During lactation stage, dairy cows require large amount of energy. Fat supplements would be a suitable choice to increase ration energy density. When considering fat supplements, the provision of fat in basal ingredients and byproducts must be accounted for first. Take forages for example, they usually contain approximately 2-3% fatty acids, with corn silage being higher than alfalfa or grasses because of the higher oil content of the corn grain. Hence, nutritionist need to account for the various byproduct feeds. Examples of byproduct feeds include distillers' grains, bakery waste, and fish meal.

​

There are currently a wide variety of fat supplements available in the market. Fat supplements would include commodities such as tallow, white grease, yellow grease, animal-vegetable blends, and also commercial fat supplements which are designed to "bypass" the rumen. Commercial fat supplements that "bypass" are much preferable as they have less effects on rumen fermentation compared to native fats. One other advantage is that they are also "dry" fats, hence they can be handled much easier without any sort of heated storage tanks.

​

There are 3 main ways to produce "bypass" fats. First, one can increase the saturation of fatty acids in the product so that the melting point is above the range of environmental temperatures (typically above 54°C). This will decrease the solubility and the potential interaction of fats with the rumen microbes. Next is to combine fatty acids with calcium to form calcium salts (or calcium soap). Due to free fatty acid required for biohydrogenation and interaction with microbes, tying up the fatty acids as soaps will be able to prevent this interaction up to a certain degree. Finally, fats can be "encapsulated" in several ways to physically prevent interaction with the ruminal microbes. These can be non-nutritive compounds (sodium alginate) or formaldehyde treatment of proteins to prevent rumen access but allow intestinal access. Of these strategies, only the first two are used widely. Formaldehyde-treated products are not approved for use in the US, although they are currently used in Australia and some other countries. 

​

Increasing the saturation is a very effective way to produce highly digestible free fatty acid products but it is not desirable for intact triglycerides. Highly saturated triglycerides such as hydrogenated tallow or hydrogenated soybean oil are very poorly digested
because not only microbial cells are denied access but also the pancreatic lipase enzyme of the cow is unable to split the fatty acids off of the triglyceride molecule. However, a moderately saturated mixture (PalmFat S100) of free fatty acid product is well digested because of the unique digestive system of the ruminants.

​

Calcium salts of long chain fatty acids is another type of fat supplement. Such products (PowerFat) are easily handled and are more "inert" in the rumen than native fats. The unsaturated fatty acids in the calcium salt products are only partially protected from rumen biohydrogenation, and this protection is less complete with PUFA than with the oleic acid found as a major component of palm oil. Fatty acids in calcium salts of palm oil is very highly digestible.