Effects of increasing chloride from potassium chloride on 7 to 12 kg nursery pig growth performance

A total of 300 nursery pigs (DNA Line 241×600, initially 7 kg) were used in a 14-d trial to determine effects of increasing dietary Cl concentrations on nursery pig growth performance. Pigs were weaned at 21 d of age. Upon entry to the nursery, pigs were grouped in pens of 5 consisting of either a 2:3 or a 3:2 ratio of barrows:gilts, and fed a common starter diet (0.33% Na and 0.76% Cl) for 7 d. On d 7 after weaning, considered d 0 in the trial, pens were blocked by BW within each sex ratio and randomly assigned to treatments, with 10 pens/treatment. Experimental treatments consisted of a control diet containing 0.33% Na and 0.55% Cl provided by 0.78% added salt and 5 diets with 0.33% Na and added potassium chloride to provide 0.09, 0.21, 0.32, 0.45, or 0.55% Cl. Dietary K was not held constant across dietary treatments. Growth performance (ADG, ADFI, G:F) was recorded at the pen level and analyzed using linear mixed models that accommodated the split-plot nature of the experimental design and recognized pen as the experimental unit for treatment. Linear and quadratic orthogonal polynomials were evaluated. Additionally, the 0.78% added salt control and 0.55% Cl treatment were compared. From d 0 to 14, ADG, ADFI, and G:F improved (quadratic, P < 0.05) as dietary Cl concentration increased from 0.09 to 0.32% with no further benefit observed thereafter. Pigs fed the control diet (0.33% Na and 0.55% Cl from added salt) showed no evidence for a difference in ADG, lower (P < 0.05) ADFI and marginally increased (P = 0.069) G:F than those fed 0.55% Cl from KCl. In conclusion, the greatest growth performance was achieved with a dietary Cl concentration of 0.32% in pigs from 7 to 12 kg.

	Cl, %
Item	0.09	0.21	0.32	0.45	0.55	0.78% added salt	SEM
ADG, g1	273	348	372	349	356	351	0.676
ADFI, g2,3	436	491	507	477	504	469	0.046
G:F1	0.628	0.712	0.734	0.733	0.708	0.749	0.069
1 Cl linear: P<0.001; quadratic: P<0.001; 2 Cl linear: P<0.05; quadratic: P<0.05. 3 Added salt diet vs. 0.55% Cl diet: P<0.05.