Abstract:Starch plays a very important role in the processing of extruded aquatic feed. It can not only enhance the stickiness of mash feed, but also play a dual role of expansion and adhesion in extruded feed. Due to the different granular structure of starch from different sources, the effects on the processing and quality of extruded aquatic feed are also different. This paper reviewed the research progress on the relationship between the basic characteristics of different starch sources and the processing and quality characteristics of extruded aquatic feed. The differences of starch components, structure, gelatinization properties, rheological properties and thermodynamic properties of different starch sources were analysed. The effects of different starch sources on the quality characteristics of extruded aquatic feed were compared. In addition, the problems and development directions of different starch sources in the research process were prospected.

Abstract:An 8-week feeding trial was conducted to study the effect of dietary n-3/n-6 fatty acid ratios on growth performance, body composition and serum antioxidant capacity of oriental river prawn (Macrobrachium nipponense). Five isonitrogenous and isolipid diets with different n-3/n-6 fatty acid ratios (D1: 0.29, D2: 0.56, D3: 1.02, D4: 2.20, D5: 8.52) were formulated to feed five groups of shrimps, respectively. Each diets was fed 4 tanks (4 replicates) with 45 prawns per tank.The results showed as follows: the survival rate of M. nipponensis was not significantly affected by n-3/n-6 fatty acid ratio in diet. The WGR and SGR of the prawns increased first and then decreased with the increasing dietary fatty acid ratios, and the WGR and SGR in D3 group was the highest and significantly higher than those of D1 group. The dietary n-3/n-6 fatty acid ratio had significant influence on the crude fat (CF) and crude protein (CP) of the whole body, and the crude fat reached the maximum value in D4 group, which was significantly higher than those in other groups. The crude protein of whole body in D3 group was significantly higher than those in D2, D4 and D5 groups. The n-3/n-6 fatty acid ratio in muscle was significantly positively correlated with the dietary n-3/n-6 fatty acid ratio. The serum superoxide dismutase (SOD) in D5 group was the highest, which was significantly higher than those in groups D1, D2 and D3, and not significantly different from that in group D4. Glutathione peroxidase (GSH-Px) reached its highest in D3 group, significantly higher than those in other groups. Serum malondialdehyde (MDA) was the highest in D5 group, which was significantly higher than those in D1 and D3 groups. The Hsp60 expression was the highest in group D4 and significantly higher than that in group D5, but not significantly different from groups D1, D2 and D3. The highest expression levels of Hsp70 and Toll in D2 group were significantly higher than those in other groups. Myd88 expression was the highest in D5 group and significantly higher than those in other groups. In conclusion, the dietary n-3/n-6 fatty acid ratio 1.02-2.20 can significantly improve the growth performance and non-specific immunity of M. nipponensis, and change the normal components and fatty acid composition of the prawn whole body.

Abstract:The aim of this study was to investigate the effects of adding extra fermented feed on the growth performance, oxidation resistance, immune function and metabolism of juvenile Chinese mitten crabs. Five experimental feeds were prepared: the commercial feed of juvenile crabs was used as the basal feed (F0), the experimental feed was made up of basal feed and extra 5% (F5), 10% (F10), 15% (F15), 20% (F20) fermented feed. 150 Chinese mitten crabs were randomly divided into 5 groups. There were 3 replicates in each group, and 10 crabs in each replicate. All the crabs were fed with the corresponding feed respectively. The feeding period was 59 days. Blood samples and hepatopancreas were collected after culture to determine the antioxidant indexes, immune indexes, and the activities of protein metabolization-related enzyme. The result showed that the weight gain rate and specific growth rate of juvenile crabs in the treatment groups were significantly higher than those in the control group (P < 0.05). The content of catalase in hemolymph first increased and then decreased with the increase of fermented feed, and those in the F5, F10 and F15 groups were significantly increased compared with the F0 (P < 0.05). The activity of acid phosphatase in each treatment group was higher than that in the control group, but the difference was not significant (P > 0.05). The content of total protein and globulin in each group first increased and then decreased with the increase of fermented feed, but the difference among groups was not significant (P > 0.05). In addition, the activities of trypsin, pepsin, aspartate transaminase and alanine transaminase in treatment groups were higher than those in F0. The addition of fermented feed can promote the growth performance of juvenile Chinese mitten crabs, and improve their antioxidant capacity, immune function and protein metabolic capacity.

