Due to its high energy density, fats and oils are important energy sources in feed formulation. However, energy is a major cost component for high performing animals. Nutritional emulsifiers can be used to improve fat digestibility and thus improve the energy efficiency, hence leading to lower feed costs.
Bile salts are natural emulsifiers. And also the monoglycerides that are formed in the intestine after hydrolysis of the fat 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.
Studies showed that an emulsifier significantly improved dry matter and fat digestibility in broilers. Photo: Bertil van Beek
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 fat). 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. A parameter to choose the optimal emulsifier for every specific application is HLB (hydrophilic-lipophylic balance). 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 almost 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.
Higher metabolisable energy in broilers
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 has been set up. The project is part of a PhD program and a cooperation between the Federal University of Lavras in Brazil and Orffa. PhD student Levy Teixeira performed a series of trials under supervision of professor Antonio Bertechini. First, a total of three trials were set up to investigate the effect of an emulsifier* 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 levels 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 2 types of oil (soybean oil and poultry fat) was made to evaluate the effect of the fat source. The nutrient digestibility and metabolisable energy (AMEn) were analysed for young (14-21d) and older birds (35-42d), based on the method of total excreta collection. 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 is shown in Figure 1 and Table 1).
Effective on both fat sources
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).
As a follow up to the metabolism trials, a performance trial was set up to validate the obtained energy upgrades. As positive control, a basal feed program was formulated with a practical fat and energy level. The starter diet contained 2% soybean oil and the finisher diet contained 4% soybean oil. Next, a negative control was formulated with a lower energy content. The energy content of the starter diet was reduced with 40 kcal/kg and the finisher diet was reduced with 75 kcal. These energy reductions were based on the obtained results in the metabolism trial and were reached by reducing soybean oil inclusions. As a third treatment the negative control was supplemented with the emulsifier to evaluate if the energy reduction could be compensated. This set up was performed with two different diet compositions, diet 1 based on solely vegetable raw materials (corn/SBM) and diet 2 based on corn, SBM and meat and bone meal. The results are shown in Figure 3.
As expected, the energy reduction in the negative control diets resulted in less efficient growth, as shown by higher feed conversions (Figure 3). The addition of the emulsifier was able to compensate the energy reduction and recovered the feed conversion back to the level of the positive control. The diets with the reduced energy were formulated with less soybean oil and therefore had a significant lower formulation cost. This trial work confirms that the addition of the emulsifier could be a practical tool for broiler nutritionists to lower feed costs.
In conclusion, the tested emulsifier improves digestibility of dry matter and fat and also improves metabolisable energy (AMEn) in broiler diets. This gives nutritionists the opportunity to formulate diets with a lower energy level, without compromising performance, resulting in lower feed costs and a more sustainable animal production.