The effect of low chloride and high bicarbonate diets on growth, blood parameters, and pulmonary hypertensive response in broiler chickens reared at high altitude

Pulmonary hypertension syndrome (PHS), commonly called ascites, is a costly metabolic disease occurring in rapid-growing chickens. Research has shown that dietary sources of energy (KHAJALI and FAHIMI, 2010) and protein (IZADINIA et al., 2010) have significant effects on pulmonary hypertensive response in broiler chickens. It has been suggested that rapid-growing broilers may be in the status of metabolic acidosis (JULIAN, 1993). Metabolic acidosis is associated with pulmonary vasoconstriction and pulmonary hypertension. Experimentally induction of metabolic acidosis initiated by infusing HCl intravenously or respiratory acidosis initiated by inhaling air containing 5% CO2 resulted in pulmonary hypertension in broiler chickens (WIDEMAN et al., 1999a). Metabolic acidosis induced by oral administration of citric acid also modulated pulmonary hypertension in broilers reared at high altitudes (HASSANPOUR et al., 2009). Chloride acidifies the diet whereas bicarbonate alkalinizes the diet. SQUIRES and JULIAN (2001) replaced dietary calcium carbonate by calcium chloride to increase the level of dietary chloride in a low-land area. Their results indicated that high chloride diets promote the onset of pulmonary hypertension because chloride causes acidosis and vasoconstriction. In this report, we describe an experiment in which sodium bicarbonate was substituted for sodium chloride in diet of broiler chickens reared at high altitude either for entire rearing period (starting from 7-day-old) or half of the period (from 21 days of age). The effect of feeding such diets on growth performance, mixed blood gas values, and pulmonary hypertensive response was studied. The objectives of the study were to investigate whether the supplementation of sodium bicarbonate instead of sodium chloride to diets of broilers kept on high altitude could result in compensating negative effects on the cardio vascular system. Materials and Methods