ARTICLE FEED & ADDITIVE MAGAZINE May 2022 65 Exogeneous bile acid can be obtained as a by-product from animal production from avian, swine and bovine sources to be used as feed additives. Avian and swine bile acid mainly consists of cholic and chenodeoxycholic acid, whereas bovine bile acid mainly consists of cholic acid and deoxycholic acid (Sheriha et al., 1968). Although exogeneous bile acids from different sources could have a different amino acid conjugation, pathway of bile acid recycling including bacterial deconjugation in the ileum allows for unconjugated bile acids to return the liver and be re-conjugated in the hepatocyte. Bile Acid Functions: 1. Facilitates fat and fat-soluble vitamin digestion and absorption a. Bile acids promote fat digestion in 3 steps: i. Emulsify fats. Bile acids are biosurfactants which allows fat to be emulsified into micro droplets. This greatly increases the total surface area of fat, increasing its availability for digestion by lipase. ii. Activates lipase. Bile salt-dependent lipase cleaves triglycerides when combining into micelles to hydrolyse fat. iii. Promote fat absorption. Only the formation of bile acids and fatty acids, could facilitate fatty acids to reach to surface of small intestinal villi and be absorbed into the lacteals. iv. Emulsifiers only acts in the first step in fat digestion, which only emulsifies the fat into micro droplets. However, bile acids can further activate the lipase and promote the digestion of fat. HLB of Bile Acid Comparing the emulsification capabilities of bile acid and other emulsifiers using the HLB or Hydrophilic-Lipophilic Balance value developed by Griffin to formulate stable emulsions. The HLB value of lipophilic emulsifier is lower than that of hydrophilic emulsifier. The intestinal track is an aqueous environment, where hydrophilic emulsifier would have a stronger emulsification effect and a higher HLB value represents better emulsification effects on oil. The HLB value of bile acids is about 18, which has excellent emulsification capabilities compared to other emulsifiers (Table 1).
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