The Effect of Continuous Intravenous Feeding of Various Substances upon the Secretion of Milk Fat

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Abstract
Continuous intraven. feeding of cows was achieved by fixing a rubber catheter in one of the subcut. abdominal mammary veins. Several substances were administered in an attempt to prevent the marked decrease in the lower fatty acids of milk fat which occurs during a fasting period of 24 hrs. The substances administered were glucose, "pepticase", Na oleate, Na acetate and Na butyrate. The animals were not allowed access to other nutrients during the course of the expts. Reichert-Meissl values, Polenske values and Iodine numbers were obtained on milk fat obtained before, during and after the administration of the above substances. Nine cows were fed by the intraven. route. 1985 g. of glucose were injd. in 31 hrs., 1984 g. of Na acetate in 22 hrs., and 1057 g. of Na butyrate in 29 hrs. Neither glucose nor Na acetate prevented the decrease in the lower fatty acids of milk fat typical of fasting. The data on Na butyrate are inconclusive, the lower fatty acids being maintained in one case but not in the 2 succeeding expts. Na oleate and a protein hydrolysate "pepticase" were ineffective in preventing the decrease in the lower fatty acids. A summary of the work to date, together with the data reported in this paper to the effect that the maintenance of the blood glucose of the fasted cow at a high level does not prevent or retard the decrease in the lower fatty acids, is believed to be conclusive evidence that the mammary gland does not synthesize the lower fatty acids from blood carbohydrate.
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