Carbonate fixation in the lactating beagle dog

¹ Department of Animal Husbandry and School of Veterinary Medicine, University of California, Davis, California

A study has been made of the importance of carbonate fixation in the synthesis of milk by the lactating beagle dog. C¹⁴-labeled biocarbonate, injected intravenously, was used as a tracer of these processes. Approximately 90% of the injected C¹⁴ appeared in the expired CO₂ by 3 hours after the injection. Milk lactose was 3.5 times more radioactive than casein; very little activity was found in the milk fat. Carbonate fixation accounted for 5.3% of lactose C, 1.6% of casein C, and 0.6% of fat C. These values are 50% lower than those found earlier for the cow. This difference was found to be consistent with accepted concepts of ruminant and nonruminant metabolism.