Cage-free egg production, more cost than benefits?

The Coalition for a Sustainable Egg Supply conducted field research on a commercial egg farm comparing three housing systems: conventional cages, enriched cages and cage-free aviary.

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Cage-free eggs cost 24 cents more per dozen to produce than eggs from hens housed in conventional cages in this study.
Cage-free eggs cost 24 cents more per dozen to produce than eggs from hens housed in conventional cages in this study.

The Coalition for a Sustainable Egg Supply conducted field research on a commercial egg farm comparing three housing systems: conventional cages, enriched cages and cage-free aviary. Environmental impact, food safety, bird performance, production costs, worker safety, and animal health and well-being measurements were made over a period of 27 months, which encompassed two single-cycle flocks. Nine papers were published in the March 2015 issue of the journal Poultry Science detailing results from research conducted on indoor air quality, food safety, egg quality, production cost and bone growth.

Cage-free eggs cost 24 cents more per dozen to produce

William A. Mathews and Daniel Sumner found that the feed costs per dozen eggs were highest in the aviary-housed hens and were lowest in the hens housed in enriched cages (Table 1). The feed cost for aviary-housed hens was 2.6 percent higher per dozen eggs than for those housed in the conventional cages. Even though feed is the largest cost component of egg production, the authors note that it is not the source of major differences in costs across these housing systems.

Pullet costs were substantially higher for the aviary-housed birds, so eggs from aviary-housed birds were 7 cents more per dozen than eggs from conventional cage-housed hens. The aviary and the enriched housing systems both have higher labor costs, resulting in more than 4 cents per dozen eggs.

Energy and miscellaneous costs constituted only a small share of total operating costs for each of the three housing types with little difference between the three types.

On average across the two flocks, operating costs were almost 14 cents higher for the aviary compared with the conventional house. Operating costs were only 2.4 cents higher for the enriched versus the conventional cages.

In this study, the aviary was the most costly system in all categories. Costs of the enriched system were close to those of the conventional system except for the labor and capital costs, which were considerably more costly.

Enriched cages have best hen-day egg production

Darrin M. Karcher and co-authors report that the hen-day egg production was similar among housing systems until the eighth four-week-period of the laying cycle at which point the hens in the enriched cages had higher production and maintained a higher level through the end of the production period. The mortality rates were similar among the housing systems until the fourth four-week period of the laying cycle at which time cumulative hen mortality in the aviary house continued to increase rapidly compared with the other housing systems, resulting in cumulative mortality 2.5 times higher in the aviary compared with the other systems.

The authors speculate that the increase in mortality in the aviary house might be due to the learning curve of managing this housing system, which was new to the farm, and the larger hen groups within the pen resulting in pecking and crowding.

The amount of feed supplied was slightly higher in the aviary but hen body weights were similar among the housing systems.

Several egg quality traits were measured from eggs collected from each of the three housing alternatives. In this study, eggshell parameters, vitelline membrane parameters, and whole egg solids were found to be more directly influenced by hen nutrition than by housing type. The authors stated that research would need to be conducted under more controlled research settings to delineate any effect of specific housing systems on egg quality measures.

Better bone strength in cage-free pullets

Hens that will be housed in cage-free aviary systems need to be raised as pullets in systems that prepare them structurally and behaviorally. A study was conducted that compared bone development and strength of pullets raised in cages and cage free. The researchers, Prafulla Regmi and co-authors, report that the skeletal loading provided by physical activities undertaken by the pullets in the aviary housing resulted in structural and material changes that improved the load-bearing capability and stiffness of the tibia and humerus. They conclude that providing greater access to activities including flying, perching and running during pullet phase can be crucial to the increased bone quality that might help prevent fractures due to osteoporosis in cage birds, and impact injuries during the production phase in the extensive systems.

Cage-free aviaries have the poorest air quality

Yang Zhao and co-authors monitored air temperature, relative humidity, ammonia and particulate matter concentrations inside the three housing types. All three housing options maintained similar temperature conditions throughout the two flock periods. The air quality inside of the conventional and enriched cage houses was comparable. The aviary house had higher ammonia and particulate matter concentrations than did the cage houses. The ammonia concentration in the aviary house occasionally exceeded 25 parts per million, a commonly used animal welfare standard upper limit for ammonia. The researchers also note that the overall ammonia concentrations observed in all three housing types in this study were at the lower end of the range observed in previous studies, which involved high-rise and manure-belt hen houses. They also suggest that ammonia mitigation practices should be explored for litter-floored aviary houses to safeguard hen and worker health and to reduce the environmental impact from house emissions.

Cage-free houses have highest airborne emissions

Tim Sheppard and co-authors found that house-level ammonia emissions were highest coming from the aviary house at 0.112 grams per hen per day, followed by the conventional cage and enriched cage houses at 0.082 and 0.054 grams per hen per day, respectively. Farm-level ammonia emissions were lower for the enriched cages, 0.16 grams per hen per day, than for the aviary or conventional cages, 0.30 and 0.29 grams per hen per day respectively. The authors note that ammonia emissions from the manure storage accounted for 60 to 70 percent of the farm-level emissions, and suggest that future ammonia mitigation efforts should focus on manure storage.

Particulate matter emissions, both particulate matter up to 10 and 2.5 micrometers in size, were highest for the aviary house at 100.3 and 8.8 milligrams per hen per day, respectively. Particulate matter emissions from the conventional and enriched cages were similar and significantly less than the aviaries, amounting to 16 percent of the aviary’s particulate matter 10 microns or less emission rate and 10–20 percent of the aviary’s particulate matter 2.5 or less emission rate. The authors state that the higher particulate matter emissions from the aviary house resulted from hen activities on the litter floor.

House-level methane emissions were similar for all houses and were at low levels, from 0.07 to 0.08 grams per hen per day.

Cage-free eggs have highest microbial load on shells

Deana R. Jones and co-authors looked at the microbial loads found on the egg shells and in the environment of the three housing systems. They found the highest levels of average total aerobic organisms were found on aviary floor and system eggs, 4.9 and 4.1 log colony forming units per milliliter, respectively. The lowest levels of total aerobic organisms were found in enriched colony cage nest box and conventional cage system wire produced egg shells, 2.6 and 2.8 log colony forming units per milliliter, respectively. Aviary floor and system wire produced eggs maintained the greatest level of aerobic organism contamination throughout the study.

Average coliform levels for all shell samples were 1 log colony forming unit per milliliter or less. The greatest average shell pool coliform count was associated with aviary floor eggs, 1.0 log colony forming unit per milliliter. There were no significant differences between shell sample types for the prevalence of Salmonella or Campylobacter serotypes. Very low levels of shell Salmonella serotype contamination occurred throughout the study, 0 to 8 percent.

The authors suggest that higher dust levels in the aviary house played a significant role in the higher aerobic plate counts found on the egg shells produced in this house. Developing a system for controlling dust in aviary houses could help reduce these plate counts. The authors also note that the enriched cage scratch pad area can be a source of aerobic and coliform microbiological contamination based on the environmental sampling conducted in this study. They also stressed the importance of the role of workers can play in preventing hens from laying floor eggs in cage-free environments, as floor eggs consistently had the highest microbial loads.

Areas for improvement

This research tested the performance of one strain of hens, Lohmann LSL, in one type each of aviary, conventional cage and enriched cage. Innovation can lead to changes in system designs or in management techniques that may improve the relative performance of the three housing systems in many areas. Field experience also suggests that different strains of hens may be better suited to one type of housing system then another, so strain choice could also affect the relative cost per dozen eggs produced in these three housing alternatives. Photo courtesy of Coalition for Sustainable Egg Supply.

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