaporative cooling pad (1.5 m × 9.4 m) on the other. The four axial flow fans were operated when the lights were on and two of them were shut down when the lights were off. Air came in through the evaporative cooling pad and the evaporative cooling ran when the ambient temperature was higher than 30 °C. Additionally, a total of 38 adjustable air inlets were distributed along the sidewall and they were fully opened due to the high ambient temperature during the experimental period. Manure was gathered in three dropping pits under the cages and scraped out of the house daily by one mechanical scraper per each pit at about 9:00 a.m. The lights were off from 8:30 p.m. to 4:30 a.m. Feed was distributed at 8:30 a.m. and 5:00 p.m. and artificial insemination was performed from 2:00 p.m. to 4:00 p.m. every day.

Figure 1. View of the cross-section showing samplings points and the house structure.

There were 74 sprayers evenly distributed in two rows along the length of the building. Each row was 3.4 m away from the sidewalls and 2.1 m above the floor (as shown in Figure 1). Each sprayer consisted of four nozzles that sprayed horizontally and in a cross pattern. The spray nozzle diameter (Wuyiduo Agricultural Machinery Co., Ltd., Shanghai, China) was 150 μm with flow rate of 135 mL min⁻¹. Spraying was administrated starting at 11:25 a.m. for 5 min in the amount of 216 mL m⁻² every day. The control was performed in three different days with a week interval between each. For these days no spraying was administrated.

Preparation of neutral electrolyzed water

Electrolyzed water with an available chlorine concentration (ACC) of 4000 mg L⁻¹ was generated by electrolysis of a 2.5% sodium chloride solution in a generator that consisted of an electrolytic cell without a separating membrane. To produce the NEW, the electrolyzed water was diluted with tap water to reach the desired ACC of 160 mg L⁻¹ and pH of 8.2. The ACC was determined by a colorimetric method using a digital chlorine test kit (RC-3F; Kasahara Chemical Instruments Corporation, Saitama, Japan) and the pH was measured using a dual-scale pH/ Oxidation-Reduction Potential (ORP) meter (HM-30 R; DKK-TOA Corporation, Tokyo, Japan) with a pH electrode (GST-5741C) measuring from 0.0 to 14.0. The pH meter was calibrated using commercial standard buffers with pH of 4.01 and 6.86 supplied by the manufacturer.

Multipoints dust sampler

A multipoints dust sampler was used to measure the dust concentration in the layer breeding house. The sampler consists of a commercially available vacuum pump, a pressure monitor, a pressure regulator, and an array of critical venturis with glass fiber filters (Wang et al., 1999). Each filter with a 37-mm glass microfiber filter (Whatman 934-AH; GE Healthcare Bio-Sciences Corp., Piscataway, NJ) was housed in a holding cassette located upstream of a critical venturi facing the evaporative cooling pad. With the vacuum pump (Busch MM-MINK; Shanghai, China) running, the air was drawn through a filter and dust was left on the filter. A constant flow through the filters was maintained because the pressure across the venturis was sufficiently higher than the critical pressure drop (Wang et al., 2002). The airflow rate through each filter was measured using a calibrated rotameter (Dwyer RMC-123-SSV Rate-Master Flow Meter; Michigan City, IN; accuracy within ±2% full-scale reading) set between the filters and the venturi. The net mass increase of dust was determined by weighting the filters before and after sampling using an electronic balance (precision: 0.1 mg; Sartorius AG, Göttingen, Germany) in a controlled environment. Filters were desiccated before sampling (filter only) and after sampling (filter + dust) to obtain the dry matter increase without the presence of moisture. The concentration of airborne dust was calculated by the following equation (Wang et al., 2002).

(1)

where C _m is dust mass concentration (mg m⁻³); m is net mass increase of the filter after sampling (mg); Q is airflow rate through the filter (L min⁻¹); and t is the duration of sampling (min).

