In early lactation, in particular, the use of propylene glycol lowers the concentration of ketone bodies in the blood, milk and urine. This special effect of the propylene glycol can be explained through its direct conversion to oxaloacetate, and the resulting rapid elimination of the frequently occurring lack of oxaloacetate. Oxaloacetate is crucial in the energy metabolism of cows. Propylene glycol thus supports the metabolism in the liver very effectively by forming fewer ketone bodies, and reduces the risk of ketosis. Other after-effects such as milk fever, placenta problems and mastitis occur less frequently as a result. The use of propylene glycol also leads directly to a higher concentration of glucose in the blood. Numerous studies have shown increased milk production has been accompanied by lower concentrations of BHB (beta-hydroxybutyrate) in the blood.
Overall, the effect of propylene glycol is different to that of glycerol. Specifically, in dairy cows that are accustomed to glycerol, using this leads to a higher concentration of butyric acids in the rumen, which can further increase the risk of ketosis. 1,2 Propandiol USP thus contributes to a higher milk yield and lifespan, and makes the health of the animals more stable.