Effects of sodium and chloride source and concentration on nursery pig growth performance.

Three studies were conducted to determine the effects of source and concentration of Na and Cl on pig growth performance from 7 to 12 kg. In all three experiments, pigs were fed a common diet (0.33% Na and 0.77% Cl) for 7 or 8 d after weaning then randomly assigned to dietary treatments. In Exp. 1, 360 mixed-sex pigs were used in a 14-d study with 15 replications per treatment and six pigs per pen. Treatments included a 10% dried whey diet with 0.60% added salt (0.37% Na and 0.75% Cl); or three diets with 7.2% crystalline lactose with either: 0.35% added salt (0.18% Na and 0.47% Cl); 0.78% added salt (0.35% Na and 0.72% Cl); or 1.15% NaHCO3 and 0.40% KCl (0.35% Na and 0.45% Cl). Pigs fed the 0.78% added salt-lactose diet had greater (P < 0.05) ADG than pigs fed the 0.35% added salt-lactose diet, with others intermediate. In Exp. 2, 360 barrows were used in a 14-d study with 12 replications per treatment and five pigs per pen. Treatments included two added salt diets (providing 0.13% Na and 0.35% Cl or 0.35% Na and 0.68% Cl), three diets with Na and Cl provided by KCl and NaHCO3 (0.13%, 0.35%, or 0.57% Na and 0.50% Cl), or a diet with NaHCO3 and CaCl2 (0.35% Na and 0.50% Cl). Regardless of Na source, ADG and ADFI increased (quadratic, P < 0.05) as dietary Na increased from 0.13% to 0.35%, with no further benefits observed thereafter. There was no evidence for differences among pigs fed NaCl or NaHCO3 nor evidence for differences among pigs fed the different Na and Cl sources at similar concentrations. In Exp. 3, 300 pigs were used in a 21-d trial with 10 replications per treatment and five pigs per pen. Treatments included a control diet with added salt to provide 0.33% Na and 0.55% Cl or five diets with 0.33 % Na and added KCl to provide 0.09, 0.21, 0.32, 0.45, or 0.55% Cl. ADG and G:F increased (quadratic, P < 0.035) as Cl increased from 0.09% to 0.32%. Pigs fed the control diet (added salt) and the 0.55% Cl diet had similar ADG. For ADG and ADFI, the broken line linear model indicated a breakpoint of 0.23% Cl. For G:F, the quadratic polynomial model suggested the maximum at 0.38% Cl. In conclusion, 7 to 12 kg pigs fed diets that contained at least 0.35% Na and 0.38% Cl had greater ADG and G:F compared to pigs fed diets with lower concentrations and minimal effects were observed among the sources of Na or Cl used in these studies.