The standard deviation can be calculated using the following equation (Wang et al., 2002):

(2)

where σ_C is the dust mass concentration standard deviation (mg m⁻³); σ_m is the dust mass increase standard deviation (mg); σ_Q is the airflow rate standard deviation (L min⁻¹); σ_t is the duration of sampling standard deviation (min); C, m, Q, and t are the average values of dust mass concentration (mg m⁻³), dust mass (mg), air flow (L min⁻¹), and duration of sampling (min), respectively.

Test points and zone division

As shown in Figure 1 and Figure 2, 12 dust sampling points were placed 3.6 m away from the sidewall. Four points were placed longitudinally (18 m apart) and three points along the height of the house (0.5 m apart). The sampling point heights were determined based on the approximate breathing heights of birds in the three tiers. Air temperature (T) and relative humidity (RH) sensors (Thermo recorder RS-11; ESPEC MIC Corp., Aichi, Japan) were positioned in the four dust sampling points 1.0 m above the floor. These sensors were calibrated using an aspirated dry-wet bulb hygrometer and set to automatically record the air temperature and relative humidity every 30 min during the experiment. Manufacturer-calibrated anemometers (QDF-6; Yanda Instrumentation Company, Beijing, China) were used to measure airflow. They were longitudinally positioned at 1.0 m height and 3.6 m away from the sidewall. To avoid the effect of the dust sampler suction pump on the airflow measurements, the anemometers were placed 3 m from the dust sampling points, as shown in Figure 1 and Figure 2.

Figure 2. View of the longitudinal section showing the sampling points.

The experimental cage area was divided into four zones (named zone 1, zone 2, zone 3, and zone 4) along the length of the building. Zone 1 was nearest to the evaporative cooling pads and zone 4 was nearest to the fans (Figure 2). After the division, the values of the three sampling points in each of the four zones were averaged to reflect the dust concentration of the four zones. The numbers of deceased birds in these basic zones were accurately recorded during the experimental period.

Experiment design and data analysis

Evaluation process of NEW spray

Changes in dust concentrations with use of the NEW spray were evaluated once a week for 3 weeks (3 days total). For each day, NEW spray was administrated starting at 11:25 a.m. and continuing for 5 min. Dust sample concentrations were collected for 3 hr before spraying (8:30 a.m.–11:30 a.m.) and for 3 hr after spraying (11:30 a.m.–2:30 p.m.). The dust concentrations were tested in the same 3-hr intervals 1 day a week without spray as a control. The test and the control test were both operated once a week for 3 weeks and data from all the 12 sampling points were collected and averaged. During the tests, the ventilation in the house was kept stable with the four fans in operation. Airflow rates were measured before (10:00 a.m.) and after (1:00 p.m.) spraying. Statistical analysis was performed using the SAS8.0 software (SAS Institute Inc., Cary, NC, USA). Student's t test was used to determine the significant differences among the means at the 5% probability level.

Diurnal changes in dust concentration

Diurnal changes in dust concentration were obtained for a 24-hr period (three time replicates obtained in three consecutive days). For each day, NEW spray was administrated starting at 11:25 a.m. and continuing for 5 min. Dust concentrations were measured every 2 hr for 16 hr with the lights on and once during the 8 hr when the lights were off and birds were resting (low activity). Thirty-six observation values (12 sampling points × 3 days) for each diurnal period were averaged to compose the presented data. Statistical analysis was performed using the SAS8.0 software. Tukey's studentized range test was used to determine the significant differences among the means at the 5% probability level.

Dust concentration in different spatial locations

According to the zone division, the values of the three vertically aligned sampling points in each of the four zones (three time replicates obtained in the three consecutive days) were averaged to reflect the dust concentrations in each zone, respectively. The air temperature, relative humidity, and airflow rate at the test point in each zone were used to generate the average air temperature, relative humidity, and airflow rate. Statistical analysis was performed using the SAS8.0 software. Tukey's studentized range test was used to determine the significant differences among the means at the 5% probability level. The numbers of deceased birds in these basic zones were accurately recorded during the 1-month experiment period.

