Category: 4. Risk factors

4. Risk factors

Farm factors
* Housing system
* Aisles and doorways
On-farm Management
* Health status of the birds
* Litter removal
* Birds collected in 1 section of the house
* Catching methods
Transport
* System
* Type of doors
* Number of birds/crate
* Climate control on the truck
* Vibrations
* Duration of the journey
* Facilities (access to water/feed)
* Climate during transport
At the slaughter plant
* Post transport handling and environment
* Shackling and stunning

4.1 Farm factors

Housing system
Houses
Further reading
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Housing system

Laying hens are kept in a variety of housing systems, varying from small sized enriched cages to large non-cage units. Although the majority of hens in Europe are kept in cages, especially in Northern Europe the number of non-cages systems is increasing. Non-cage systems comprise simple single tier barn units, but also multitier aviary systems.

With regards to risk for injuries and DOAs (birds dead on arrival) the housing system does have an influence:

  • First the housing system can have an influence on the health of the birds and thus on the fitness for travel. In non-cage systems birds are more likely to come into contact with their own manure, which means a risk for worms, coccidiosis and infectious diseases. These diseases form a risk for bird health and often cause mortality. Weeks et al (2012a) found higher mortality in non-cage systems compared to colony cages. They also found an increased risk of DOA in flocks with poor feather cover, poor health, lower body weight and higher cumulative mortality.
  • Second the housing system as such can have an influence on the ease of catching the birds. Furnished cages have cage doors and the depth of the cage makes it difficult to catch the birds. Having people catching birds on both sides of the system or people driving the birds to the catchers may help. Another difficulty of these systems is the number of tiers and accessibility of the cages. Finally cage houses often are large, increasing the distance from cage to truck. If catchers have to walk the full length of the house many times, this will influence their handling of birds and may result in extra injuries. Non-cage systems require catching birds in the dark. At night, the majority of birds are on the top floor, which requires catchers to climb onto the system, catch birds and hand them over to helpers down in the litter area. As in cages bids have to be drawn from behind perches, feed troughs and out of nest boxes, but under dark circumstances this may lead to more damage to the birds. Also catchers often have to walk through the litter, which is a very uneven surface and may cause birds to bounce into furniture, possibly leading to injured birds. Large henhouses often are subdivided into sections by means of wire. Walking from one section to the other is possible, but doors have to be opened and as catchers are passing these doors in the dark, there is an additional risk for birds bouncing into door posts.

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Aisles and doorways

The efficiency of catching and crating birds is also influenced by the condition of the aisles in housing systems. Wide aisles with clean concrete floors allow the use of carts or small motorized equipment to bring crates into the house, thus reducing the distance birds need to be carried.

Other factors may also influence the possibilities to bring crates into the house, such as the size of doorways and obstacles preventing the use of carts.

Cart to facilitate bringing crates into the house
Figure: Cart to facilitate bringing crates into the house

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Further reading (by language)

 

4.2 On-farm management

Health status of the birds
Litter removal
Feed withdrawal
Birds collected in 1 section of the house
Catching methods
Further reading
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Health status of the birds

Healthy birds will be more capable to endure the stress of transport and arrive at the slaughter house in good condition. Birds with some kind of health condition, but still fit enough for travel, are more likely to die during transport. To increase the chance for survival additional measures can be taken. For instance, vitamin c provision through the drinking water prior to transport can reduce the effects of stress and may increase survival rate.

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Litter removal

Removing litter from the aisles will enable the use of carts in the house or smoothen the path catchers need to walk. This will lead to less damaged birds.

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Feed withdrawal

In general it is advised to withdraw food several hours before catching the birds so that the intestines are empty and no soiling of the birds with manure occur, in the crates as well as on the slaughter line. Common practice is to have the feeders empty in the morning of the day the birds will be transported. However, there is a lot of variation. There is discussion about the legally allowed duration of this feed deprivation. For laying hens no legal requirements are in force, but there are several codes of Practice (see more details here).

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Birds collected in 1 section of the house

To reduce walking distances for the catchers sometimes birds from the far compartments are moved to the front compartments on the afternoon prior to depopulation. Although this moving of birds was done in a calm way, Van Niekerk et al. (2014) found more damaged birds at the slaughter house for this practice compared to flocks that had not been moved.

