Increase Of Dietary Lipid Level Research Articles

The Dietary Lipid Requirement for Ovarian Maturation and Health in Female Giant River Prawn, Macrobrachium rosenbergii Broodstock

The dietary lipid level is closely associated with ovarian maturation of broodstock. However, optimal lipid requirements during broodstock gonad development for aquatic animals remain limited. In order to assess the impact of dietary lipid levels (6%, 8%, 10%, 12%, and 14% lipid, denoted as L6%, L8%, L10%, L12%, and L14%) on the ovarian maturation, antioxidant status, and messenger RNA (mRNA) expression of genes involved in the lipid metabolism of Macrobrachium rosenbergii broodstock (initial weight 10.53 ± 1.97 g), this study carried out an 8‐week feeding experiment. The findings showed that while there was no significant difference in the survival rate across the groups (p > 0.05), the weight gain observed in prawns fed the 8% lipid‐level diet was significantly higher than those fed other diets (p < 0.05). The hepatosomatic index and the gonadosomatic index showed a significant increase with the rise in dietary lipid level (p < 0.05). More ovaries from M. rosenbergii broodstock reached stages Ⅲ and Ⅳ after being supplemented with dietary lipid levels between 8% and 14%. Serum glucose content did not show any significant difference among all groups (p > 0.05), but serum triglyceride and total cholesterol content increased followed by a decreasing trend with increasing levels of dietary lipids, both peaking in the prawns fed a 10% lipid‐level diet. Furthermore, the progesterone (PROG) and 17β‐estradiol (E2) content of prawns fed the 10% and 12% lipid‐level diets were significantly higher compared to other groups (p < 0.05). Based on serum E2 and PROG content, the optimal lipid level needed for maximal ovarian maturation was determined to be 11.79% and 10.88%, respectively. Moreover, there were more endogenous vitellogenic oocytes in prawns fed 8% and 10% lipid‐level diets, with a more compact arrangement compared to the less tightly arranged structure of the ovarian tissue in prawns fed other diets. With the increase in dietary lipid levels, there was a significant increase in the activity of superoxide dismutase. The activities of total antioxidant capacity and glutathione peroxidase initially increased and then decreased significantly, peaking at prawns fed 8% and 10% lipid‐level diets, respectively (p < 0.05). The malondialdehyde content reached its lowest point in prawns fed a diet containing 10% lipid. In addition, the mRNA expressions of hepatopancreatic diacylglycerol acyltransferase and acetyl‐CoA carboxylase showed the highest values in prawns fed a 10% lipid diet. Conversely, there was a significant decrease in the mRNA expression of carnitine palmitoyltransferase‐1a in the hepatopancreatic as dietary lipid levels increased. The highest mRNA expression of fatty acid‐binding proteins was observed in prawns fed an 8% lipid diet. In conclusion, dietary lipid levels ranging from 8% to 11.79% are beneficial for ovarian maturation and health of M. rosenbergii broodstock.

Effects of Dietary Protein and Lipid Levels in Practical Formulation on Growth, Feed Utilization, Body Composition, and Serum Biochemical Parameters of Growing Rockfish Sebastes schlegeli.

A 3 × 2 factorial experiment (protein levels, 42%, 46%, 50%; lipid levels, 9%, 12%) with three replicates was conducted in a circulating water system to investigate the effects of dietary protein and lipid levels on growth, feed utilization, body composition, and serum biochemical parameters of growing rockfish Sebastes schlegeli (initial weight, 29.98 ± 0.10 g). After an 8 weeks feeding trial, growth performance in terms of final body weight, percent weight gain, and specific growth rate increased with the increase of dietary protein level when fish fed diets containing a consistent level of dietary lipid. The feed conversion rate and daily feed intake were significantly affected by dietary protein and lipid levels, and decreased as dietary protein level increased from 42% to 46% or dietary lipid level increased from 9% to 12% (P < 0.05). Survival rate, viscerosomatic index, and hepatosomatic index were unaffected by dietary protein level (P > 0.05), but significantly increased with the increase of dietary lipid level (P < 0.05). On the contrary, condition factor was unaffected by dietary lipid level (P > 0.05), but significantly increased with dietary protein level increasing up to 46% (P < 0.05). The moisture contents of muscle and liver significantly decreased, but the whole-body crude lipid content, the crude protein and lipid contents of muscle increased as dietary protein or lipid level increased (P < 0.05). The contents of isoleucine, leucine, histidine, glycine, alanine of muscle, as well as the proportions of C14 : 0, C20 : 1, and C22 : 1n-9 in total fatty acids were higher in fish fed diets containing 12% lipid than those fed 9% lipid (P < 0.05), while C18 : 1n-9 and C18 : 2n-6 followed an opposite trend. The contents of phenylalanine, lysine, and tyrosine as well as the proportions of C18 : 0, C18 : 2n-6, C22 : 1n-9, and C22 : 6n-3 in total fatty acids decreased with the increase of dietary protein level (P < 0.05). Serum cholesterol and low-density lipoproteins increased significantly with dietary protein or lipid levels increasing, but TG concentration was elevated significantly in fish fed diets containing 12% lipid. Considering the present results in terms of growth and feed utilization, the suitable protein and lipid levels in diet for growing rockfish were 46% and 12%, respectively.

