Fat digestibility, in particular, will be affected to a large extend by bacteria that impair the function of bile acids, vital components of the fat digestibility apparatus. These bacteria are more pronounced in disbalanced gastro-intestinal tracts and form especially a threat when the usage of antibiotics is limited. Low fat digestibility will imply a loss of energy which will not be available for growth. To counteract this suboptimal situation a nutritional emulsifier can be added to the diet. This additive does not only safe costs in healthy animals but also supports flocks with intestinal health issues.
Bile acids as natural emulsifiers
Fat digestion is to a large extend dependent on bile acids, next to pancreatic lipase and colipase. Bile acids, synthesized in liver cells, will act at the lipid/water interface and help in the formation of micelles, sphere-like aggregates of fat in water. Bile acid-containing micelles augment the activity of lipase towards the digestion of lipids. Prior to secretion in the intestine, conjugation with taurine or glycine takes place in liver cells to form conjugated bile acids (figure 1). Only conjugated bile acids are able to act efficiently as an emulsifier. The unconjugated forms are insoluble in water due to their specific molecular structure and subsequent acid-base properties. They will be excreted in feces. Both commensal, symbiotic and pathogenic intestinal bacteria are capable of hydrolyzing the amide bond and remove glycine and taurine. Clostridium perfringens, for example, was shown to express high levels of the bile salt hydrolase enzyme (Knarreborg et al. 2002). When hydrolyzed, the bile salt is in its unconjugated form and loses its ability to act as a natural emulsifier, resulting in a decreased fat digestion.