Cholesterol and short-chain fatty acids in diets for Atlantic salmon Salmosalar (L.): effects on growth, organ indices, macronutrient digestibility,and fatty acid composition

The influence of dietary cholesterol (CHOL) and short-chain fatty acids (SC FA; sodium salts of acetic, propionic and butyric acid, 5:5:2 w/w/w) on gro wth, organ indices, macronutrient digestibility, and fatty acid composition of Atlantic salmon Salmo salar was investigated. Salmon (initial average w eight 0.7 kg) held in seawater (7 degrees C) for 175 days were fed one of s ix diets: 1, without CHOL/SCFA supplement; 2, with 0.5% SCFA; 3, with 2.0% SCFA; 4, with 1.0% CHOL; 5, with 1.0% CHOL and 0.5% SCFA; 6, with 1.0% CHOL and 2.0% SCFA. Neither SCFA nor CHOL supplements had any significant effects on specific g rowth rate (SGR), mortality, apparent digestibility coefficients (ADC) of m acronutrients, total lipid content. Hepatosomatic index (HSI) was slightly increased in salmon fed the CHOL supplement (P < 0.05). Hepatic CHOL concen tration, but not the hepatic CHOL pool, was significantly increased (P < 0. 001) by dietary CHOL supplementation. The fatty acid compositions of fillet and gut tissues were not influenced b y dietary treatment, while significant effects of CHOL supplements were obs erved in faeces and liver. Less saturated fatty acids and more mono- and po ly-unsaturated fatty acids were excreted with faeces in salmon fed CHOL sup plements. Salmon fed CHOL supplements significantly reduced the relative co ncentration of hepatic palmitic acid (C16 : 0 ), arachidonic acid (C20 :4 n -6) and docosahexaenoic acid (C22 : 6 n-3), while the contents of oleic aci d (C18 : 1 n-9) and eicosenoic acid (C20 : 1 n-9) were significantly increa sed. SCFA did not influence the observed effects of dietary CHOL. The present study shows that dietary CHOL supplements profoundly altered ex cretion and liver metabolism of individual fatty acids in salmon. The impac t of this alteration on physiological performance has not been elucidated.