Body temperature and blood chemistry responses in broiler cockerels given a single intravenous injection of Na+ or Ca++ before an acute heating episode.

Eight-week-old broiler cockerels were injected intravenously with avian saline containing additional Na+ as NaCl or Ca++ as CaCl2. After the injections half of the chickens were heated at 45 degrees C. and the others were maintained at 24 degrees C. Cloacal body temperatures were determined and blood samples were collected before heat exposure and at 30 minute intervals until the chickens had been heated for 120 minutes. Na+ did not affect body temperature of chickens in the 24 degrees C. environment, but Na+-treated chickens in the 45 degrees C. environment had significantly elevated body temperatures compared to the heated controls. Ca++ caused a significant decrease in body temperature of the non-heated chickens, but it was without effect in heated chickens. Neither Na" nor Ca++ altered the responses of plasma glucose, cholesterol, and calcium during the heating episode. However, Ca++ caused a significant rise in plasma inorganic phosphate in non-heated chickens and prevented the rapid decline in the heated chickens. Na+ caused a significant fall in plasma inorganic phosphate in non-heated chickens, but it did not alter the plasma phosphate response to acute heat stress. The present experimental resultn chickens in a moderate temperature environment, and suggests that Ca++ initially exerts a peripheral rather than a central effect in decreasing the body temperature.