Eggshells are composed of around 95% calcium carbonate, a mineral that is very important for industry, nutrition and agriculture. There are many studies trying to find new ways to utilize this resource and their natural absorbent properties, as in treating cadmium in wastewater.
So, never toss out those egg shells. They’re not garbage, but can be very useful around the house and yard. They also help to save you money by replacing many expensive, toxic chemical products you might have normally used otherwise.
Most good quality eggshells from commercial layers contain approximately 2.2 grams of calcium in the form of calcium carbonate. About 95% of the dry eggshell is calcium carbonate weighing 5.5 grams. The average eggshell contains about 0.3% phosphorous, 0.3% magnesium, and traces of sodium, potassium, zinc, manganese, iron and copper. If the calcium from the shell is removed, the organic matrix material is left behind. This organic material has calcium binding properties, and its organization during shell formation influences the strength of the shell. The organic material must be deposited so that the size and organization of the crystalline components (mostly calcium carbonate) are ideal, thus leading to a strong shell. The majority of the true shell is composed of long columns of calcium carbonate. There are other zones that are involved in the self-organization giving the eggshell its strength properties. Thus, shell thickness is the main factor, but not the only factor, that determines strength. At present, dietary manipulation is the primary means of trying to correct eggshell quality problems. However, the shell to organic membrane relationship is also critical to good shell quality and must be considered.
An eggshell that is smooth is desirable, as rough-shelled eggs fracture more easily. Large eggs will usually break more easily than small ones. The main reason for this is that the hen is genetically capable of placing only a finite amount of calcium in the shell. As the hen ages and the eggs get bigger, a similar amount of calcium has to be spread over a larger surface. Therefore, controlling the rate of egg weight change can influence eggshell quality as the hen ages. Controlling feed intake by changing the temperature inside the layer house influences egg size. It must be remembered that many factors can influence the amount of calcium being laid down by the hen. Just because an eggshell is thick does not necessarily mean that it is strong. Sometimes a thinner eggshell is stronger than a thicker eggshell. The reason for this is due to the shape and organization of the organic and inorganic components of the shell.
Usually, eggshell quality is not as much of a problem in cooler environments as it is in hot environments. One of the contributing factors causing poorer eggshell quality in hot weather is hens not consuming adequate feed. This can lead to problems in body weight, egg production, egg size, and eggshell quality if measures are not taken to assure adequate daily nutrient and energy consumption. When environmental temperature becomes excessively hot, feed intake decreases, and energy becomes the first limiting factor to the hen. Inadequate consumption of amino acids, calcium, phosphorus, and other nutrients can usually be corrected by adjusting the nutrient density of the diet. However, it must not be forgotten that in hot weather, unlike cooler weather, the laying hen has to make critical life sustaining physiological adjustments in order to cope with the increased environmental temperature.
The laying hen, through panting, resists the rise in body temperature during periods of heat stress. At the same time, the acid-base balance in the bird's blood is changed. We sometimes forget that the laying hen has to cool her body in extremely hot environments and this will shift her physiological priorities from producing eggs and maintaining an...