Energy is a major dietary cost component for high performing animals. Due to its high energy density, fats and oils are important energy sources in feed formulation. Improving the energy efficiency of these raw materials can result in feed cost savings.
Bile salts are natural emulsifiers. The monoglycerides that are formed in the intestine after hydrolysis of the fat also act as emulsifiers. Nevertheless, the capacity of these natural emulsifiers can be a limiting factor for fat digestion. Young animals have a limited production of bile salts and therefore fat digestibility is limited in the early stage of life. Apart from this, the characteristics of the dietary fat and the amount of added fat can restrict the digestibility, also in older animals. Different characteristics of the fat explain the differences in digestibility. In general, saturated fatty acids (mostly found in animal fat) are digested less easily compared to unsaturated fatty acids (like in vegetable oils). High levels of free fatty acids limit the digestibility. The use of a nutritional emulsifier is an effective tool to improve the fat digestibility. Obviously, the positive effect of adding such emulsifiers is more pronounced for lower digestible fats, but also in high digestible fats (like soybean oil) very positive effects can be observed.
Importance of hydrophiliclipophylic balance
Hydrophilic-lipophylic balance (HLB) is a parameter to choose the optimal emulsifier for every specific application. An emulsifier with a low HLB is more fat soluble (lipophilic) and an emulsifier with a high HLB is more water soluble (hydrophilic). Due to the fact that an animal consumes around twice as much water as feed, the intestine is a very watery environment. The goal of a nutritional emulsifier is to optimise the emulsification and micelle forming in the intestine and therefore an emulsifier with a high HLB (hydrophilic) is most preferred.
Several published trials have shown the benefits of a nutritional emulsifier. In order to understand the effect more in detail, an extensive research project in broilers was undertaken as part of a PhD program in a cooperation between the Federal University of Lavras in Brazil and Orffa. A total of three trials were undertaken to investigate the effect of the emulsifier Excential Energy Plus on nutrient digestibility and metabolisable energy in broilers. Fat digestibility can be influenced by different variables and these were taken into account in the set up. The amount of fat and the type of fat are important variables, as well as the age of the animal. To investigate the effect of inclusion level of fat, diets were formulated with increasing level of soybean oil (0%, 1.5%, 3%, 4.5% and 6%). Every level of oil was tested with or without emulsifier and this was done in two basal diets (different diet compositions). Also a set up with two types of oil (soybean oil and poultry fat) was made to evaluate effect of fat source. The nutrient digestibility and metabolisable energy (AMEn) were analysed for young (14- 21d) and older birds (35-42d), based on method of total excreta collection.
Apparent metabolisable energy
The results showed that the emulsifier significantly improved dry matter and fat digestibility and this resulted in a higher metabolisable energy (AMEn) both for the young birds as well as for the older birds (data for old birds shown in Table 1 and Figure 1). The additional trials showed that there was no effect of diet composition. In both diet types (vegetable diet and diets with animal by-products) comparable positive effects of the emulsifier were obtained. From the comparison between soybean oil and poultry fat it could be concluded that the emulsifier was effective on both fat sources (Figure 2).