Fatty Acid Synthesis During Fasting and Bovine Ketosis

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Abstract
A study was made of the changes which occur in the fatty acid composition of milk fat during fasting and clinical ketosis. Samples were taken from normal Jersey, Holstein, and Guernsey cows and from the same cows following a 5-day fast or during an acute attack of ketosis. The low molecular weight fatty acids fell on the average 36 and 64 mol% from normal milk fat values in ketotic and fasted cows, respectively. A compensatory increase was noted in the long-chain fatty acids, palmitoleic, stearic, and especially oleic. Further, the percent decrease in the individual low molecular weight fatty acids appeared to be inversely proportional to their concentration in normal milk fat. This observation is not consistent with the hypothesis that a specific enzymatic defect inhibits fatty acid formation from acetate during fasting or clinical ketosis. Similarly, it seems unlikely that the diminished lipogenesis from acetate results from the preferential utilization of plasma lipid fatty acids or a shift in the normal pathway of acetate metabolism, i.e., from lipogenesis to gluconeogenesis. It was concluded that the cause of impaired acetate utilization during ketosis will remain obscure until the major pathways of fatty acid synthesis are more fully understood.