Effects of diets containing different carbohydrates on starved condition in juvenile tilapia Oreochromis niloticus x O-aureus

Diets containing 40% of either starch or glucose were fed to triplicate groups of tilapia Oreochromis niloticus x O. aureus (initial weight: 0.80 +/- 0.01 g) for 8 weeks, followed by a fasting of 1, 2 and 3 weeks. In starvation, fish previously fed the diet containing glucose showed significant (P<0.05) weight loss compared with fish fed the diet containing starch. Liver glycogen was higher in fish fed a starch diet compared with fish fed a glucose diet during both feeding and fasting periods. Starvation also resulted in decreased liver glycogen in fish as the fasting period increased. Plasma glucose was higher in starch-fed fish during feeding and 1 week after fasting compared with glucose-fed fish. Plasma glucose of both dietary groups was lower in starvation than in the feeding period. Elevated plasma glucose was found 3 weeks and 2 weeks after fasting in fish prefed with starch and glucose diets, respectively. Plasma triglyceride increased as the fasting period increased in both groups. In starvation, plasma triglyceride were higher in fish prefed the starch diet than fish fed the glucose diet. Relative to the glucose diet, body lipid content was higher in fish fed the starch diet prior to fasting and 1 week after fasting. These data suggest that the physiological responses of tilapia during starvation are affected by prefasting diets containing different carbohydrates.