Research into the housing of laying hens in Australia showed both advantages and disadvantages for hen welfare from increasing the floor space available to caged hens, showing that it is possible that such a change would not result in overall welfare benefits to the hens to justify the reduced returns on investments for the egg industry that would result from increasing space allowances.

The research also finds a newly developed “enriched” laying hen cage from Britain is unsuitable for Australia’s larger-sized laying strains and may result in increased mortality during hot weather in naturally ventilated sheds.

While the existing Australian Code of Practice specifies a minimum space allowance of 450cm2 per hen for four or more hens in one cage, producers are concerned about what they may need to do to modify or replace existing cages if Australian authorities follow the lead of their European counterparts and legislate to increase minimum space allowances.

With funding from the Rural Industries Research and Development Corporation, and support of the University of Queensland and the Queensland Egg Producers’ Association, Geoff Stewart, from the School of Veterinary Science and Animal Production at the University’s Gatton College, experimented with housing for laying hens as part of his PhD thesis.

The first experiment investigated the benefits of modifying existing cage arrangements used in the egg industry in Australia to increase space available for each laying hen by over one-third.
A second two-stage experiment evaluated the use of the newly designed “Edinburgh Modified Cage” (EMC), developed in Britain to provide “cage enrichments” designed to allow natural hen behaviours such as nesting, perching and dust bathing, for their suitability in Australian conditions.

A third experiment is also reported here that was conducted by Roland Bishop from Agriculture Western Australia to investigate the effect of space allowance on the production and welfare of laying hens.
 

The Studies

Experiment 1

This experiment investigated the effect of modifying these cages by either completely or partially removing (leaving one third at the front of the cages) the side-wall between two cages to allow for the movement of hens over a greater floor area. This created double cages capable of holding six layers.

The rationale behind removing only two-thirds of the common partition was to offer a “hide” within the double-cage for protection of hens lower in the pecking order and to provide extra cage floor support at the front of the cage next to the feed trough.

The double-cage configuration meant four or more hens could be housed in compliance with the stricter European regulations.

The experiment was carried out using the most common strain of laying hen in Australia at the time (1994) – the Hyline-CB. Hens were given constant access to the standard Gatton College layer diet formulated for a daily intake of 110 grams.

A year’s production data was recorded, including daily egg production, mortality, feed consumption, progressive body weight, and egg grades. Feather score and cage condition were also monitored.
The trial was carried out in a gable-type shed with ridge ventilation, temperature-activated fans and relatively old, double-sided aluminium foil ceiling insulation with external white roof paint. The northern- and western-side walls were wire mesh and slats respectively and the eastern and southern walls were solid and partially solid corrugated galvanised iron with wire mesh.

There were six cage configurations, three each for the current space allowance (450cm2 per bird) and for high space allowance (675 cm2 per bird).

The current space allowance arrangements were:

The high space allowance arrangements were:

A total of 540 hens were involved giving six groups (replicates) of each of these six configurations.
 

Experiment 2

The experiment compared mortality, hen day and hen housed production, feed consumption, bone strength, feather condition, foot and claw condition, and assessed the welfare aspects associated with the use of EMC’s in Australia.

The results from this experiment demonstrated serious problems with EMC’s when used to house large Australian strain laying stock such as Tegel Blacks. Since the smaller European-bred Isa Brown strain had recently entered the commercial egg market in Australia at this stage, a second trial was held to compare the performance of an existing medium-size Australian laying hen, the Hyline-CB, with the Isa Browns at different stocking densities in the EMC’s. The researchers repeated the methodology undertaken in the first EMC experiment.

In order to test the EMC, the University of Queensland commissioned 18 cages to be built, at a cost of $5600, based on drafting plans designed and supplied by the Institute of Ecology and Resource Management at the University of Edinburgh.

Table 1. The EMC specifications:
 

Total width	950mm (250mm wide nest box, 700mm wide feed trough)
Total depth	360mm
Perch	700mm x (50mm x 25mm) rectangular, levelledÐedge pine/distance between the perch and the feed trough = 185mm/distance between the perch and the back of the cage = 125mm
Sand box	250mm wide by 360mm long
Height	Front - 470mm: back - 520mm

The nest box opening was 140mm wide and the sand box opening was 150mm wide. Mechanical independent door closers (that could be opened or shut when required) were provided for both the nest and sand boxes. The nest box was lined with “Astroturf” polymer matting as a nest base.

