Histo-architectural and histochemical changes in the liver and intestine of Labeo rohita: integrative effect of water temperature and dietary protein level

This study aimed to study the histo-architectural and histochemical changes in the liver and intestine of Labeo rohita fingerlings due to the integrative effect of short-term exposure to higher temperature and dietary protein levels. Six hundred Labeo rohita fingerlings (average weight 6.78 ± 0.05 g) were distributed into 24 tanks, with 25 fingerlings in each tank. The tanks were divided into eight experimental groups, with three replicates for each tank. Half of the experimental groups were maintained at an ambient water temperature of 260C, while the other half were kept at 320C for one week and then shifted back to 260C for four weeks. The fingerlings were fed with either of four diets, each containing different protein levels of 20%, 30%, 40% or 45% protein. At the end of the experiment, the hepatosomatic index (HSI) and visceral index (VI) of the juveniles were increased with the increase in dietary protein level, however significantly lower HSI was recorded at 320C compared to 260C. Juveniles exposed to elevated temperature (320C) for one week registered significantly higher (p < 0.05) liver glycogen content compared to 260C. Amylase, protease, and alkaline phosphatase activity in the intestine of juveniles were significantly (p < 0.05) higher at elevated temperature (320C) and decreased after 4 weeks of decrease in temperature from elevated temperature (320C) to ambient temperature (260C). The 45% CP fed group at 260C showed mildly desquamated mucosa in the liver whereas mucosa was found absent at 320C. Marked loss of mucosa was found in the intestine of L. rohita fed with 45% dietary protein after five weeks either at 260C or 320C. Overall it concludes that the dietary protein level and water temperature interactions are more effective in maintaining the histo-architectural structure of the liver and intestine, which responds to increased digestive enzyme activity.