Composition of milk fat in normal, ketotic and fasting cows.

By means of gas chromatography the authors have found changes in the composition of the milk fat in ketosis and after fasting, the concentration of short-chain fatty acids falling and of long-chain rising. This is interpreted as indicating that no essential difference in this respect exists between ketotic cows and cows after a period of fasting associated with hyperketonaemia. Since clinically healthy cows without hyperketonaemia likewise had a lowered concentration of short-chain and elevated concentration of long-chain fatty acids in the milk fat if they received a low-energy diet during the first weeks after calving, the authors question whether the impaired lipogenesis reported by others in primary ketosis is not a physiological consequence of fasting and therefore lacks aetiological significance for the primary ketosis.