A special fully insulated (both walls and roof) shed with full-length closable ridge ventilation and two large roller shutter doors for additional summer ventilation was built at Toowoomba to house the experiment. Twelve panels of opaque roofing provided an even distribution of light throughout the shed.

In the first stage of this experiment, 80 19-week old hens were introduced – 28 Tegel Blacks, 24 Hyline-CBs and 28 Aztecs.

Space allowance for the first stage of the experiment was set at the very high level of four hens per EMC (ie 855cm2 per hen). The floor area of the scratch tray was not included in the space allowance determination as it did not affect the overall cage dimensions and might be closed off for a significant part of the day.

A group of four hens from both the heavy and light body-weight strains were housed in conventional 50cm x 50cm cages (designed and manufactured by Harrison, Villawood, NSW) in the same shed adjacent to the EMCs and were used as an initial guide for comparison. No spare Hyline-CB’s were available to put in the conventional cages.

Although these cages are designed for five hens under the Australian Code of practice, only four birds were used in each (providing 625cm2 per hen) in order to have the same group size as the EMC’s.

All hens were fed a commercial laying mash formulated for 110g per day intake.

The lighting pattern was fixed at 16 hours of light a day between 4am and 8pm. The nest and sand box closers were left open for the entire experiment to establish natural laying patterns, and river sand was provided in the scratch boxes to a depth of 2.5cm.
 

Feed consumption was measured fortnightly for a period of four days with an average feed consumption calculated and feed costs, egg returns and margins evaluated. Other measurements included the position in the cage eggs were laid, egg quality and egg grades.

Feather cover was given a score on a “poor to good” scale (1-5) and foot condition was observed and any broken toe-nails and foot pad abrasions/cuts or inflammation/swelling recorded. Mortality was logged as it occurred but no hens were replaced.

On completion of the trial, all the hens were weighed, euthanased and humerous, femur, tibia and metatarsus bone strength measurements were taken.

The second stage of the EMC experiment was carried out in 1996. It was designed to investigate space allowances that would more accurately reflect commercial space allowances expected to be used in EMC’s in the UK and to investigate the performance of layer strains more suited to EMC housing.

The hens were housed in the EMC’s from 20-weeks of age and were located side by side in the same shed (high rise with automatic fans, foggers and shutters). All were given the standard Gatton College layer diet formulated for an intake of 110g per day.

Eggs were collected daily and the position of lay in the EMC’s was recorded.
Hens were given 100 per cent access to nest boxes and scratch trays to enable assessment of the pressure of use on each part of the EMC under different space allowances.

As an additional part of the experiment, it was decided that two of the groups of hens would be denied access to the scratch trays for the first six weeks in order to see if early laying behaviour patterns influenced long term behaviour.

Experiment 3

Assessments were made of the effects of space allowance on egg production, egg quality, physiological stress, behaviour, feather cover, bone strength, body weight and feed intake in two commercial strains of laying hen, Tegel Queens and Hazlett Browns.
 
 

The results

Experiment 1

The impact of social interaction between hens is influenced by both space allowance and the number of hens in the group as the hens try to develop a stable “pecking order”. In the experiment using the modified Californian-style cages, the research showed there may be no welfare advantages to the hens by increasing space available to each bird if the hens develop additional anti-social vices.

At both the current and high space allowances used in this experiment, the double cages with the one-third partition resulted in lowest bird mortality while the high space allowance in the double cages without the partial partition resulted in the highest mortality (mainly Marek’s disease). Hens in this configuration also suffered the greatest amount of feather pecking. The results show the problems with larger group sizes and the benefits of the partial partition, possibly in providing a “hiding” area for hens at the bottom of the peck order.

