Rumen-protected and rumen-unprotected fats

Diet fat concentration can be increased by adding vegetable or fish oils, or higher fat ingredients such as brewer’s or distiller’s grains. However, fat/oil from these sources is released in the rumen and is described as ‘rumen-unprotected’, ‘free’ or ‘rumen-active’ and can lead to issues in the animal such as reduced fibre digestion.

Alternatively, fat may be added in ‘rumen-protected’ form. Rumen-protected sources of fat avoid the problems in the rumen associated with rumen-active oil sources, passing through the rumen with minimal negative effects on fibre digestion.

Hence, when evaluating fat in diets, it is important to look at both the amount of fat in the total diet and the source of that fat.