Fats and emulsifiers in feeding broiler chickens (review)

The increase in feed prices determines the need to optimize the rationing of high-energy ingredients of the diet, as well as various approaches to improving the efficiency of their use in the digestive process. In industrial poultry farming, fats, having a high energy value, serve as indispensable components of the diet (V.I. Fisinin et al., 2000; V.I. Fisinin et al., 2011). They provide high productivity and economic efficiency (N.C. Baião et al., 2005; M. Nayebpor et al., 2007; H. Fébel et al., 2008), play an important role in the regulation of metabolism, deposit energy, performing a protective function, serve as solvents and carriers of vitamins, hormones, as well as an obligatory component of nervous tissue (A.V. Arkhipov, 2010; M. Poorghasemi et al., 2013; R. Rodriguez-Sanchez et al., 2019). A wide variety of fats and oils and by-products of processing are available for use in diets, for example, animal fats and vegetable oils (soy, corn, sunflower, palm, hemp, mustard, etc.), sunflower fusel (a by-product of the conversion of sunflower seeds into vegetable oil), acidified soapstocks (by-products refining of vegetable oil, mainly containing free fatty acids), hydrogenated fats (A.V. Arkhipov, 2007; V.A. Manukyan et al., 2018; L.N. Skvortsova et al., 2013). The choice of fat for use in feeding farm animals and poultry is largely determined by both its cost and quality characteristics. The main factor that affects the release of energy from fat entering the body with food is its digestibility (V. Ravindran et al., 2016; R. Rodriguez-Sanchez et al., 2019; B. Jimenez-Moya et al., 2021). The digestion of fats is a complex process that requires a sufficient amount of bile acid salts and enzymes (S. Leeson et al., 2009). In addition, the correction of the diet with lipids is effective, but economically impractical. The increase in prices for animal and vegetable fats currently encourages interest in the search and use of alternative energy sources in the feed of farm animals or substances that enhance the processes of digestion and assimilation of lipids, in order to reduce the cost of production (S.A. Miroshnikov et al., 2005; O. Lyutykh, 2020). One of the approaches to increase the amount of available fats can be the use of synthetic and natural emulsifiers. Popular emulsifiers usually consist of hydrophilic and hydrophobic components that can reduce the surface tension of fat and water, reduce chylomicrons of fat, improve emulsification and increase fat absorption, make up for the deficiency of bile acid and lipase in the digestive tract of poultry (M. Rovers et al., 2014; M. Jansen et al., 2015). Natural emulsifiers include bile acids and salts, including cholic and henodeoxycholic, taurocholate, lecithin, casei, phosphatide concentrates, some of which can be produced in the animal’s body (M. Soares et al., 2002). Bile acid salts reduce the tension of the oil-water interface, activate pancreatic lipase, and also prevent the denaturation of this enzyme when it throws the surface of emulsified fat droplets (M. Boesjes et al., 2014; Y. Xu, 2016; X.K. Ge et al., 2019). Synthetic emulsifiers (lysolecitin, lysophosphatidylcholine, mono- and polyoxyethylene glycol dioleates) improve liver and bile duct function, accelerate weight gain and improve feed conversion, increase growth rates and nutrient digestibility (B. Zhang et al., 2011; M.M. Gheisar et al., 2015; S.D. Upadhaya et al., 2018). Consequently, the strategy of using emulsifiers and enzymes can be an effective tool for improving the digestion of fats both in young birds with functional immaturity of the digestive system and in adults to further reduce feed losses due to the intensification of the digestive process. The use of this approach will provide increased digestibility and digestibility of nutrients while reducing the introduction of vegetable and animal fats into the diet of broiler chickens.