Seasonal changes in the white blood cell system, lyzozyme activity and cortisol level in Arabian brood mares and their foals.

In 34 pure-breed Arabian horses divided into four groups (Gr. I, ten pregnant mares; Gr. II, seven barren mares; Gr. III, ten foals born in 1981; Gr. IV, seven foals born in 1982) seasonal changes in the white blood cell system, cortisol level and lyzozyme activity were studied. Seasonal periodicity was found in all groups for the number of lymphocytes, segmented neutrophils and eosinophils and cortisol level. Leukocyte periodicity was found in three groups, but not in the barren mares. In lyzozyme activity there was periodicity in three groups but not in the youngest foals. In the stab neutrophils, basophils and monocytes no cycle was observed. The behaviour of the indices studied showed the influence of age of the horses (mature vs young) and the physiological state of the mares (pregnancy or barrenness).