Blood Clearance of Escherichia coli and Evaluation of Mononuclear-Phagocytic System as Influenced by Supplemental Dietary Zinc Methionine in Young Turkeys

Abstract

The influence of diets containing Zn-Met on in vitro and in vivo uptake of Escherichia coli by the mononuclear-phagocytic system was evaluated. Female Nicholas turkeys reared in battery brooders were supplemented with 40 μg 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 basal diets contained 130 μg Zn/g and the Zn-Met diets contained 165 μg Zn/g. Each diet was fed to three replicate pens of 8 birds in Experiment 1 and three pens of 16 birds in Experiment 2. Body weight gain, feed conversion (FC), and clearance of injected E. coli from blood were determined in Experiments 1 and 2. Abdominal exudate cells (AEC) were recruited by intra-abdominal Sephadex injection. Substrate adherence potential and incidence of macrophages in AEC, phagocytosis of E. coli 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 ≤ .003) only in Experiment 2. Dietary Zn-Met increased mean adherence of cells by 69% (P ≤ .001). The number of phagocytized E. coli per macrophage did not differ significantly between treatments; however, E. coli clearance 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 ≤ .02). Plasma ALKP activity was marginally suppressed in plasma from poults supplemented with Zn-Met.