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Recent Research on Shell Strength

Sep 27, 2013


A nutritional study conducted by Dr. Sally Solomon from the Institute of Biodiversity, Glasgow, United Kingdom, published in British Poultry Science* indicates the effect of bioplexed micro- mineral supplementation on shell strength through the production cycle.

The experimental design included a control diet, supplementation with sodium selenate a bioplexed selenium supplement (Sel-plex®) (Alltech) and a combination of Sel-plex® and Bioplex® a combination of mineral proteinates. 

Bioplex® supplied iron and copper at a level of 5 ppm and manganese and zinc at 20 ppm in diets. Selenium was supplemented in the form of either selenate or the commercial Sel-plex® additive at 0.3% in diets to provide 3 ppm selenium.

A significant age effect was demonstrated for egg weight, total shell thickness and dynamic strength. As expected, breaking strength declined with age with the greatest change occurring between 38 and 58 weeks in all treatments.  This parameter was associated with changes in the structure of the shell as monitored by ultra-structural visualization of the strata of the shell with special emphasis on the mammillary layer.  Strength is imparted by fusion and confluence of the mammillae. Calcite is the dominant morphological form of calcium carbonate and strength is reduced by inclusion of abnormal forms of mineral including aragonite and veterite which can be observed in electron microscope preparations. At 58 weeks of age the combination of Sel-plex® and Bioplex® contributed to confluence among mammillae and this favorable characteristic continued through to termination of the trial at 72 weeks of age.

Solomon indicated the important role of the protein matrix in molding mineralization of the shell and determining form.  Proteins associated with this process include ovocleidin 17 and ovalbumin.  Both proteins are associated with the mammillary layer but ovalbumin is a factor in formation of the palisade stratum.

Selenium, manganese, zinc, copper and iron are absorbed from the intestine more readily in bioplexed form.  These elements are critical to a number of enzymatic processes which lead to optimal shell formation and are all essential nutrients contributing to shell strength.

*Solomon, S.E. and Bain, M.M. (2012) Structural and Physical Changes in the Hen’s eggshell in Response to the Inclusion of dietary Organic Minerals. British Poultry Science.  53:343-350.