Study On The Application Of Ethanol Extract From Chlorella Vulgaris In Feed Of The Juvenile Darkbarbel Catfish Pelteobagrus Vachelli

Ethanol extract from Chlorella vulgaris is rich in bioactive substances and it has a broad application prospect in aquatic feed without using any antibiotics.This thesis was conducted to investigate the effects of dietary ethanol extract from Chlorella vulgaris on growth performance,body composition,digestive enzymes activities,and antioxidant capacity of juvenile darkbarbel catfish Pelteobagrus vachelli.Results are as follows:1.Effects of dietary ethanol extract from Chlorella vulgaris on growth performance and body composition of juvenile darkbarbel catfish Pelteobagrus vachelli.Six isonitrogenous and isolipidic diets with approximately 40% of protein and 8% of lipid were formulated.In total of 540 juvenile fish were randomly divided into 6 dietary groups of 3 replicates each,and fed basal diet supplemented with 0(T0),0.25(T1),0.5(T2),1(T3),1.5(T4)and 2.5%(T5)of ethanol extract from Chlorella vulgaris.Fish with initial body weight of 1.85 ± 0.01 g were fed with the six experimental diets.The feeding trail was lasted for 56 d.Results showed that the final body weight,weight gain rate and the specific growth rate increased with increasing level of ethanol extract from Chlorella vulgaris(P> 0.05),whereas the feed coefficient decreased(P> 0.05).No difference was observed in survival rate among groups.Growth performance was significant difference(P <0.05)among treatments at the end of feeding trail.The final weight,weight gain rate and the specific growth rate in T4 and T5 were higher(P <0.05)than those in control diet.Similarly,the condition factor,viscerosomatic index and hepatosomatic index in T1-T5 diets were higher thanthose in control diet(P>0.05).Body composition were affected by treatments with moisture,ash,crude protein content decreased and crude fat increased with increase levels of ethanol extract in diets.2.Effects of dietary ethanol extract from Chlorella vulgaris on digestive enzyme activities of juvenile darkbarbel catfish Pelteobagrus vachelli.At the end of the feeding trial,the digestive enzyme activities in stomach,intestine,heaptopancreas of Pelteobagrus vachelli were tested.Results showed that the protease activity of stomach and intestinein diets of T1~T5 were higher than those in control(P>0.5).However,as the level of ethanol extract from chlorella vulgaris increased,protease activity of hepatopancreas increased(P>0.5),the amylase activity of stomach increased at begining and then desreased.The enteric amylase activity in diets of T1-T5 were higher than that in control.No difference was observed in activities of gastric lipase,intestine lipase and hepatopancreas lipase among treatments(P> 0.05).3.Effects of dietary ethanol extract from Chlorella vulgaris on serum indexes and antioxidant capacity of juvenile darkbarbel catfish Pelteobagrus vachelli.At the end of feeding trail,the blood samples were collected to determine the physiological and biochemical indexes as well as antioxidant capacity.Results indicated that aspatate transaminase activity in diets of T1~ T5 were higher than that in control diet and which was also absorved to have a significantly difference among T1,T3 and T4 diets.Concentration of malondialdehyde in T4 was lower than that in T0~T2 diets(P<0.05).The superoxide dismutase activity in diets of T3~T5were higher than that in T0~T2 diets(P<0.05).Morever,the total antioxidant capacity in diets of T1~T5 was higher than that of control diet(T0).Results demonstrate that supplementing 1.5% of ethanol extract from Chlorella vulgaris could signifycantly improve growth performance and antioxidant capacity of Pelteobagrus vachelli.