Egg shells are primarily made up of calcium carbonate, which accounts for about 95% of their composition. This mineral has various applications in industry, nutrition, and agriculture. Numerous studies are being conducted to explore innovative ways to use this resource and take advantage of its natural absorbent properties. For example, it could potentially be used to treat cadmium in wastewater. Therefore, it is important not to dispose of egg shells as waste but instead recognize their usefulness in your home and yard. Additionally, they can help you save money by replacing expensive and harmful chemical products that you might otherwise use. Typically, high-quality eggshells from commercial layers contain approximately 2.2 grams of calcium in the form of calcium carbonate.
Approximately 95% of the dry weight of eggshell is made up of calcium carbonate, weighing about 5.5 grams. In addition to calcium, the typical eggshell contains approximately 0.3% phosphorous and magnesium each, as well as small amounts of sodium, potassium, zinc, manganese, iron, and copper. The remaining substance left after extracting calcium from the shell is known as the organic matrix. This organic material has the ability to bind with calcium and its structure during shell formation impacts the strength of the shell. It is crucial for this organic substance to be deposited correctly in order for the size and arrangement of its crystalline components (primarily composed of calcium carbonate) to be optimized for a strong shell.
The true shell is predominantly made up of calcium carbonate, arranged in long columns. Other regions contribute to the self-organization process, which gives the eggshell its strong characteristics. Therefore, shell thickness is the main determinant of strength although not the sole factor. Currently, modifying the diet is the primary method used to address issues with eggshell quality. However, it is equally important to consider the relationship between the shell and the organic membrane for good shell quality. Ideally, a smooth eggshell is preferred as rough-shelled eggs are more prone to fracturing. Comparatively, larger eggs are more likely to break than smaller ones.
The primary cause of variations in eggshell quality is the hen’s genetic capacity for calcium deposition in the eggshell. As the hen gets older and lays larger eggs, it becomes necessary for the same amount of calcium to cover a larger surface area. Therefore, controlling the rate at which the weight of the eggs changes can affect eggshell quality as the hen ages. By manipulating the temperature inside the layer house, feed intake can be regulated, ultimately impacting egg size. It is essential to remember that several factors can influence how much calcium is deposited by the hen, and thickness does not necessarily indicate strength in an eggshell.
Sometimes, a thinner eggshell can have more strength than a thicker one, depending on the shape and organization of its organic and inorganic components. In cooler climates, eggshell quality is typically not a big concern but becomes significant in hotter weather. Insufficient feed consumption by hens during hot conditions can lead to lower eggshell quality, which can negatively impact body weight, egg production, egg size, and overall shell quality. To prevent these problems, it is essential to make sure that hens consume enough nutrients and energy every day.
During hot weather, hens have reduced appetite due to the high environmental temperature. This limits their intake of energy. To tackle this problem, adjusting the nutrient density in their diet can usually solve the issue of insufficient consumption of amino acids, calcium, phosphorus, and other nutrients. However, it is important to understand that laying hens need to make significant physiological adjustments in response to higher temperatures during hot weather. Panting is a mechanism employed by laying hens to prevent body temperature from rising when they experience heat stress.
At the same time, the bird’s blood acid-base balance is altered. It is important to remember that laying hens need to regulate their body temperature in extremely hot environments, which means their main focus shifts from producing eggs and maintaining a strong eggshell to simply staying alive. This makes it challenging for any age bird to achieve optimal egg mass (egg production multiplied by egg weight) and high-quality eggshells. While not all chicken diseases result in decreased eggshell quality, egg production typically decreases in these situations.
Infections such as infectious laryngotracheitis may impact the number of eggs produced, but not necessarily their quality. However, viral diseases like egg drop syndrome (EDS), avian influenza (AI), Newcastle disease (ND), and infectious bronchitis (IB) can have a severe effect on both the internal and external quality of eggs. While there may be a decrease in the quantity of collectable eggs, the total count of eggs might remain unchanged since non-collectable eggs, such as shell-less or ultra-thin shells, are lost beneath the cages. This phenomenon is commonly observed with EDS.
It has been determined that the EDS virus specifically impacts the shell gland, while ND and IB can affect all parts of the reproductive tract. If we had to identify one disease as causing the majority of production losses in egg layers, it would be infectious bronchitis. This coronavirus has a tendency to target the mucus membranes in both the respiratory and reproductive tracts. In some cases, certain strains of IB virus can affect the kidney as well. As a result, not only does eggshell quality suffer, but internal quality also deteriorates.
