Descriptive results
General farm characteristics
A total of 358 broiler-farms were included in this study. Seventy-eight percent (n=278) of the farms stated that the production of broilers was their only activity on the farm; 80.1% (n=281) was part of a quality assurance scheme and 52.8% (n=186) were part of an integrated system with some degree of standardized management procedures.
Housing
An overview of the descriptive results for subcategories “Floor quality”, “Ventilation” and “Heating” is provided in table 1. The average broiler farm contained three broiler houses of 24 years old with each of them housing approx. 24 000 broilers using an average density of 17.5 day old chicks per square meter. Almost half (n=160) of the mechanically ventilated houses also contained specific ventilators meant for the recirculation of air inside the broiler house. Natural ventilation was still present in 7.3% (n=26) of broiler farms. A cooling system of some type was present in 71.5% (n=256) of all broiler farms for the prevention of heat stress in broilers. The most common type of cooling system was based on the creation of a fog in the neighbourhood of the air inlets of the broiler house, i.e. 78.8% (n=201), of which the position of the fog system was located inside the house in 79.6% (n=160) of the cases. Pad cooling was present in 20.7% (n=53) of farms that had a cooling system.
Table 1: Descriptive results of the housing of the broiler farms included in the study.
Subcategory
|
Situation on farm
|
Number of farms4
|
% of total
|
Floor quality1
|
Smooth impervious
|
132
|
37.7
|
|
Fair condition
|
46
|
13.1
|
|
Cracked to some degree
|
165
|
45.9
|
|
Compacted earth
|
15
|
4.2
|
|
|
|
|
Ventilation²
|
Roof ventilation
|
104
|
29.1
|
|
Cross ventilation
|
74
|
20.7
|
|
Roof x Tunnel ventilation
|
72
|
20.2
|
|
Tunnel
|
40
|
11.2
|
|
Cross x Tunnel ventilation
|
37
|
10.3
|
|
Natural ventilation
|
26
|
7.3
|
|
Other
|
5
|
1.4
|
|
|
|
|
Heating system³
|
Direct
|
194
|
54.3
|
|
Indirect
|
164
|
45.7
|
1Floor quality was scored into four categories from “smooth impervious” (best situation) to “compacted earth” (worst situation). ²The type of ventilation system used to refresh the air inside the broiler house. ³The heating system was classified into two categories: direct heating (CO2 is produced inside the broiler house) and indirect heating (no CO2 is produced inside the broiler house. 4 Number of farms that have this situation on farm, a total of 358 broiler farms participated in this study.
Feed and water supply
Two types of feed systems were used in broiler farms: pan feeders (n=268, i.e.74.9%) and feeding troughs (n=90, i.e.25.1%). Pan feeders had an average length of 1.97 cm per broiler and with feeding troughs an average length of 2.74 cm was available per broiler (based upon the number of broilers placed in the broiler house). The type of feed provided to broilers was a mixed feed compound in 199 farms (i.e.55.6%), while the other farms used a concentrated feed and added other ingredient (e.g., whole wheat (150 farms, i.e. 94.3%), maize (2 farms, i.e. 1.3%) or a combination of whole wheat and maize (7 farm, i.e.4.4%)). The main sources of drinking water were municipal water (n=158 farms, i.e.44.0%) and by using a ground well (n=188 farms, i.e. 52.4%), for ground wells the average depth was 91.9 meter. About half of the farms (n=177, i.e. 49.4%) used water disinfection protocols to sanitize the drinking water, the most commonly used chemicals for disinfection were chlorine dioxide (n=90, i.e. 51.1%) and peroxides (n=39, i.e. 22.2%). The drinking system of the investigated broiler farms was on average 16 years old. Over 89% of all broiler farms (i.e. 319 farms) used nipple drinkers with 13.3 chicks per drinking nipple. A minority of the farms was equipped with cup drinkers (n=20, i.e. 5.6%) or round drinkers (n=19 farms, i.e. 4.8%).