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Catching methods

Hens are removed from cages either individually or in groups of 2 or 3 by pulling them out by one leg despite recommendations to handle poultry by two legs (e.g. UK Codes of Recommendation). In non-cage systems birds are taken from the perches at night. In aviary systems usually groups of 3 birds are held by one leg and brought outside to the crates. If the hen house is suitable, the crates may be brought in on carts, reducing the distance catchers have to walk with the birds. Experienced catching crews work calmly and with groups in each aisle, working in line from one end to the other end of the house. This causes a minimum of disturbance of the birds, reducing the number of birds that start running around. Birds that are moving away are collected at a later stage, when they have sat down elsewhere.

A direct comparison of different catching and carrying methods for end-of-lay hens showed that plasma corticosterone (stress hormone) concentrations were significantly higher when they were removed from their cages three at a time and carried in an inverted position from the house, than when they were removed singly and crated before removal from the house (Knowles and Broom, 1993).

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Further reading (by language)

English

Catching methods

  • Knowles, T.G. and Broom, B.M. (1993) Effect of catching method on the concentration of plasma corticosterone in end-of-lay battery hens. Veterinary Record 133, 527-528.

Nederlands

Hennen die verzameld worden in 1 sectie van de stal

4.3 Transport

System
Type of doors
Number of birds/crate
Climate control on the truck
Vibrations
Duration of the journey
Facilities (access to water/feed)
Climate during transport
Further reading
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System

Kristensen et al. (2001) evaluated a modular system for depopulating battery cages and found a significant reduction in the time each bird was handled from 64.5 s to 4.5 s. Compared with manual handling there was no difference in the proportion of damaged birds in the small trial, but the catchers preferred the modular system.

Van Niekerk et al. (2014) found that the use of carts to bring crates into the henhouse reduced the percentage of damaged birds in the slaughter plant.

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Type of doors

Crates or modules with large doors will reduce the risk of broken wing. Sliding doors may reduce the incidence of trapped birds.

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Number of birds/crate

The number of birds per crate influences the microclimate around the birds. Higher stocking densities may be used in winter, but precautions should be taken for those birds during the time in lairage as temperatures may get too high. Based on recent research (Richards et al., 2012) there is a strong argument for using different stocking rates in different areas of the load (in particular for reduced numbers in drawers at the top-front of the load) if this could be achieved in practice.

Delezie et al (2007) found that stocking density during transit had a greater influence on levels of stress in broilers than feed withdrawal or transportation. The stocking densities recommended by European legislation (EC, 2005) may be used as a guide that needs adjusting according to weather, bird condition and journey duration.

Guideline of space allowances for poultry in transit (EU, 2005)

 

Weight of poultry (kg) Space allowance (cm2/kg)
Chicks (day old) 21-25 cm2/chick
<1.6 180 – 200
1.6 – 3.0 160
3.0 – 5.0 115
> 5.0 105

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Climate control on the truck

All studies addressing climate during transport found a large variation depending on the position on the truck (Webster et al., 1992; Kettlewell et al., 1993; Weeks et al., 1997; Richards et al., 2012), with naturally ventilated trucks showing the largest variation. Therefore temperature control on trucks is essential to maintain temperatures at an acceptable level. To realise this for all birds, temperature recording should be done on all trucks on various locations on the truck in close vicinity to the birds. Temperatures should be both recorded and linked to an in-cab monitoring and alarm system. As a guide, that should be modified according to individual loads and vehicle designs, Weeks et al (1997) indicated poorly-feathered end-of-lay birds at 22-28oC were likely to be thermally comfortable at the usual high stocking densities. EFSA (2011) recommended that specific thermal limits should be defined. In winter it is especially important to minimise wind chill by the use of curtains and parking in the lea of buildings or trees and to avoid birds becoming wet.

