Effects of environmental temperature on the concentration of serum estradiol, progesterone, and calcium in maturing female domestic fowl.

The effects of environmental temperature on serum estradiol, progesterone, and calcium concentration in White Plymouth Rock pullets were investigated from 12 to 24 weeks of age. Pullets were grown from 10 weeks of age in individual cages at constant environmental temperatures of 13 C, 25 C, or 35 C. Serum estradiol land progesterone concentrations were measured by the use of radioimmunoassay. Serum calcium was measured by an atomic absorption spectrophotometer. There were no significant differences in growth rate or concentration of serum estradiol, progesterone, or calcium between pullets kept at 13 C and 25 C. There was a marked increase in serum estradiol and calcium concentration before onset of lay. There were high correlations between serum estradiol and calcium concentration in pullets kept at 13 C (r = .803) and 25 C (r = .813). Progesterone concentration in pullets kept at 13 C and 25 C reached a peak at 20 weeks of age. By contrast, pullets kept at 35 C had significantly lower growth rates and lower concentrations of serum estradiol, progesterone and calcium than those kept at the other two environmental temperatures. The high environmental temperature of 35 C inhibited growth and delayed sexual maturation of pullets.