Studies on the Digestive Tube Index and the Activity Distribution of Two Digestive Protease Activity in NEW GIFT Tilapia(Oreochromis niloticus)

Digestive tube index and the activity distribution of pepsin and trypsin In NEW GIFT Tilapia (Oreochromis niloticus) were studied.It was found that Oreochromis niloticus had intestinal length (IL) /total length (TL) of 4.921 ± 0.187, intestinal weight (IW) /body weight (BW) of 0.018 ± 0.002, and hepatopancreas weight (HW) /BW of 0.014±0.003, splanchnic weight (SW) /BW of 0.039±0.007.The result showed that Oreochromis niloticus was a kind of heterophagous fish with partial phytophagy food habit.After starvation and refeeding, Pepsin activity increased to a maximum of 167.872Uat 12h.However, it reduced from12hto 96h;especially 12hto 24h, the decrease rate was significant.Trypsin activities of hepatopancreas, foregut, midgut and hindgut were tested.The specific activity of trypsin in four organs was in the order of hepatopancreas<midgut<foregut<hindgut.The Trypsin activities in four parts increased up to a maximum during the first stage, then decreased smoothly.trypsin activity of each tissues was significant difference (P<0.05) 。