Evaluation of effects of compound oil and low fish meal feed on the cultivation of Trachinotus ovatus 

ZHENG Jun1, XIE Dizhi1, YE Rukai1, ZHANG Haitao2, WANG Zhaoduo2, XIE Ruitao2, LI Yuanyou1

（1. College of Marine Sciences of South China Agricultural University , Guangzhou〓510642, China; 

2.China Key Laboratory of Aquatic, Livestock and Poultry Feed Science and Technology in South China,

 Ministry of Agriculture and Rural Affairs, Guangdong Evergreen Feed

 Industry Co., Ltd., Zhanjiang Guangdong〓524000, China）

Abstract: 

Cumulative studies have shown that adequate lipid consumption is beneficial for improving the growth, protein efficiency ratio, and nitrogen and phosphorus retention of fish, as well as saving dietary protein and cost. Golden pompano Trachinotus ovatus, one of the promising candidates for intensive aquaculture in southern China with an annual production of around 240,000 tons, is a carnivorous marine fish. The dietary protein requirement of T. ovatus is relatively high at around 50%. Based on the essential fatty acids (EFA) requirement of T. ovatus［1.241.73% n3 high unsaturated fatty acids (HUFA), ratio of DHA to EPA about 1.4］, the compound oil products (BO, consisting of fish, soybean, rapeseed and perilla oils with proper proportions) were developed by our group. In the previous studies, the growth promoting effects of compound oil and low fish meal diets (6 % fish meal) on Trachinotus ovatus was similar with control diets (fish oil and 20 % fish meal, prepared by smallscale production technology and culture conditions). To further evaluate the largescale application effect of compound oil products and low fish meal diets on the culture of Trachinotus ovatus, four isoproteic (48%) and isolipidic (11%) diets (D1 D4) were formulated by the largescale production process in a local feed company. Based on the commercial feed of Trachinotus ovatus (containing 20% fish meal), D1 contained 10% fish oil, D2 10% compound oil, D3 8% compound oil +4% fat powder. While diet D4 was low fish meal diet (containing 6.6% fish meal) with compound oil + fat powder. Each diet was fed to triplicate groups of Trachinotus ovatus juveniles (initial body weight about 64.75 g) in floating pond cages (2 m×2 m×1.5 m, 100 fish per cage) for 8 weeks. During the 8week feeding trial, the water temperature was 26.532.5 ℃, salinity was 2732 ‰. Fishes were fed to nearly satiation twice a day at 8∶〖KG-*2〗00 and 16∶〖KG-*2〗00. At the end of the feeding trial, all fishs were weighed after being fasted and anesthetized with 0.01% 2phenoxyethanol. Six fishes per treatment were sampled for measuring body proximate composition, six fish were sampled for measuring muscle texture and the remaining six fish per treatment were sampled for collecting serum, liver, dorsal and ventral muscle. All samples were quickly frozen in liquid nitrogen and then stored at -80°C until analysis. The comparative analysis of growth performance, proximate composition of the whole body and muscle, serum biochemical parameters and hepatic antioxidant parameters, muscle fatty acid profiles, edible quality, and texture was studied among the four groups. The results showed that the final weight, weight gain rate (WGR), specific growth rate (SGR), daily intake rate (DFR), condition factor (CF), hepatosomatic index (HSI), viscerosomatic index (VSI) and survival rate (SUR), as well as proximate composition (moisture, crude fat, crude protein, crude ash) of all body displayed no significant difference among the four dietary groups (P>0.05). However, the feed coefficient (FC) of fish in diet D2 was lower than that of fish in the other three diets, and even significantly lower than that of fish in diet D1 (P<0.05). Comparing to D1 and D2 groups, low serum glutamic oxalacetic transaminase (GOT) and glutamicpyruvic transaminase (GPT) activities, and low density lipoprotein (LDL) levels were detected in D3 and D4 groups, and triglyceride (TG) level in D4 group was significantly lower (P<0.05). While serum highdensity lipoprotein (HDL) and total cholesterol levels (TCHO), acid phosphatase (ACP) activities were comparable among four groups (P>0.05). In terms of hepatic antioxidant parameters, there was no statistic difference in hepatic total antioxidant capacity (TAOC), catalase (CAT), superoxide dismutase (SOD) activities among the four groups (P>0.05), while low hepatic malondialdehyde (MDA) levels were observed in fish in diet D3 and D4. In terms of muscle nutrition, the crude protein and moisture content in the dorsal muscle of T. ovatus showed significant differences among four dietary groups (P<0.05). Specifically, the crude protein content of dorsal muscle was significantly higher in fish in D3 and D4 than that of D1 group (P<0.05). In addition, D2 group had lower dorsal muscle moisture content than the D1 group (P<0.05). while there was no difference in dorsal muscle moisture of fish among D1, D3 and D4 groups (P>0.05). The crude protein and moisture content of abdominal muscle showed no significant difference among four dietary groups (P<0.05), while crude lipid content in D4 group was significantly lower than that in D3 group (P<0.05). The fatty acid composition of dorsal and abdominal muscle of fish displayed parallel change pattern with the dietary fatty acid. Comparing to D1 group, the dorsal and abdominal muscle ARA, EPA, DPA DHA, HUFA and n3 polyunsaturated fatty acid (PUFA) content of D2D4 groups were significantly lower, while their monounsaturated fatty acid (MUFA) and n6 PUFA content were significantly higher (P<0.05). High dorsal muscle saturated fatty acid (SFA) levels were detected in D1D3 groups, while high abdominal muscle SFA levels were detected in D2 and D3 groups. Moreover, although the texture properties (tenderness, hardness, springiness, chewiness, gumminess, and cohesiveness) and edible quality (cooked meat rate and water holding capacity) of muscle showed no significant difference among four groups (P>0.05), numeric values of muscle texture in T. ovatus in D4 were higher than those in diet D1. These results indicate that compound oil and lowfish meal diets exhibit the same growthpromoting effect on Trachinotus ovatus as control diets (containing fish oil and 20 % fish meal), and also is beneficial to improving hepatic health, muscle quality, which can be widely applied in the culture of T. ovatus. The results obtained here lay foundation for the application of highefficiency and low fish meal diets in aquaculture.〖HJ〗

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Keywords: 

Trachinotus ovatus; compound oil; low fish meal feed; growth performance; muscle quality