Paying attention to body condition score, feed intake and energy metabolism can help minimize the risk of your transition cows developing fatty liver. Even moderate cases of this condition can result in decreased milk production and poor reproductive performance.
How does fatty liver develop? A dairy cow often reduces her feed intake before calving. After calving, milk production requires her to use a lot of energy. She can’t eat enough to meet her energy needs, so she starts mobilizing body reserves. You notice the effect of this negative energy balance as a loss in body condition score during early lactation. It’s normal for the cow, but in some cases it leads to fatty liver, estimated to affect half of mature dairy cows to a moderate or severe extent during the transition period.
Most of the cow’s energy reserve is in her body fat. When she needs this energy, she breaks down the fat into non-esterified fatty acids (NEFAs). They’re released into her bloodstream and processed by her liver. In excess amounts, however, NEFAs can be toxic. Excess breakdown of body fat causes high NEFA levels in the blood. When levels exceed the liver’s capacity to process them, they start accumulating. Fat deposits in the liver interfere with the organ’s function. Remember that these problems originated with the degree and duration of negative energy balance and the amount of body fat metabolized.
New research has shown that more than just fatty acids are released into the bloodstream when body fat is broken down. Dr. Richard Vernon, a British dairy researcher, reviewed the interactions between fat tissue and liver in the development of fatty liver. His review highlighted the role of several hormones released from fat, collectively called adipocytokines, as important factors in fatty liver development. These hormones signal the brain, resulting in reduced appetite. That increases or prolongs the negative energy balance as the cow continues to draw on her body fat reserves.
One of the adipocytokines is leptin. Cows carrying the genotype that programs for reduced leptin activity are less subject to appetite suppression when experiencing negative energy balance in early lactation. Currently, the best recommendations to avoid health issues resulting from negative energy balance are to dry cows off at a recommended body condition score of 3.5 to 3.75. Also, you have to manage the two most important details of feeding transition cows: optimizing feed intake and improving energy metabolism.
Optimize feed intake by:
•using high-quality feeds in a comfortable environment
•including brous byproduct feeds
•feeding minerals close to recommended levels
Improve energy metabolism with feed additives such as rumen-protected choline and Rumensin. You can’t manage the hormonal signals that may control appetite by nutritional means yet. However, by paying attention to nutrition and management details during the transition period, you can avoid fatty liver and other health issues associated with excessive negative energy balance. PD
—From Western Dairy Digest, Vol. 8, No. 1
