Egg Industry Center

Research Library

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.

Bird Health


Discussing the risks that exist with multi-age sites regarding disease management, this white paper outlines eradication, vaccination, biosecurity and farm hygiene for main points of discussion. The main message is that hens living in constantly challenged microbial environments will produce a continued immune response which is detrimental to them over time.

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 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.

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.

Gut microbiota impacts hen health and production. Hens in cage free systems are able to move more freely, engage with their environment and have different nutritional and management requirements. Little is known about how CF housing alters hen physiology and health.

In this study, researchers explored how cage free (CF) and conventional (CC) housing systems alters hen physiology and health by comparing and correlating eukaryotic (cells where DNA is within a distinct nucleus) microbiota in the ileal (third part of the small intestine). This study expands on previous work comparing and correlating prokaryotic (cell where there is no distinct nucleus) ileal microbiota using 16s rRNA gene amplicon sequencing. 25 hens where randomly chosen and weighted from two different houses of a CF or CC housing system at a single commercial facility. Hens were fed a standard corn-soybean diet.

Sampling found that in comparison to prokaryotic communities the eukaryotic communities had
relatively low species diversity and evenness. 83 correlations were found between prokaryotic and
eukaryotic species. Significant differences between the CC and CF ileal communities were observed at the whole community level. Disease causing organisms were present in ileal communities of both housing types, but were more abundant in CF samples, possibly due to increased exposure to fecal matter. The ileal microbiota relationships discovered may have important implications for designing probiotics.

Producer Takeaway: The ileal microbiota relationships discovered may have important implications for designing products to further enhance bird health. Cage-free hens had more disease causing organisms present than caged hens. 

X-rays may help genetics companies.

The development of alternative housing systems has increased the opportunity for falls and collisions, which are associated with kneel injuries and bone damage. It has been suspected that genetic factors underlie susceptibility of hen’s bone quality issues; however, assessment of bone quality parameters is made post-mortem which makes it hard to implement genetic selection to improve bone quality. Previous technologies for live bird evaluation are too time consuming to be practical. Researchers used 50 end of lay (~65 wks) Lohmann brown hens to optimize the assessment of images obtained through X-ray exposure of the dead hens. Hen bones were then measured through the traditional post-modem bone quality measuring system. Next, diet manipulation of Hy-line Brown Layers was used to produce a large range of bone breaking strength and density values. Live radiographs were taken three times throughout the various feeding trials and the hens were culled for post-mortem assessment. The methodology developed for measuring bone qualities with x-ray imagery correlated strongly with accepted post-mortem bone quality measurements for bone density. Reproducibility and repeatability of this technology; in addition to its portability, rapid image-taking ability (45 sec), and lack of need for sedation makes this a practical method to measure laying hen leg bones for reduced damage and fracture. In addition, human radiation exposure allowed for over 60,000 radiographs to be taken per year before reaching regulated maximum annual dosage limits.

Producer Takeaway: New technology makes it possible for genetics companies to evaluate bone quality measurements in live birds. This may speed up the genetic selection process for laying hen leg bone strength traits. 

Reducing ammonia gas (NH3) is key to employee and animal welfare, as well as good environmental stewardship. Sodium butyrate is a commonly used as a feed additive to help regulate ammonia emissions. Researchers observed its interactions with the cecum to discover its capabilities.

The sodium butyrate and cecal content of 30 Lohmann pink laying hens was measured through in-vitro fermentation experiments and NH3-producing bacteria experiments. Results showed that  sodium butyrate reduced the total gas production of cecal microorganisms. Addition of sodium butyrate decreased NH3 production and increased the nitrate content in the fermentation experiments, indicating that sodium butyrate could promote nitrogen fixation and reduce the free nitrogen content. Testing showed that sodium butyrate significantly downregulated the expression of bacterial genes related to ammonia emissions during metabolism. The optimal supplementation level in this study was 0.15%.

Producer Takeaway: Results showed that sodium butyrate has the following effects in the cecum; reduced the abundance of harmful bacteria, increased beneficial bacteria, and reduced ammonia emissions from bacterial metabolism. 

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