Hypercalcemic effect of potassium iodide on serum calcium in domestic fowl

Five experiments were conducted to determine the influence of potassium iodide (KI) on serum calcium in the laying hen. Serum calcium was significantly increased when hens were fed a diet containing 5000 p.p.m. I as KI. This occurred even though feed consumption, egg production and size of ovary and oviduct were significantly decreased. In some hens fed KI, serum calcium was increased to as high as 70 mg. %, a 163% increase. Most of the increase was in the form of non-diffusible calcium. Hens fed a diet containing 0.05% calcium had significantly reduced serum calcium values. When these calcium-deficient hens were fed 5000 p.p.m. I as KI, a significant increase in serum calcium occurred within 3 days and within 7 days their average serum calcium value was significantly greater than that of hens fed a diet containing 3.00% calcium. A combination of KI plus estradiol was significantly more effective in increasing serum calcium than was either compound alone. Although these data gave no indication as to the mechanism of action of KI on serum calcium they do offer a new model in which to study calcium metabolism in the laying hen.