Validation of a simple binary scoring system for assessment of welfare measures of 10-day-old commercial broilers and their correlation with environmental parameters

The procedures in this study were carried out in accordance with the accepted ethical standards and all the welfare parameters were measured carefully with proper hygienic maintenance. The study was conducted over a spring period (March to June, 2013) in South Korea. The broiler flocks studied were on a farm that grew chicken in a modern production system. Management and husbandry data were recorded for the house. This information included house and wall type, floor type, date of floor cleaning, temperature (air and body), total number of birds on site (at the time of visit), total number of birds originally placed in house, total number of birds in house (at the time of the visit), age at day of inspection, parent flock age(s), genotype, average bird weight at time of visit (taken from records of weights taken by the producer), feed quality and time interval, feed withdrawal rate, number of stock workers and number of visit per hours, vaccination for disease and time of vaccination, mortality/month, culls/month, when a month cull rate was high and why (throughout the year) and when a month mortality rate was high (Table 1).

All the welfare measures and environmental parameters were measured at nine points inside a chicken house at 15 cm above the floor, which corresponded to the nose height of the chickens and data was collected in triplicate from each point. The arithmetic means and SD of the each variable were calculated before further statistical analysis. Air temperature and relative humidity were measured with a hygrothermograph (SK-110TRH, SATO, Tokyo, Japan). Air speed was measured with an anemometer (model 6112, KANOMAX, Osaka, Japan). Light intensity (lux) values were recorded using a light meter (ANR-F9 LUX METER, Tokyo Photo-electric Co. Ltd, Japan) held at arm’s length and at bird height. The greenhouse gases concentrations in particular CO₂ and NH₃ were measured using a GASTECH device (Pump kit No. 101). A GASTECH device was used despite having several limitations because it is simple to handle and a typical farmer can easily identify the various compounds with the help of this instrument.

Airborne bacterial counts were measured using a settle-plate method. This is a direct method for assessing the likely number of microorganisms depositing onto the product or surface in a given time. It is based on the fact that in the absence of any kind of influence, airborne microorganisms, typically attached to larger particles, will deposit onto open culture plates. Tryptic soy agar (Merck, Darmstadt, Germany) was used for enumeration of total airborne bacteria, and Chromocult Coliformen agar (Merck, Darmstadt, Germany) was used for Total Coliforms and Escherichia coli. After sampling, the plates were incubated at 37°C for 48 h, and the colonies were counted and calculated as colony-forming units. Samples were collected from nine points in triplicate.

In the field observations, two observers scored birds using the binary system in the commercial flock. Walking ability (lameness) and leg health was inspected and scored according to the definitions given in Table 2. Walking ability was recorded for 15 chickens at nine designated points enclosed in a small frame and when allowed to walk out one-by-one. The ease with which the birds walked was scored after observing nine walking areas. A further 15 chickens were examined for HB and FPD.

The details of management, husbandry and environmental parameters data were evaluated under the guidelines of Ross Broiler Management Manual [12]. The statistical evaluation was carried out with an SPSS software package (SPSS Inc., Chicago, IL). Pairwise correlations (Kendall’s τ-b correlation coefficients) were calculated among environmental parameters and welfare measures.

The means of the environmental parameters in the broiler house are presented in Table 3. The mean values for air temperature, relative humidity, airspeed and light intensity were 32.6° C, 0.12 m/s, 43.5% and 7 lux, respectively (Table 3). The broiler farm was equipped with a mechanical ventilation system provided with fans (with slot inlet at a sidewall), which controls air temperature and relative humidity better than naturally ventilated systems or systems with fan-assisted drop-down ventilation, indicating a more effective mixing of air and flow over the birds. The mean air temperature and relative humidity in the house were within the recommended range [12].

Jones et al. [4] emphasized the importance of temperature and relative humidity to the health and mortality of broiler chickens produced in a northern European climate by analyzing the temperature and humidity profiles throughout the growth cycle. Jones et al. [4] found that high temperature and relative humidity adversely affect the lameness, FPD and mortality. Air speed has also been shown to significantly affect broiler performance [8]. Deep et al. [13] showed that light intensity did not affect broiler production and mortality, but did affect carcass characteristics.

The mean concentrations of CO₂, and NH₃ were 1755.5 and 4.0 ppm, respectively, in the house within the farm across nine different points (Table 3). The concentrations of these gases were within the recommended range suggested for broiler houses [12]. CO₂, originating from animal respiration as well as from manure breakdown, is an important gas in confined animal buildings. Concentrations and emissions of CO₂ have sometimes been used to estimate poultry house ventilation rates [14,15]. High concentrations of NH₃ inside animal houses represent potential health hazards to humans and animals [16]. The mean concentration of TAB, TC and TE in the broiler houses were 277.1, 53.6 and 7.2 (cfu/m³), respectively (Table 3). It has been shown that dead and partially decomposed air microbes may cause inflammation in the respiratory organs, and antigens and allergens may activate the immune system, leading to allergic reactions [17,18].

The results of the welfare parameters evaluated from a broiler house at nine different points are presented in Table 3. Based on the mean score of the evaluation of the incidence and severity (degree) of welfare parameters (lameness, FPD and HB), it was found that most of the birds walking ability (lameness 0) was very good with mean score of 97% (Table 4). However, hock burn (hock 0) and footpad (footpad 0) conditions were very poor with mean score of 58.5% and 20.7%, respectively (Table 4).

The relationships between environmental parameters and welfare measures are presented in Table 5. The number of birds walking well (lameness 0) was negatively correlated with relative humidity (P < 0.05). Dawkins et al. [5] also found that the percentage of broilers with good walking ability (lameness 0) was negatively correlated with relative humidity. Furthermore, light intensity was found negatively correlation with foot pad dermatitis (FPD 0) (P < 0.01). Footpad dermatitis is caused by a multifactorial problem including various endogenous and exogenous factors [19]. Some of previous studies also showed that light intensity levels affect the footpad health of broilers [13,20]. Our results are in agreement with several other studies that have reported that environmental condition of the house is very crucial to bird welfare [4,5,8].