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Welfare and cost implications of aviary housing systems

19-04-2023 | |
Welfare and cost implications of aviary housing systems

The egg production sector in the United States is facing demands from buyers and policy-makers to change the standards for laying hen housing systems and to apply alternative systems to balance environmental enrichment with environmental containment and disease control. These changes come at a cost.

The go-to alternative housing systems to meet future demands is the aviary housing system. Here, birds have access to an open litter floor, nest boxes and perches. In addition, laying hen housing systems must ensure that feed, water, light, air quality, space and sanitation are provided in a way that supports good health and welfare, protects birds from disease, injury and predation, promotes food safety and provides for the expression of the birds’ natural behaviour.
The new standards, including expansion of the living space for laying hens, are associated with higher production costs. However, there are some concerns regarding bird health, welfare, resource use efficiency and the cost implications of aviary housing systems due to a lack of knowledge about system performance and more complex environments which, in turn, could affect producers’ decision-making when considering the alternative housing system.

 

Impact on production costs

A study by Matthews and Sumner in 2015 showed that egg production costs and feed costs per dozen eggs were much higher for the aviary housing system compared to conventional housing. In addition, labour and pullet costs were higher in an aviary system compared to a conventional system.
However, there was no significant difference in energy and other costs between the systems, as these amount to a small part of the total operating costs. Total capital investments per hen-capacity and capital costs per dozen eggs for the aviary system were higher than those of the conventional housing system. The average operating costs for the aviary system were about 23% higher and the average total costs were about 36% higher compared with the conventional housing system.

A study by Xin and others in 2012 demonstrated that the average daily emission rates of ammonia, carbon dioxide and methane for the aviary housing system were 0.15, 78, and 0.10 g/bird/day, respectively, which were higher than the reported values for manure-belt hen houses. In addition, the aviary housing system had less egg production per hen housed during the production period, higher cumulative mortality and a poorer feed conversion ratio.
The production cost for the aviary housing system was about 60% more than that of the conventional housing system due to higher housing and equipment costs relative to the larger space per bird housed in the aviary housing system.

Impact on laying hen welfare

Aviary housing systems provide birds with more behavioural freedom, as well as sufficient access to litter, nests and perches which improves their welfare. In addition, aviary housing systems allow more bird activity which may result in increased bone density and strength. Aviary-raised hens spend more time walking and have more behavioural opportunities, such as increased foraging, dust bathing and comfort behaviours, as well as a reduction in stereotypies. In non-cage systems, including aviary housing systems, bird health can be compromised due to a greater risk of bacterial and fungal infection spreading among the birds.
Other welfare challenges include feather pecking, toe pecking, vent/cloacal pecking and cannibalism, which persist after switching to an aviary housing system and are more prevalent in the laying period. Severe feather pecking causes feather loss and increases food consumption in defeathered birds which leads to compromised welfare, greater mortality and economic losses.

Laying hens in aviary housing systems with perches are inclined to suffer more injuries due to landing failures when jumping from one perch to another. High perch usage in hens also makes them more susceptible to keel bone deformation. Generally, increased group size and extensive housing systems lead to a greater risk of injurious pecking and pecking mortalities. In litter-based systems, air quality is lower due to increased levels of ammonia, dust and bacteria. Increased levels of ammonia are associated with a detrimental impact on birds’ respiratory tracts and can also lead to keratoconjunctivitis.
Dust is composed of inorganic and organic compounds and can be a vector of micro-organisms and toxins which, in high concentrations, may compromise the health and welfare of both birds and their caregivers.

How to improve the situation

Research studies have found that some risk factors for plumage condition, egg production and mortality are linked to the housing system and management. Thus, making adjustments to the aviary housing design may help to improve laying hen welfare and performance. Pötzsch and others in 2001 showed that feeders mounted on wire mesh and drinkers placed on plastic slats were risk factors for increased feather pecking and vent pecking in aviary housing systems.
A study by Heerkens and others in 2015 demonstrated that wire mesh used as flooring material in the aviary housing system was associated with better plumage scores, fewer wounds, higher production rates and lower mortality compared to plastic slats as flooring material. In addition, they found that red mite infestation was more prevalent in aviaries with plastic slatted flooring compared to wire mesh flooring.
Laying hens in housing infested with red mite showed a poorer plumage condition, increased cloacal discharge and greater mortality. Wire mesh flooring systems are also more hygienic because the waste is more effectively compressed through the wire mesh onto the manure belt. The presence of a free-range area also reduces stocking density and provides more opportunities for species-specific behaviours.
Another risk factor is the presence of a perch versus a platform in the aviary housing system. A platform provides more space for walking which creates less disturbance or competition in front of the nest and leads to less tail pecking.

Constant monitoring

More spacious housing allows greater freedom of movement but is often associated with more hazardous conditions – such as disease outbreak, injurious pecking and flock mortality – if not managed carefully. Several aviary housing system properties can be identified as risk factors for injurious pecking, variability in production rate and mortality. Therefore, close monitoring of the birds, followed by some adjustments to the aviary housing design and bird management can help to improve laying hen health, welfare and performance.

Azarpajouh
Samaneh Azarpajouh Author, veterinarian
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