Comparison of cholestane and yttrium oxide as digestibility markers for lipid components in Atlantic salmon (Salmo salar L.) diets

The study aimed to test the similarity between apparent digestibility coefficients (ADC) calculated using either yttrium oxide or cholestane. Atlantic salmon were fed three diets containing a different mix of oil sources: diets contained only canola oil (CO), canola oil and fish oil (CFO), or canola oil and thraustochytrid meal (CTH) (a marine microorganism with potential as an alternative oil source). Both markers were concentrated by the same amount in the faeces compared to the diets. ADC values using cholestane tended to be higher than yttrium, and there was a significant marker effect for crude protein, energy, total lipid and triacylglycerol. Although statistically significant the marker effect was due to numerically small differences in ADC values and probably of limited biological significance. ADC values for the majority of fatty acids did not show marker effects. Consequently, it was concluded that the broad similarity in the digestibility of lipid components between markers validated the use of cholestane for calculating lipid digestibility in Atlantic salmon. © 2003 Elsevier Science B.V. All rights reserved.