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Synopsis
Food and calcium intake and egg shell strength were measured for 24 d with 40 laying hens fed on a daily ration of either 120 g of an all‐mash diet containing 3.25% Ca or 111 g of a 0.6% Ca diet plus 8.7 g of oyster shell. The additional calcium source was offered for a 3¼‐h period beginning at 09.00, 14.00 or 17.15 h.
Consumption of oyster shell was lowest in the morning. When the calcium meal was offered at this time, the hens slightly increased their calcium ingestion on oviposition days. However, calcium intake was higher on ovulation days when oyster shell was offered after 14 h. In each case, actual requirements seemed to be one of the main factors for determining calcium appetite.
Variations of food intake in relation to laying cycle were evident with the control diet but disappeared when oyster shell was offered separately in the afternoon. Consumption of low Ca diet was greater than that of control diet only when oyster shell was given in the late afternoon of days without ovulation.
The best egg shell quality was obtained by offering oyster shell between 14.00 h and 17.15 h but the difference with control was rarely significant. Practically it is recommended that oyster shell is given at least 3 h before light extinction.
