Effect of induced molting on heterophil function in white leghorn hens

This study was undertaken to determine the effects of induced molt on basal functional activities of heterophils from aging hens. For this purpose, he terophils from both molted and unmolted hens were examined by in vitro bioa ssays for functional responsiveness and efficiency. We evaluated the abilit y of the heterophils to migrate to chemotactic stimuli, phagocytize opsoniz ed and nonopsonized Salmonella enteritidis (SE), and generate an oxidative burst in response to inflammatory agonists. A significant (P < 0.001) heter ophilia was found in the molted hens within 2 days after feed withdrawal an d remained throughout the length of the experimental feed withdrawal period . No significant differences were found in the random migration of heteroph ils from either group. The chemotactic movement of heterophils from molted hens was not affected until 8 days after feed withdrawal when compared with heterophil chemotaxis from unmolted hens. A significant decrease in chemot axis by the heterophils from molted hens was observed days 8-12 after feed withdrawal (P < 0.05). Significantly (P < 0.05) fewer heterophils from molt ed hens were able to phagocytize opsonized (59% vs. 38%) and nonopsonized ( 26% vs. 15%) SE within 2 days after feed withdrawal. Likewise, significantl y (P < 0.05) fewer bacteria were phagocytized per heterophil from the molte d hens when compared with the number of bacteria per heterophil from the un molted hens. The oxidative burst of heterophils stimulated by either opsoni zed zymosan A or phorbol myristate acetate of heterophils from molted hens was significantly (P < 0.05) reduced when compared with that generated by h eterophils from the unmolted hens. These results indicate that feed withdra wal to induce molt alters the number and function of peripheral blood heter ophils. This decreased efficiency of heterophil functional activity appears to play a role in the increased susceptibility of molting hens to SE infec tions.