Egg Industry Center

Research files are added periodically on a range of topics found in this library. Library resources consist of old and new research related to the egg production and processing industry.



Alternative housing styles may affect stress levels of hens. In the Coalition for Sustainable Egg Supply (CSES) study researchers reviewed the impact of housing systems on bird stress through assessment of laying hen blood chemistry.

The wing vein blood of two flocks at weeks 18 and 77 was used to determine the heterophil-lymphocyte ratios (H/L) and total white blood cell counts (TWBC). H/L values from aviary housed and conventional caged birds were not statistically significant, while the H/L ratio of enriched colony birds was two times higher. However, the high variability among cages suggests the H/L ratio is not an effective indicator of stress when applied alone.

The TWBC analysis indicated an increase in the number of white blood cells, and a high frequency of irregularly structured cells, which signify a higher stress response. However, it was noted that the presence of bacteria, fungi and yeasts in the blood could have accounted for these elevated levels as well.

Housing systems are found to affect the bone quality of pullets. The Coalition for Sustainable Egg Supply (CSES) study randomly selected and euthanized 120 pullets at 16 weeks of age from both conventional cage (CC) and aviary (AV) housing systems. Their tibia and humerus bones were collected and analyzed by computed tomography. Brachial vein blood samples were also taken from random birds at weeks 4, 8, 12 and 16 to analyze serum relevant in quantifying systemic bone markers. Overall, CC pullets were found to have longer bones while AV birds had stronger bones relative to bone width and cortical thickness. The improved load-bearing capabilities and stiffness in the AV pullet tibia and humerus bones were likely due to the number of activities available to birds in that housing style.

The impact of hen housing on egg production performance and egg quality was studied by the Coalition for Sustainable Egg Supply (CSES) study which analyzed eggs for shell strength, shell thickness, Haugh unit, vitelline membrane properties and egg solids. 24 eggs were randomly selected and assessed from each housing system. Diets were specifically formulated for conventional cage, aviary and enriched colony systems based on hen productivity and feed ingredients available while being cost efficient. Dietary changes were found to have the most impact on shell parameters, vitelline membrane parameters and egg total solids contrary to the laying hen housing system. Specific dietary changes and results for each element may be found in the article. Further research needs to be conducted in controlled research settings to determine any affect on housing systems on egg quality.

Alternative housing systems impact indoor air quality differently. The Coalition for Sustainable Egg Supply (CSES) study monitored indoor air quality over a 27-month period among three housing systems to quantify indoor gaseous and particulate matter (PM) concentrations, thermal environment and building ventilation rates. A mobile air emission-monitoring unit (MAEMU) was used to collect and analyze air samples from three locations per house and one ambient location. Aviary houses had a difficult time maintaining temperature compared to conventional caged and enriched colony systems and were found to have poorer indoor air quality with higher ammonia levels, PM levels and carbon dioxide concentrations. Methane concentrations were similar for all three housing types and there was no significant difference in relative humidity.

The Welfare Quality Assessment (WQA) was used in part of the Coalition for Sustainable Egg Supply (CSES) project to compare hens in three housing systems: aviary (AV), conventional cage (CC) and enriched colonies (EC). Lohmann LSL Classic White laying hens were placed in all three housing systems at 19 weeks of age and assessed at 52 and 72 weeks for the duration of two flocks. Evaluators used both the WQA and necropsies to assess welfare and found the WQA tool to be an acceptable method regarding hen welfare, as the results from both methods yielded similar results. AV and EC systems had more keel abnormalities and fewer foot abnormalities than CC houses. The overall feather cover was found to be the best in AV hens, although their feathers were the dirtiest.

The impact of open access to litter on hen behavior and welfare was studied to better understand its influence on overall bird wellbeing when in a commercial aviary housing system. This study observed two flocks of Lohmann White laying hens specifically regarding dust bathing and piling behaviors in an aviary system that had the ability to confine birds for part of the day. Hens were observed from weeks 19 and 17 to weeks 77 and 78 respectively. Hens did not appear to have a preference of location within the open litter area, as the entire area was used. Peak dust bathing was found to occur in the afternoon and late morning. 174 incidents of piling were recorded with variations in size, duration and time of occurrence. While dust bathing is a natural behavior important to hen welfare, further research is needed to investigate the implications of piling as it could lead to welfare concerns.

A study was conducted to analyze how space affects feeding behavior. Lohmann Selected Leghorn Lite hens were housed in both small furnished cages and large furnished cages at two different stocking densities for each type of cage: 748 cm 2/hen (116 in 2/hen) and 520 cm 2/hen (81 in 2/hen). Feeders were ran five times a day at 0500, 0800, 1100, 1400 and 1700 hours. Lights came on at 0500 and turned off at 1900. A digital recording was scanned at the chain feeder every 15 minutes after feeding for an hour to count the number of birds presently feeding. Aggressive pecks and displacements were recorded as well. Results concluded there was little evidence that space allowance and cage size influenced feeder competition or aggressive pecks and displacement behaviors, as the percentage of birds feeding was similar regardless. The frequency of aggressive pecking was low as well as the feeder competition; however, researchers did note that the greatest number of hens fed at 1700 hours.

A two-part study measured hen performance in relation to space allowance. At 18 weeks old, four groups of Lohmann Selected Leghorn Lite hens were housed in either smaller furnished cages (SFC) or larger furnished cages (LFC) with access to nesting areas, perches and scratch mats. Two stocking densities for each type of cage were used: 748 cm 2/hen (116 in 2/hen) and 520 cm 2/hen (81 in 2/hen). Feed was given five times a day. At weeks 30, 50, 60 and 70; 20% of the hens were randomly selected to evaluate production parameters such as hen day egg production, egg weight, egg shell deformation, breaking strength of femur, tibia or humerus, birds suffering from keel bone deformations or foot health scores. While performance and mortality were not significantly affected by cage size or space allowance, hens with less space had higher feed disappearance and poorer feather cleanliness and condition; hence, the animal welfare was found to decrease with lower space allowance. There was no difference in bone strength or foot health scores between the two treatments.

The mineral content of whole dried eggs was reviewed with respect to the influence of factors other than hen dietary formulation. Researchers compared hen strain, age and rearing systems using TA Tetra White (TW) and Hy-Line Brown (HB) hens at 44, 68 and 88 weeks of age while housed in either conventional cages, enriched systems, cage-free or free-range systems. Results yielded that enriched housing systems had lower levels of Magnesium and Manganese than conventional cages. Age only appeared to affect Manganese levels with younger birds having higher levels than older birds. Hen strain highlighted differences in Calcium and Copper levels with higher levels in TW hens, while HB eggs were higher in Iron, Magnesium and Manganese. Egg size did not vary within any of the defined parameters. Because of the small differences in egg mineral content, it is unlikely that age, genetic strain, and housing system would have any significant impact on human nutrition.

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