Nitrogen balance studies with the milk-fed lamb

Abstract

1. Five male cross-bred lambs at the age of 3 weeks were starved for a period of 4 days. The utilization of nitrogen, energy and minerals was compared with the pre-starvation and post-starvation periods, when the lambs were given reconstituted dried whole cow's milk.2. The mean loss in weight during starvation was 253 g/24 h. The gain in weight during realimentation was significantly greater than that in the pre-starvation period, when adjusted for differences in energy intake.3. The urinary loss of N during starvation was 478 mg N/kg live weight 24 h. During realimentation the urinary N loss was greater than during the pie-starvation period. A higher urea excretion during realimentation was responsible for the increased urinary N.4. Excretion of ammonia, creatine, amino acid and purine base N increased during starvation. Excretion of creatinine N remained constant.5. The increase in total sulphur excretion during starvation was due mainly to an increase in the inorganic sulphate fraction. The ratio of N to S of 27: 1 during starvation was much greater than would be expected from the katabolism of muscle tissue alone (ratio N to S = 16.2:1).6. The titratable acidity and acetone excretion in the urine increased during starvation.7. There was a marked reduction in the urinary excretion of chloride, potassium and sodium during starvation, an increase in the excretion of phosphorus, but little change in the excretion of calcium and magnesium. The loss of minerals was not closely related to the losses predicted from muscle tissue alone.8. Pulse rate, respiratory rate, and rectal temperature all decreased during starvation. Heat production decreased after 1 day of starvation, but was relatively constant thereafter.9. Blood urea concentrations did not change significantly during starvation.10. The results for the lamb were in reasonable agreement with published results for the calf, except for the marked ketone acidosis and considerable increase in the excretion of purine N. The losses during starvation differed from those with the adult sheep in showing a relatively greater loss of body protein.