Simultaneous dietary fat and biotin deficiencies in brook trout suppressed weight gain, feed/gain efficiency, swimming stamina, and total liver lipids. Dietary fat alone reduced body water, increased body fat and ash, reversed the elevating effect of biotin plus fat on liver palmitic and stearic acids, and widened the 16:0 to 16:1, 18:0 to 18:1, 18:2 to 20:4 and 18:3 to 22:5 liver fatty acid ratios. Fat also accentuated the accumulation of liver oleic and linoleic acids caused by biotin deprivation and apparently prevented docosapentaenoic acid biosynthesis in biotin-deprived trout. Fish fed fat with no biotin had the least, and those fed biotin with no fat the most, liver acetyl CoA carboxylase (ACC) and pyruvate carboxylase (PC) activities. Those fed neither supplemental biotin nor fat and those fed both showed equal liver ACC activity.

Journal of Nutrition↗

USGS1974

Effect of feeding brown trout (Salmo trutta) a diet pelleted in dry and moist forms

Growth rate, body composition, and intake of either dry matter or energy did not differ significantly ( P > 0.05) between two groups of juvenile brown trout ( Salmo trutta ) fed either a low- or high-moisture semipurified diet at different rates to compensate for a diet energy density gradient. Feed/gain efficiency, on an as-fed basis, was significantly greater ( P < 0.01) in fish fed the low-moisture diet, but did not differ ( P > 0.05) when compared on the basis of dry matter or energy intake.

Journal of the Fisheries Research Board of Canada↗

USGS1973

Changes in the visual pigments of trout

The proportions of two visual pigments (rhodopsin and porphyropsin) were examined in four species of trout under experimental and natural conditions. Brook trout ( Salvelinus fontinalis ), rainbow trout ( Salmo gairdneri ), and brown trout ( Salmo trutta ) have different relative proportions of visual pigments in their retinae. The visual pigment balance in wild cutthroat trout ( Salmo clarki ) is related to forest canopy (access to light) and season. The brown trout have a more red-sensitive and less labile pair of visual pigments than brook or rainbow trout, which respond to photic conditions by increasing the proportion of porphyropsin (in light) and increasing rhodopsin (in darkness). The brown trout have a high percentage of porphyropsin, regardless of experimental conditions. This result does not reflect an inability to form rhodopsin but rather may relate to a consistently high proportion of 3-dehydroretinol in the pigment epithelium. The possible advantages and mechanisms of environmental control of trout visual pigment absorbance, as currently understood, are discussed.

Canadian Journal of Zoology↗