Studies on the Bovine Electrocardiogram. I. Electrocardio-graphic Changes in Calves on Low Potassium Rations. ∗

Four calves were placed on a semipurified ration which analyzed 0.10-0.12% potassium. Four control calves were given the same ration except that potassium was added to bring the level of this constituent to 0.35%. The animals were placed on this ration at 160 days of age. Previous to this they received whole milk and a small amount of hay and grain.

Electrocardiograms were usually taken at monthly intervals, but for some periods more frequently. The electrodes, which were of the German silver plate type, were placed on the upper part of the 2 fore limbs and just above the hock on the left hind leg. The areas on which the electrodes were placed were clipped, cleaned and covered with electrode paste applied with vigorous rubbing.

Serum potassium determinations were made on all calves at 2-week intervals, more often when deemed necessary, by a modification of the titrimetric method of Shohl and Bennett. 1

Plasma calcium, phosphorus, and magnesium determinations were carried out at weekly intervals in order to make certain that the ration was not deficient in these elements.

Blood Changes. Calf C 394. On the 270th day of the experimental period this calf had a serum potassium value of 17.0 mg %. Seventy days later this value had fallen to 10.2 mg % and for a period of about 60 days it remained below 13.5 mg %. On the 350th day of the experiment the potassium in the ration was increased to 0.20% for a period of 130 days after which the potassium was again reduced. During this 130-day period the serum potassium level increased to 18.0 mg %, and it has since varied between 15 and 18 mg % in spite of the reduction of potassium in the ration.