Sodium and chloride requirements of yellow-feathered chickens between 22 and 42 days of age

Sodium and chloride are the key factors maintaining normal osmotic pressure (OSM) and volume of the extracellular fluid, and influencing the acid-base balance of body fluids. The experiment was conducted to investigate the effects of dietary Na+ and Cl- level on growth performance, excreta moisture, blood biochemical parameters, intestinal Na+-glucose transporter 1 (SGLT1) messenger RNA (mRNA), and Na+-H+ exchanger 2 (NHE2) mRNA, and to estimate the optimal dietary sodium and chlorine level for yellow-feathered chickens from 22 to 42days. A total of 900 22-day-old Lingnan yellow-feathered male chickens were randomly allotted to five treatments, each of which included six replicates of 30 chickens per floor pen. The basal control diet was based on corn and soybean meal (without added NaCl and NaHCO3). Treatments 2 to 5 consisted of the basal diet supplemented with equal weights of Na+ and Cl-, constituting 0.1%, 0.2%, 0.3% and 0.4% of the diets. Supplemental dietary Na+ and Cl- improved the growth performance (P<0.05). Average daily gain (ADG) showed a quadratic broken-line regression to increasing dietary Na+ and Cl- (R2=0.979, P<0.001), and reached a plateau at 0.1%. Supplemental Na+ and Cl- increased (P<0.05) serum Na+ and OSM in serum and showed a quadratic broken-line regression (R2=0.997, P=0.004) at 0.11%. However, supplemental Na+ and Cl- decreased (P<0.05) serum levels of K+, glucose (GLU) and triglyceride. Higher levels of Na+and Cl- decreased duodenal NHE2 transcripts (P<0.05), but had no effect on ileal SGLT1 transcripts. The activity of Na+ /K+-ATPase in the duodenum decreased (P<0.05) with higher levels of dietary Na+ and Cl-. In conclusion, the optimal dietary Na+ and Cl- requirements for yellow-feathered chickens in the grower phase, from 22 to 42 days of age, to optimize ADG, serum Na+, OSM, K+ and GLU were 0.10%, 0.11%, 0.11%,0.17% and 0.16%, respectively, by regression analysis.