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Lactic Acid, Pyruvic Acid, Amino Acids, Acetone Bodies, Oxygen, Carbon Dioxide, and Hemoglobin in Arterial and Mammary Venous Bloods of Cows under Various Physiological Conditions

Department of Dairy Industry, Storrs Agricultural Experiment Station, Storrs, Connecticut

ABSTRACT

1. The respiratory quotient of the active mammary glands of both normal and fish-oil-fed cows under nembutal anesthesia exceeded unity with mean values of 1.27 and 1.31 respectively. In experiments with nonanesthetized cows in which the per cent of fat and the low fatty acids of milk fat had been depressed by feeding fish oil, the respiratory quotient exceeded unity in 9 of the 15 experiments with a mean quotient of 1.16. On the basis of these data the suggestion that a metabolic relationship exists between the respiratory quotient of the gland and the synthesis of the lower fatty acids of milk is still in doubt.
   
2. Numerous experiments on cows under anesthesia confirm the earlier report (19) that the mammary gland does not utilize a significant amount of blood lactic acid. The mean arteriovenous value for 22 experiments was + 0.18 mg. per cent.
   
3. The mean arteriovenous difference for pyruvic acid in 26 experiments was + 0.047. Consequently, blood pyruvic acid appears to be of little significance in the metabolism of the active mamary gland.
   
4. The arteriovenous differences of lactic acid and pyruvic acid were not altered significantly on fish-oil-fed, fasted, or nonlactating cows from that observed on normal lactating cows.
   
5. Neither the utilization of amino acids nor acetone bodies were altered significantly by depressing the per cent of milk fat and the lower fatty acids by feeding fish oils.
   
6. Arteriovenous hemoglobin studies on anesthetized cows confirm earlier observations that little or no arteriovenous change occurs in unagitated cows. The per cent hemoglobin difference for 42 experiments on anesthetized cows was 0.40 and exceeded one per cent in only 5 cases.