Milk production places a strain on the body of ruminants like cows. As a cow begins lactating, or producing milk, her body begins burning stored fat. The cow's body can go overboard and burn only fat for energy, resulting in health problems. Many farmers supplement their dairy cattle's diet with propylene glycol to help regulate the cows' metabolism.
Absorption in the Rumen
A scientific study published in the Journal of Animal Feed Science and Technology indicated that within 30 minutes of eating food supplemented with propylene glycol, levels in the blood will increase by 100 to 300 percent. Propylene glycol molecules have no magnetic charge, so they are absorbed easily and rapidly through the non-charged membranes of the cells that line a cow's rumen. The rumen is a stomach partition where food ferments with the help of beneficial bacteria that help cows digest high-fiber plant matter.
Promoting Insulin Production
Once in the blood stream, a metabolism study conducted by Drs. Kristensen and Raun showed that propylene glycol effectively stimulates the pancreas to release more insulin. Directly, propylene glycol makes tissues more resistant to the influence of insulin. This means that even though cells are receiving the hormone stimulus, they are not absorbing glucose, the product of carbohydrate digestion, out of the bloodstream. As part of a feedback loop, the pancreas compensates for the elevated blood glucose levels by increasing the rate of insulin secretion.
A condition called ketosis occurs when the products of digesting fat, ketone molecules, accumulate in the liver and bloodstream. One particular type of ketone, acetone, can wreak havoc on cows' health and milk production. The Merck Veterinary Manual explains that ketosis can eventually lead to lack of appetite, dehydration, aggression and even a lack of coordination in pregnant cows. As the liver breaks down propylene glycol, it produces propionate. Propionate is an important part of a chemical reaction that recycles ketones, reducing the amount of acetone in the blood and re-balancing blood fluids.
Managing Liver Function
The same reaction in which the liver uses propionate to remove acteone from the blood also turns ketones into glucose. Glucose can be used immediately for energy without side effects or stored as glycogen. When blood glucose levels are low, liver function is also low. However, with the addition of propylene glycol, the liver remains active: converting blood ketones to glucose, storing glucose as glycogen, or breaking down glycogen to provide more glucose for instant energy. A blood glucose study conducted by Drs. Pickett, Piepenbrink and Overton suggested that supplementing cows' diets with propylene glycol does not significantly raise blood sugar because excess sugar is being stored in the liver as glycogen.
Propylene glycol helps manage blood sugar levels with increased insulin production and the recycling of ketones into glucose. Normalized blood sugar levels work to increase a cow's metabolism--the rate at which it burns food for energy. This in turn increases appetite and feed consumption. By preventing the loss of appetite or by restoring it early in lactation, farmers can stop dairy cattle from going off their feed and eliminate the subsequent reduction in milk volume.