Effect of L-carnitine supplemented diets with varying protein and lipid levels on growth, body composition, antioxidant status and physio-metabolic changes of white shrimp, Penaeus vannamei juveniles reared in inland saline water

Addition of suboptimum protein and higher lipid in the diet can be a better strategy to develop an environment friendly feed for cultured species. But very high amount of dietary lipids can cause metabolic burden to the species leading to growth retardation and lipid accumulation in the body of the animals. In this context, a feeding trial of 60 days was conducted to find out the effect of L-carnitine supplemented diets with different protein and lipid levels on growth, feed conversion, nutrient utilization, body composition, antioxidant status and physio-metabolic responses of Penaeus vannamei juveniles reared in inland saline water (ISW) of 10 ppt salinity. Three hetero-nitrogenous (36.17, 33.13, 30.11% crude protein, CP), hetero-lipidic (5.12, 8.15, 11.17% lipid) and hetero-caloric (378–411 Kcal digestible energy or DE/100 g) diets were supplemented with three levels (0%, 0.05% and 0.1%) of L-carnitine to prepare nine experimental diets viz. P36L5C0 (36% CP, 5% lipid and 0% L-carnitine), P36L5C0.05 (36% CP, 5% lipid and 0.05% L-carnitine), P36L5C0.1 (36% CP, 5% lipid and 0.1% L-carnitine), P33L8C0 (33% CP, 8% lipid and 0% L-carnitine), P33L8C0.05 (33% CP, 8% lipid and 0.05% L-carnitine), P35L8C0.1 (33% CP, 8% lipid and 0.1% L-carnitine), P30L11C0 (30% CP, 11% lipid and 0% L-carnitine), P30L11C0.05 (30% CP, 11% lipid and 0.05% L-carnitine) and P30L11C0.1 (30% CP, 11% lipid and 0.1% L-carnitine). Six hundred and seventy-five (675) acclimated P. vannamei juveniles (average body weight, 4.02 ± 0.01 g) were randomly distributed to nine treatments viz. P36L5C0, P36L5C0.05, P36L5C0.1, P33L8C0, P33L8C0.05, P33L8C0.1, P30L11C0, P30L11C0.05 and P30L11C0.1in triplicate following 3 (protein-lipid levels) × 3 (dietary levels of L-carnitine) factorial design. The shrimp fed with 33% protein, 8% lipid and 0.05% L-carnitine showed significantly (p < 0.05) the highest weight gain percentage, specific growth rate, protein efficiency ratio, lipid efficiency ratio, and protease activity and the lowest feed conversion ratio. The hepatopancreas somatic index (HPSI) value, whole body lipid content and activities of amylase and lipase significantly (p < 0.05) increased with increase in dietary lipid level with the highest values found in 11% lipid fed group, but dietary L-carnitine caused the decreasing trend of HPSI and increasing trend of lipase respectively with the lowest and the highest values in 0.05% L-carnitine fed group. Similarly, the 0.05% L-carnitine fed group showed significantly higher body lipid content and amylase activity than its non-supplemented counterpart. Body moisture content significantly decreased with increase in dietary lipid level with the lowest value in 11% lipid fed group. However, dietary L-carnitine did not affect the body moisture level. The 33% protein, 8% lipid and 0.05% L-carnitine fed group exhibited significantly higher Carnitine palmitoyl transferase-I and glucose-6-phosphate-dehydrogenase activity than non-supplemented groups. The shrimp of 11% lipid fed group showed significantly lowest serum total protein and the highest serum glucose, cholesterol and triglycerides, gill and hepatopancreatic superoxide dismutase (SOD) and catalase (CAT) and hepatopancreatic malondialdehyde (MDA). But, 0.05% L-carnitine fed group showed significantly higher serum total protein and lower serum glucose, cholesterol and triglycerides and lower tissue SOD, CAT and MDA. In conclusion, P. vannamei juveniles reared in 10 ppt ISW and fed with 33% crude protein, 8% lipid and 0.05% L-carnitine diet can exhibit better growth performance, body lipid content, antioxidant status and physio-metabolic responses. This information will be useful in formulating the L-carnitine supplemented eco-friendly low protein high lipid or energy (LPHL or LPHE) feed for profitable culture of P. vannamei in ISW.

