Studies on the Relationships between Rumen Acids and Fat Metabolism of Ruminants Fed on Restricted Roughage Diets

The feeding of restricted roughage with high levels of concentrates produced significant declines in milk fat in lactating cows and goats. Associated with the decline in milk fat were a signficant increase in the concentration of tureen propionie acid and a deeremse in blood ketone bodies. There was a decrease in arterial-blood acetic acid and in the arterial-nmmmary difference under conditions of ground and restricted-roughage feeding. The feeding of sodium acetate tended to increase low milk fat, and the feeding of sodium propionate tended to lower it further. An hypothesis regarding a mechanism of milk-fat depression based on the antiketogenic properties of propionic acid is discussed.