OXYGEN-TRANSPORT AND UTILIZATION DURING FEEDING IN THE YOUNG LAMB

1. Five lambs (19-27 days old) were studied to determine the effects o f feeding on cardiorespiratory function. 2. Each lamb was instrumented to record cardiac output, aortic and pulmonary artery pressure and ar terial and mixed venous oxyhaemoglobin saturations (S-a,S-O2 and S-v,S -O2). 3. During feeding, arterial haemoglobin desaturated and resatura ted sequentially during the periods of sucking and non-sucking. The na dir of these S-a,S-O2 desaturations (83 +/- 2%, mean +/- S.E.M.) was s ignificantly lower than the baseline value (92 +/- 2%, P less than or equal to 0.05, ANOVA). S-a,S-O2 returned to the baseline level between periods of sucking. S-v,S-O2 also decreased (55 +/- 3% baseline, 46 /- 3% sucking, P less than or equal to 0.05) but, in contrast to S-a.o 2 it remained significantly lower than baseline levels in the pauses b etween periods of sucking. 4. Arterial pressure increased during feedi ng (94 +/- 4 mmHg baseline, 113 +/- 6 mmHg feeding, P less than or equ al to 0.05), while heart rate and cardiac index did not change. 5. Tot al body oxygen consumption rose during the pauses between sucking peri ods (10.9 +/- 1.1 ml O-2 min(-1) kg(-1) baseline, 13.9 +/- 1.2 ml O-2 min(-1) kg(-1) non-sucking, P less than or equal to 0.05) and was prov ided for by a significant increase in total body oxygen extraction as systemic oxygen transport was unchanged. 6. Our results reveal that du ring feeding in young lambs oxygen consumption increases and body stor es of oxygen (e.g. S-v,S-O2) become depleted; this combination may pro mote rapid arterial desaturation and cyanosis during feeding.