Using milk fat test as a ketone indicator, cows may be at risk for ketosis if milk fat test is over 4.5% for Holsteins. A milk or urine ketone test is a better indicator of elevated ketones. Drenching cows at risk with 8 to 16 ounces (1/2 to 1 pint) of propylene glycol (PG) twice a day is recommended starting three days prepartum and continuing until the fresh cow takes off and is healthy. Higher levels of PG can negatively impact rumen bacteria. Drenching PG is better than feeding or topdressing. With drenching, a larger amount of PG is absorbed and converted to glucose by the liver. This causes an insulin response which increases glucose uptake into the cell, reducing fat mobilization and ketone production. Mike Hutjens, Extension Dairy Specialist, University of Illinois - Illini DairyNET

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