Abstract:An 8-week growth trial was conducted to determine the effects of dietary protein levels on growth, body composition and health status of paddlefish (Polyodon spathula). Five experimental diets were formulated to contain 35.44%, 37.20%, 39.19%, 42.05% and 45.30% dietary crude protein (CP) with 5% lipid levels, respectively. At the end of the experiment, fish fed 35.44% to 42.05% CP diet resulted in significantly higher weight gain rate and specific growth rate, and both decreased at 45.30% CP level. The protein efficiency rate did not change significantly when the dietary CP increased from 35.44% to 42.05%; however, it significantly decreased when protein level reached 45.30%. The body composition of the experimental fish did not change significantly with the increase of dietary protein levels. The protein apparent digestibility coefficients (ADC) of 39.19% CP level is significant higher compared with other groups, which was contrary to lipid ADC and dry matter ADC. Liver lipase activity of P. Spathula peaked with the fish fed 42.05% CP level. The highest superoxide dismutase activity of the P. spathula was observed in the 37.20% treatment, and the activity of catalase significantly increased when CP level reached 39.19% compared to the 35.44% treatment. Based on second-order polynomial regression analysis of weight gain rate and specific growth rate, the recommended dietary protein level for P. spathula diet is 40%-41%.

Abstract:This study was conducted to investigate the effects of dietary n-3 highly unsaturated fatty acids (n-3 HUFA) on growth performance, non-specific immunity, expression of some immune-related genes and resistance to Vibrio harveyi in juvenile hybrid grouper (Epinephelus fuscoguttatus ♀×E. lanceolatu♂). Six isoproteic and isolipidic experimental diets were formulated with graded levels of n-3 HUFA (0.65%, 1.00%, 1.35%, 1.70%, 2.05% and 2.40% of dry matter, respectively), and 0.65% group was used as control group. Each diet was randomly allocated to triplicate groups of fish in 1 000 L fiberglass tank, and each tank was stocked with 40 fish [initial weight (12.06 ±0.01) g] for 8 weeks. Results showed that feed conversion ratio (FCR), survival rate (SR), hepatosomatic index (HSI) and condition factor (CF) were not significantly affected by dietary n-3 HUFA levels. Weight gain (WG) and specific growth rate (SGR) in 1.35% group were significantly higher than those in 2.40% group. Crude lipid of body in 1.00% group was significantly lower than those in 1.70% and 2.40% groups Liver and muscle fatty acid profiles reflected that of diets. Before challenge, the activity of serum superoxide dismutase (SOD), catalase (CAT) and content of complement 3 (C3) in 1.35% and 1.70% groups significantly higher than those of control group. After challenge, serum CAT, glutathione peroxidase (GSH-Px), lysozyme (LZM) and C3 all increased sharply, while SOD showed the opposite trend. Before challenge, the expression levels of intestine toll-like receptor 22 (TLR22) and myeloid differentiation factor 88 (MyD88) mRNA in 2.40% group were significantly increased, and the expression levels of tumour necrosis factor α (TNF-α) and interleukin 1β (IL-1β) mRNA in 2.05% group were significantly higher than those in 1.00% and 1.35% groups. In addition, the TLR22 and IL-1β mRNA levels in kidney of 1.70% group were significantly lower than those in control group. After challenge, the expression level of MyD88 mRNA in intestine of 1.35% group was significantly higher than that in 1.00% group and from 1.70% to 2.40% group, while TNF-α and IL-1β obtained minimum values in 1.70% group. In the kidney, the interleukin 10 (IL10) mRNA expression was significantly higher in 1.70% group than those in other groups, while the IL-1β expression in 1.70% group showed the opposite trend and significantly lower than that in 2.40% group. Results of this study suggested that moderate dietary n-3 HUFA (1.47%-1.70% HUFA) could improve the growth performance, non-specific immunity and inhibit the inflammatory response of hybrid grouper.