Treatments and diseases
An overview of the responses regarding the main health problems in the investigated broiler farms is provided in table 2. The majority of investigated broiler farms used a standard anti-coccidial treatment in the feed (346 farms, i.e. 96.6%). Vaccination against coccidiosis was performed in all flocks in only 6 farms (i.e. 1.7% of farms). Alternating vaccinated against coccidiosis and flocks treated with anti-coccidials was done in 42 farms (11.8% of broiler farms). The most frequently used anti-coccidials in starter feed were narasin-nicarbazine (n=197, 54.9%), nicarbazine (n=58, 16.2%), monensin-sodium (n=39, 11.0%), narasin (n= 26, 7.2%) and salinomycin (n= 23, 6.3%). For grower feed the most commonly used anti-coccidials were monensin-sodium (n= 151, 42.1%), narasin-nicarbazine (n=121, 33.7%), salinomycin (n=38, 10.7%) and narasin (n= 31, 8.6%). In finisher feed the main anti-coccidials were narasin (n=219, 61.1%), monensin-sodium (n=55, 15.5%), salinomycin (n=43, 12.0%) and narasin-nicarbazine (n=24, 6.6%). When a withdrawal period was required for the anti-coccidial, the feed was on average two days free of anti-coccidial before loading (thinning included). Thinning of the flock before complete emptying of the broiler house was done in 70.1% of all broiler farms (n=251). About half of these broiler farms (n=125, 49.8%) restarted with in feed-anti-coccidials after thinning.
Table 2. Number and % of farms with health problems in 2016.
Health problems
|
No problem
|
Mild problem
|
Clinical problem
|
|
N1
|
%
|
N1
|
%
|
N1
|
%
|
Coccidiosis
|
232
|
64.9
|
94
|
26.3
|
32
|
8.8
|
Septicemia before 7 days of age
|
149
|
41.6
|
57
|
15.9
|
152
|
42.4
|
Septicemia after 7 days of age
|
154
|
43.0
|
61
|
17.0
|
143
|
39.9
|
Dysbacteriosis
|
217
|
60.6
|
94
|
26.2
|
47
|
13.1
|
Necrotic enteritis
|
274
|
76.4
|
68
|
18.9
|
17
|
4.7
|
Wet litter syndrome
|
145
|
40.4
|
190
|
53.1
|
23
|
6.5
|
High mortality
|
284
|
79.2
|
56
|
15.7
|
18
|
5.1
|
Bad flock uniformity
|
189
|
52.7
|
160
|
44.7
|
9
|
2.6
|
1Number of farms, in total 358 farms participated in the study.
Specific broiler information
Approximately 56.9% of all questioned broiler farmers (n=204) knew the age of the breeder parent stock from which their day old chicks originated. The initial bodyweight of day old chicks was known by 83.1% (n=297) of all broiler farmers and 95% (n=282) of them used such information to adapt the production management e.g. by using a higher set temperature in case of a low initial bodyweight. The transport time between the departure of day old chicks from the hatchery and the arrival in the broiler house was less than four hours in 81.6% of all broiler farms (n=292), while 2.8% of all farmers (n=10) received day old chicks after more than eight hours. The majority of broiler farms (n=255) always received day old chicks as hatched (71.3%), i.e. with no sex differentiation.
Table 3. Descriptive results of the production management of the broiler farms included in the study.
Subcategory
|
Situation on farm
|
Number of farms5
|
% of total
|
Date of placement1
|
Complete area of the house³
|
206
|
57.5
|
|
Floor temperature measured4
|
263
|
73.6
|
Light intensity
|
Adapted during production cycle
|
245
|
68.5
|
Litter material
|
wood shavings
|
102
|
28.5
|
|
cut straw
|
90
|
25.1
|
|
peat
|
46
|
12.8
|
|
rice hulls
|
39
|
10.9
|
|
complete straw
|
31
|
8.7
|
Daily data registration
|
water intake
|
314
|
87.7
|
|
feed intake
|
146
|
40.8
|
|
bodyweight
|
97
|
27.1
|
Light during catching²
|
Adaptation of light
|
349
|
97.5
|
|
- Decrease of light intensity
|
181
|
51.8
|
|
- Use of red lights
|
105
|
30.1
|
|
- Use of blue lights
|
63
|
18.1
|
1Date when day old chicks are placed into the broiler house; ²Light that is used when broilers are caught for transport to slaughterhouse; ³Day old chicks have access to the full floor area of the broiler house; 4Floor temperature is measured when day old chicks are placed into the house; 5Number of farms that have this situation on farm.