By means of trailer roof vents and side curtains on-board temperature can be varied and maintained within acceptable limits (Burlinguette et al., 2012). during milder ambient conditions (9.8°C) on-board temperature ranged between 10.3 and 16.7°C if both vents and curtains were open. As external temperatures dropped, the side curtains and some of the roof vents were closed. This resulted in increasingly variable and more extreme thermal conditions, with heat and moisture accumulated along the mid-line of the load near the front of the lead trailer and near the back of the rear trailer. At an ambient temperature of -22.1°C, temperatures within the trailer varied widely between -20.7 to 21.7°C with an estimated 58.6% of the load volume being exposed to temperatures below 0°C. In addition, the trailer humidity ratio rose and conditions approached saturation (relative humidity>80%) in 55.2% of the load volume. Rectal temperatures showed that during winter weather in Canada, when the trailer is closed up and tarped, both hypothermia and hyperthermia occurred within the same trailer (Knezacek et al., 2010).

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Vibrations

Chickens find vibration below 5 Hz particularly aversive, Randall et al. (1997) concluded that the resonant frequencies of 1-5 Hz found on transporters are undesirable. Thus vibration should be reduced, for example by using air suspension. Appropriate methodology to compare aversiveness of concurrent stressors during transport is being developed, initially using thermal and vibrational stressors (e.g. MacCalium et al., 2003).

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Duration of the journey

Typical times in transit are unreported in most countries, but vary considerably. A small study of 24 commercial end-of-lay hen journeys in the UK found mean marketing time to range from 5.4 – 17.6 h (Richards et al., 2012). In the USA and Canada a review of DOAs (birds dead on arrival) by Newberry et al., (1999) found a substantial increase in hen mortality with marketing time for example from 0.7% (under 12 h) to 9.9% (over 24 h). A study in The Netherlands on 24 commercial layer flocks revealed a journey time of on average 2 hours and a total transport duration (thus including time in lairage) of on average 10 hours (Van Niekerk et al., 2014). These flocks were all slaughtered in the same plant in the Northern part of The Netherlands. Flocks located in the southern part are mostly slaughtered in Belgium and journey times will be limited. Some of the Dutch flocks are slaughtered in Eastern Europe (e.g. Poland), resulting in long journeys and even longer transport durations.

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Facilities (access to water/feed)

In general no food or water is supplied to end-of-lay hens during the journey. However, for long journeys water supply is obligatory on the trucks and for even longer distances also food should be supplied.

For transport of pullets and breeding stock water supply systems have been developed for application on trucks. Mostly these comprise a water tank connected with tubes to fixed water systems in container units. For providing water to birds in crates different systems are used. These consist of loose tube systems that are attached to the crates. Side branches with nipple drinkers are stuck into the crates. The system is placed after the crates are loaded on the truck and is connected to a water tank on the truck.

Drinking water into crates on a truck
Figure: Drinking water into crates on a truck

A Dutch slaughter plant has water supply for end-of-lay hens in the lairage. This is realized by sliding tubes with nipple drinkers between the crates.

Figure: Drinking water into crates at lairage
Figure: Drinking water into crates at lairage

Solid food is never supplied to birds on transit. Apart from the issue of soiling with manure, experts indicate that birds on transport easily vomit and can choke in the food. Instead liquid nutrients are added to the drinking water.

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Climate during transport

EFSA (2011) advices specific temperature limits during transport. They regard 24 – 25°C in the containers as a maximum for broilers, at a relative humidity of 70%. EFSA also advices to use mechanical ventilation for transports over 4 hours. Weeks et al. (1997) indicate that air velocity during transport should be 0.3 – 1.0 m/s at environmental temperatures of 10 – 15°C for broilers and 22–28°C for poorly feathered laying hens. Stocking density in the crates plays an important role and should be adjusted according to body weight of the birds and climatological circumstances (Mitchell and Kettlewell, 1998).

