Laying hen responses to acute heat stress and carbon dioxide supplementation: II. Changes in plasma enzymes, metabolites and electrolytes.

Exposure of laying hens to an acute heat stress period (38 degrees C) produced a decrease (P < or = 0.05) in blood plasma magnesium compared with pre-heat stress (23 degrees C) levels. Blood plasma glucose, alkaline phosphatase, total protein, uric acid and creatinine were not changed (P > or = 0.05) by exposure to 38 degrees C compared with the first 23 degrees C exposure. Inorganic phosphorus, calcium, potassium and sodium levels were not affected by acute heat-stress exposure or carbon dioxide addition. These results suggest that acute heat stress had no dramatic effect on plasma enzymes, metabolites and electrolytes of laying hens.