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 the unique property that the emulsifier can dissolve both in fat and in water and can aid in mixing these two fractions. In the animal, fat digestion occurs in a few steps. 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 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. Exogenous nutritional emulsifiers can therefore assist in improving fat digestibility and energy efficiency. Their positive effect will be more pronounced at higher levels of added fat. Even with highly digestible fats (e.g. soybean oil) there is a significant effect.
Effects on digestibility
Nutritional emulsifiers are known for their effect on energy digestibility, especially in poultry. Increased fat digestion is of main focus, but the digestibility of other nutrients (e.g. crude protein) is also of interest. Several faecal metabolic studies by Orffa provide insight into these effects. Diets in these studies were formulated based on maize, soybean meal, wheat, meat and bone meal in varying concentrations. The oils added included vegetable oils (e.g. soybean oil, mixed vegetable fatty acids) and animal fats (e.g. poultry fat). After an adaptation period, faeces were collected at the end of the metabolic period for a number of consecutive days and analysed. The results show that adding a nutritional emulsifier increases energy, crude fat, dry matter and crude protein digestibility on average by 76 kcal/kg (AMEn), 2.81%, 1.41% and 1.68%, respectively. It is important to note that the increase in energy digestibility depends on the crude fat percentage in the diet.
Improving feed efficiency & saving costs
Based on this understanding of energy digestion using nutritional emulsifiers, it is possible to implement this strategy in commercial feeds. By supplementing a nutritional emulsifier and implementing its matrix value (e.g. AMEn = 200,000 kcal/kg) in feed formulation software it is possible to produce energy reduced and cheaper diets without impacting performance. Given increasing raw material costs, the effect of the nutritional emulsifier provides an opportunity to reduce the negative impact on feed prices. The return on investment (in energy-reduced diets) ranges from 3:1 to 7:1, depending on the animal species. In addition to the application in energy-reduced diets there is also the possibility to supply a nutritional emulsifier on top in the feed. This will result in heavier animals needing less feed. Significant improvements in body weight (BW) and feed conversion ratio (FCR) can be seen (Table 1). These results also imply improved sustainability. Using less fat in the feed, in energy-reduced diets, and less feed, when supplied on top, results in more sustainable production.