Partition removal provided hens with a choice of the area of the cage they could access at any time. Also, three watering points would be available at no extra cost in every cage where nipples or cups were used or there would be access to a longer length of water trough space where trough drinkers were in use, meaning more hens could choose to drink from the trough at any one time.

This extra water access could prove significantly beneficial under Australian summer conditions in semi-controlled environment layer houses.

On the negative side, higher space allowances resulted in birds becoming more obese, which could lead to fatty liver problems towards the end of the lay, particularly during the Australian summer, with obese birds the first to die in sudden onsets of hot weather.

Cannibalism through vent “peck out” in this experiment involved only two hens, both from the high space allowance double cages.

The effect of high and low stocking density and cage configuration on gross $ return per sq. metre of cage space from 22 to 78 weeks of age. Different superscripts after each value denote significant difference at P<0.05: SEM=13.91. Returns calculated using average gross prices paid to Sth. Qld. producers in 1996 (excluding any grading, marketing, and administrative charges) as follows: Hen depreciation = started pullet price ($6.50) – cull value ($0.20). Gross return = gross value of eggs – (feed costs plus hen depreciation)

Small group sizes proved valuable, with the best feather condition at the end of the lay shown by hens housed in pairs in single cages.

The current space allowance resulted in less first quality eggs and more cracked eggs. At the current space allowance the double cage without the partial partition had the highest incidence of cracked eggs due to sagging of the cage floor leading to more collisions between eggs in the “roll out” trays. Space allowance did not affect the gross return per hen housed but the current space allowance gave a better gross return per square metre of cage floor area.
 

Experiment 2

More cracked and dirty eggs were produced in the EMC’s than in conventional cages. Eggs laid in the EMC nest box are concentrated into smaller “roll out” areas, providing greater chance of collision. Furthermore, some hens chose to lay while standing on the perch.

The need to replace sand in the scratch trays in the EMC’s twice a week created a significant extra labour cost. Egg laying in the scratch trays also increased labour as they had to be hand collected. Scratch tray egg laying led to hygiene problems and to the development of the undesirable habit of egg eating by hens. Some of this could be avoided by closing off the scratch tray each day until most eggs were laid or by completely denying access to scratch trays for the first six weeks of lay, when laying behaviour patterns are being set.
 

Experiment 3

Weight gain was marginally affected by space allowance and tended to increase as space allowance increased until a peak was reached after which further increases in space allowance caused a decrease in weight gain. Higher weight gains resulting from increases in space allowance may be a problem as hens of both strains were above the breeders recommended bodyweights.

The major differences in measures relating to welfare were between the two strains. Bone strength was unaffected by space allowance but was significantly different for the two strains. The two strains of hens were also found to be quite different in their desires to perform particular behaviours such as preening, toe pecking and mock dust bathing.
Furthermore, the two strains responded differently to changes in space allowance for some behaviours, indicating that increasing space allowance may not benefit all strains of hen in this regard. The behaviour that was most strongly affected by space allowance was changing position, which increased significantly with increased space for both strains of hen.

Physiological measures of stress showed no benefits of increasing space allowance. Blood corticosterone levels, which are an indication of acute stress, were unaffected by space allowance. Furthermore, heterophil/lymphocyte ratios, an indicator of long term stress, showed there was no difference in stress levels between hens given the highest and lowest space allowance, while intermediate space allowances resulted in higher stress levels.

The tables on the next page outline major findings from the report
 

Summary

Although increasing space allowance improved egg size, egg numbers per hen and egg quality in one experiment this was not consistent, and the sheer volume from current space allowances still meant better returns on investment overall. Increasing the space allowance improved some aspects of bird welfare but worsened others resulting in no clear benefit to overall bird welfare.

Net financial returns per square metre of cage floor space were around 25 per cent less with high space allowance cages compared with the current space allowance.

Positive welfare benefits for hens would be essential to obtain industry support for increasing space allowance and even if demonstrated, it would be difficult to convince lending institutions that more money should be invested into egg farms for hen welfare if investment returns are not improved.

The experiments using EMC’s highlighted the need to test overseas technology under Australian conditions before recommending or enforcing its use. Under Australian conditions the EMC could not be shown to provide an overall welfare benefit for laying hens.