A high-fat diet alters lipid accumulation and oxidative stress and reduces the disease resistance of overwintering hybrid yellow catfish (Pelteobagrus fulvidraco♀×P. vachelli♂)

This study was carried out to investigate the influence of dietary lipid levels on the growth, immune response, and disease resistance of hybrid yellow catfish (Pelteobagrus fulvidraco♀×P. vachelli♂) during overwintering. Yellow catfish (initial body weight: 49.42 ± 1.33 g) were fed isonitrogenous diets (crude protein 40%) with three lipid levels (low lipid: 8.57%, medium lipid: 12.65%, and high lipid: 16.60%) for five weeks before the overwintering stage, and then all fish were fasted during overwintering. After overwintering, a bacterial challenge test was performed. The results showed that dietary lipid levels had no influence on the growth of hybrid yellow catfish before or after overwintering, but the high lipid (16.60%) diet significantly reduced the survival rate of the fish after bacterial challenge (P < 0.05). Crude whole-body fat content in each treatment after overwintering was significantly lower than that before overwintering. In addition, the liver lipid content significantly increased with increasing dietary lipid levels (P < 0.05). Before overwintering, expression levels of genes related to lipogenesis and lipolysis pathways in liver tissue were down-regulated by the 16.6% lipid diet (P < 0.05). Plasma superoxide dismutase (SOD) activities and malondialdehyde (MDA) contents were enhanced with the increase of dietary lipid level before the challenge test. Plasma SOD activities and MDA contents were significantly decreased in the high lipid group, and plasma cortisol content and lysozyme (LYZ) activity in the 16.60% lipid group were significantly higher than those in the 8.57% lipid group (P < 0.05) at 12-h post bacterial challenge. The mRNA expression levels of toll-like receptor 2 (tlr2) in spleen post-challenge were significantly downregulated compared to pre-challenge (P < 0.05). The transcriptional levels of interleukin 1β (il-1β), tumor necrosis factor α1 (tnfα1), interleukin 10 (il-10), and immunoglobulin M (igm) in spleen or kidney were significantly increased post-challenge compared to pre-challenge, and the relative expression levels of immune-related genes in the high lipid group were greater than those of the low lipid group post-challenge (P < 0.05). The results indicated that high dietary lipid (16.60%) induces oxidative stress and reduces disease resistance of hybrid yellow catfish through a pathway involving regulation of tlr and the inflammatory response during overwintering.

An investigation on the optimal lipid level for juvenile Chinese mitten crab ( Eriocheir sinensis ) reared under three salinities: Survival, growth, digestive enzyme activities, antioxidant capacity and body composition

A 56-day feeding experiment was performed to investigate the effects of the dietary lipid level on the survival, growth performance, digestive enzyme activities and antioxidant capacity of Eriocheir sinensis reared under three salinities. Six feeds with graded levels of lipids (5%, 7%, 9%, 11%, 13% and 15%) were formulated by including fish oil as the main lipid source. Sixty crab individuals (initial weight: 0.21 ± 0.02 g) were assigned to each aquarium. In total, 18 aquariums were distributed under each salinity condition. Each feed was randomly allocated to three parallel tanks of crabs. The feeding experiment lasted for 56 days. Results showed that the survival rate of E. sinensis fed diets with 7%–15% lipids just showed a decreasing tendency as the salinity increased. The highest weight gain rate (WGR) was found in the treatment with 11%, 9% and 5% lipid at the salinity of 0.5‰, 2‰ and 6‰ respectively. At the salinity of 0.5‰, 2‰ and 6‰, the highest activities of antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase) were detected in the treatments with 11%, 13% and 7% lipid respectively. As the salinity increased, the protein and lipid contents showed an increasing trend, while the moisture content showed an opposite trend. At each salinity, arachidonic acid and docosahexaenoic acid increased, while saturated fatty acids and monounsaturated fatty acids decreased with the increase of dietary lipid level. These results indicated that increasing salinity resulted in decreased antioxidant enzyme activities and increased malondialdehyde content in the juvenile E. sinensis, especially when they were fed diets with relatively higher lipid level. Based on WGR, digestive enzyme activity and antioxidant capacity, the optimal lipid level was estimated to be 8.28–13%, 7.54–13% and 5–8.89% for juvenile E. sinensis reared at the salinity of 0.5‰, 2‰ and 6‰ respectively.

Effect of dietary lipid levels on growth, body composition, and enzyme activities of larvae of butter catfish, Ompok bimaculatus (Actinopterygii: Siluriformes: Siluridae)

