Effects of Dietary Zinc Level and an Inflammatory Challenge on Performance and Immune Response of Weanling Pigs

Two experiments were conducted to determine the effect of dietary zinc level on growth performance and immune function in normal (Experiment 1) and immunologically challenged (Experiment 2) weanling pigs. Treatments consisted of the following: i) a corn-soybean meal basal diet containing 36.75 mg/kg total Zn, ii) basal diet+60 mg/kg added Zn as $ZnSO_{4}$, iii) basal diet+120 mg/kg added Zn as $ZnSO_{4}$. Each diet was fed to six pens of four pigs per pen (Exp. 1) or six pens of three pigs per pen (Exp. 2). In Exp. 1, the dietary zinc level had no effect on average daily growth (ADG), average daily feed intake (ADFI), or feed conversion ratio (FCR). Concentrations of tissue and serum zinc were not affected. Peripheral blood lymphocyte proliferation (PBLP) was not affected by dietary treatments. Supplementation of 120 mg/kg Zn decreased (p<0.05) the antibody response to bovine serum albumin (BSA) on d 7 compared with pigs fed the basal diet, but not on d 14. In Exp. 2, LPS challenge had no effect on ADG, ADFI and FCR in the entire trial (from d 0 to 21). LPS challenge significantly decreased ADG and ADFI (p<0.01) from d 7 to 14, but FCR was not affected. LPS challenge increased PBLP (p<0.05) and serum concentration of interleukin-1 (IL-1) (p<0.01), whereas the antibody response to BSA and serum concentration of interleukin-2 (IL-2) were not affected. Supplementation of Zn did not affect ADFI and FCR from d 7 to 14, but there was a trend for ADG to be enhanced with Zn supplementation (p<0.10). Supplementation of Zn tended to increase PBLP (p<0.10). Dietary treatment had no effect on the antibody response to BSA or concentrations of serum IL-1 and IL-2. Results indicate that the level of Zn recommended by NRC (1998) for weanling pigs was sufficient for optimal growth performance and immune responses. Zn requirements may be higher for pigs experiencing an acute phase response than for healthy pigs.