BLOOD CLEARANCE OF ESCHERICHIA-COLI AND EVALUATION OF MONONUCLEAR-PHAGOCYTIC SYSTEM AS INFLUENCED BY SUPPLEMENTAL DIETARY ZINC METHIONINE IN YOUNG TURKEYS

The influence of diets containing Zn-Met on in vitro and in vivo uptak e of Escherichia coli by the mononuclear-phagocytic system was evaluat ed. Female Nicholas turkeys reared in battery brooders were supplement ed with 40 mu g Zn/g as Zn-Met in a corn soybean meal diet from 1 to 3 wk of age. Chemical analysis of the basal diets indicated that the ba sal diets contained 130 mu g Zn/g and the Zn-Met diets contained 165 m u g Zn/g. Each diet was fed to three replicate pens of 8 birds in Expe riment 1 and three pens of 16 birds in Experiment 2. Body weight gain, feed conversion (FC), and clearance of injected E. coli from blood we re determined in Experiments 1 and 2. Abdominal exudate cells (AEC) we re recruited by intra-abdominal Sephadex injection. Substrate adherenc e potential and incidence of macrophages in AEC, phagocytosis of E. co li in vitro in terms of percentage phagocytic macrophages, and number of internalized E. coli per phagocytic macrophage, were quantified in Experiment 1. Plasma Zn concentrations and plasma alkaline phosphatase activity (ALKP) were determined in Experiment 2. Supplemental Zn-Met improved 3-wk BW gain (P less than or equal to .003) only in Experimen t 2. Dietary Zn-Met increased mean adherence of cells by 69% (P less t han or equal to .001). The number of phagocytized E. coli per macropha ge did not differ significantly between treatments; however, E. coli c learance from blood was significantly improved in poults receiving Zn- Met in Experiment 2. Plasma Zn was higher in poults supplemented with Zn-Met prior to and after E. coli administration (P less than or equal to .02). Plasma ALKP activity was marginally suppressed in plasma fro m poults supplemented with Zn-Met.