The Indian butter catfish, Ompok bimaculatus (Bloch, 1794), is a high-value catfish that has gained immense consumer preference in South-East Asia. However, information on the nutritional requirements of this species is scanty. Hence, an experiment was conducted to evaluate the effects of varying dietary lipid levels on growth, body composition, and activities of digestive and metabolic enzymes in larvae. Three isonitrogenous (40% crude protein) diets were formulated by supplementing fish and vegetable oil (1:1) at 4.5% (D1), 7% (D2), and 9.5% (D3) levels (containing crude lipid 5.7%, 8.0%, and 10.45%, respectively in diets D1–D3) to a fish meal- and oilcake-based formulated diet. Experimental diets were fed to butter catfish larvae (0.15 ± 0.01 g) in triplicate groups for a period of 42 days. Proximate compositions of the experimental diets, as well as fish carcass, were analyzed using standard procedures (AOAC 2005). Digestive and metabolic enzyme activities were analyzed at the completion of the experiment by standard methodology. Butter catfish larvae fed the diet D2 (8% crude lipid) resulted in the best performance in terms of weight gain (final weight 1.40 ± 0.07 g), net weight gain (1.31 ± 0.06 g), specific growth rate (5.50 ± 0.05% · day−1), and protein efficiency ratio (2.39 ± 0.17). The highest lipid deposition (2.90 ± 0.12%) in the carcass was also recorded in fish reared on diet D2. The final weight, net weight gain, protein efficiency ratio, and specific growth rate were significantly (P &amp;lt; 0.05) higher in D2 having 8% lipid. Moisture and lipid contents of the whole body were significantly (P &amp;lt; 0.05) higher in larvae fed diet D2. Amylase activity in fish significantly (P &amp;lt; 0.05) decreased with increasing dietary lipid levels. The maximum alkaline protease, pepsin, and lipase activities were noticed in the larvae fed diet D2. Progressive decrease in liver glucose-6-phosphate dehydrogenase activities and significant increase (P &amp;lt; 0.05) in the activities of neoglucogenic enzymes (glucose-6-phosphatase and fructose-1,6-bis phosphatase) were noticed with an increase in dietary lipid levels. Significantly lower (P &amp;lt; 0.05) activities of LDH, ALT, and AST were recorded in the group fed diet D2. Results of the study indicated that 8% crude lipid in the diet could assure optimum growth and survival of butter catfish larvae during early development. An appraisal on growth, body composition, and digestive as well as metabolic function in the butter catfish larvae recorded in the study might provide some important information to consider application of formulated diets for the larviculture of Ompok bimaculatus.

Effect of dietary lipid levels on growth, body composition, and enzyme activities of larvae of butter catfish, Ompok bimaculatus (Actinopterygii: Siluriformes: Siluridae)

The Indian butter catfish, Ompok bimaculatus (Bloch, 1794), is a high-value catfish that has gained immense consumer preference in South-East Asia. However, information on the nutritional requirements of this species is scanty. Hence, an experiment was conducted to evaluate the effects of varying dietary lipid levels on growth, body composition, and activities of digestive and metabolic enzymes in larvae. Three isonitrogenous (40% crude protein) diets were formulated by supplementing fish and vegetable oil (1:1) at 4.5% (D1), 7% (D2), and 9.5% (D3) levels (containing crude lipid 5.7%, 8.0%, and 10.45%, respectively in diets D1–D3) to a fish meal- and oilcake-based formulated diet. Experimental diets were fed to butter catfish larvae (0.15 ± 0.01 g) in triplicate groups for a period of 42 days. Proximate compositions of the experimental diets, as well as fish carcass, were analyzed using standard procedures (AOAC 2005). Digestive and metabolic enzyme activities were analyzed at the completion of the experiment by standard methodology. Butter catfish larvae fed the diet D2 (8% crude lipid) resulted in the best performance in terms of weight gain (final weight 1.40 ± 0.07 g), net weight gain (1.31 ± 0.06 g), specific growth rate (5.50 ± 0.05% · day−1), and protein efficiency ratio (2.39 ± 0.17). The highest lipid deposition (2.90 ± 0.12%) in the carcass was also recorded in fish reared on diet D2. The final weight, net weight gain, protein efficiency ratio, and specific growth rate were significantly (P &amp;lt; 0.05) higher in D2 having 8% lipid. Moisture and lipid contents of the whole body were significantly (P &amp;lt; 0.05) higher in larvae fed diet D2. Amylase activity in fish significantly (P &amp;lt; 0.05) decreased with increasing dietary lipid levels. The maximum alkaline protease, pepsin, and lipase activities were noticed in the larvae fed diet D2. Progressive decrease in liver glucose-6-phosphate dehydrogenase activities and significant increase (P &amp;lt; 0.05) in the activities of neoglucogenic enzymes (glucose-6-phosphatase and fructose-1,6-bis phosphatase) were noticed with an increase in dietary lipid levels. Significantly lower (P &amp;lt; 0.05) activities of LDH, ALT, and AST were recorded in the group fed diet D2. Results of the study indicated that 8% crude lipid in the diet could assure optimum growth and survival of butter catfish larvae during early development. An appraisal on growth, body composition, and digestive as well as metabolic function in the butter catfish larvae recorded in the study might provide some important information to consider application of formulated diets for the larviculture of Ompok bimaculatus.

Excessive Dietary Lipid Affecting Growth Performance, Feed Utilization, Lipid Deposition, and Hepatopancreas Lipometabolism of Large-Sized Common Carp (Cyprinus carpio).

