The welfare of laying hens kept in different housing systems in New Zealand has been studied by independent experts in order to compare the health and well-being of hens kept in cages, barns and on free-range. The report was published in March 2009 following a scientific study by principal investigators, Hugh Black (veterinarian and Technical Liaison with AsureQuality) and Neil Christensen (registered specialist in avian medicine at Avivet Ltd).

The report – Comparative Assessment of Layer Hen Welfare in New Zealand – says that the aim of this survey was to conduct a science-based comparative assessment of the welfare of laying hens in commercial production systems in New Zealand. The collection and analysis of data were focussed on outcomes in terms of hen welfare.

Farms and Parameters Surveyed

The survey was carried out on a selection of 60 layer hen farms in the six following categories: large cage, small cage, large free-range, small free-range, organic free-range and barn categories. The farms had been selected to provide a fair representation of the two major brown layer breeds (Shaver Brown and Hyline Brown) farmed in New Zealand, plus a representation of the locally bred Ranger bird used at the time the survey was carried out by a small number of organic farms. The farms were also selected to represent the geographical spread of egg production in New Zealand, and care was taken to include representation of all the major suppliers of equipment.

The authors say that data were collected on farm-level variables and bird-level variables that affect hen welfare, taking account of both biological function and feelings approaches to animal welfare assessment. In cage systems, thirty birds were assessed on each farm. In free-range and barn systems, 30 birds were weighed but the behavioural assessment was carried out on a range of birds within easily assessable distance. The average numbers assessed in the non-cage groups ranged between 61 and 128 birds.

Two farm visit assessments were made, the first soon after peak lay (average age at first visit: 32 weeks), and the second examining birds from the same flock towards the end of their laying period (average age at second visit: 62 weeks).

The period on investigation started in early June 2007 and finished at the end of June 2008.

Results

The report presents the findings of the two series of farm visit assessments in a total of 35 tables. These describe the results of the assessment of overall farm practices, individual bird level physical assessment, flock level performance, flock behavioural assessment and faecal corticosterone analysis. Statistical analysis of the results is provided.

The tables are supplemented by a number of figures and graphs.

Discussion

* "Any consumer seeking value-based protein can be assured that he or she need not avoid eggs produced in any farming system in New Zealand on the ground that birds are suffering unnecessarily in that system."

The authors emphasise that no major adverse welfare issues were highlighted by their survey, and there was generally a high level of compliance with the Code of Welfare and its Minimum Standards.

Between- and within-farm variation

On the subject of weighing frequency, they mention that current husbandry requirements have changed so that Minimum Standards were not generally adhered to in the area of weighing birds during rearing or during lay. The Code may reflect the situation some years ago prior to the introduction of modern light hybrids, when feed and weight restriction during rearing and laying were essential to maintain welfare and production.

The survey found that weighing was used as a production management aid in approximately half of large cage farms but in fewer than 20 per cent of other management types. Nevertheless, flocks' average weights were found to be maintained close to breeders' guides although there was considerable variation in weight amongst flock members. However, the high percentage of birds in lay indicated to the authors that any variance from the Minimum Standard 2f of the Code had at most a small effect on bird welfare.

Mortality

A feature of the cage production systems in the study was the lack of variability between and within flocks in respect of many of the parameters included in the survey. This covered performance measures, including mortality, amongst cage flocks. Cage production systems on both large and small farms showed the lowest levels of mortality. Mortality was significantly higher on free-range farms than for cages. Barn production systems showed mortality rates intermediate between cage and free-range systems but the differences were not significantly different to either.

Mortality rates are a crude measure of welfare, but an important one, worthy of considerable weighting in any comparison of the relative merits of any production system, as hens generally suffer during the period of morbidity preceding death.

Cannibalism, feather pecking and beak trimming

In this study, birds' integument (feathers and skin) was scored using the Tauson scoring system. It showed a significant increase in the level of wounds in organic free-range flocks at the time of the second visit, a factor not observed for other systems. Large free range flocks had more wounds than the reference large cage flocks.

