Blood oxygen binding in double-muscled calves and dairy calves with conventional muscle conformation

Objective-To assess in vivo blood oxygen binding in double-muscled calves and dairy calves with conventional muscle conformation. Animals-58 dairy and 48 double-muscled calves. Procedure-Calves were classified as neonatal (24 hours old) or older calves (2 to 26 days old). Venous and arterial blood samples were collected, and hemoglobin concentration, pH, P-CO2, and P-O2 were determined. Blood oxygen equilibrium curves (OEC) under standard conditions were constructed, and the oxygen exchange fraction (OEF) and the amount of oxygen released at the tissue level by 100 mi of blood (OEF Vol%) were calculated, Results-In each breed, partial pressure of oxygen at 50% saturation of hemoglobin (P-50) under standard conditions was significantly higher in older than in neonatal calves, indicating a right shift in OEC with age. Venous P-50 was significantly lower in neonatal double-muscled calves than in neonatal dairy carves, but arterial and venous P-50 were significantly higher in older double-muscled calves than in older dairy carves, in double-muscled, but not in dairy, calves, OEF was significantly higher in older than in neonatal calves. In neonatal carves, OEF Vol% was not significantly different between breeds, but OEF Vol% was significantly higher in older double-muscled calves than in older dairy calves, Conclusions and Clinical Relevance-The lower OEF in neonatal double-muscled calves, compared with dairy calves, could contribute to the higher sensitivity of double-muscled calves to hypoxia, Blood oxygen affinity decreased with age, but OEF and OEF Vol% were unchanged with age in dairy calves, whereas they increased with age in double-muscled calves.