An 82-day study was conducted to assess the effect of the dietary lipid levels on growth performance, feed utilization, lipid deposition, and hepatopancreas lipometabolism of large-sized common carp (Cyprinus carpio). Six isonitrogenous (300 g/kg protein) pelletized diets with different dietary lipid levels (30, 60, 90, 120, 150, and 180 g/kg) were fed in triplicate to fish groups with 75 individuals (with an initial mean weight of 247.00 ± 16.67 g). The results showed that there was a significant increase in weight gain (WG) rate (WGR), specific growth rate (SGR), and protein efficiency ratio (PER) as dietary lipid levels increased from 30 to 60 g/kg (p < 0.05) and then there was a decline. Feed conversion rate (FCR) was observed to be significantly lower in 60 g/kg lipid treatments (p < 0.05). Muscle crude protein contents were obtained to be significantly higher in 60 and 90 g/kg treatments (p < 0.05). The crude lipid content in the hepatopancreas increased significantly with an increase in dietary lipid levels (p < 0.05). The expression of lipoprotein lipase (LPL) and carnitine palmitoyltransferase-1 (CPT1) in the hepatopancreas was significantly downregulated with an increase in dietary lipid levels while the expression of growth hormone (GH), insulin-like growth factor-1 (IGF-1), fatty acid synthase (FAS), acetyl-CoA carboxylase-1 (ACC-1), and sterol regulatory element binding protein (SREBP) was upregulated first in 30 and 60 g/kg lipid treatments and then downregulated significantly in other treatments. The results revealed that excess dietary lipid supplements (more than 60 g/kg) would inhibit WG and would aggravate the lipid decomposition in the hepatopancreas. Based on WGR and FCR, the dietary lipid levels of 59.5 and 70.4 g/kg were optimal for growth performance and feed utilization of large-sized common carp.

Physiological and metabolic protein‐sparing effects of dietary lipids on common snookCentropomus undecimalis(Bloch, 1792) juveniles

Carnivorous common snook (Centropomus undecimalis) has potential for aquaculture, but its protein requirement in diet is 500 g kg−1 and the energetic role of lipids in this species has not been explored. Thus, this study investigated the ability of juvenile common snook (8.7 ± 1.2 g) to use dietary lipids as an energy source. The fish were fed four practical diets with two protein levels (400 and 500 g kg−1) associated with two lipid levels (60 and 120 g kg−1) for 12 weeks. Growth performance significantly improved with increasing dietary lipid levels, but no significant difference was observed at the protein level. Fish fed the 400:60 (protein: lipid level) diet exhibited significantly higher feed conversion ratios than those fed 400:120, 500:60 and 500:120 diets, but fish fed the 400:120 diet had significantly higher protein efficiency ratios. Juvenile common snook showed the ability to modulate digestive protease and lipase secretion when dietary protein or lipid levels were modified. The activity of alanine aminotransferase decreased as the dietary lipid level increased (p < .05), while fructose-1 and 6-bisphosphatase activities were not significantly affected by dietary protein or lipid levels. Glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and pyruvate kinase activities increased as dietary protein and lipid levels increased (p < .05). The results of this study indicate that an increase in dietary lipid level has a protein-sparing effect and that the diet containing 400 g kg−1 protein with 120 g kg−1 lipid is suitable for growth and effective protein utilization in common snook.

Molecular characterization and expression profiles of six genes involved in vitellogenic deposition and hydrolysis of Chinese sturgeon (Acipenser sinensis) suggesting their transcriptional regulation on ovarian development

Ovary development of Chinese sturgeon (Acipenser sinensis) in controlled breeding has been reported to respond to dietary lipid levels. However, the corresponding molecular regulatory mechanism about ovary development of Chinese sturgeon is still unclear. To elucidate the molecular mechanism of vitellogenic deposition and hydrolysis, six key genes, namely, vtgr (vitellogenin receptor), atp6v1c1 (Vacuolar H+-ATPase subunit c1), atp6v1h (Vacuolar H+-ATPase subunit h), ctsb (cathepsin B), ctsd (cathepsin D) and ctsl (cathepsin L) involved in vitellogenic deposition and hydrolysis of Chinese sturgeon were cloned and characterized, and their spatio-temporal mRNA expression profiles as well as transcriptional responses to dietary lipid level were investigated. The full-length cDNA sequences of these six genes showed similar domain structure to their respective orthologous genes from other vertebrates. Tissue-specific expression patterns of these genes were observed in ovary, liver, muscle, spleen, brain, gill, intestine, heart, stomach and kidney. Ovarian expression level of vtgr was the highest in stage II, and ctsl expression was the highest in stage IV, while the mRNA expressions of other 4 genes were the highest in stage III. The increase of dietary lipid level promoted ovary development and elevated the expressions of vtgr, atp6v1c1, atp6v1h, ctsb and ctsd in the ovary. The results of the present study indicated that these genes are crucial for vitellogenic deposition, and provided a preliminary understanding on the molecular regulation of vitellogenic deposition and hydrolysis during ovary development of Chinese sturgeon.

