Immunological and hematological characterizations of the wasting pig syndrome.

After weaning, pigs may develop a wasting syndrome characterized by slow growth, decreased disease resistance, and increased mortality. This study was conducted to determine whether differences in immune indices exist between wasting and normal pigs of a common age. Treatments were normal controls (N), wasting pigs (WP), and WP treated with the neuroleptic drug amperozide (WPA). Blood samples were taken on the day of treatment (d 0) and 7 and 21 d after treatment. Cortisol concentrations and hematological values were measured, and functional immune assays were conducted on all samples. Body weight was lower (P < .05) for wasting pigs at the start of the study. Wasting pigs and WPA also had fewer (P < .05) white blood cells, lymphocytes, and monocytes than normal pigs. The neutrophil:lymphocyte ratio, an index of stress, was greater for WP and WPA (.79, .92, and .59 +/- .07 for WP, WPA, and N, respectively; P = .008). Functional in vitro immune assays did not differ between groups. Differences in numbers of lymphocytes and monocytes in wasting pigs may result from chronic stress and contribute to the decreased disease resistance and increased mortality seen in these pigs.