Nutritional Factors Affecting Eggshell Quality

The following article is a special collaboration from AFMA (Animal Feed Manufacturers Association) www.afma.co.za
We thank their kind support.

ABSTRACT
The hen's eggshell has a perfectly ordered structure, sequentially elaborated during a defined period in the isthmus and the uterus. It is composed of calcium carbonate pervaded by a small amount of organic components, which are believed to influence calcite nucleation and growth and consequently, the biomechanical properties or the eggshell. Eggshell quality, therefore, depends on the supply of ionic material, calcium and carbonate and also on the organisation of eggshell deposition. At the production level, management as well as nutritional and environmental factors, influences eggshell quality. Adequate dietary levels of calcium have to be provided during the rearing, transition and laying periods but increasing the level of calcium further or the use of Ca step-up phase feeding system is poorly efficient. Factors favouring the supply of calcium during eggshell formation, i.e. during the night, are more important. Midnight feeding can improve eggshell quality. The use of coarse particle size of calcium improves eggshell quality especially in old hens compared to young ones and in hens suffering high temperatures. Th origin of the calcium source has little affect on the response. Particle size should be between 1 and 4 mm. Pelleting process (crumble feed) decreases calcium particle size and could therefore reduce the positive effects of Ca particle size. An elevated consumption of saturated fatty acids leads to the formation of calcium soaps and decreases calcium and fat retention. There are no negative effects on shell quality when dietary fat is lower than 6%. High levels of dietary phosphorus are detrimental to eggshell quality and 0.3% available phosphorus allows normal performance and bone integrity. Dietary Na (minimum 0.12%) and K levels have little effect on eggshell quality but elevated chloride (>0.2%) is unfavourable. Mg is largely supplied by the vegetal foodstuffs (1500 mg/kg) and can depress eggshell quality when in large excess (>5000 mg/kg). Synthetic zeolites (0.75%) with high cationic-exchange capacity slightly improve shell quality but they solubilized in the intestine and provide aluminium. Other natural clays have little effect on shell quality. Increasing vitamin D dietary level has no influence on eggshell quality and dietary supplementation with its active metabolite has low effects.




High temperatures decrease eggshell quality as a consequence of the reduced Ca consumption and the respiratory alkalosis induced by hyperthermia. The positive effects of nutritional factors (coarse calcium particle, zeolites) are more pronounced in hot environments, and additional factors may be useful: carbonated the incidence of eggshell breakage, which remains elevated despite considerable efforts in manipulating the nutritional, environmental or genetic factors.