Production management and performances
An overview of different aspects of the production management of the farms included in the study was provided in table 3. Farmers tended to start preheating their broiler houses on average 34.7 hours before placement with an average set temperature of 33.2°C. During the first three days after placement, a lighting schedule of an average of 68.2 hours of light (i.e. 94.2% of the time) was used in the broiler house. During the rest of the production period, an average of 5.9 hours of darkness per 24 hours was provided to the broilers.
At 15.5% of broiler farms (n=55) extra drinkers were provided to the day old chicks and these were removed after 4.9 days on average. Almost all broiler farms (n=339, 94.6%) provided extra feeders for day old chicks. The majority of broiler farmers (n=273, 76.3%) checked crop fill of chicks during the first 24 hours after arrival on the farm. The average feed withdrawal time before loading was 7.3 hours, while water was withdrawn only very shortly before loading, i.e. on average 0.5 hours before loading. A number of parameters can be registered automatically on a daily basis in broiler farms, farmers were questioned about the registration of average body weight, average feed intake and average water intake (see table 3). The majority of farmers (n=348, 97.2%) compared the recorded information with data from previous batches or general schemes. The flow rate of the drinking system was checked daily by 53.9% of all farmers (n=193), while 42.2% of farmers (n=151) did not check water flow rate every day but checked flow rates as soon as abnormal fluctuations in the daily water intake were observed. Drinking nipples and feeding system were checked daily by 94.1% of the farmers (n=337). Almost all broiler farmers (n=352, 98.3%) stated that when abnormal birds (e.g. runt or lame birds) were observed during daily inspection, these animals are culled. Forty percent of the questioned farmers (n=143) stated that they received no information at all from the slaughterhouse regarding health and/or welfare parameters of their broilers.
A summary of the specific health and performance parameters for broiler farms is provided in table 4. These values are based on 2309 flocks from 358 broiler farms.
Table 4. Performance and health parameters based on 2309 flocks from 358 broiler farms in 2016 originating from 7 EU member states.
Parameter
|
Average
|
Median
|
SD1
|
Minimum
|
Maximum
|
Average age at slaughter (days)
|
41.33
|
41
|
3.62
|
30.26
|
58.01
|
Average weight at slaughter (kg)
|
2.47
|
2.50
|
0.43
|
1.66
|
3.31
|
Overall mortality (%)
|
3.82
|
3.70
|
1.40
|
1.00
|
14.86
|
First week mortality (%)
|
0.94
|
0.90
|
0.51
|
0.03
|
3.29
|
Dead on arrival (%)
|
0.20
|
0.14
|
0.37
|
0.01
|
4.60
|
Condemnation rate (%)
|
1.23
|
1.00
|
0.92
|
0.05
|
6.73
|
Feed conversion rate
|
1.74
|
1.70
|
0.17
|
1.23
|
2.06
|
Daily gain (gram/day)
|
59.79
|
60.62
|
5.89
|
41.19
|
72.95
|
EPI2
|
338.41
|
345.85
|
53.07
|
183.93
|
432.17
|
1Standard deviation; 2European Production Index, calculated by multiplying average bodyweight with livability, dividing this result by the product of FCR and average age. This result multiplied with “100”, provides the EPI. Livability is defined as the percentage of the total number of broilers at placement that reaches slaughter-age.
Risk factor analysis
Eight linear mixed models were fitted based on these health and performance parameters. A summary of the significant risk factors is provided in table 5.