Abstract:An 8-week feeding trial was conducted to evaluate the effects of dietary fiber on growth performance, plasma biochemical indexes, intestinal histology, and structure of intestinal bacteria of juvenile Jian carp (Cyprinus carpio var. jian). Five isonitrogenous and isolipidic diets were formulated to contain 1.8%, 5.2%, 8.8%, 12.2% and 15.8% cellulose, respectively. The results indicated that Jian carp fed the diets containing 8.8% fiber had significantly higher weight gain rate(WGR)、specific growth rate (SGR) and protein efficiency ratio (PER) than those fed the other fiber diets, while plasma alanine amiotransferase (ALT) and aspartate transaminase (AST) activities significantly decreased. Viscerosomatic index (VSI), hepatosomatic index (HSI), triglyceride (TG), total cholesterol (TC) and glucose (GLU) contents significantly decreased with increasing dietary fiber levels. Compared to the control, the carnitine palmitoyltransferase I (CPT-1), adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and peroxisome proliferator–activated receptor (PPAR-α) activities in liver significantly increased in fish fed the diets with 5.2%, 8.8% or 12.2% fiber levels. Moreover, the histological structures of midgut and hindgut were impaired in fish with 15.8% fiber, and the intestinal microbial ecosystem investigation showed an beneficial effects at a higher supplemental level (15.8%), and improvement in liver histostructure at high fiber levels. These findings indicated that dietary fiber levels could improve liver function and intestinal health of Jian carp; also, higher dietary fiber levels have a positive impact and decrease the potential risk of disease in Jian carp. Based on SGR, a dietary fiber level of 9.19% was optimal for growth performance of juvenile Jian carp.

Abstract:A 65 d feeding trial was conducted in a float cage to study the effect of dietary n-3/n-6 HUFA(D1:14.28, D2:9.26, D3:5.66, D4:3.06, D5:2.02, D6:1.50) on growth, body composition and fatty acid composition of tissue in juvenile rockfish (Sebastes schlegeli). Six diets were formulated to feed six groups of juvenile S. schlegeli [mean initial weight (36.30±0.03) g], respectively. Each diet was randomly fed to triplicate groups of 30 fish per cage. The results show that: ①Dietary n-3/n-6 HUFA had no significant impact on the survival rate of fish (P>0.05).With the decreasing of dietary n-3/n-6 HUFA, the weight gain rate first increased and then decreased, the feed conversion ratio (FCR) showed an opposite trend, and the weight gain rate of D2 and D3 groups was significantly higher than that of other groups (P<0.05). ②The crude fat in the whole fish and muscle showed a trend of increased first and then decreased, which reaching their peaks in group D2 and D3, respectively(P<0.05).The crude fat in the liver first decreased and then increased, and the D2 group was significantly lower than the other groups (P<0.05).③ The content of C20:4n-6 in all tissues were increased with the decreasing of dietary n-3/n-6 HUFA. C20:5n-3, C22:6n-3 and n-3/n-6 HUFA in all tissues showed an overall decreased trend. ④The fatty acid composition of fish body was affected by the dietary, in order of abdominal fat, muscle, whole fish and liver. The dietary C20:4n-6 was negatively correlated with C20:5n-3 of all tissues. Under this experimental conditions, the appropriate proportion of dietary n-3/n-6HUFA (5.66-9.26) can significantly improve the growth of experimental fish, and modify body composition and fatty acid composition of tissues. The univariate quadratic regression analysis, based on weight gain rate and feed conversion ratio, showed that the appropriate proportion of n-3/n-6 HUFA in the dietary of juvenile S. schlegeli is 8.93 and 8.70, respectively.

Abstract:In order to study the effects of replacement of soybean oil (SO) with black soldier fly larvae oil (BSO) in grass carp production practice, five isolipidic and isonitrogen experimental diets were formulated by replacing 0% (SO), 25% (BSO25), 50% (BSO50), 75% (BSO75) and 100% (BSO100) of SO with BSO, respectively. After 56 days of feeding, the changes of growth performance, body composition, serum biochemical indexes, antioxidant capacity, intestinal and liver tissue structure, and intestinal microbiota of grass carp were detected. The results showed that there were no significant differences in WGR, FCR, SGR, VSI, CF and HSI among the treatment groups. Compared with the SO group, the activity of serum superoxide dismutase (SOD) in BSO25 and BSO50 groups was significantly higher, malondialdehyde (MDA) activity in BSO75 and BSO100 groups was significantly decreased, and the catalase (CAT) activity was significantly increased in BSO50, BS075 and BSFO100 groups. The morphology of liver cells in BSO100 group was mostly of irregular shape, with unclear boundaries between cells. The enzyme activity of AST, ALT and LDL-C in serum was significantly higher than that of SO group. The community diversity indexes Sobs, Shannon and the richness indexes Chao, Ace in the BSO100 group were significantly higher than those in the SO group. The results showed that 100% soybean oil replaced by BSO did not affect the growth of grass carp, and it could enhance the antioxidant capacity and the abundance and diversity of intestinal microbiota. However, in group BSO100, the liver was damaged, and long-term feeding will have an adverse effect on the body. Therefore, in the feed, BSO should not completely replace soybean oil. It is suggested that the replacement ratio should not exceed 75%.

