Effects Of Hydrolyzed Feather Meal Replacing Fish Meal On The Growth Performance,Fillet Quality And Immunity Of Pengze Crucian Carp(Carassius Auratus Var.Pengze)

At present,the high cost and insufficient supply of fish meal have become one of the important factors restricting the rapid development of China's aquaculture industry.As a high-quality protein source which was widely used in aquatic livestock and poultry breeding,the feather meal is a ideal protein to replace the fish meal.Pengze crucian carp(Carassius auratus var.Pengze),a unique and important economic fish of Jiangxi,were served as research object in this study.The object of this study was to examine the effects of hydrolyzed feather meal replacing fish meal on the growth performance,fillet quality,immunity,and antioxidant status of Pengze crucian carp.300 tails carp with initial weight of 12.89 ± 0.04 g were randomly divided into 5 treatments(3 cages(1.5×1.5×1.5 m)for each treatment group,20 fish per cage).Fish were fed with basic diet(Control group)and diets with fish meal replaced by the same amount protein of hydrolyzed feather meal at 15%(F15 group),30%(F30 group),45%(F45 group),and 60%(F60 group)for 70 days.The results of this study were as follows:The replacement of 15~45% fish meal protein had no significant effect on the growth,whereas the growth performance of carp was inhibited when the replacement level reached 60%(P < 0.05).The replacement level of 15~60% fish meal protein by hydrolyzed feather meal showed no significant effect on the feed utilization efficiency of carp.The crude fat content of the body increased with the increase of replacement level,and it in F30,F45 and F60 groups was significantly higher than that of the Control group(P < 0.05).The crude protein content of the body had decreased trend with the increase of replacement level,and it in F30,F45 and F60 groups was significantly lower than that of the Control group(P < 0.05).Hydrolyzed feather meal had no significant impacts on ash composition,hepatosomatic index,viscerosomatic index of the carp.Furthermore,fish meal replaced by hydrolyzed feather meal affected the fillet quality of carp in terms of a significant impacts on springiness,cohesiveness,gumminess,chewiness,and resilience(P < 0.05).Compared with the Control group,the content of urea,ammonia,total cholesterol,high-density lipoprotein and low-density lipoprotein,and activity of lactate dehydrogenase in serum was increased with the icrease of replacement level of hydrolyzed feather meal.The above serum indexes of carp were significantly lower than that in Control group when the replacement level reached 45%(P < 0.05).Hydrolyzed feather meal replacing fish meal affected the activities of digestive enzymes in intestinal tract,and 30~45% replacement levels could significantly elevated the activities of intestinal amylase,lipase and protease in comparsion with that in Control group(P < 0.05).In addition,the feather meal significantly changed the intestinal morphology,and the high replacement level resulted in a significant reduction in muscle thickness(TM),fold height(HF),enterocyte height(HE),and microvillus height(HMV)of intestine(P < 0.05).Among them,the replacement level of 60% had most significant negative effects on the intestinal morphology(P < 0.05).The replacement of fish meal by hydrolyzed feather meal did not significantly affect the liver morphology,but affected the glucose metabolism process within liver.High levels of feather meal replacement significantly reduced hepatic glycogen content and lactate dehydrogenase enzyme activity in liver tissue(P < 0.05).Hydrolyzed feather meal replacement can significantly reduce the activities of acid phosphatase and catalase(P < 0.05),and the activitiy of catalase decreased with the increase of the replacement level of hydrolyzed feather meal,but feather meal showed no significant effects on the activies of total superoxide dismutase and alkaline phosphatase in serum.Hydrolyzed feather meal increased the activities of acid phosphatase and alkaline phosphatase in the intestinal tissue of carp.In addition,although high-level feather meal replacement significantly improved the intestinal antioxidant indice,such as glutathione peroxidase,reduced glutathione,and total superoxide dismutase,but the content of malondialdehyde also increased significantly with the increase of replacement level(P < 0.05),indicating hydrolyzed feather meal significantly increasing the oxidation level of carp.The above results showed that hydrolyzed fish meal protein replacing 45% fish meal protein had no significant effects on the growth performance of Pengze crucian carp,but the digestive,immune and antioxidant indice in serum,liver and midgut tissues and histomorphological structure have been significantly adversely affected;the replacement level of 60% significantly inhibited the growth of carp.In summary,the replacement level of fish meal protein by the protein of hydrolyzed feather meal in the feed used by Pengze crucian carp farming should not exceed 45%,and 30% is a suitable replacement level.