PSIV-B-19 - Determining the Effect of Zinc Status on Eye Health and Its Relationship with Infectious Bovine Keratoconjunctivitis in Beef Calves

Abstract: Crossbred beef calves (n = 30) were stratified by gender and BW and placed into 1 of 16 dry lot pens. Pens were allocated to either: 1) the control treatment (CON) with calves fed a basal ration containing 31 mg of zinc/kg DM; or 2) Zn supplemented treatment (SUP) with calves fed the basal ration supplemented with 30 mg of zinc/kg DM (provided as zinc amino acid complex). Growth performance was recorded every 28-d during the 143-d study. On d 115, cattle were given a commercial vaccine containing M. bovis and M. bovoculi bacterins. Blood samples were collected and analyzed for serum zinc, alkaline phosphatase activity (ALP, 28-d intervals), and vitamin A (d 0 and 143). Samples for serum and tear IgG concentrations specific for M. bovis and M. bovoculi were taken on d 115, 129, and 143. Data were analyzed as repeated measures, where appropriate, using the MIXED procedure of SAS. Dietary zinc status did not impact liver or zinc concentrations (P ≥ 0.36), BW (P ≥ 0.66) or ADG (P ≥ 0.14). There was no effect of treatment (P ≥ 0.16) or treatment by time interaction (P > 0.39) on tear IgG specific for either M. bovis or M. bovoculi. However, serum IgG concentrations specific for M. bovis were greater (P = 0.02) in CON calves compared with SUP calves, and serum IgG concentrations specific for M. bovoculi tended (treatment by time, P = 0.08) to increase more in CON calves. Both serum and tear IgG concentrations specific for either bacterin increased (day effect, P < 0.001) from d 115 to 143. Results did not support a relationship between dietary Zn and eye health in cattle. However, this could be explained by the similarity in liver and serum zinc concentrations.