POTASSIUM-CHLORIDE IMPROVES THE THERMOTOLERANCE OF CHICKENS EXPOSED TO ACUTE HEAT-STRESS

Experiments were designed to test the hypothesis that chicks that dran k an electrolyte solution containing K prior to and during an acute ex posure to heat would have greater thermotolerance than chicks that con sumed only water. In three experiments, 5- or 7-wk-old male chickens d rank distilled water (control), or .3, .6, or .9% KCl solutions (Exper iments 1 and 2), and .6 or .9% KCl or .8% KHCO3 solutions (Experiment 3) for 48 h before acute heat stress (HS) and during HS. Body temperat ure (T-b), blood pH, partial pressure of blood carbon dioxide (pCO(2)) , ionized Ca (Ca2+), plasma Na, K, Cl, total Ca, inorganic P (P-i), an d osmolality (Osm), and water consumption were determined. Water intak e increased with the concentration of KCl. Before HS, .6% KCl increase d plasma K and Ca2+ whereas .9% KCl resulted in a marked increase in K , Ca2+, Na, Cl, and Osm and a decrease in pH. During HS,.6% KCl-birds had lower hyperthermic T-b and pH values and higher Ca2+ and K concent rations than controls. Plasma Na and Osm of .6% KCl birds decreased wh ereas those of the control birds remained unchanged. Providing K as KH CO3 aggravated respiratory alkalosis and failed to influence either T- b or plasma electrolytes, suggesting that the beneficial effect of .6% KCL may in part be attributed to the accompanying Cl. Hyperthermic T- b and Ca2+ values were highly correlated. The results showed that .6% KCl solution reduced HS-related responses and indicated a relationship among supplemental KCl, blood Ca2+, and T-b.