INFLUENCE OF AGE AND BREED ON THE BINDING OF OXYGEN TO RED-BLOOD-CELLS OF BOVINE CALVES

The influence of somatic growth and genetic selection on the whole blo od oxygen equilibrium curve (OEC) was measured under standard conditio ns in double-muscled and dairy calves during their first 3 mo of life. Crossbreed animals were also investigated. Hemoglobin, 2,3-diphosphog lycerate (DPG), Cl, and P-i concentrations were also measured. The per centage of fetal hemoglobin (HbF) was determined. The influence of exo genous Cl, P-i, and pH on the OEC was also assessed. The Po-2 at 50% h emoglobin saturation (P-50) increased during somatic growth, probably because of the increase in DPG recorded in double-muscled neonates and to the progressive disappearance of HbF in both breeds. The oxygen ex change fraction (OEF%) was used to assess the combined influence of th e OEC shift and OEC shape changes on blood oxygen desaturation under s tandard conditions, when the Pot decreases within a physiological rang e. The OEF% showed an increase during the first month, then a stabiliz ation. The effects of Cl, P-i, and pH in Friesian calves were similar as in adult cattle. Double-muscled neonates had a lower P-50, OEF% val ues, and DPG concentrations and higher hemoglobin and Cl concentration s than Friesian neonates. The P-i concentration and the percentage of HbF were similar in both breeds. The pH and the Cl concentration had s ignificantly less effect on the OEC in double-muscled than in Friesian calves. Crossbreed animals exhibited intermediate parameter values, b etween those recorded for double-muscled and Friesian calves. All diff erences between breeds progressively disappeared during the first mont h. These data show that blood function changes markedly in calves duri ng the first month of life and that genetic selection can alter blood function.