A 3-month feeding trial was conducted to investigate the effects of dietary carbohydrate source on the growth
performance, apparent digestibility coefficients and liver glucose enzyme activity in juvenile blunt snout
bream. Six experimental diets were formulated to contain 33% wheat starch, corn starch, dextrin, maltose, glucose
or cellulose. At the end of the experiment, the best final body weight (18.4 g), specific growth rate (SGR,
2.46%/day), feed conversion ratio (FCR, 1.41 g feed/g gain) and protein efficiency ratio (PER, 2.22 g gain/protein)
were found in the group fed with the dextrin diet, while the poorest values were observed in the group fed with
the cellulose diet among the treatments. Fish fed with the glucose (1.55 g feed/g gain) or maltose (1.53 g feed/g
gain) diet showed significantly higher FCR than those fed with the dextrin diet (1.41 g feed/g gain). Dietary cellulose
caused the highest feed intake (2.91 g/fish/day) and FCR (1.87 g feed/g gain) among the treatments. The
apparent digestibility coefficient (ADC) of dry matter was significantly lower in fish fed with the cellulose diet
than those fed with other diets. ADC of protein was independent of dietary carbohydrate source. The highest
ADC of energy was observed in fish fed with diets containing glucose, maltose or dextrin; followed by wheat
starch, corn starch and cellulose. Carbohydrate source did not affect whole body moisture, protein and ash contents,
and plasma total protein and cholesterol contents. Lipid contents of whole body and plasma triglyceride
contents increased with increasing carbohydrate complexities. Plasma glucose contents and liver enzyme activities
were affected by sampling time and dietary carbohydrate source. Fish fed with the dextrin diet showed the
highest liver glucokinase (GK), pyruvate kinase (PK) and glucose-6-phosphate dehydrogenase (G6PDH) activities,
and the lowest glucose-6-phosphatase (G6Pase) activity among all the groups. Significantly higher G6Pase
activity was observed in fish fed with the glucose diet than those fed with the dextrin or wheat starch diet at
2 h postprandial. These results indicated that dextrin was the best dietary carbohydrate source for juvenile
blunt snout bream, based on growth performance, feed utilization, ADC and liver glucose enzyme activities.