The effect of reciprocal crosses between dwarf and normal parents on blood constituents of the progeny.

1. Heterozygous cockerels which inherited the sex-linked recessive dwarfing gene (dw) from a normal dam had significantly different contents of sodium and potassium in the blood serum compared with heterozygous cockerels from dwarf dams. 2. Hemizygous dwarf pullets had a significantly lower packed cell volume than normal pullets, while mean corpuscular haemoglobin concentration was significantly lower in the normal pullets. 3. Total serum calcium values were significantly higher in normal pullets. Sodium concentration was higher in dwarf pullets. It is suggested that the better adaptation of dwarf pullets to higher temperatures might be due to their capacity to retain more water in body tissue under a stressful environment.