Effects of Feeding Fats on Rumen Fermentation and Milk Composition

Milk yields of high-producing dairy cattle demand that energy intake be maximized. Energy intake is not only important during the period of peak milk production but also must be sufficient to maintain persistency of production and support body weight gain following peak milk yield. To increase ration energy density, cereal grains are used to replace forages, but this practice is limited since a certain amount of effective fiber is required to optimize ruminal fermentation, enhance nutrient digestibility, and maintain DM intake. Recent research indicates that low forage diets can be fed if starch digestion is monitored by considering source of starch, processing and particle size of the cereal grain, and nonforage fiber sources are used to dilute starch from the ration (Firkins et al., 2001). Because fat is much higher in energy per unit of weight than cereal grains, it is used to increase energy density of diets. Digestion and absorption of fat, suggested feeding guidelines for various fat sources, and the effects of feeding supplemental fat on milk composition will be discussed in this paper.