Due to fat's higher energy density, incorporating it into rations may be a successful way to get more energy into the cow with the same feed volume. This is one approach to meeting the energy requirements of higher milk production without the negative metabolic effects associated with high grain feeding. However, the wrong kind or amount of added fat can create other negative metabolic problems. A producer should consider supplemental fat when high quality forages are not readily available and fat can be bought economically. Saturated fats are generally of animal origin and are solid at room temperature.
Unsaturated fats are primarily of vegetable origin and are liquid at room temperature.
The unsaturated fats are soluble in rumen fluid and may inhibit rumen fermentation and fiber digestion. Therefore, supplemental vegetable fats are of little or no advantage in most rations, especially when whole soybeans, cottonseeds, or sunflower seeds are being fed. The amount of vegetable fat already in the ration is the key factor in deciding whether to add supplemental vegetable fat. For example, a ration containing soybeans may already have all of the vegetable fat advisable. However, saturated fats such as tallow are generally insoluble in rumen fluid, have little negative impact on rumen fiber digestion, and offer the most potential for increased milk production.