The first linear model included overall mortality as the dependent variable. The following three independent variables were identified as potential risk factors: mortality rate after 7 days; floor quality and the occurrence of neonatal septicemia on the farm. The higher the mortality rate after 7 days, the higher the overall mortality was in the investigated flocks. Poor floor quality was a significant risk factor for overall mortality in broilers as farms with lower quality floors with cracks, in their broiler houses appeared to have significantly higher overall mortality rates. The third risk factor for overall mortality was the occurrence of problems with neonatal septicemia.
Four significant risk factors were found for first week mortality: floor quality, ventilation type, presence of other professional activities of the farmer and the occurrence of problems with neonatal septicemia. The risk was higher in farms with cracked floors compared to floors without cracks, in farms using tunnel or roof ventilation, in farms in which the farmer had multiple professional activities and in farms experiencing neonatal septicemia in combination with tunnel ventilated broiler houses.
For mortality after 7 days, only one significant risk factor was found i.e. poor floor quality (cracks are present in the floor in which pathogens might survive from previous flocks) of the broiler house.
Table 5. Multivariable linear mixed models related to performance and health parameters in 2309 flocks from 358 broiler farms in 7 EU member states.
Model
|
Dependent variable
|
Independent variable1
|
p-value
|
B-value
|
1
|
Overall mortality rate
|
Mortality rate after 7 days
|
<0.001
|
1.03
|
|
|
Floor quality²
|
<0.001
|
- 0.72
|
|
|
Neonatal septicemia
|
<0.001
|
0.22
|
|
|
|
|
|
2
|
First week mortality rate
|
Floor quality
|
0.004
|
- 0.67
|
|
|
Ventilation type³
|
<0.001
|
0.72
|
|
|
No other professional activities by farmer
|
<0.001
|
0.24
|
|
|
Neonatal septicemia4
|
0.014
|
- 0.12
|
|
|
|
|
|
3
|
Mortality rate after seven days
|
Floor quality
|
0.046
|
- 0.35
|
|
|
|
|
|
4
|
Dead on arrival
|
Light management during catching5
|
0.003
|
0.09
|
|
|
Type of drinking system
|
<0.001
|
- 0.41
|
|
|
Daily growth (g/d)
|
<0.001
|
0.01
|
|
|
|
|
|
5
|
Condemnation rate
|
Type of drinking system
|
0.001
|
- 1.40
|
|
|
Daily growth (g/d)
|
<0.001
|
0.05
|
|
|
Feed withdrawal time
|
<0.001
|
- 0.12
|
|
|
Number of birds in the broilerhouse
|
0.002
|
0.02
|
|
|
Presence of recirculation vents
|
0.039
|
0.25
|
|
|
Septicemia after seven days
|
0.012
|
0.23
|
|
|
Type of feed
|
<0.001
|
0.75
|
|
|
Ventilation type3,6
|
0.057
|
- 0.31
|
|
|
|
|
|
6
|
Feed conversion rate
|
Daily growth (g/d)
|
<0.001
|
- 0.01
|
|
|
Light intensity adaptations
|
0.013
|
0.02
|
|
|
Ventilation type3
|
0.001
|
- 0.03
|
|
|
Necrotic enteritis problems
|
0.014
|
- 0.02
|
|
|
Daily check of drink water flow
|
0.002
|
- 0.03
|
|
|
|
|
|
7
|
Daily growth
|
Feed conversion rate
|
<0.001
|
- 29.35
|
|
|
Coccidiosis problems
|
0.004
|
1.33
|
|
|
|
|
|
8
|
European production index
|
Sex of day old chicks7
|
< 0.001
|
34.54
|
|
|
Dysbacteriosis problems
|
0.002
|
14.97
|
|
|
Evaluation of daily registered results
|
<0.001
|
- 33.94
|
|
|
Daily inspection of feed and water system
|
0.029
|
- 12.80
|
|
|
Type of drinking system8
|
0.006
|
54.37
|
|
|
Type of feed9
|
0.024
|
- 13.01
|
1Only the statistically significant risk factors in the final models are presented; 2The reference used for floor quality was a floor in perfect conditions without cracks; 3The reference used for type of ventilation was roof ventilation; 4This was only the case in tunnel-ventilated broiler houses; 5The reference for light adaptation was dimming the light intensity; 6Interpreted as a trend, as it was not significant (p >0.05); 7If only male chicks were housed, a higher EPI was present; 8The reference used for drinking system was the nipple drinking system; 9Only the case when dysbacteriosis was absent in the flock.