Effects of dietary lipid levels on growth, feed utilization, digestive tract enzyme activity and lipid deposition of juvenile Manchurian trout,Brachymystax lenok(Pallas)

Six isoproteic diets were designated to evaluate the effects of dietary lipid levels (from 70 to 270 g/kg) on the growth performance, feed utilization, digestive tract enzyme activity and lipid deposition of juvenile Brachymystax lenok (average initial weight 0.54 ± 0.04 g). Each diet was fed to triplicate tanks (30 fish per tank) in an indoor closed recirculating system for 9 weeks. Final body weight and weight gain were highest in fish fed 190 g/kg diet and lowest in fish fed the 70 g/kg diet. Specific growth rate of fish fed with 190 g/kg diet was significantly higher than those fed with 70 and 270 g/kg diets (p < .05). Protein efficiency ratio of fish fed with 70 g/kg diet was significantly lower than the 110–230 g/kg treatments and was not significantly different from the 270 g/kg treatment. Fish fed with 270 g/kg diet had significantly higher hepatosomatic index and viscerosomatic index than those fed with 70–190 g/kg diets (p < .05). Intraperitoneal fat ratio and the whole-body lipid content had a trend to increase with increase in dietary lipid level. Muscle crude lipid content increased up to 190 g/kg with increase in dietary lipid level. Lipid retention decreased with increase in dietary lipid level, while no significant differences in protein intake and retention levels were observed in fish among all treatments. Lipase activity of the mixture of pyloric caeca and foregut in fish fed 190 and 230 g/kg diets was significantly higher than those fed 70 and 110 g/kg diets. Midgut and hindgut lipase activities of fish were significantly higher than those fed the 190 and 230 g/kg diets. In conclusion, based on the second-order polynomial model of WG and FCR, this study suggested that 173.8–195.0 g/kg dietary lipid levels were appropriated for B. lenok.

Growth performance and metabolic response of juvenile grouper Epinephelus moara (Temminck &amp; Schlegel, 1842) fed low dietary protein and high lipid levels

Nine test diets were formulated at three low levels of crude protein (P; 35%, 40% or 45%) and three high levels of crude lipid (L; 9%, 12% or 15%) to investigate whether Epinephelus moara differs in the nutrient requirements from any of the other closely-related grouper species, and if there are any indications that a further decrease in protein with increasing dietary lipid would induce a higher protein-sparing effect. Fish (20.34 ± 0.82 g/ind) were distributed among 27 experimental cages (100 cm diameter, 80 cm depth), with 20 fish per cage and three replicates for each test diet. The experiment was conducted over an 8-week period at a temperature of 23.9–25.7°C. Weight gain and specific growth rate (SGR) tended to increase either with an increase in dietary protein level (at the same lipid level) or with the increase in dietary lipid level (at the same protein level, except at the 45% protein level). The highest weight gain and SGR occurred in fish fed the diet P45/L12. The serum cholesterol, high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) contents in fish were significantly increased as the dietary lipid increased. The increase of dietary protein significantly decreased the activities of serum and hepatic alanine aminotransferase (ALT) as well as aspartate aminotransferase (AST). Hepatic fatty acid synthase (FAS) activity significantly increased with the decrease of dietary protein and lipid levels (p < .05). However, lipoprotein lipase (LPL) activity showed an inverse trend compared to FAS. Hepatic glutamate dehydrogenase (GDH) activity significantly increased with the increase in the dietary protein level. In conclusion, the results reveal that growth performance and metabolic responses of E. moara are dependent on dietary protein and lipid levels, and that protein-sparing action can be induced by increasing the dietary lipid. To support the feeding and growth of juvenile E. moara under the present conditions, 45% protein and 12% lipid are adequate.

Optimum Dietary Protein and Lipid Levels in Juvenile Filefish, Stephanolepis cirrhifer, Feed

AbstractA feeding trial was designed to assess the effects of dietary protein and lipid content on growth, feed utilization efficiency, body composition, and hematological indices of juvenile filefish, Stephanolepis cirrhifer. Eight experimental diets were formulated with a combination of four protein (35, 40, 45, and 50%) and two dietary lipid levels (7 and 14%). Each diet was fed to triplicate groups of fish (3.2 ± 0.06 g) to apparent satiation for 8 wk. Fish growth performance and feed utilization were significantly affected by increasing dietary protein and lipid levels, with no significant interactions between factors. The highest growth performance value, in terms of weight gain, was observed in groups fed the diets with 50% protein (399%). However, fish fed the diet containing 45% protein had comparable growth (357%) while achieving relatively higher protein efficiency ratio. Hepatosomatic index was significantly affected by interaction of dietary lipid and protein with the highest values observed in those fish fed the highest protein (45–50%) and lipid (14%) diets. There was a significant increase in body lipid content (5.1 to 6.6%) and a decrease in body protein (15.8 to 14.8%) and ash (2.47 to 2.16%) with increasing dietary lipid levels from 7 to 14%. Muscle lipid content was significantly affected by both dietary protein and lipid levels and tended to increase with increasing dietary protein and lipid levels, ranging from 0.13 to 1.20%. Liver lipid content (65.9 to 68.7%) was significantly increased with the increase in dietary lipid levels while liver moisture content (28.9 to 25.9%) showed a clear decreasing trend. Hematological values were also altered with the increase in either dietary protein or lipid levels. These findings may suggest that a diet containing 45% protein and 7% lipid, with a protein to energy ratio of 23.8 mg/kJ, could deliver sufficient nutrient and energy to support acceptable growth and feed utilization and avoid excessive fat deposition in juvenile filefish.

