| Summary: | High levels of soybean meal in diets fed to salmonids causes reduction in gross response parameters; however, the cause of the limitation remains speculative. Three studies were conducted to determine the effects of soybean antinutritional factors (ANF) on salmonids. In studies one and two, the effects of dietary soybean lectin (SBA) on feed consumption, weight gain, specific growth rate (SGR), serum insulin levels and gut histology of rainbow trout and Atlantic salmon were investigated. Triplicate groups of rainbow trout and Atlantic salmon were fed purified diets containing graded levels of SBA (4-80 mg/kg diet and 3.5-70 mg/kg diet, respectively). Weight gain and feed efficiency were not significantly affected by dietary SBA levels; however, weight gain of rainbow trout fed any level of SBA was lower than in fish fed the control diet. Rainbow trout fed the diet containing 60 mg/kg SBA exhibited significantly lower feed consumption than fish fed all other diets. Baseline serum insulin levels were not significantly affected by dietary treatment in either study; however, Atlantic salmon fed all levels of SBA did exhibit non-significant decreases of insulin at one- and three-hours post-prandial. There were no significant alterations in the microscopic structure of distal sections of the gastrointestinal tract in rainbow trout or Atlantic salmon. In the third study, the effects of feeding SBA, trypsin inhibitors (TI) and oligosaccharides (OLIG) to rainbow trout were investigated. Eight purified diets were formulated, consisting of a control and all possible combinations of the three ANF. In addition to the responses evaluated in the prior studies, serum chemistry values were evaluated. Weight gain and SGR of trout fed only SBA or TI was significantly decreased in comparison to fish fed neither ANF. A significant reduction in protein retention was observed in trout fed TI. A significant increase in amylase and one-hour post-prandial insulin response as a result of feeding OLIG was also detected. No significant ...
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