Abstract:Exosome, a 30-150 nm vesicle, is secreted by a variety of cells, which influences or changes the behavior of recipient cells by transferring proteins, lipids, mRNAs and miRNAs, etc., and has been proved to be a new mode of intercellular communication. Exosomes have been found to be involved in the processes of fat synthesis and obesity, liver steatosis, insulin resistance, immune regulation, inflammatory response, tumorigenesis, vascular and neurogenesis, and osteogenesis. This article mainly expounds the formation and biological characteristics of exosomes, separation and identification method of exosomes. Moreover, it expounds the potential functions of adipose-derived exosome in the physiological and pathological process, and summarizes the research progress of exosomes in aquatic animals. It will provide new approach to lipid metabolism, pathological mechanisms of related diseases and potential intervention target. Also, it will provide basic theoretical knowledge of the role of exosome in glucose and lipid metabolism disturbance of fish.

Abstract:This experiment was aimed to investigate the effects of lysine on growth, feed utilization, serum biochemical indexes, lysine metabolism enzyme activity and its related gene expression of Leuciscus brandti. Six isoenergetic (17 MJ/kg) and isonitrogenous (37% CP) experimental diets were formulated with different levels of lysine (1.82%， 2.27%， 2.72%， 3.17%， 3.62% and 4.07%). Total 900 L.brandti with initial weight (13.44 ±1.10) g were randomly divided into 6 groups (3 replicates per group and 50 L.brandti per replicate) and were reared with 6 experimental diets for 8 weeks. The results indicated that when the dietary lysine level reached 3.17%, the weight gain (WG) and specific growth rate (SGR) of L.brandti in this group not significantly different from that in the 3.62% group, but significantly higher than that other groups (P < 0.05). The feed efficiency (FE) and protein efficiency (PER) of the 2.27%, 2.72%, 3.17%, 3.62% and 4.07% groups were significantly higher than that of the 1.82% group (P < 0.05). When the lysine level is 3.17%, the content of insulin-like growth factors-1 (IGF-1), total cholesterol (TC), total amino acid (TAA), total protein (TP), globulin (GLB) and albumin (ALB) were significantly higher than those of the 1.82% group in the serum (P < 0.05); at the same time, the content of blood urea nitrogen (BUN), the alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were significantly lower than those of the 1.82% group (P < 0.05). In the hepatopancreas, the lysine-ketoglutarate reductase (LKR) activity among all groups had significant differences (P < 0.05), and it increased significantly with the increase of lysine level; the aminoadipate-semialdehyde synthase (AASS) activity among the 2.72% group, 3.17% group, 3.62% group and 4.07% group had no significant difference, but they were significantly higher than those of the 1.82% group and 2.27% group (P < 0.05). In the serum, the LKR activity among the 2.72% group, 3.17% group and 3.62% group had no significant difference, but they were significantly higher than the 1.82% group and 4.07% group (P < 0.05); the AASS activity of the 2.72% and 3.17% groups was significantly higher than that in 1.82% and 2.27% groups, and significantly lower than that in 3.62% and 4.07% groups (P < 0.05). In the hepatopancreas, the AASS gene expression among the 2.72% group, 3.17% group, 3.62% group and 4.07% group was no significant difference, but they were significantly higher than the 1.82% group (P < 0.05); the cationic amino acid transporter-1(CAT1) gene among the 3.17% group and 3.62% group was no significant difference, but they were significantly higher than those of the 1.82% group, 2.27% group, 2.72% group and 4.07% group (P < 0.05). In conclusion, when the lysine level was 3.17% of the diets or the lysine level was 8.5% of the protein, it could promote the growth, feed utilization, protein metabolism, lysine metabolism and transport ability of L.brandti.

