Dietary Calcium and Phosphorus and Variations in Plasma Alkaline Phosphatase Activity in Relationship to Physical Characteristics of Egg Shells

THE alkaline phosphatase activity of the domestic fowl as related to dietary calcium has been the subject of a number of investigations. Common (1936) was the first to demonstrate a higher and more variable phosphatase activity in laying hens than in cocks and a still higher activity if the hens were on a low calcium diet. Since then many workers, including Hurwitz and Griminger (1961) and Dumanovsky (1962), have reported a decrease in the enzyme activity as the dietary calcium increased. Hurwitz and Griminger (1961) reported that 2.6% dietary calcium was the lowest calcium level which resulted in minimum alkaline phosphatase activity in hens. Although considerable research has been conducted on the relationship of plasma alkaline phosphatase and level of dietary calcium, few studies have been conducted on the activity of this enzyme in relation to egg shell calcification. The close relationship between skeletal metabolism and shell formation is well…