Results and Discussion

Thermal environmental conditions in the period

During the period of the experiment, the air temperature and relative humidity in the house were 22.1–27.6 °C and 73–97%, respectively. Meanwhile, the air temperature and relative humidity outside the building were 23–39.7 °C and 65–97%, respectively. The average house temperature (24.7 ± 1.8 °C) was lower than the average outside temperature (30.5 ± 6.4 °C), whereas the average relative humidity in the house (87% ± 3%) was higher than outside the house (67% ± 2%).

Reduction of dust concentration due to NEW spray

As shown in Table 1, the dust concentration between 11:30 a.m. and 2:30 p.m. was 34% higher than the dust concentration between 8:30 a.m. and 11:30 a.m. without spraying NEW. However, in the condition of spraying NEW starting at 11:25 a.m. and continuing for 5 min, the dust concentration was nearly the same after spraying (11:30 a.m.–2:30 p.m.) as compared with the 3-hr time interval (8:30 a.m.–11:30 a.m.) immediately before. Compared with the control treatment without NEW spray, the airborne dust level was reduced by 34% in the 3 hr after spraying 216 mL m⁻² neutral electrolyzed water in the house. Researchers found that spraying water in a swine gestation house during feeding resulted in 75% dust concentration reduction (Zhu et al., 2005) and Takai and Pedersen's experiment (2000) showed that 29% airborne dust could be reduced by spraying water 19 times per day. Because water spray can result in a dust concentration reduction, it seems necessary to carry out further studies comparing the different effects between NEW spray and water spray on dust reduction potential in poultry houses.

Table 1. Dust concentration variations with or without neutral electrolyzed water spray

	Dust Concentration Variations
Treatment	8:30 a.m.–11:30 a.m.	11:30 a.m.–2:30 p.m.
NEW spray ^A	0.65 ± 0.22 ^a	0.65 ± 0.23 ^b
Without spray	0.77 ± 0.21 ^a	1.03 ± 0.29 ^a
Notes: Values reported as the means ± standard deviations with n = 36.
^ANEW spray was administrated starting at 11:25 a.m. for 5 min.
^a,bMeans in the same column followed by different superscript letters are significantly different as determined by Student's t test (P < 0.05).

Dust concentrations variations in 24 hr

Large diurnal variation occurred and several dust concentration peaks were recorded (Figure 3). The dust concentration was significantly higher during the periods of feed distribution (1.13 ± 0.13 mg m⁻³) and artificial insemination (0.72 ± 0.12 mg m⁻³) compared with after NEW spray (0.47 ± 0.09 mg m⁻³) and during lights-off period (0.29 ± 0.07 mg m⁻³) in the three consecutive testing days (P < 0.05). Dust concentrations during lights-on period were 1.66 times higher than that during lights-off period. This is similar to published results indicating dust concentration ratios of 2.51:1 (Lim et al., 2003) and 2:1 (Hinz and Linke, 1998) between lights-on and lights-off periods. Dust concentration in poultry buildings in northern Europe was also studied and showed higher dust concentrations in the day compared with night (Takai, 1998). The lights-on time dust concentration was apparently influenced by the bird activities, operations of feed delivery and disinfection equipment, and worker activities (e.g., floor and cage cleaning and artificial insemination). The dust concentration increased significantly after the lights were turned on at 4:30 a.m., mainly because of the increased bird activities (P < 0.05). The highest peak occurred at 8:30 a.m.–10:30 a.m. and was likely because the managing activities during this period (e.g., feeding, manure scraping, and cage cleaning). The dust concentration decreased to less than 0.5 mg m⁻³ at 12:30 p.m.–2:30 p.m. as a result of the NEW spray. It is likely that worker activity (artificial insemination) may have caused the airborne dust concentration peak in the afternoon.

Figure 3. Dust concentration variations in 24-hr house operation. Vertical bars represent means ± standard deviations with n = 36. Vertical bars labeled with different letters indicate significant difference (P < 0.05).

