A comparison of the effects of carbohydrate and fat as energy sources in trout and chick diets on tissue glycogen concentration and on the rate of glycogen depletion from the tissues during a subsequent period of fast
Creators: name: Hickling, David Robert
Publisher: name: University of British Columbia
Year: 2010

description: Rainbow trout, about one-year-old, were fed diets containing either glucose (C) or herring oil (F) as the non-protein energy source for a period of two weeks. As well, they were fed each diet at satiation (C-2, F-2) and at levels half that (C-l, F-l). The trout were subsequently fasted and sampled for tissue glycogen, protein, dry matter and glucose-6-phosphatase activity at full feeding and at 2, 4, 8, 10, 13 and 16 days of fasting. The livers of the C-fed fish had 12% wet weight glycogen and the livers of the F-fed fish had 3% wet weight glycogen at full feeding. Upon fasting, glycogen concentrations in the F-fed fish livers fell to basal levels of 1% by 2 days while glycogen concentrations in the C-fed fish livers fell to basal levels only after 10 days. The protein concentration in the trout livers was inversely related to the glycogen concentration. The amount of liver protein in the trout carcass, however, was directly related to dietary carbohydrate levels. Trout liver glucose-6-phosphatase activity increased as fasting progressed but there were no treatment differences in enzyme activity. The muscle of the C-2 fed trout contained .4% glycogen at full feeding. The muscle of the other dietary treatments contained .1-.15% glycogen. It appears that trout muscle stored dietary carbohydrate that was not taken up by the liver or that was not oxidized. Upon fasting there was a depletion in muscle glycogen to basal levels of .05% after 4 days. Thereafter there occurred a rebound in muscle glycogen to levels at or greater than full-fed levels followed by a decline back to basal values. The rebound was greater and peaked earlier (8 days) in the C-fed trout than in the F-fed trout (10 days). Broiler (BR) and White Leghorn (WL) pullet chicks were fed diets, where 25% of the energy was supplied as corn starch (C) or corn oil (F), for a three-week period. The chicks were then fasted and sampled for tissue glycogen, protein and dry matter at full feeding and at 8, 16, 24, 32, 44, 56, 80, 104 and 128 hours of fasting. The BR livers contained more glycogen (3%) than the WL livers (2%) and the C-fed chicks had greater liver glycogen concentrations (3%) than the F-fed chicks (2%) at full feeding. Upon fasting, liver glycogen fell to basal levels of .03% after 8 hours. Thereafter there was a rebound increase in liver glycogen levels to a peak of 1% and a subsequent tapering off. The rebound occurred earlier in the C-fed chicks than in the F-fed chicks. The peak was attained earlier in the WL (32-44 hours) than in the BR (50 hours). The amount of liver protein in the C-fed chicks was higher than that in the F-fed chicks over the entire fasting period. Chick muscle glycogen concentrations were initially higher in the C-fed than in the F-fed chicks and higher in BR (1.2%) than in WL (.8%). Upon fasting, BR muscle glycogen concentrations were maintained while those of WL fell to .3%. There were erratic fluctuations in muscle glycogen levels.