Abstract:This study investigated the protective effect of myo-inositol on oxidative damage of head kidney and spleen in juvenile grass carp (Ctenopharyngodon idella) induced by Aeromonas hydrophila. A total of 540 C. idella [(221.83±0.84) g] were fed six diets with graded levels of myo-inositol [27.0(unsupplemented), 137.9, 286.8, 438.6, 587.7, 737.3 mg/kg] for 10 weeks. Subsequently, a challenge test was conducted by injection of A. hydrophila and the survival rates recorded for 14 days. The results indicated that compared with myo-inositol deficiency (basal diet, unsupplemented), optimal myo-inositol supplementation decreased reactive oxygen species (ROS), malondialdehyde (MDA), and protein carbonyl contents, and increased the activities and mRNA levels of superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferased and glutathione reductase, and contents of glutathione in the head kidney and spleen after injection of A. hydrophila. Meanwhile, compared with myo-inositol deficiency (basal diet, unsupplemented), optimal myo-inositol supplementation up-regulated NF-E2-related factor 2 (Nrf2) mRNA and protein levels, and down-regulated Kelch-like ECH-associated protein-1 (Keap1) a and b mRNA levels in the head kidney and spleen after injection of A. hydrophila. These results suggested that optimal myo-inositol supplementation could protect fish head kidney and spleen structural integrity through increased antioxidative ability after injection of A. hydrophila. Finally, based on the antioxidant indices ROS content in the head kidney and spleen after injection of A. hydrophila, the myo-inositol requirement for juvenile C. idella was estimated to be 452.1 and 449.0 mg/kg diet, respectively.

Abstract:The shortage of fishmeal is an urgent problem to be solved in the research of aquaculture nutrition. Given that fish by-product accounts for more than 60% of processed fish biomass, more efficient use of marine protein from fish by-products and improving their nutritional value are important ways to alleviate fish meal shortage at present. Fish protein hydrolysate, which mainly contains a mixture of small peptides and free amino acids, is produced by hydrolyzing fish by-products. More and more studies have proved that fish protein hydrolysate has a beneficial effect on the growth performance of aquatic animals. This paper reviews the preparation of fish protein hydrolysate, its nutritional characteristics and study on aquaculture nutrition. This study systematically discusses the research results of fish protein hydrolysate in the field of aquaculture nutrition in recent years, and proposes further research directions in aquafeed, in order to provide reference for the study of fish protein hydrolysate in aquaculture nutrition and aquafeed application.

Abstract:To study the effect of lipid level on the expression of carnitine palmitoyl transferase I (CPT1) gene in the body tissues of Micropterus salmoides and the expression patterns of different growth stages, three different isonitrogenous diets with graded levels of lipid [6% (low lipid), 12% (medium lipid) and 18% (high lipid)] were fed to M. salmoides with the initial weight of (23.60 ±1.26) g. Tissue samples of liver, intestine, kidney and muscle were taken on the 30th, 60th and 90th day of feeding, and the 18S was used as the internal reference gene. The real-time PCR experiment was performed with CPT1 specific primers, and the relative expression data of CPT1 gene were obtained by 2^−△△C_T method. The results showed that the expression level of CPT1 gene was the highest in the liver, followed by intestine and kidney, and the expression level was lower in gill filament, heart, muscle, stomach, brain and spleen; at different fat levels, the expression of CPT1 increased with the increase of lipid level; in different growth stages, the expression of CPT1 increased with the prolongation of feeding time. The results showed that the increase of lipid level and feeding time would induce the expression of CPT1 gene, and CPT1 gene may play a certain role in the decomposition of fat in M. salmoides.

Abstract:To investigate the effects of adding sodium chloride (NaCl) to diets on the growth performance and flesh quality of Ctenopharyngodon idella, five diets were prepared with NaCl addition at 0 (control diet), 10, 20, 30, 40 g/kg and fed to C. idella with an initial body weight of (12.26±0.03) g. After 60 days of feeding, 10 and 20 g/kg NaCl groups showed the similar growth to the control, while 30 and 40 g/kg NaCl groups had lower weight gain and higher feed conversion ratio than the control. No significant differences were observed in flesh proximate composition except ash among all the groups, and the ash content increased with the increasing NaCl level. The water-holding capacity was significantly decreased by the supplementation of NaCl except in thawing loss of 10 g/kg NaCl group. The addition of 10 and 20 g/kg NaCl increased the total free amino acids contents, but the supplementation of 20, 30, 40 g/kg NaCl significantly decreased the contents of free Glu and Asp in flesh. Dietary NaCl decreased the flesh hardness and the supplementation of 30 and 40 g/kg NaCl decreased the flesh chewiness, but there was no significant difference in elasticity and resilience among all the groups. In intestinal histology, the villus height and the villus width of 30 and 40 g/kg NaCl groups were significantly lower than those of the control, and the supplementation of NaCl significantly increased the muscular thickness. In conclusion, the supplementation of NaCl (10-40 g/kg) in diet did not improve the growth performance and flesh quality of C. idella.

