Propylene Glycol and Glycerol as a Feed Additive for Lactating Dairy Cows: An Evaluation of Blood Metabolite Parameters

An extensive trial for testing the antiketogenic potency of glycerol and propylene glycol (DL-1,2 propanediol) was conducted with milking Holsteins and Ayrshires over a 2-yr period. Through weekly blood analyses of free fatty acids, glucose, β-hydroxybutyrate, and acetoacetate for an 8-wk period post-partum, it was possible to classify these cows as normal, clinically ketotic, and subclinically ketotic. The results showed that in cows that were not stressed by either high lactation yield or low concentrate intake these chemical additives only slightly depressed blood ketones and free fatty acids below control values. The beneficial properties of these additives became obvious in cows stressed by adverse environmental factors and slightly reduced levels of concentrate intake. In these cows, the addition of propylene glycol to the concentrate ration significantly reduced blood ketones and plasma free fatty acids and increased the concentration of blood glucose. It was concluded that the use of propylene glycol as a feed additive (3 and 6% of the concentrate) should be economically attractive in high-producing dairy herds because it will significantly decrease the incidence of clinical and subclinical ketosis in cows during the immediate postpartum period (4–8 wk) when they are most susceptible to the metabolic disorder.