The influence of temperature on the apparent nutrient and fatty acid digestibility of Arctic charr, Salvelinus alpinus L
1998
Olsen, R.E. | Ringo, E.
To study the influence of temperature on the nutrient and fatty acid digestibility of salmonid fish, Arctic charr. Salvelinus alpinus L., were fed dry pelleted diets at 10 and 0.6 degrees C for 81 days. The diets had a carbohydrate/lipid content of 23.7/13% and 6.4/27% and a constant protein content of around 50%. At the end of feeding period, gut contents were collected from the mid- and hind-gut regions, and analysed for the apparent digestibility coefficient (ADC) of nutrients using chromic oxide as digestibility marker. Fish maintained at 0.6 degrees C had a lower ADC of protein, carbohydrate, lipid and dry matter compared to those maintained at 10 degrees C. This shows that increased gastrointestinal holding time following low temperature adaptation does not fully compensate for lowered digestive/absorptive metabolism. Feeding high carbohydrate diets had no significant influence on nutrient utilization at 10 degrees C, but appeared to reduce the ADC of most macronutrients at 0.6 degrees C. The ADC of the individual fatty acids increased with decreasing chain length and increased with unsaturation. Maintaining the fish at 0.6 degrees C significantly reduced the ADC of saturated fatty acids, while the monounsaturated fatty acids, and in particular, the polyunsaturated fatty acids were hardly influenced by environmental temperature. It is suggested that the reason may be a shift in digestive lipase specificity caused by changes in the substrate state or lowered solubilization of saturated fatty acids in bile micelles, which thus reduces the uptake into the enterocyte.
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