Abstract:Oxidative decomposition of carbohydrate is an important source of energy for fish. Since carbohydrates are relatively cheap, adding appropriate amounts of carbohydrates to the feed can save protein, reduce feed costs, and reduce ammonia nitrogen excretion. However, a large number of studies have shown that fish have low ability to utilize carbohydrate. When carbohydrates content in the feed exceeds a certain level, the fish will suffer from impaired disease resistance, growth retardation, fatty liver, and higher mortality. Gut microbiota participates in the metabolism of various nutrients such as carbohydrates, lipids and amino acids, which significantly affects the animal nutritional metabolic processes. Increasing the utilization rate of feed has important practical significance for increasing fish production and farmers’ income. This review starts from the carbohydrate metabolism of fish and targets the microbial flora of fish digestive tract. Further, it explains the ways and possible mechanisms associated with the regulation of fish carbohydrate metabolism by gut microbiota. This review may provide new perspectives for efficient carbohydrates usage and protein saving in fish culture.

Abstract:The objective of this study was to assess the optimal dietary lipid requirement of red swamp crayfish broodstock(Procambarus clarkia), In present study, 324 crayfish with average initial body weight of (15.46±0.20) g were randomly divided into 6 groups with 3 replicates of 18 crayfish in each replicate. Crayfish in each group were hand-fed a semi-purified diets containing different lipid levels [1.98% (control group), 4.12%, 4.98%, 7.89%, 10.48% and 11.89%] for 8 weeks. At the end of feeding trial, growth performance, muscle composition, reproductive performance, activities of digestive enzyme in hepatopancreas, and hemolymph biochemical indexes were measured. The results showed as follow, 1) as dietary lipid level increasing, the weight gain rate(WGR) and specific growth rate(SGR) of crayfish broodstock increased at first and then decreased. The feed conversion ratio(FCR) and hepatosomatic index(HSI) showed a increase trend, and were highest in 11.89% group. 2)The dietary lipid levels did not significantly affect the muscle moisture and ash contents. The lipid content of the muscle gradually increased as dietary lipid level increasing, and then tended to decrease, and was highest in 5.84% group. 3)With the increase of lipid levels, gonad index, egg-carrying rate and egg carrying capacity of crayfish broodstock were increased at first and then decreased; all of them in 7.89% group were highest. 4)The total protein (TP) content of haemolymph trended to decrease as dietary lipid level increasing. Alanine aminotransferase(ALT) activity and aspartate aminotransferase(AST) activity in haemolymph significantly increased as dietary lipid level increasing, both of them in 11.89% group was highest. The dietary lipid level did not significantly affect the glucose content of haemolymph. 5)The dietary lipid level significantly affected the activities of hepatopancreas protease and lipase, but not amylase activities. Broken-line regression analysis using WGR as response criteria shows that the optimal requirement of dietary lipid for red swamp crayfish broodstock is 7.60%. The comprehensive analysis of growth performance, muscle composition, reproductive performance, activities of digestive enzyme in liver, and hemolymph biochemical indexes showed that appropriate lipid level for red swamp crayfish broodstock was 7.60%~7.89% under this trial condition.

Abstract:Creatine (Cr) is an amino acid derivative, also known as N-methylphthalic acid or musclin. It has been widely used to improve human health, especially for promoting muscle growth. This paper reviewed the synthesis, transport and storage of creatine in animals, and the role of creatine in energy metabolism in muscle and liver. We analyzed the effects of dietary creatine supplementation on animal growth and slaughter performance, and reviewed the studies for the effects of dietary creatine on meat quality, including muscle pH, water holding capacity and flesh color. Finally, the prospects of further research on application of creatine in aquatic animals were discussed.

