This is to complement the low natural levels available in feed ingredients. Unfortunately, these supplemented pigments can be expensive and their absorption suboptimal. Also, recent EU legislation will come into force later this year reducing the maximum allowed inclusion of these compounds. Luckily, their fat-solubility provides an opportunity. Nutritional emulsifiers are feed additives able to increase fat digestibility, both significantly and economically. Whilst improving the energy uptake and metabolization, the activity of a nutritional emulsifier also increases, indirectly, the uptake of these fat-soluble pigments. It is worthwhile investigating this effect of nutritional emulsifiers in more detail.
Mode of action
An emulsifier is a molecule with a water-soluble (hydrophilic) part and a fat-soluble (lipophilic) part. The combination of these two components in one molecule gives it a unique property. The emulsifier can dissolve in fat as well as in water and can aid in mixing these two factions. In the animal, fat digestion occurs in a few steps (Figure 1). Initially, large fat globules are emulsified in the watery environment of the gut. Normally, fat and water do not mix, and therefore, bile salts assist in this mixing process as natural emulsifiers. Smaller fat droplets are formed and increase the contact surface for the lipase enzyme. This enzyme, produced by the pancreas, breaks down fat. The next step is the formation of micelles. Micelles are water-soluble aggregates of lipid molecules (e.g. carotenoids) containing both polar and non-polar groups. When micelles come into contact with the micro villous membrane, they are disrupted and the fatty acids are absorbed by the lipophilic cell membrane. Bile salts and monoglycerides aid as natural emulsifiers in the formation of micelles. Nevertheless, the capacity of these natural emulsifiers can be a limiting factor for fat digestion. Nutritional emulsifiers can therefore assist in improving fat digestibility and energy efficiency. Results show that a nutritional emulsifier is able to increase crude fat digestibility by 2.81% on average. Its positive effect will be more pronounced at higher fat levels. Even with highly digestible fats (e.g. soybean oil) significant effects are shown.