The Effect of High Temperature on the Blood Calcium of the Laying Hen

Calcium and phosphorus balances with laying birds

“…Calcium sulphate gave the highest amount of calcium in the egg contents, but it was very poor from the point of view of shell formation, and in addition it produced a high negative calcium balance, indicative of poor utilization. However, Conrad (1939) has shown that with high temperatures the thickness of the shell and also the blood calcium level decrease; thus, since the calcium sulphate period was in March and April, whilst the other two periods were in November and December, it may be that this temperature effect exaggerated the poorness of calcium sulphate as a supplement. Calcium gluconate gave egg shells poorer than carbonate, but the calcium of the egg content was better; furthermore, the calcium balance over the whole period was positive.…”

“…From this brief review it is clear that there is still some disagreement on the subject of blood calcium and phosphorus in laying hens, and perhaps the work of Conrad (1939), who showed that rises in temperature from 70 to 90° F. cause a 25-35 % decrease in blood calcium, may explain the discrepancies, or at least some of them. Despite the contradictions certain facts do emerge.…”

The Changes in Egg Quality Resulting from Force Molting White Leghorn Yearling Hens

“…Since the data of Conrad (1939) and of Warren and Schnepel (1940) respectively, show that high constant temperatures will cause decreases in blood calcium and shell thickness it might be questioned whether the improvement in shell quality was due to the rest provided by the molt or to decreased temperatures following the molt. In the first experiment the average maximum atmospheric temperature during the pre-molt observation period in July was 80°F.…”

Sources of Calcium for Laying Chickens During Hot Weather

“…Several years later, Warren and Schnepel (1940), reported that when hens held under controlled air temperatures were subjected to a temperature of 90 degrees F., there was a striking reduction in the thickness of their egg shells. In connection with the latter experiment, Conrad (1939) obtained data showing that the thinning of egg shells under high air temperatures is associated, or at least coincident, with a decrease in the blood calcium level of the laying chicken.…”