Shell strength

Egg shell quality is extremely important to table egg producers.  Egg shell quality has a direct impact on profitability because any broken, cracked, or misshapen eggs will result in a loss to the producer.  Some of the factors that influence egg shell quality include: nutrition, feed management, stress, the age of the hens, and mechanical equipment.  Understanding these factors that affect shell quality will have a positive impact on your bottom line.

Nutrition
Nutrition plays a significant role in minimizing cracks within the flock.  A properly balanced feed will give the laying hen the nutrients she requires to produce an egg a day, along with the shell needed to protect that egg.  The three main nutrients that nutritionists typically take into consideration when shell quality problems arise are calcium, phosphorus, and vitamin D3.  These three nutrients each play a crucial role in shell formation.  The calcium status of a laying hen is very important because the hen must consume enough calcium to lay down an egg shell each day, as well as supporting her health and wellbeing.  In addition to this, she must replenish the calcium stores within the body so calcium is available for use the next day.  The calcium required to create the shell is obtained from two different forms, the medullary bone reserves and directly from the feed she consumes.  Medullary bone reserves of calcium are located within the long bones of the body and the hen is able to mobilize these reserves to supply part of the calcium required to produce the egg shell every day.  The remaining calcium required for the egg shell is obtained from dietary calcium comes from the digestive tract and is directly absorbed into the bloodstream.  A deficiency in calcium will cause an immediate decrease in shell quality and if prolonged, the medullary bone reserves can become depleted.  A hen in this state will begin to suffer a deterioration in egg shell quality, mobility problems, and soft bones.  Phosphorus is also important as it plays a key role in the storage of calcium in the medullary bone reserves.  Calcium is stored in these reserves as calcium phosphate, and for that reason phosphorus must be available in order for these reserves to be replenished.  Finally, vitamin D3 plays an important role in egg shell quality because it promotes calcium absorption from the digestive tract into the blood stream of the bird.  Once absorbed, the calcium is available to become part of medullary bone reserves to be laid down as part of the shell or for maintenance calcium requirements used to maintain the existing skeletal frame of the hen.  Additional calcium, phosphorus, and vitamin D3.   can be added to the diet when egg shell quality issues arise on farm, however this should be done in close consultation with your nutritionist as any imbalances in these nutrients can cause further deterioration to egg shell quality.   While additional nutrients may help solve the problem, nutrition cannot be looked at in isolation as many factors contribute to these situations.  For example, if the hen is not consuming enough feed, changes need to be made in the barn to encourage this consumption.  Because shell quality issues are typically complex and have many contributing factors, nutritionists will focus on balancing the nutrition, while also considering environmental issues that may be contributing to the problem.

It takes approximately twenty-one hours for the shell to be laid on the egg and a significant portion of this high calcium demand takes place when the lights are off.  Consequently, feed management plays a key role in maintaining shell quality.  It is important to make sure that the feeders are being run close to when the lights go off in the barn to ensure the hen is able to consume adequate calcium to support egg shell formation through the dark period.  In addition to the importance of feed timing, the form of calcium being provided in that feed can impact the ability of the hen to create a high quality egg shell.  Providing large particle calcium as a portion of the calcium in the feed will give the hen a source of calcium that is retained for a longer period of time.  This is because large particle calcium is less soluble than fine particle and will remain in the gizzard longer, making it available during the dark period when the bird is not consuming feed.  Research has proven that the hen also has a specific appetite for calcium and her appetite changes throughout the day.  By providing a portion of calcium as large particle calcium, the hen is able to selectively regulate her calcium intake throughout the day as her appetite for calcium changes.  In the late afternoon, when the demand for calcium is highest in the hen, having large particle calcium available allows her to choose to increase calcium consumption to meet her needs.  

Stress
Stress is known to cause disruption to the egg formation process which can lead to misshapen eggs, wrinkled and thin shells, as well as discoloured shells in brown egg strains.   Stresses in the barn can come in many forms, including disease, heat stress, excessive and sudden noises, mismanagement or failure of lighting programs, poor barn environment, and aggression from other birds.  These types of stresses can cause a disruption to the egg formation process because they will cause the hen to either hold on to her egg or lay the egg too soon.  Because stress influences the timing of the egg being laid, there can be an ongoing effect in the following days as the sequence of eggs has been disrupted and it takes time to get this corrected within the hen’s body.  Taking the time to observe what is happening in your barn will help you in the long run.  This includes ensuring the inlets and fans are providing adequate air flow, double checking that the lights are going on and off at the times they are set for, and observing bird behavior to look for signs of disease or aggression.  Solving these problems as soon as possible by changing fan settings, adjusting lighting schedules, dimming lights to control aggression, and contacting a vet if a disease is suspected will minimize stressors in your barn and have a positive impact on egg shell quality.

Bird age
The incidence of cracks is also affected by the age of the bird.  When the hens are young and first coming into production, there can be some thin or shell-less eggs.  This could be caused by the immaturity of the reproductive tract.  Typically this only happens to one or two eggs before the reproductive tract begins to function correctly.  The incidence of thin shells can increase as birds get older because the eggs become larger.  As eggs get larger, the amount of shell material being contributed to each egg remains virtually the same. Consequently, the shell has more surface area to cover, which may lead to thinner shells that are more prone to cracks.  Using management and nutrition tools to manage the egg size within the flock will help minimize the increase in cracks as the flock ages.  This includes working with nutritionists to review the diets to ensure that the nutrients are being fed at the appropriate levels for the age of hen, stage of production, and egg size.  This will help prolong eggs in the large category, rather than encouraging an increase in egg size.

Equipment
Egg collecting equipment such as egg belts, transfer points, escalators, packers, and egg saver wires can also contribute to cracks in the barn.  Any aspect of these systems that contributes to the rough handling of eggs as they move through the system can increase the incidence of cracks.  Being diligent in inspecting and reviewing the equipment, as well as the frequency of egg collection, on a regular basis will help to minimize cracks being caused by mechanical damage.  A regular routine can be established by ensuring maintenance logs are kept with details of problems found and how they were fixed, as well as posting a regular maintenance schedule that all employees have access to.  

While it is impossible to completely eliminate all egg shell quality issues within a laying hen flock, a reduction in the numbers of eggs lost over time is possible.  Working closely with your nutritionist to use nutritional strategies is one option to maintaining optimum shell quality. Managing the many factors within your barn that can contribute to decreased shell quality, such as feed management, stress, and egg collection equipment, will also have a positive influence on shell quality.  Combining good management practices with respect to barn environment, and management as well as building a strong relationship with a nutritionist will optimize your chances of decreasing the number of damaged eggs being produced, which means a healthier flock and more money in your pocket.