Effects Of Different Dietary Lipid Sources On Flesh Quality Of Black Carp（Mylopharyngodon Piceus）

Black carp（Mylopharyngodon piceus）,as the main economic farmed fish in China,is loved by the majority of consumers.However,due to the shortage of fish oil in the farming process,there is a general decrease in the quality of aquatic products after replacing fish oil with other lipid sources,such as reduced nutritional value,poor texture and obvious earthy smell.This study was conducted to investigate the effects of different lipid sources on the flesh quality of black carp,to find appropriate lipid sources to replace fish oil,and to provide a theoretical basis for the subsequent research.Fish oil（FO）,pork lard（PL）,rapeseed oil（RO）,com oil（CO）,peanut oil（PO）and soybean oil（SO）were used as lipid sources to prepare six kinds of isonitrogenous and isoenergetic feeds.A total of 540 juvenile black carp with an initial weight of（5.25 ± 0.25）g were selected and randomly divided into 6 groups with 3 replicates of 30 fish in each group.Each group was fed with six different lipid sources and the culture cycle was 180 days.The results showed as follow:1.Growth performance,blood physiological and biochemical indexes and muscle nutrients were investigated:The weight gain rate（GW）and specific growth rate（SGR）of PL,RO,CO,PO and SO groups were not significantly different from those of FO group（P>0.05）.The lipid source had no significant effect on the number of leukocytes and erythrocyte pressure volume in the blood（P>0.05）,while the concentrations of lymphocytes in PL and PO groups were significantly lower than those of FO,RO,CO and SO groups（P<0.05）.The serum triglyceride（TG）content was significantly lower in the RO,CO and PO groups than in the FO,PL and SO groups,while the high-density lipoprotein cholesterol（HDL-C）content was significantly higher than in the FO,PL and SO groups（P<0.05）.The alkaline phosphatase（ALP）activity in serum was significantly higher in the FO and RO groups than in the PL,CO,PO and SO groups（P<0.05）.The crude protein content in muscle of FO,PL,RO,CO and PO groups was significantly higher than that in SO group,while crude lipid content in muscle of PL and SO groups were significantly higher than those of the FO,RO,CO and PO groups（P<0.05）.The water-soluble protein content in muscle was significantly lower in the RO,CO,PO and SO groups than in the FO and PL groups（P<0.05）.And the content of salt-soluble protein in the muscle of RO group was significantly higher than that of CO,PO and SO groups in FO,PL groups（P<0.05）.2.Muscle texture,tissue structure and protein degradation were investigated:The muscle firmness was significantly higher in the FO,RO and SO groups than in the PL,CO and PO groups,while muscle resilience was significantly lower in the SO group than in the FO,PL,RO,CO and PO groups（P<0.05）.The diameters of dorsal muscle fibers were significantly higher in the SO group than in the other groups（P<0.05）.The muscle fiber density in the PO and SO groups was significantly lower than that in the other groups（P<0.05）.The muscle fibers of the dorsal muscles in the FO,PL and RO groups were structurally and regularly shaped,with uniform nuclear distribution and no aggregation,and the muscle fibers were closely aligned with each other without curvature.The structure of the muscle fibers in the CO,PO and SO groups was incomplete,twisted and deformed in a jagged shape,with some nuclear cells showing aggregation and the presence of vacuolation.The Cath-B content in the muscles of the SO group was significantly higher than that in the FO,PL,RO,CO and PO group（P<0.05）.3.Fatty acid composition,antioxidant indexes and flavor in muscle:The content of saturated fatty acids in muscle of RO group was significantly lower than that of FO,RO,CO,PO and SO group（P<0.05）.There no significant difference in C18:3n-3 content among all groups（P>0.05）.PUFA content of muscle of PO group was significantly lower than that of FO,PL,RO,CO,SO groups（P<0.05）,and the content of DHA（C22:6n-3）was significantly lower than that the other groups（P<0.05）.The total antioxidant capacity（T-AOC）of muscles in FO RO and SO groups was significantly higher than in PL and PO groups,but all were significantly lower than in CO group（P<0.05）.The content of malondialdehyde（MDA）in muscles in FO,PL and SO groups was significantly higher than in RO and CO groups（P<0.05）.The content of 1octen-3-ol in the dorsal muscles of PL,CO and PO groups was significantly higher than that of FO,RO groups（P<0.05）.The content of nonanalin the dorsal muscles of PL,PO and SO groups was significantly higher than that of FO,CO and RO groups（P<0.05）.The content of benzaldehyde in the dorsal muscles of FO,RO groups was significantly higher than that of PL,CO,PO and SO groups（P<0.05）.In conclusion,different lipid sources in the feed have no effect on the growth performance of black carp,and fish oil and rapeseed oil can improve the muscle nutritional value,texture and flavor when used as lipid sources,thus improving the flesh quality of black carp.