Relationship of Plasma Free Fatty Acids to Other Blood Components in Ruminants under Various Physiological Conditions

Abstract
The normal concentrations of plasma free fatty-acids (FFA) and their relationship to blood sugars and blood ketones were determined in cows and goats. Plasma FFA concentrations in cows and goats were within the ranges reported for nonruminant species (100-2000 [mu]g/l), but were lower (200-300 [mu]eg/l) than values reported for nonruminants under normal nonf asting conditions. The plasma FFA concentration was depressed 4-6 hours after feeding, at which time blood sugars were depressed and blood ketones increased. The plasma FFA concentration increased, while the blood sugars were depressed and blood ketones increased upon fasting. The response of all blood components to feeding or fasting was much greater in milking than in dry animals. Correlations under fed and fasting conditions were: sugar vs ketones, -.54, -.63; sugar vs FFA, .01, -.75; ketones vs FFA, .10, .81. Blood sugar may control ketogenesis under both fed and fasting conditions, but plasma FFA are a primary source of ketones only under fasting conditions. The plasma FFA concentration which was elevated at parturition, was not consistently higher at the time of peak milk production.