What Is Ketosis?
Ketosis is caused by the incomplete metabolism of body fat which has been mobilized to supply energy demands. The characteristics of ketosis include: reduced milk yield, loss of body weight, loss of appetite, and occasionally, signs of nervousness. Sometimes these signs are clearly recognized (clinical) but, often, they are not easily seen (subclinical). By nature of their high energy demands, most of today's high-producing dairy cows experience some sub-clinical ketosis during the first 5 to 7 weeks of their lactation.
In the rumen, starch is generally broken down by the microbes to form propionate. Fiber is mostly converted to acetate or butyrate. All three of these volatile fatty acids are absorbed through the rumen wall and transported to the liver.
Propionate is used by the liver to make glucose. Glucose is used by the cow to make lactose, the sugar in milk. For this reason, total milk production is very closely related to the total glucose supply at the udder.
Propionate's second function involves the cow's fat metabolism. When the cow's energy demands for milk production exceed the amount of energy she is eating, she begins to break down some of her body fat stores. Fats are first broken down into smaller pieces, called non-esterified fatty acids (NEFA's), and carried to the liver. At the liver, they are broken down to form acetate and through this process, energy is generated. Acetate must then be broken down to carbon dioxide and water to yield more energy, however, this process requires some propionate. If there is not enough propionate available (which is often the case when cows are making a lot of milk sugar), the excess acetate builds up in the liver, then acetate molecules combine to make acetone, acetoacetate, and beta-hydroxybutyrate. These products are released from the liver into the cow's bloodstream, causing the ketosis symptoms.
Prevention of Ketosis
Inclusion of 125 grams FF KET Energy in the ration, provides a extra daily dose of propionate which reduces both subclinical and clinical ketosis. Propionate is used as a glucose source to make milk lactose (or milk sugar). Propionate is also used at the liver to convert acetate (from mobilized fat) to energy. Some researchers believe that calcium propionate mainly spares dietary protein from being metabolized to glucose. Thus, with the addition of calcium propionate in the diet, more amino acids are available for conversion to milk protein and total milk production increases.