The authors highlighted the difference in the practice of beak-trimming. Six of the 10 organic free-range flocks were not beak-trimmed, and the others had used a laser beak trimmer. Eight per cent of the other extensive flocks and 16 per cent of the cage flocks were not beak-trimmed. In the case of the cage-housed flocks, this included the largest flocks, where the standards of light and environmental control allow birds to be farmed without trimming their beaks.

It was felt that some allowance should be made for the fact that the organic free-range flocks were on average five weeks older than for the sample as a whole, but the elevated levels of aggression shown by these birds, coupled with the presence of an effective means of conveying aggression in the form of a sharp non-trimmed beak underlies the high level of wounds in free-range flocks. The fact that the wounds do not transfer to a higher level of mortality probably reflects the increased opportunities for escape provided by these systems.

There was a significant reduction in feather covering in cage systems by the time that the birds reached 60 weeks of age compared to non-cage systems. The investigators note that feather loss was greatest in those birds (cage birds) producing the most eggs, reflecting abrasion of feathers on cages and other equipment, although they remark that no clear relationship has been established between feather cover and bird welfare. Their results show that feather loss is more marked in cage birds than in birds housed in non-cage systems, but the presence of wounds is more prevalent in the latter.

Assessment of 'suffering' and 'pleasure'

Animal welfare studies have attempted to assess feelings experienced by animals: the absence of strong negative feelings, usually called 'suffering', and (probably) the presence of positive feelings, usually called 'pleasure'. The report says that in any assessment of animal welfare, these feelings should be assessed but it highlights the difficulties of objective measurement. Instead, indirect methods are used, which are usually derived from assessing the changes in an animal's body (e.g. feather cover, wounds) and functions (egg production) and also from their behaviour.

Although science can be of enormous help in resolving animal welfare problems, the authors emphasise that the driving force behind this science is society's ethical concern about the quality of life experienced by farm animals. Social attitudes vary, even between developed OECD societies, leading to differences in legislation relating to welfare issues.

One of the outcomes of this survey, say its authors, is that any consumer seeking value-based protein can be assured that he or she need not avoid eggs produced in any farming system in New Zealand on the ground that birds are suffering unnecessarily in that system.

Are non-cage systems more 'welfare-friendly'?

This study has focussed on defining welfare outcomes for layer hens based on known needs and the authors highlight the difficulty in defining the term 'welfare friendly'. They say their findings for faecal corticosterone and behavioural and biological factors do not support the contention that confinement induces high levels of stress in laying hens.

Whilst a recent Pew report claims that good welfare can no longer be assumed based on high productivity and/or absence of disease, the authors say that good hen welfare is almost always accompanied by low mortality and high levels of productivity.

The study confirms previous work in other countries that free-range hens are at greater risk from disease morbidity and mortality, and are exposed to more aggressive behaviour from their peers.

Finally, the authors of the report generally found more variation within than between farm types for several variables used to assess hen welfare in their study. The exception was for the large cage farms, which showed very little variation as a group).

Examples of good and poor hen management practices impacting on bird welfare were apparent in each of the farm systems examined.

Conclusions

The report's authors say that their findings indicate that cage and free-range layer hens are similarly adapted to their environments, and show similar stress levels as measured by faecal corticosterone tests.

They found significant differences in mortality, feather cover and wound prevalence were found between farm types. A range of management standards was found within each farming system although large cage farms systems showed least internal variation.

The investigators refer to a previous report carried out by New Zealand's National Animal Welfare Advisory Committee (NAWAC) in 2004. A draft of Layer Hens Code of Welfare stated that NAWAC was 'unable to recommend replacement of current cage systems with alternative systems until such time as it can be shown that, in comparison to current cage systems, alternative systems, in the context of supplying New Zealand's ongoing egg consumption needs, would consistently provide better welfare outcomes for birds and be economically viable'.

The authors of the new report say their findings support this conclusion, and that little has changed in the interim. They add that the science–based approach of their work will lead to improved layer hen welfare outcomes via the revised codes of welfare.

Further Reading

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You can view the full report Comparative Assessment of Layer Hen Welfare in New Zealand by clicking here.

May 2009