Two trials with terminal cross Duroc sired pigs were conducted to evaluate the influence of potassium (K) source and inclusion level in postweaning diets. In Exp 1, 1,712 pigs (11.9 ± 0.3 kg) were assigned to either a control diet (0.22% Na, 0.44% Cl, and 0.78% K), or the Control diet supplemented to 0.96% K from KCl (0.23% Na, 0.56% Cl), KHC03 (0.22% Na, 0.33% Cl), or KCl balanced to the same Na and Cl (KCl Low Cl) as the KHC03 treatment (n = 8). Pens were weighed on d-0 and 21. In Exp 2, 950 pigs (13.0 ± 0.9 kg) were fed one of five diets. The control diet from Exp 1 was used and was supplemented with 0.09% or 0.18% K from KCl or KHC03 (n = 8). All diets contained 0.22% Na. Diets were formulated to 0.40, 0.48, 0.56, 0.33, and 0.33% Cl for the control, 0.09 and 0.18% added K from KCl and 0.09 and 0.18% added K from KHC03 respectively. During Exp. 2, pens were weighed on d-0, 14, and 28. In both experiments, Na and Cl levels were manipulated by altering levels of dietary NaCl and NaPO4. Data was analyzed using the GLM procedures of SAS with pen as the experimental unit for gain, intake and feed conversion. In Exp 1, intake was unaffected by treatment (P>0.10). Gain increased in a KCL Low Cl< KHC030.10). Gain, however, was numerically higher for the 0.18% added K treatments resulting in an improvement (P<0.001) in gain to feed. From day 14 28, intake was not affected by treatment (P>0.10), however, gain and gain to feed were poorer (P<0.0001) when K level was increased compared with the controls. Gain and gain to feed were significantly lower (P<0.05) for the pigs fed diets with 0.18% added K from KHC03. These results suggest benefit to short-term (<14-d) K supplementation at 21-d post-weaning, however, long-term (> 21-d) K supplementation may be detrimental to gain and gain to feed, particularly if the supplemental K (0.18%) is supplied as KHC03.

supplement (n = 15; 12% crude protein). Within supplementation strategy, steers were assigned to either no implant, one implant at d 0 and one implant at d 56 (EI), or one implant at d 56 (LI). Steers were weighed at the initiation and termination of experiment to determine average daily gain (ADG). Blood samples were collected on d 0, 62, and 108, and blood metabolites were quantified. Supplemented steers had greater (P < 0.0001) ADG than non-supplemented steers (0.93 ± 0.05 vs 0.57 ± 0.04 kg/d, respectively). Implanted steers (EI and LI) tended to have increased (P = 0.13) ADG compared with non-implanted steers. Concentrations of prolactin and T4 were decreased (implant x time; P < 0.05) in control and LI (one steroid implant) steers but not EI (two steroid implants) steers at 108 d compared to d-62 concentrations. Cortisol was influenced by a supplement x implant interaction (P < 0.05). Supplemented EI steers had increased cortisol compared to supplemented LI steers (58.8 ± 10.0 vs 35.3 ± 9.2 ng/mL for EI and LI steers, respectively). However, non-supplemented LI steers had increased concentrations of cortisol compared with non-supplemented EI steers (56.8 ± 6.6 vs 42.2 ± 6.4 ng/mL for LI and EI steers, respectively). Supplemented steers, independent of timing of implantation, had increased (P < 0.001) concentrations of IGF-I compared with nonsupplemented steers (211.5 ± 19.9 vs 122.7 ± 11.8 ng/mL, respectively). Concentrations of T4 at d-0 were positively correlated (P < 0.05; r = 0.33) with ADG of steers. Management strategies may alter animal physiology, and those strategies should be considered when using physiological markers for the prediction or selection of animal growth.