A silicon requirement for normal skull formation in chicks

Studies were undertaken to investigate the effect of feeding a silicon (Si) -deficient diet containing a natural protein in place of the crystalline amino acid-based diets used in earlier studies. Feeding this Si-deficient basal diet with or without supplemental Si to day-old cockerels under trace element-controlled conditions resulted in the production of skull abnormalities in the deficient chicks under conditions of near optimal growth. On macropathological examination, gross changes were found in the architecture of the skulls of the deficient chicks; the frontal area was narrower and the dorsal median line at the frontal parietal junction was depressed with a narrowing both posterior and laterally, forming a stunted parietal, occipital and temporal bone area. X-ray and histological examination of this area showed less trabeculae and calcification. Biochemical analyses of the skull frontal bones for bone mineral, non-collagenous protein, hexosamine and collagen demonstrated that the frontal bones from the Si-deficient chicks had a significantly reduced collagen content. In this study, the major effect of Si appears to be on the collagen content of the connective tissue matrix, a deficiency resulting in abnormal skull matrix formation. Support is given to the earlier postulate that Si is involved in an early stage of bone formation.