UTILIZATION OF DIFFERENT DIETARY STARCH SOURCES AND TOLERANCE TO GLUCOSE LOADING IN ATLANTIC SALMON (SALMO-SALAR), DURING PARR-SMOLT TRANSFORMATION

Gelatinised wheat, corn and oats were evaluated as starch sources in d iets for Atlantic salmon during 54 days of feeding from March to May, during which time the fish underwent a parr-smelt transformation. At t he end of the feeding period, selected fish from each group were injec ted with glucose to test whether starch source adaptation influenced g lucose regulation capacity of the fish. All diets contained equal amou nts of starch energy, crude protein and crude lipid. In spite of signi ficant growth, with specific growth rates of 0.17-0.24 and a similar c ondition factor of 1.2 for all groups, both lipid and glycogen stores in whole body, muscle and liver decreased as a consequence of parr-sme lt transformation, season or water temperature. The feed conversion ra tio was found to be substantially improved in fish fed with the wheat compared to corn or oat diet. In all groups haematological values, pla sma protein and glucose concentrations were within the normal range de scribed 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 gl ucose after 1 h, with values ranging from 40 to 45 mM, followed by a s low 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-smelt transformation of salmon kept at 2-3 degrees C from Ma rch 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. (C) 1998 Elsevier Science B.V.