Comprehensive morphologic, hematologic, biochemical, clinical, bacteriological and bacteriostatic investigations were carried out with newly hatched birds with and without visible pathologic deviations. It was found that birds of lower vitality were characterized by lower motor activity; weak response to external stimuli; lacking or weak pecking reflex; small, dull, and deep slightly moving or immobile eyes, with eyelids partially or fully covering the eyes; soft, colorless bill, empty crop, enlarged and stiff abdomen, imcompletely closed navel; the down being short, thin, lacking in brilliancy pigment, and density, wet and dirty; the birds having lower body weight and lower temperature, hemoglobin, erythrocyte, total protein, blood sugar, pseudoeosinophil, and eosine values; higher lymphocyte, basophile, and monocyte values; with enlarged gallbladder containing darkcolored and dense bile; the digestive viscera having lower volume; the gizzard with a dark-colored cuticle; dark intestinal content; enlarged residual yoke persisting for five days and more; inadequate adaptability to stress factors; higher death rate. It is concluded that the lack of vitality or the presence of weakness (Debilitas vitae) is diagnostically important so far as the health status of newly hatched birds is concerned. Debilitas vitae is expressed by atypical pathologic deviations and inadequate adaptability in view of the environmental conditions.