Effects of dietary protein and lipid levels with different protein-to-energy ratios on growth performance, feed utilization and body composition of juvenile red-spotted grouper,Epinephelus akaara

An 8-week feeding trial was conducted to assess dietary protein and lipid levels on growth performance, feed utilization and body composition of juvenile red-spotted grouper (7.85 ± 0.03 g fish−1). Nine semi-purified diets were formulated containing varying protein levels (440–520 g kg−1, dry matter) and lipid levels (60–120 g kg−1, dry matter). The weight gain of juvenile Epinephelus akaara was affected by dietary protein (p = .005) and its interaction with dietary lipid (p = .020). Viscerosomatic index, intraperitoneal fat ratio and whole-body lipid level increased with increasing dietary lipid level (p < .001). Nitrogen retention was not affected by dietary protein and lipid, while lipid retention decreased with increasing dietary lipid level (p < .001). The plasma blood urea nitrogen increased with increasing dietary protein level (p = .003). This study showed that diet with 520 g kg−1 protein and 60 g kg−1 lipid with 30.58 mg kJ−1 P:E provided a maximal growth for this species. Moreover, an increase in dietary lipid levels (from 60 to 90 g kg−1) could reduce the protein requirement (from 520 to 480 g kg−1) without affecting the growth performance, while higher fat deposition was observed in fish fed high-lipid diets.

Optimum dietary lipid requirement of Pangasianodon hypophthalmus juveniles in relation to growth, fatty acid profile, body indices and digestive enzyme activity

The present experimental trial was conducted to determine the optimal dietary lipid requirement of juveniles of Pangasianodon hypophthalmus (Sauvage, 1878) commonly referred to as the striped catfish using completely randomized design (CRD). Purified diets with five different dietary lipid levels (3, 6, 9, 12 and 15%; fish oil/sunflower oil (1:1) were used to feed triplicate groups of Pangasius with initial mean weight of 13.54–14.12 g twice a day for 8 weeks. The highest weight gain (P < 0.05) was observed in fish fed with 9 and 12% lipid diets, followed by diet with 6% lipid, then by 15% lipid diet, and the lowest weight gain was observed in fish fed with 3% lipid. Other parameters such as specific growth rate (SGR), feed efficiency (FE) and protein efficiency ratio (PER) showed the same trend of weight gain. The hepatosomatic index (HSI), viscerosomatic index (VSI) and intraperitoneal fat (IPF) values increased with the increase of dietary lipid level. The feed conversion ratio (FCR) (P < 0.05) showed significant effects (P < 0.05) with variations in dietary lipid levels. The minimum FCR (1.95) was observed at 9% lipid inclusion-fed fishes and maximum FCR (3.53) was noticed at 3% lipid inclusion fed fishes. Higher and lower digestive enzyme activities were respectively observed in 9 and 15% lipid diets. The muscle fatty acid profile also varied with different dietary lipid levels. The higher level of ω-3, ω-6 fatty acid contents was recorded in the muscle of fish fed with 9% lipid diet, and lower level of fatty acid content was recorded in fish fed with 3% lipid diet. However, using second-order polynomial regression analysis, the optimal dietary lipid requirement of P. hypophthalmus juveniles was found to be 10.1%.

Effects of dietary lipid level and n-3/n-6 fatty acid ratio on growth, fatty acid composition and lipid peroxidation in Russian sturgeonAcipenser gueldenstaedtii

The growth performance, fatty acid composition, hepatic lipid content, hepatic somatic index and lipid peroxidation in Russian sturgeon were investigated using diets containing three lipid levels 50 g kg−1 (L5), 150 g kg−1 (L15) and 250 g kg−1 (L25) and three n-3/n-6 fatty acid ratios (1 : 3, 1 : 1 and 3 : 1) for 8 weeks. Weight gain significantly increased with the increase in dietary lipid levels at n-3/n-6 fatty acid ratios of 1 : 3 and 1 : 1, but not at the 3 : 1 ratio. Correspondingly, fish survival gradually decreased with the increase in dietary lipid at the 3 : 1 n-3/n-6 fatty acid ratio. The dietary lipid level significantly affected the composition of whole-body fatty acid. The retention of highly unsaturated fatty acid dramatically decreased at the level of 250 g kg−1 dietary lipid. The liver malondialdehyde increased with the increase in dietary lipid levels and the n-3/n-6 fatty acid ratios. The contents of lipid and triglyceride in the liver and the hepatic somatic index also increased with the increase in dietary lipid. The diet combination of L25 + 3 : 1 showed the highest aspartate transaminase and alanine transaminase, indicatives of hepatic injury. This study indicates that the L25 + 1 : 3 diet can improve fish growth performance, whereas the L25 + 3 : 1 diet may lead to poor growth performance due to high lipid peroxidation.

