The relationship between reproductive activity and blood calcium in the calcium‐deficient hen

Abstract

The dependence of reproductive activity in the laying hen upon adequate Ca intake was investigated. The response of plasma luteinizing hormone [LH] concentration in Ca-deficient, as compared with Ca-replete hens, to injections of LH releasing hormone and progesterone suggested that the primary site of reproductive dysfunction is the hypothalamus rather than the pituitary gland. Laying hens, when presented with a Ca-deficient diet, ceased to lay as the plasma ionized Ca concentration decreased to < 1.0 mM, supporting the view that there is a threshold of blood Ca activity below which reproductive activity ceases. Supplementation of the diet with Ca produced an immediate restoration of plasma ionized Ca concentration to normal, despite an interval of a few days before the plasma total Ca returned to normal and egg laying resumed.