The ability to digest lipids is not fully developed in young animals. But several studies have demonstrated that the supplementation of bile salts, lipase or phospholipids to young animals improves the digestibility of fats. These studies show that lipid digestive processes are not fully functional in young animals.
The amount of bile salts excreted by the gall bladder is one of the key factors influencing lipid digestibility in animals. The emulsifying properties of bile salts enhance fat digestion by reducing the size of the large fat globules derived from the fatty part of the feed. The efficacy of the lipase released in the small intestine increases with decreasing fat particle size. Furthermore, bile salts enhance the formation of a micellar phase in the small intestine which enhances fatty acid digestibility in dry diets (Bayler and Lewis, 1963). This micellar phase transports the end products of the fat digestion through the small intestine's membrane (Gurr and James, 1971).
When a shortage of emulsifying molecules such as bile salts appears, fat digestibility will significantly decrease. Freeman et al. (1968) reported that in young pigs, the capacity of the small intestine to absorb micellar lipid exceeds normal influx into the gut. Therefore, entry of fatty acids into the micellar phase limits fatty acid digestibility (Bayler and Lewis, 1963). Emulsifying agents promote the incorporation of fatty acids into micelles. Augur et al. (1974) and Polin (1980) reported increased digestibility of fat when an emulsifier was mixed with the fat before it was fed to rats and chicks.
Figure 2. Nutritional trials in broiler diets
Increased digestibility
Nutritional emulsifiers mimick and fortify the effect of the natural bile salts in poultry and pigs. These nutritional emulsifiers are put on a vegetable carrier to facilitate the use of the product in animal feed formulations. The inclusion of nutritional emulsifiers in broiler and swine diets has been shown to result in increased fat and feed digestibility.
A typical characteristic of nutritional emulsifiers is a low hydrophilic-lipophilic balance (HLB). In contrast with technical emulsifiers with a higher HLB, nutritional emulsifiers can be highly soluble in the watery environment of the intestine (Figure 1). To test the efficacy of nutritional emulsifiers, a wide range of scientific trials were conducted worldwide in nursery, growing and fattening pigs and in broilers.
Emulsification of fat (as in milk) may improve fat digestibility and growth performance of animals fed supplemental fat. Jones et al. (1992) reported an increase in fat digestibility when emulsifiers were added to nursery diets containing soybean oil or tallow, but not in diets containing lard. However, other studies using soya lecithin as an emulsifier did not show a benefit in weanling pigs or in growing-finishing pigs as measured by growth performance and fat digestibility. These studies indicate the importance of emulsifiers on fat digestion.
In all trials discussed here, a control treatment fed a standard diet is compared to a treatment fed on the same standard diet but supplemented with 500 ppm of the nutritional emulsifier. All the results (feed conversion and final weight) of the test treatment are expressed as a percentage of the growth parameters measured in the control group.
Figure 3. Nutritional trials in nursery pig diets
Pig and broiler trials
Nutritional emulsifiers in broiler diets have been tested in a large number of trials at a number of universities, including KU-Leuven (Catholic University of Leuven, Belgium), the Wageningen University (The Netherlands) and the Universidade de Porto Alegre (Brazil). The results of these trials are summarised in Figure 2.
These trials demonstrate a positive effect on the feed conversion (FC) ratio and on the slaughter weight of the broilers. The supplementation of 500 ppm of nutritional emulsifier to broiler diets is capable of increasing the final weight of broilers with 2 to 5 percent and reducing the FC with 2.8 to 5 percent.
Similar trails were conducted with both nursery and fattening diets. Nutritional emulsifiers were added in a control diet at a concentration of 500 ppm. The results of these growth trials are expressed in the same way as the tests with broilers. The results of the nursery and fattening trials are depicted in Figure 3 and 4 respectively.
The results of the swine trials demonstrate that the effect of nutritional emulsifiers is more pronounced in younger animals. When nutritional emulsifiers are supplemented in nursery diets, an improvement in final weight and FC can be expected of 5 to 9 percent and 2.6 to 5.8 percent, respectively. However, the results in the fattening trials still demonstrate an improvement of 2 to 6 percent in final weight and 1.7 to 6.3 percent in FC.
Figure 4. Nutritional trials in fattening pig diets
Improving fat digestion
The nutritional emulsifiers improve the natural fat digestion in three ways: by enhancing the formation of emulsion droplets, by stimulating the formation of micelles and by increasing the concentration of monoglycerides in the intestine (see Figure 5).
By increasing the number of emulsion droplets formed, the size of these droplets will decrease. This will increase the total surface of the emulsion droplets on which the lipase enzymes can act. This process increases the amount of monoglycerides that are formed in the intestine. These monoglycerides also act as emulsifiers that further improve fat digestion. Furthermore, the stimulation of the formation of more and smaller micelles also enhances fat digestion.
Figure 5. The effects of nutritional emulsifiers on fat digestion
Reducing feed costs
Due to the positive effect of the newly developed nutritional emulsifiers, it is possible to decrease the total energy content of broiler and pig feed by 3 percent when 500 ppm of the emulsifier is added. This statement is tested in many different growth trials.
With the current high prices of feed energy, this new technology can help to reduce feeding costs.
One trial demonstrates the potential for reduced feed costs. In this trial, 160 crossbred fattening pigs (Piétrain x Hypor) of approximately 10 weeks old were used. The pigs were housed under normal commercial conditions with 12 animals per pen. Three different diets were used: a control diet, a diet with a 3 percent reduction in metabolic energy and a diet with 3 percent reduction in metabolic energy but supplemented with 500 ppm of nutritional emulsifier. The results of this trial are depicted in Table 1.
The energy reduction results in a significant increase in feed conversion during the fattening period compared to the control group. A slight growth decrease in this period can be noted when pigs are fed on an energy-reduced diet compared to the control treatment. This study showed the positive effect of a nutritional emulsifier in an energy-reduced diet compared to a non-supplemented energy-reduced diet. The nutritional emulsifier treatment had a significantly lower feed intake. A significant reduction in overall feed conversion ratio could be detected in the nutritional emulsifier group compared to the low energy group.
Other trials in broilers and nursery pigs showed similar results: a reduction of 3 percent of energy content in the feed can be compensated by an inclusion of 500 ppm of the nutritional emulsifier in broiler and pig feed respectively.
Nutritional emulsifiers can also increase carcass quality in pigs. The corrected meat building index (MBIc) can even be improved when nutritional emulsifiers are used in fattening diets.
Nutritional emulsifiers have been shown to compensate for an energy reduction in broiler and pig diets without reducing growth parameters. In some nutritional emulsifier supplemented diets, the growth parameters and carcass quality are even improved in an energy-reduced diet. With the current sky-high prices for feed ingredients, nutritional emulsifiers can help to reduce the total feed cost.
By increasing the number of emulsion droplets formed, the size of these droplets will decrease. This will increase the total surface of the emulsion droplets on which the lipase enzymes can act. This process increases the amount of monoglycerides that are formed in the intestine. These monoglycerides also act as emulsifiers that further improve fat digestion. Furthermore, the stimulation of the formation of more and smaller micelles also enhances fat digestion.
