Nutritional factors affecting eggshell quality
1999
Nys, Y. (INRA, Nouzilly (France). Station de Recherches Avicoles)
Eggshell quality is influenced by management, nutritional and environmental factors. Adequate dietary levels of calcium have to be provided during the rearing, transition and laying periods but further increasing the level of calcium or the use of Ca step-up phase feeding system is poorly efficient. Factors favorising the supply of calcium during eggshell formation, i.e during the night, are more important. The use of coarse particle size of calcium improves eggshell quality especially in old hens compared to young ones and in hens suffering from high temperatures. High levels of dietary phosphorus are detrimental to eggshell quality. Dietary Na and K levels have a low effect on eggshell quality but elevated chloride is unfavourable. Mg is largely supplied by the vegetal feed and can depress eggshell quality when in large excess. Synthetic zeolites with high cationic-exchange capacity slightly improve shell quality. Other natural clays have a low effect on shell quality. High temperatures decrease eggshell quality as a consequence of the reduced Ca consumption and the respiratory alkalosis induced by hyperthermia.
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