EFFECT OF ESTRADIOL-17-BETA ON PLASMA CALCIUM IN LAYING HENS

The effect of low doses of oestradiol-17 beta on plasma levels of calc ium and phosphorus in laying hens was examined. The ape of birds was 1 3 months. Water and feed were provided ad libitum. Feed was a standard commercial meal (N2) containing 40.44 g calcium/kg and 2.17 g phospho rus/kg. Hens were given an i.m. injection of 0.3 mg oestradiol dipropi onate/kg body weight (n = 5) or 0.03 mg oestradiol dipropionate/kg bod y weight (n = 5) and the control laying hens (n = 5) were given an i.m . injection of sterile saline. Blood samples were taken from the vena basilica immediately before the oestradiol or saline injection and the n 1 h, 2 h, 3 h, 24 h and 96 h after treatment to determine the concen tration of ions. The calcium concentration in both oestradiol injected groups of hens decreased gradually to the 24 h after treatment (P < 0 .004). Both doses of oestradiol increased the plasma calcium concentra tion 72 h after its depression. The calcium concentration in control h ens decreased gradually to the 3rd h after saline treatment (P < 0.002 ) and then returned to the pre-treatment level 24 h after saline injec tion. The plasma level of calcium 24 h after treatment in control hens in comparison with both oestradiol-treated groups was significantly h igher (P < 0.002). Concentrations of phosphorus in hens treated with 0 .3 mg oestradiol or saline fell steadily to the 24th h after treatment (P < 0.002) and then returned to the pre-treatment level (P < 0.002). The changes in phosphorus levels after injection of 0.03 mg oestradio l were not significant. The results suggest that low doses of oestradi ol may induce changes in plasma calcium levels.