It is common for watery whites to persist for a long time after egg production resumes. This can occur due to infectious bronchitis (IB) outbreaks, which may also cause brown shell eggs to appear pale in color. To fully understand the factors that affect egg shell quality, it is important to comprehend the process of preserving it.
An egg shell mainly contains 94 to 97% calcium carbonate and around three percent organic matter and egg shell pigment. The shell also has approximately 8,000 microscopic pores.
The shell of the egg is safeguarded by a mucous coating known as the cuticle or bloom, which acts as a barrier against bacteria. The shell’s quality can be assessed by its color, shape, and structure, offering options like white, tinted, or brown. Prior to being laid, multiple factors can impact the overall quality of the shell.
The thickness of an egg shell is determined by two factors: the duration it spends in the shell gland (uterus) and the rate of calcium deposition during shell formation. If the egg has a short time in the shell gland, its shell thickness will be reduced. The time of day when the egg is laid also affects its shell thickness. In general, if it is laid earlier in the day or during the light part of the photoperiod, its shell will be thicker. Additionally, different bird strains may vary in their ability to deposit calcium at a faster rate for eggshell formation.
Another factor that affects the functional quality of the egg shell is the age of the hen. As the hen gets older, the thickness of the shell generally decreases. Other factors that determine egg shell quality include the presence of abnormal ridges, calcium deposits, or body checks. The asthetic quality of egg shells refers to factors that are visible to consumers, such as the shell’s integrity, cleanliness, shape, and color. There are several factors that impact asthetic egg shell quality.
Several factors influence the visual appearance of an egg shell, including wash water temperature, condensation moisture on the shell, refrigeration temperature, and mechanical handling. These same factors also affect the occurrence of “thermal” cracks. Moreover, it is essential for the egg shell to possess the capability to defend against microorganisms and bacteria which can lead to internal contamination. The cuticle or bloom naturally produced by hens forms a protective barrier that effectively blocks bacteria from entering through the shell’s pores.
Washing eggs removes the cuticle on the surface, making it easier for bacteria to enter. However, the two inner shell membranes still act as barriers and protect against bacterial invasion. Maintaining good egg shell quality requires proper flock management, including nutrition and environmental conditions. This can result in high-quality shells. To ensure this, producers should avoid disturbing birds and allow eggs to spend a normal time in the shell gland without stressing the flock. Although not widely practiced, an “ahemeral” lighting program has effectively increased the time eggs spend in the uterus and resulted in thicker shells.
Nutritionally speaking, it is crucial for the producer to provide a properly formulated ration with the correct amount of calcium and phosphorus in the diet. The recommended ratio is usually 3.5-3.75% calcium and 0.45% phosphorus. The production of eggs with thick and strong shells typically happens in young flocks, while older flocks may experience more shell breakage and produce eggs with thinner shells, especially a few months after molting. Additionally, it is essential for the producer to keep a close watch on the flock’s health.
Producers need to regularly monitor their flock for diseases like Infectious Bronchitis and Newcastle, as these can cause abnormal texture and shape of egg shells. It is important to follow management practices to prevent the flock from being affected by these diseases. A common issue with egg shell quality is the occurrence of body checks, which are eggs that crack in the uterus during shell formation and then have the shell form over the crack.
In a newsletter published by the University of Georgia (Commercial Egg Tips), Robert Bastian provided suggestions for producers to decrease the issue of body checks in eggs. He advised: 1) preventing overcrowding of hens in cages to minimize contact between the hens and the cage sides, resulting in fewer body checked eggs, 2) utilizing relatively young flocks as older flocks tend to produce more body checked eggs, and 3) implementing a lighting program that does not exceed the duration of the longest natural light in open houses.
Several procedures must be adhered to in order to preserve the aesthetic quality of egg shells. Regular egg gathering helps prevent dirt and stains from accumulating on the shell. Furthermore, when washing eggs, ensure that the temperature of the wash water is approximately 20°F higher than that of the eggs. This measure is instrumental in preventing the occurrence of thermal cracks, also known as “blind checks”.
Today’s in-line commercial egg gathering has greatly reduced the occurrence of broken and cracked eggs. However, it remains crucial for producers to remain vigilant about issues within the collection system that could potentially harm the eggs. To prevent microbial contamination on the egg shells, it is essential to follow proper washing and egg processing methods. The use of suitable sanitizing agents is of utmost importance in order to maintain clean egg shells that are free from bacterial contamination.
