Abstract: TaimenHuchotaimenwith initial body weight of (6.90±0.04)g were reared in a 220 L indoor flowing glass fiber reinforced plastic tank and fed diets in which fish meal was replaced by 0, 25.0%, 37.5%, 50.0%, 62.5%, 75.0%, 87.5% and 100.0% of soy protein isolate(SPI), diet containing 40.0% fish meal as control, with triplicates of each 100 fish at water temperature of 9.8-16.2 ℃ for 56 d to evaluate the effects of replacing fish meal with SPI on the activities of digestive enzymes and histological structure of digestive tract of taimen. It was found that protease, lipase and amylase activities in stomach, foregut, midgut, pyloric caeca and pancreas were significantly decreased with increasing SPI content (P<0.05). Heights of intestinal villi and microvilli were also shown to be significant decrease (P<0.05), and damaged intestinal structural integrity, fused microvilli, even abscission, and more hepatic vacuoles were observed in the taimen fed high dietary levels of SPI (87.5% and 100.0%) under a microscope, even with blurred boundaries, and shifted and dissolved or vanished nuclei in hepatic cells. It is concluded that fish meal replacement by high level of SPI leads to decline the digestive enzyme activity and to cause loss of function of liver and intestine.
2018, Vol. 33 