Effect of dietary lipid level on growth performance, feed utilization and body composition by juvenile red spotted grouper (Epinephelus akaara)

This study was designed to determine the effect of dietary lipid level on growth performance, feed utilization and body composition of juvenile red spotted grouper, Epinephelus akaara. Triplicate groups of 12 fish (IBW = 2.51 g) with three isoenergetic and isonitrogenous experimental diets formulated by increasing lipid levels (5.98, 9.11 and 12.57 %) were fed to satiety for 8 weeks. At the end of the feeding trial, weight gain and specific growth rate were significantly higher for the fish fed diets with 9.11 and 12.57 % compared to the treatment which containing 5.98 % dietary lipid levels. With the increase of dietary lipid levels, feed conversion ratio decreased but protein efficiency ratio increased. As dietary lipid level increased, viscerosomatic index and intraperitoneal fat ratio increased dramatically, while no significant difference in hepatosomatic index was found in this experiment. In conclusion, under the experimental conditions, the increase of dietary lipid level beyond 9.11 % had no further beneficial effects.

Physiological and reproductive response to varying quantitative lipid inclusion in diets for Gulf killifishFundulus grandisBaird and Girard

Successful culture of Gulf killifish Fundulus grandis as a live marine baitfish in the south-eastern United States has experienced low fecundity as a primary restriction. Hence, the ability to optimize reproduction in captive populations may increase the potential for viable large-scale production. Broodfish nutrition is an expanding field of aquaculture, and improved nutritional status has been shown to increase reproductive output in some cultured fish. This study examined changes in quantitative inclusion of lipid as fish oil in complete diets fed to actively spawning Gulf killifish and its effects on physiological and reproductive parameters and subsequent larval morphometrics. An increase in dietary lipid levels across a gradient from 4.0 to 13.8% did not affect periodic fecundity, egg size, embryo viability rate, sperm motility, hepatosomatic index or liver total lipid content. Intraperitoneal fat increased significantly in fish fed higher lipid levels, while gonadosomatic index was significantly higher in the lowest lipid content group. Larvae produced by fish fed higher lipid levels had significantly increased endogenous nutritional resources at hatch while standard length was unaffected. No strong reproductive benefits of increased lipid inclusion were found in Gulf killifish.

Effects of practical dietary protein to lipid levels on growth, digestive enzyme activities and body composition of juvenile rice field eel (Monopterus albus)

A 10-week feeding experiment was conducted to evaluate the effects of dietary protein to lipid ratios (P/L) on growth, intestinal digestive enzyme activities and body composition in juvenile rice field eel (Monopterus albus) (initial mean body weight of 65.76 ± 1.07 g, mean ± SEM). Nine test diets were formulated in a 3 × 3 factorial design to contain three protein levels (350, 400 and 450 g kg−1) for each of three lipid levels (40, 80 and 120 g kg−1), respectively. Each diet was randomly assigned to triplicate groups of 60 fish per net cage (1.5 × 2.0 × 1.5 m). Results showed the survival was above 96 % and was not affected by dietary treatments. Fish fed the diet with 450 g kg−1 protein and 40 g kg−1 lipid showed the best weight gain (WG) (103.95 %) and feed conversion ratio (1.60) (P < 0.05). WG, protein efficiency ratio and energy retention increased with the increasing in lipid at 350 g kg−1 protein level (P < 0.05). However, WG showed a little decline with increasing dietary lipid when fish fed the diets with 400 and 450 g kg−1 protein level, but no significant difference was observed (P < 0.05). Hepatosomatic index, visceralsomatic index and intestinal lipase activity increased with the increasing of dietary lipid level irrespective protein level. Intestinal trypsin activity increased with the increasing of dietary lipid level when fish fed the diets with 350 g kg−1 protein, but showed converse trend when fish fed the diets with 400 and 450 g kg−1 protein. Serum triglyceride, body lipid and energy were positively correlated with the dietary lipid. Results of the present study showed that the dietary protein/lipid ratio of 450/40 g kg−1 is considered optimum for rice field eel under culture conditions, and the increase in dietary lipid level has no efficient protein-sparing effect when fish fed the diets with 400 and 450 g kg−1 protein level.

Effect of different dietary lipid levels on the reproduction ofRhamdia quelen(Quoy and Gaimard, 1824)

Lipids include some of the most important nutrients that affect the survival and growth of fishes in their early life stages. Lipid deficiency prior to spawning may significantly reduce egg production, hatchability and the number of surviving larvae. In this study, we investigated the effects of isocaloric diets containing 80, 140 and 200 g kg−1 of lipids (lipid source, soy oil) for 90 days. The following data were collected at 0, 45 and 90 days: final weight; length; conditioning factor; hepatosomatic, gonadosomatic and visceral fat indices; total plasma protein; testosterone; 17s-estradiol; free amino acids; and ovary and muscle fatty acid profiles. Additionally, fecundity, oocyte production, egg morphometric parameters, and larval and postlarval growth were evaluated. Results were not statistically different for husbandry and biochemical parameters, but visceral fat content increased with increase in dietary lipid levels. The fatty acid profiles and composition differed among dietary treatments. The egg diameter and area were significantly low in fish fed the 200 g kg−1 lipid diet, thereby hindering growth, survival and weight compared to those in postlarval fish (P < 0.05). The best reproductive rates were obtained when using diets containing 80–140 g kg−1 total lipids.