Induction of a pause in laying by corticosterone infusion or dietary alterations: effects on the reproductive system, food consumption and body weight.

A pause in laying was induced in hens by infusing 30 micrograms corticosterone/h, feeding diets deficient in calcium or sodium and by food and water withdrawal. In hens infused with corticosterone, food consumption remained high and body weight was unchanged, although liver weight doubled. The other treatments were associated with a decline in food consumption and a loss of body weight but liver weight was unchanged. The weight of the ovary was reduced most severely in hens infused with 30 micrograms corticosterone/h, but the number of follicles weighing more than 12 mg was not altered by any of the treatments. A decrease in the number of large, yolk-filled follicles was matched by an increase in the numbers of small follicles. All treatments resulted in an increase in the number of atretic follicles. All treatments produced an elevation of plasma corticosterone concentrations within the normal physiological range, and a decrease in plasma LH concentrations. These features may constitute part of the physiological mechanism causing regression of the ovary and the cessation of egg-laying, but they do not prevent recruitment of small follicles to the stage which precedes entry into the hierarchy of large, yolky follicles.