Search

The need for manganese for normal skeletal development appears to be related to its role in proteoglycan biosynthesis. The purpose of this research was to characterize the proteoglycans synthesized under conditions of manganese deficiency. The proteoglycans were extracted from epiphyseal growth plate cartilage and the monomers separated by cesium chloride density gradient centrifugation followed by column chromatography. The proteoglycan monomers from normal cartilage contained primarily (92%) chondroitin sulfate side chains with keratan sulfate being a minor (8%) component. Manganese deficiency reduced the total amount of cartilage proteoglycans. Of the monomers present in deficient cartilage, the majority (75%) were similar to those found in normal cartilage. Cartilage from deficient chicks also contained a second monomer fraction (25%) characterized by a reduced carbohydrate content. Thus, in addition to a reduction in total proteoglycan content, manganese deficiency results in qualitative changes in the proteoglycans present in epiphyseal growth plate cartilage.

An experiment with a factorial arrangement of treatments was conducted using five levels of dietary calcium and two levels of zeolite A. When dietary calcium was deficient or marginal, zeolite A improved calcium utilization, as evidenced by improved growth rate and a reduction in rachitic lesions. There was little benefit from adding zeolite A to diets adequate in calcium. The effect of zeolite A on the incidence of tibial dyschondroplasia was inconsistent.

The influence of the sex-linked dwarfing gene (dw) on growth and skeletal development in young male broiler chicks was investigated. Chickens that were homozygous (dw/dw) for the dwarfing gene had significantly lower BW and tibiotarsus lengths when compared with the heterozygous (Dw/dw) or normal (Dw/Dw) genotypes. All genotypes exhibited similar incidences of tibial dyschondroplasia. In contrast to several other types of dwarfism, there was no effect of the dw gene on the width of the epiphyseal growth plate or the proteoglycan content of this tissue.