Abstract:The present study was conducted to determine the potential mechanisms of dietary lipid level influencing lipid deposition in the ovary of yellow catfish Pelteobagrus fulvidraco. For this purpose, two experiments were designed. In vivo, yellow catfish were fed with three diets containing 6.98%, 11.34% and 15.41% of lipid levels. In vitro, the primary oocytes from yellow catfish were incubated with three fatty acid levels (0, 0.2 and 0.5 mmol/L), respectively. Triacylglyceride (TG) contents, methylation level of PI3KCa, and enzymes activities of FAS, G6PD, 6PGD, and ME, as well as the mRNA level of PI3KCa, DNMTs and other genes involved in lipid metabolism were determined in the ovary and oocytes of yellow catfish. GSI increased with increasing dietary lipid levels. Among three lipid treatments, TG content and the enzyme activities of FAS, G6PD, 6PGD, and ME, and mRNA expression of LPL and CD36 were highest in the 11.34% of dietary lipid level in the ovary; CPT IA mRNA expression was the highest for fish fed 15.41% dietary lipid; the lowest mRNA level of PI3KCa and the highest methylation percentage of PI3KCa promoter at -64 and -52 CpG sites were found in the 15.41% of dietary lipid group; Dietary lipid levels influenced the mRNA level of DNMT3b, but not the expression of DNMT1 and DNMT3a. DNMT3b mRNA expression was the highest in 15.41% of dietary lipid group, indicating that DNMT3b was more sensitive than DNMT1 and DNMT3a in response to dietary lipid level. In contrast, the in vitro study indicated that TG content, enzyme activities of FAS, G6PD and ME, and G6PD mRNA expression were the highest in the 0.5 mmol/L FA group, and mRNA expression levels of CPT IA, ACCb, LPL and CD36 were the highest in the control; FA incubation significantly increased the mRNA level of PI3KCa, reduced mRNA levels of DNMT1 and DNMT3b, but showed no significant effect on the methylation of PI3KCa promoter and on mRNA expression of DNMT3a.

Abstract:Trace elements, as cofactors or structural components of various enzymes, participate in various metabolic processes and play a key role in maintaining animal health and normal physiological function. Although trace elements requirements for animals are very small, lack, excess or imbalance of intake will bring serious adverse effects on animal growth, metabolism, immunity and reproduction. In this review, the effects of trace elements on growth and metabolism, immunity, disease prevention, gonadal development and other aspects of shrimp, and the mechanism of absorption, transport and metabolism of inorganic and organic trace elements were systematically summarized, which might provide theoretical basis for the development of shrimp feed in the future.

Abstract:In the current production of aquafeeds, oils are usually added directly or by vacuum coating. However, few reports were seen about the application of fat powders in aquaculture. In this study, with soybean oil (SO, linoleic acid∶linolenic acid = 9∶1) and blend oil consisting of soybean oil and rapeseed oil (BO, linoleic acid∶linolenic acid = 5∶1) as dietary lipids, four formulated feeds (SOl, BOl, SOp and BOp) were prepared by adding SO or BO in liquid or powder forms. After the tilapia juveniles (GIFT Oreochromis niloticus) with an initial average weight of 15.38 g were fed with the diets in indoor aquarium for 8 weeks, the growth indexes including weight gain rate, specific growth rate, feed coefficient, hepatobody ratio and viscera ratio showed no significant difference among the four groups. However, compared with the corresponding indexes in fish fed SOl, the liver catalase and superoxide dismutase activity were significantly increased, while the muscle crude ash content was significantly decreased in fish fed SOp; the serum levels of triglyceride and low density lipoprotein, as well as the whole fish water content were significantly reduced, while the liver total antioxidant capacity, whole fish protein content and muscle shear force values were significantly increased in the SOp, BOl, BOp groups. In addition, the serum catalase activity and muscle hardness of BOp group were significantly higher than those of SOl, BOl and SOp groups. The fatty acid composition of liver and muscle showed little difference among the groups, reflecting the fatty acid profile of feed. The results indicated that compared with liquid oil, fat powder had no adverse effect on the growth of tilapia and could improve the health and muscle quality of fish. The effect of blend oil is better than that of soybean oil. Combined with the advantages of packaging, transportation, storage and usage, fat powder is worth promoting and applying in aquaculture production.