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Further reading (by language)

English

Number of birds/crate

Vibrations

  • Kettlewell, P., Mitchell, M. and Meehan, A. (1993) The distribution of thermal loads within poultry transport vehicles. Agricultural Engineer 48, 26-30.
  • Richards, G.J., Wilkins, L.J., Weeks, C.A., Knowles, T.G. and Brown, S.N. (2012) Evaluation of the microclimate in poultry transport module drawers during the marketing process of end of lay hens from farm to slaughter. Veterinary Record, in press

Facilities

  • Newberry R.C., Webster A.B., Lewis N.J. and Van Arnam C. (1999) Management of spent hens. Journal of Applied Animal Welfare Science, 2, 13–29.
  • Richards, G.J., Wilkins, L.J., Weeks, C.A., Knowles, T.G. and Brown, S.N. (2012) Evaluation of the microclimate in poultry transport module drawers during the marketing process of end of lay hens from farm to slaughter. Veterinary Record, in press

Climate during transport

Nederlands

Faciliteiten

 

4.4 At the slaughter plant

Post transport handling and environment
Shackling and stunning
Further reading
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Post transport handling and environment

Thermal conditions at the end of the journey must be considered as it can take 2-3 hours to manually unload pullets. Spent hens may also have to wait at the processing plant either on the vehicle or unloaded in modules or stacks of crates. In both instances a well-designed lairage is preferable to remaining outside exposed to the elements. It is important that the birds themselves receive adequate ventilation. The model birds used by Webster et al (1992) and Weeks et al. (1997) indicated that the hens frequently experienced conditions of substantial heat and cold stress in lairage during loading and unloading. Van Niekerk et al. (2014) measured temperatures during transport and lairage. Despite the use of a covered lairage and ventilation, temperatures clearly went up substantially during lairage. Thus the duration of such times needs to be kept to a minimum of preferably less than 1 hour.

Temperature during transport (average ambient temperature 4.5 degrees C)
Figure: Temperature during transport (average ambient temperature 4.5 degrees C). Temperature coding: first letter refers to position on truck (L=left side of truck, M=middle side of truck, R=right side of truck), second letter refers to logger position in crate (L=left, R=right); trucks were 3 stacks of crates wide and 12 stacks of crates long, all crates with loggers were positioned 2-3 stacks from the rear end of the truck.
Temperature during transport (average ambient temperature -4.7 degrees C)
Figure: Temperature during transport (average ambient temperature -4.7 degrees C). Temperature coding: first letter refers to position on truck (L=left side of truck, M=middle side of truck, R=right side of truck), second letter refers to logger position in crate (L=left, R=right); trucks were 3 stacks of crates wide and 12 stacks of crates long, all crates with loggers were positioned 2-3 stacks from the rear end of the truck.

A controlled environment providing adequate ventilation while avoiding excessive wind and air movement (except in hot weather) onto the birds is highly desirable. There should also be sufficient space around each module or stack for effective air exchange and flow. Monitoring the condition of birds and their environment in lairage is as necessary as it is during the journey. In practical terms, birds observed to be panting will become progressively dehydrated and increasingly heat stressed.

Following arrival at the processing plant most end-of-lay hens are manually removed from the containers. Where electrical stunning is used, live birds are suspended by their legs from shackles for conveyance to the bath. Many birds react to this potentially painful procedure by struggling, flapping their wings and attempting to righten themselves. This can lead to injury and reduces the chance that the bird will be effectively stunned prior to slaughter. To reduce the stress of hanging birds in shackles, Liner et al. (2011) found that struggling was reduced through the use of a breast support conveyor. Observations in U.S. slaughter plants showed that providing a breast rub made from strips of smooth conveyor belting will also reduce struggling and flapping.

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Shackling and stunning

Bird welfare is greatly improved when the labour intensive, stressful and often painful procedure of removing them from the containers and hanging them on shackles is eliminated. Controlled atmosphere (gas) stunning of chickens is now the commercial norm in some countries, with welfare and meat quality benefits such as reduced breast muscle haemorrhaging and bone breakages (Raj et al., 1997, Hoen and Lankhaar, 1999). Automation of shackling is has been investigated (e.g. Lee, 2001; Tinker et al., 2005) and is easier with gas-stunned birds than conscious ones that may flap, struggle and experience pain when shackled (Sparrey and Kettlewell, 1994).

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Further reading (by language)

English

Post transport handling and environment

  • Lines, J.A., Jones, T.A., Berry, P.S., Spence, J., and Schofield, C.R. (2011) Evaluation of breast support conveyor to improve poultry welfare on the shackle line, Veterinary Record, 168:129.

Shackling and stunning

Nederlands

Hanteren en omgeving na het transport