SPECIAL STORY FEED & ADDITIVE MAGAZINE February 2021 51 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. IMBALANCED MICROFLORA AND ITS EFFECT ON FAT DIGESTIBILITY The influence of microbiota, antibiotics and conjugated bile acid concentration on the adsorption of fat was investigated in broilers (table 1). The group without antibiotics showed high numbers of Clostridium perfringens in the small intestine and lower amounts of conjugated bile acids. Lower amounts of conjugated bile acids reduced the absorption of fatty acids and fat soluble compounds (e.g. α-tocopherol). Lipase activity was also assessed and shown to be decreased in antibiotic free birds, suggesting an effect of the conjugated bile salts on the activity of lipase (Knarreborg et al. 2003). The same trend was observed in another trial (table 2). In this study the effect of the microbiota on the conjugated bile acid status and subsequent fat digestion was compared between birds reared in sterilized conditions and conventional reared birds. Birds reared in sterilized conditions showed a higher lipid fecal apparent digestibility compared to conventionally reared birds, confirming the negative Figure 1: Conjugation with taurine or glycine to form a conjugated, active bile salt Table 2: Lipid fecal apparent digestibility (%) in broilers (Maisionnier et al. 2003) Broilers, d21 Conjugated bile acids (µmol/g) Lipid fecal apparent digestibility (%) a,b Different superscript shows significant difference between groups (P<0,05) Limited microflora (birds reared in sterilized conditions) Conventional microflora (conventional reared birds) 17a 88,9a 3,3b 81,4b Table 1: Contents of the proximal part of the small intestine in chickens and ileal absorption coefficients at day 35 (Knarreborg et al. 2004) Broilers, d35 Clostridium perfringens (log10 CFU/g digesta) Conjugated bile acids (µmol/g digesta) Total fatty acid absorption (%) a,b Different superscript shows significant difference between groups (P<0,05) Contents of the proximal part of the small intestine Ileal absorption coefficients With antibiotics Without antibiotics 5,48a 11,7a 82a 7,14b 8,88b 73b
RkJQdWJsaXNoZXIy MTUxNjkxNQ==