The analysis for farm specific risk factors for high number of dead on arrival (DOA) to slaughterhouse identified three significant variables: the type of light adaptation when broilers are caught, the drinking system and the daily growth during the cycle. The use of red lights for catching broilers increased the risk for dead on arrival in the slaughterhouse in comparison with decreased light intensity. The other methods of light adaptation had no significant effect. Other significant risk factors were not using nipple drinkers system and higher daily growth.
Seven significant risk factors and one borderline non-significant factor could be associated with condemnation rate: drinking system, daily growth, feed withdrawal time, ventilation system, average house size, the presence of recirculation vents, problems with septicemia after the first seven days and the type of feed that was used during the grower phase. The usage of cup drinkers was associated with a lower condemnation rate in comparison with nipple drinking systems, while no significant effects were noticed for the other types of drinkers. A significant positive association was found between increasing daily growth and increasing condemnation rate at slaughterhouse. Sufficient feed withdrawal time was associated with lower condemnation rates. Condemnation rates further increased with higher capacity of a broiler house (i.e. the number of birds that can be housed in the same airspace), in case no recirculator vents (which are used to mix up the air in a broiler house) were present in the broiler house, when there were septicemia problems after seven days of age and in case of concentrate + wheat was used compared to the use of complete compound feed. Although not statistically significant, there was a trend that condemnation rate was lower in cross ventilated broiler houses in compare to roof ventilated houses.
Feed conversion rate (FCR) was significantly associated with five variables: daily growth (DG), the possibility to change light intensity, type of ventilation, the occurrence of necrotic enteritis (NE) and daily check of drinking water flow rate. A clear significant negative association was found between DG and FCR. Feed conversion rate was significantly higher in broiler houses that could not adapt the light intensity of the broiler house. A clear effect of the type of ventilation system was found on FCR. Roof ventilated broiler houses appeared to have the best FCR, followed by cross ventilated and cross x tunnel ventilated broiler houses. FCR was significantly lower in mechanically ventilated broiler houses compared to natural ventilated broiler houses. The absence of problems associated with NE was associated with a significantly better FCR. FCR was significantly better in farms that did not perform a daily check of the flow rate of the drinking system, but systematically checked the flow rate of the drinking system in case abnormal fluctuation of the water intake occurred.
For DG only FCR and the occurrence of problems with coccidiosis infections were risk factors. A negative association was found between FCR and DG. Farms that stated to have no problems with coccidiosis during the production period were found to have a significantly higher DG.
Six variables significantly influenced European Production Index (EPI): Sex of day old chicks (male chicks had a higher EPI), the occurrence of problems with dysbacteriosis, if farmers compared their daily registered results with results from previous batches, if farmers checked the drinkers and feeders on a daily basis, the type of drinkers and the type of feed. The EPI was significantly higher in broiler farms that only housed male broilers compared to farms that housed only female broiler or a mix of both genders (as hatched). Farms that only housed female broilers had a significantly lower EPI. Farms that encountered no problems with dysbacteriosis had a significantly higher EPI compared to farms that had problems with dysbacteriosis. Farmers that did not compare their recorded information (e.g. bodyweight, feed- and water intake) with data from previous batches or general schemes had a significant lower EPI in comparison with farmers that compared flock results. Farmers who stated that they did not check the feeders and drinkers frequently had a significant lower EPI compared to farmers who did this on a daily basis. Farms with nipple or cup drinkers had a better EPI compared to farms with round drinkers. There was no difference between farms with nipple and cup drinkers. Broiler farms that had no problems of dysbacteriosis and used a concentrate with whole wheat, had a significant lower EPI compared to farms without problems of dysbacteriosis that used a complete compound.