Voluntary food and calcium intake by the laying hen

Synopsis

Two experiments, each of 40 d duration, are described in which a diet rich in calcium (3.5% Ca) or one deficient in calcium (1% Ca), but with oyster shell offered separately, were fed ad libitum to four laying hens. The voluntary consumption of food and oyster shell was automatically recorded every 2 h. The hourly consumption of the high Ga diet increased during the afternoon while the daily pattern of consumption was modified by the position of the egg in the clutch.

When the low Ca diet was fed with oyster shell, the daily consumption was increased but the effect of the position of the egg in the clutch was reduced. The ingestion of oyster shell was very high between 16.00 and 20.00 h when egg calcification was in progress; after the last oviposition of the clutch this elevated level of intake remained though to a lesser degree. In relation to the stage of egg formation, the voluntary intake of oyster shell increased sharply between 4 and 12 h after the former oviposition.

These results confirm that the laying hen can discriminate between food and calcium intake. It seems that appetite for calcium is firstly related to light‐dark cycles with a modulation of the afternoon peak by ovulation and then egg shell calcification.