The induction of ketosis in the lactating dairy cow

Summary Injections of l-thyroxine into normal dairy cows at the beginning of lactation resulted in animals fed on a high protein diet becoming ketotic. Some of the symptoms observed in the induced ketotic cows showed many similarities when compared with those associated with the spontaneous condition. In most cases the levels of the constituents estimated in the blood of the induced ketotic cows were similar to those measured in blood from spontaneous cases. A histological examination of the liver from an induced ketotic cow showed a considerable increase in the fat content, particularly in the centrilobular regions. The fat content of this tissue amounted to 26% with a concomitant depression of liver glycogen to only 10% of the normal level. Diet was found to play an important role in the susceptibility of cattle to the induced ketosis, since animals fed on rations containing a lower level of protein were more resistant. Attempts to induce ketosis in cows 6—8 months after calving were completely unsuccessful. The part played by the thyroxine and the diet in the induction of ketosis is discussed.