Dietary electrolyte balance: implications in heat stressed broilers

Modern fast-growing meat-type broiler chickens are facing difficulties in coping with heat stress. The increase in broiler growth rate increases their body heat production. The global environmental temperature is also showing an upward trend. This situation demands an efficient means to economically improve the thermotolerance of broiler chickens in hot climates without affecting their productivity. Different managemental. techniques and dietary modifications have been employed to overcome the adverse effects of heat stress. These strategies may often have proved beneficial but not all the time. Some of them even increased the cost of production. Many of these techniques did not show promising results, especially at higher ambient temperatures. This is probably due to not considering the loss of electrolytes during the periods of heat stress when panting birds are experiencing respiratory alkalosis. During heat stress, the loss of carbon dioxide (CO,) through respiration and bicarbonate ions coupled with monovalent cations (particularly sodium and potassium) through urine, disturbed the acid-base balance (respiratory alkalosis). The corrections in blood acid-base balance have been achieved by electrolyte supplementation, either through drinking water or feed. These electrolytes, in different amounts and proportions, proved beneficial for broilers under different heat stress regimens. The proportions of sodium, potassium and chloride in diets determine the dietary electrolyte balance (DEB = sodium plus potassium minus chloride, milliequivalents per kg). The discrepancies exist among different research workers about an appropriate DEB for heat-stressed broilers. Different environmental conditions in which broilers are reared; heat stress regimens (cyclic, acute, chronic), feeding regimens, source of electrolyte salts, combination of different electrolyte sources and the bird's genotype itself are factors that influence the requirements of a particular electrolyte as well as their balance in the diet. This review considers the usefulness and limitations of DEB equation, and the impact of different DEB on live performance, carcass characteristics, mortality and blood parameters in broilers reared under heat stress environments.