Utilisation of different dietary starch sources and tolerance to glucose loading in Atlantic salmon (Salmo salar), during parr- smolt transformation
1998
Hemre, G.I. | Hansen, T.
Gelatinised wheat, corn and oats were evaluated as starch sources in diets for Atlantic salmon during 54 days of feeding from March to May, during which time the fish underwent a parr-smolt transformation. At the end of the feeding period, selected fish from each group were injected with glucose to test whether starch source adaptation influenced glucose regulation capacity of the fish. All diets contained equal amounts of starch energy, crude protein and crude lipid. In spite of significant growth, with specific growth rates of 0.17-0.24 and a similar condition factor of 1.2 for all groups, both lipid and glycogen stores in whole body, muscle and liver decreased as a consequence of parr-smolt transformation, season or water temperature. The feed conversion ratio was found to be substantially improved in fish fed with the wheat compared to corn or oat diet. In all groups haematological values, plasma protein and glucose concentrations were within the normal range described for Atlantic salmon, whereas low plasma triacylglycerol levels were observed, ranging from 3.3 to 3.8 mM. After glucose loading and during the first 3 h of recovery, a decrease in plasma triacylglycerol levels was observed. Glucose loading resulted in peaking of plasma glucose after 1 h, with values ranging from 40 to 45 mM, followed by a slow return to initial values within 2 days in corn starch adapted fish and 4 days in wheat and oat starch adapted fish. The results suggest that parr-smolt transformation of salmon kept at 2-3 degree C from March to May results in decreased body reserves of lipid and glycogen in spite of constant food intake, when the diet contained 10% starch and 30% lipid.
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