POPULATION DEVELOPMENT OF ORNITHONYSSUS-SYLVIARUM (CANESTRINI AND FANZAGO) ON LEGHORN ROOSTERS INOCULATED WITH STEROIDS AND SUBJECTED TO EXTREMES OF SOCIAL-INTERACTION

High levels of social interaction or dietary administration of corticosterone or desoxycorticosterone were shown to increase resistance of roosters to Ornithonyssus sylvarium infestation. The concentration of steroid in the feed which produced this effect was critical, and increasing concentrations past this level did not appear to augment resistance. Roosters maintained under low levels of social interaction were more affected by steroids in the feed than were their high stress counterparts as measured by weight gain and selected organ weight. No difference in antibody production against horse erythrocytes was noted between birds under high and low levels of social stress, or between birds receiving different steroid treatments. Histologic examination of tissue dorsad to the cloaca indicated that mite population differences in response to stress or steroid treatment may be linked to capillary density at the skin surface. © 1979.