Effects of increasing salt concentration on growth performance of 11 to 30 and 27 to 65 kg pigs

Two experiments were conducted to evaluate the effects of added salt on pigs weighing 11 to 30 kg and 27 to 65 kg. Treatments were assigned in a randomized complete block design based on BW with pen as the experimental unit. In Exp. 1, 300 pigs (DNA 241×600; initial BW 11.3 ± 0.22 kg) were assigned to 1 of 5 dietary treatments containing 0.20, 0.35, 0.50, 0.65, or 0.80% salt which provided calculated total dietary Na concentrations of 0.10, 0.16, 0.22, 0.28, and 0.34% and calculated total dietary Cl concentrations of 0.23, 0.32, 0.41, 0.50, and 0.59%. There were 12 replications/treatment and 5 pigs/pen. Treatment diets were corn-soybean meal-based and fed for 27 d. From d 0 to 27, ADG and G:F improved (quadratic, P<0.05 and 0.064, respectively) up to 0.50% added salt with little benefit thereafter. In Exp. 2, 1,188 pigs (PIC 359×1050; initial BW 27.1 ± 0.31 kg) were assigned 1 of 4 dietary treatments containing either 0.10, 0.33, 0.55, or 0.75% added salt which corresponded to calculated total dietary Na concentrations of 0.10, 0.19, 0.28, and 0.36% and calculated total dietary Cl concentrations of 0.23, 0.36, 0.49, and 0.61% (all levels above NRC requirement estimates). There were 27 pigs/pen and 11 replications/treatment. Dietary treatments were corn-soybean meal-based with 20% dried distillers grain with solubles and fed for 44 d. Overall, there was no evidence for differences to indicate that increasing salt beyond 0.10% improved ADG (0.85, 0.85, 0.85, and 0.85 kg/d ± 0.008; P>0.690, respectively), ADFI (1.67, 1.69, 1.71, and 1.68 kg/d ± 0.035; P>0.734, respectively), or G:F (0.512, 0.502, 0.499, and 0.506 ± 0.009; P>0.598, respectively). In conclusion, results of these studies indicate a minimum inclusion of 0.50% added salt (total diet Na of 0.22% and Cl of 0.41%) for 11 to 30 kg pigs and there was no benefit to include over 0.10% added salt (total dietary Na of 0.10% and Cl of 0.23%) for 27 to 65 kg pigs.

Exp. 1 (d 0-27)
Item	Added salt, %					Probability, P <
	0.20	0.35	0.50	0.65	0.80	Linear	Quadratic
ADG, g	661	695	718	721	723	0.001	0.005
ADFI, g	1,075	1,089	1,116	1,142	1,129	0.001	0.211
G/F	0.616	0.638	0.643	0.631	0.641	0.024	0.064
SEM = 10.0, 15.8, and 0.006 for ADG, ADFI, and G/F, respectively.