Dust concentrations and mortality in different zones

The values of airborne dust concentration and bird mortality in the four zones are shown in Table 2. The results showed that the air temperature, airflow rate, dust concentration, and number of dead birds increase from zone 1 to zone 4 in the tunnel-ventilated layer breeding house. Previous studies have shown that the dust spatial distribution changes as the ventilation rate increases. Also, increasing ventilation rates within a certain range resulted in a decrease of the overall average dust concentration (Wang et al., 2000). It is suggested that the tunnel ventilation system has an effect on the increasing dust levels from zone 1 to zone 4 in the house. By placing the exhaust fans at one end of the house brings the airborne dust from the upstream side down to the fan units. This results in the accumulated dust concentration along the building from zone 1 to zone 4. The increasing air temperature from zone 1 to zone 4 might also affect the increasing dust levels due to the influence of air temperature on the bird activities. Researchers have studied the effect of total dust on bird mortality and showed that each 0.1 mg m⁻³ increase of total dust level will bring about two more dead birds (Guarino, 1999). As shown in Table 2, the increased thermal stress and dust concentration may have large effects on mortalities going from zone 1 to zone 4. Because the death of birds could be attributed to varying factors, it seems necessary to carry out further studies on the effects of total dust on bird mortality in poultry houses.

Table 2. Dust concentrations and dead birds in different spatial zones

	Air Thermal Environment
Zones	Air Temperature (°C)	Relative Humidity (%)	Airflow Rate (m sec^−1)	Dust Concentrations (mg m^−3)	Dead Birds (1 Month)
Zone 1	23.5 ± 1.7 ^c	85 ± 3 ^b	0.98 ± 0.11 ^c	0.52 ± 0.29 ^c	21
Zone 2	24.4 ± 1.2 ^b	87 ± 3 ^a	1.05 ± 0.11 ^b	0.57 ± 0.30 ^c	25
Zone 3	24.9 ± 1.5 ^ab	87 ± 3 ^a	1.08 ± 0.05 ^ab	0.66 ± 0.30 ^b	34
Zone 4	25.3 ± 1.3 ^a	88 ± 2 ^a	1.10 ± 0.04 ^a	0.77 ± 0.38 ^a	42
Notes: Values reported as the means ± standard deviations with n = 81.
^a,b,cMeans in the same column followed by different superscript letters are significantly different as determined by Tukey's studentized range test (P < 0.05).

Conclusions

Neutral electrolyzed water spray during production is a promising and effective approach to reduce dust in layer breeding houses. The results provide findings on dust reduction by NEW spray in laying hen operations, airborne dust concentration variation during a 24-hr operation time, and dust concentration distribution in different spatial zones for a typical tunnel-ventilated layer breeding house.

•	Compared with the control treatment without spray, the airborne dust level was reduced 34% in the 3 hr after spraying 216 mL m−2 neutral electrolyzed water in the hen house.
•	The average dust concentration was significantly higher during the periods of feed distribution (1.13 ± 0.13 mg m−3) and artificial insemination (0.72 ± 0.12 mg m−3) compared with after NEW spray (0.47 ± 0.09 mg m−3) and during lights-off period (0.29 ± 0.07 mg m−3) in the three consecutive testing days (P < 0.05).
•	The air temperature, airflow rate, dust concentration, and number of dead birds increased from zone 1 to zone 4 along the length of the house from the evaporative cooling pad to fans in the tunnel-ventilated layer breeding house. The tunnel ventilation system and the increasing temperature were associated with the increasing dust levels from zone 1 to zone 4 in the house.

Acknowledgments

This study was funded by the China Agricultural Research System (CARS-41) National Department Public Benefit Research Foundation of China (200903009) and National Fund of Natural Science (30871957). The authors would also like to thank Huamu Animal Husbandry Co., Ltd., Shijiazhuang, Hebei Province, China.