The alleviating effect of dietary electrolyte balance levels on heat stress via regulating water and ion metabolism in Pekin ducks.

1. The objective of this study was to evaluate the effects of dietary electrolyte balance (DEB) concentrations on growth performance, heat sensitivity biomarkers and water and ion metabolism of meat ducks under heat stress (HS).2. A total of 400, 28-d-old Cherry Valley male meat ducks were randomly divided into five treatment groups (eight pens per treatment with 10 birds/pen), with dietary different DEB values, 120, 160, 200, 240 and 280 mmol/kg.3. Ducks in the 240-mmol/kg DEB group had a tendency (p = 0.098) for increased body weight at 41 d of age. The 240-mmol/kg DEB group displayed the numerically highest daily gain, the best FCR and lowest mortality among all treatment groups. Serum corticosterone (CORT) concentration in ducks from the 240-mmol/kg DEB group was significantly lower than that in the 280-mmol/kg DEB group (p < 0.05) and chlorine concentration had a tendency to fall (p = 0.083).4. The 240-mmol/kg DEB group significantly upregulated the expression of aquaporins (AQP) mRNA in the small intestine (AQP3 and AQP7), kidney (AQP3, AQP7, AQP9 and AQP10) and thenasal salt gland (AQP3 and AQP10). In addition, it upregulated the expression of ion transporter (Na-K-Cl cotransporter and Na-/K-ATPase) mRNA in the small intestine, kidney and nasal salt gland.5. Based on the overall benefits in growth performance, biochemical measures, tissue AQP and expression of ion transporters, an optimal level of DEB in diets for heat stressed ducks was 240 mmol/kg.