Effect of supplemental sodium chloride and hydrochloric acid added to initial starter diets containing spray-dried blood plasma and lactose on resulting performance and nitrogen digestibility of 3-week-old weaned pigs

Four experiments evaluated the efficacy of Na or Cl or their combination ad ded to weanling pig diets that contained plasma protein and lactose an pig performance and N digestibility. The four experiments used a total of 563 c rossbred pigs weaned at 22 +/- I d of age averaging 6.4 kg body weight. The basal diet in each experiment contained 5.8% plasma protein and 20% lactos e and analyzed .20% Na and .23% CI. In Exp. I, NaCl was added to treatment diets at 0, .20, .40, or .60%. The trial was conducted for a 21 d period in a randomized complete block (RCB) design in seven replicates. Improved gro wth rates (P < .01) and gain:feed ratios (P < .01) occurred up to a dietary salt level of .40%. In Exp. 2, we evaluated the interaction of Na and Cl o n pig performance. The experiment was a 2 x 2 factorial arrangement in a RC B design conducted in seven replicates. Total dietary Na was .20 or .36%, a nd CI was included at .25 or .45%. Although there was a numerical increase in pig gains with added Na, the response was not significant (P > .15), but both gains (P < .01) and gain:feed ratios (P < .01) increased at the highe r dietary Cl level. In Exp. 3, we evaluated the effect of five dietary leve ls of Cl added at .06% increments to a basal diet that analyzed .34% Na and .20% Cl on postweaning pig performance. The experiment was a RCB design co nducted in eight replicates. A growth response (P < .01) to the .38% Cl lev el occurred during the initial 14-d postweaning period and to the .32% Cl l evel from 14 to 21 d. Gain:feed ratio increased each week with added Cl, bu t it was significant only for the period from d 0 to 7 d (P < .01). A N dig estibility trial, using the diets of Exp. 3, constituted Exp. 4, and groups of three pigs per stainless steel metabolism crate were pair-fed to pigs f ed the basal diet. The experiment was a RCB design conducted in three repli cates over a 3-wk period. The results demonstrated a weekly decrease in fec al N (P < .01), no effect on urinary N (P < .15), improved N retention (P < .01), and an improved apparent N digestibility (P < .01) to the .38% dieta ry Cl concentration during the initial 2 wk postweaning. These experiments suggest that although plasma protein contributed Na and Cl to the initial d iets of weaned pigs, additional Na and Cl, but particularly CZ, improved pi g growth, N retention, and N digestibility. The results suggest a dietary m inimum of .38% total Cl level during the initial 2 wk postweaning.