Effect of supplemental sodium chloride, sodium phosphate, or hydrochloric acid in starter pig diets containing dried whey

Three experiments involving a total of 606 pigs weaned at 23 +/- 2 d of age were used to evaluate the effects of added dietary Na or Cl or both in combination (NaCl) on postweaning performance responses. A basal diet without added NaCl was formulated to 1.20% lysine using a corn-soybean protein mixture with 20% dried whey (C-SBP-DW) and was used in all experiments. The analyzed content of the basal diet for the three experiments averaged 19% Na, .37% Cl, and 1.37% K. In Exp. 1, NaCl was added to treatment diets at 0, .20, .40, and .60% at the expense of corn. The experiment was a randomized complete block (RCB) design conducted in 14 replicates using a total of 336 pigs (six pigs/ pen). The results demonstrated a linear (P < .01) growth response during the 0- to 7-d and a quadratic (P < .08) response during the 8- to 14-d period. Gain:feed ratio improved quadratically (P < .08) for the 0- to 14-d period. In Exp. 2, Na2HPO4 added to the C-SBP-DW basal diet provided supplemental Na levels of 0, .08, .16, and .24% Na to four treatment diets. The experiment was conducted in six replicates in a RCB design using a total of 144 pigs (six pigs/pen). The results demonstrated a linear (P < .05) growth response during the 0- to 7-d period as Na level increased, but not thereafter, and an improved gain: feed ratio (P < .05) for the 0- to 14-d period. In Exp. 3, Cl was added as HCl at 0, .05, or .10% Cl to the basal C-SBP-DW diet. The experiment was a RCB design conducted in six replicates using a total of 126 pigs (five or six pigs/pen between replicates). The results demonstrated a linear growth (P < .01) and feed intake (P < .08) response during the 0- to 7-d and the 0- to 14-d period to increasing levels of Cl. Feed intake also increased for the 0- to 7-d (P < .08), and 8- to 14-d (P < .05) periods. Stool looseness was unaffected by any of the dietary variables in the three experiments. These results suggest that the NRC (1988) recommendations for Na and Cl for young pigs (< 10 kg BW) may need to be increased.