Effects of Lactobacillus rhamnosus ATCC 7469 on Different Parameters Related to Health Status of Rainbow Trout (Oncorhynchus mykiss) and the Protection Against Yersinia ruckeri

In the current study, we investigated the effect of a probiotic bacterium (Lactobacillus rhamnosus ATCC 7469) microencapsulated with alginate and hi-maize starch and coated with chitosan on improving growth factors, body composition, blood chemistry, and the immune response of rainbow trout (initial weight: 18.41 ± 0.32 g). Four experimental diets were formulated to feed fish for 60 days. They were control diet without any additive (C), diet added with beads without probiotic (E), a probiotic sprayed to the diet (L.r), and encapsulated probiotic supplemented diet (E-L.r). The results indicated that feeding with E-Lr significantly improved weight gain (84.98 g) and feed conversion ratio (0.95) compared to the other groups (P < 0.05). Also, fish fed E-Lr diet had a significantly higher value of whole-body protein (17.51%), total protein in the blood (4.98 g/dL), lysozyme (30.66 U/mL), alternative complement pathway hemolytic activity (134 U/mL), superoxide dismutase (203 U/mg protein), and catalase (528.33 U/mg protein) (P < 0.05) as compared to those fed the control diet. Similarly, a higher relative expression of immune-related genes such as interleukin-1 (Il-1) and tumor necrosis factor-alpha (TNF-1α) were reported in those fed E-L.r and L.r diets respectively. Interestingly, the fish fed dietary E-L.r had a significantly lower value of lipid in the whole body (4.82%) and cholesterol in the blood (160.67%) in comparison with those fed the control diet (P < 0.05). At the end of the experiment, all groups were challenged by Yersinia ruckeri where the survival rate of rainbow trout fed dietary E-L.r (70.36%) was statistically higher than that of the others (P < 0.05). Overall, the results suggested that encapsulated probiotic Lact. rhamnosus ATCC 7469 acted better than unencapsulated probiotic and has a potential to improve growth performance, flesh quality, and the immune response of rainbow trout.

     

The role of glucagon in the regulation of myocardial lipoprotein lipase activity

The role of glucagon in regulating the lipoprotein lipase activities of rat heart and adipose tissue was examined. When starved rats were fed glucose, heart lipoprotein lipase activity decreased while that of adipose tissue increased. Glucagon administration to these animals at the time of glucose feeding prevented the decline in heart lipoprotein lipase activity, but had no effect on the adipose tissue enzyme. When glucagon was administered to fed rats, heart lipoprotein lipase activity increased to levels found in starved animals but there was no change in the adipose tissue enzyme. It is suggested that the reciprocal lipoprotein lipase activities in heart and adipose tissue of fed and starved animals may be regulated by the circulating plasma insulin and glucagon concentrations.     

Myonuclear apoptosis occurs during early posthatch starvation

Apoptosis is a naturally occurring process; it is important for the final shape and size of developing tissues, and it is characterized by some morphological features such as plasma membrane blebbing, nuclear breakdown, chromosomal fragmentation and apoptotic bodies followed by phagocytosis. The objective of the study was to evaluate the occurrence of apoptosis in chickens immediately posthatch under fed and starved conditions. Male broiler chickens were or were not provided feed for the first 3 days posthatch. Chickens were killed immediately after hatch, at 1 day of age, at 2 days of age and at 3 days of age. The Pectoralis thoracicus was removed, fixed, dehydrated, cleared and embedded in paraffin. Muscle sections were labeled using terminal deoxynucleotidyl transferase (TdT)-mediated dUTP Nick-End Labeling (TUNEL) for detection of apoptotic nuclei. Body weights were lower (P<0.05) in the starved compared to the fed group at 2 and 3 days posthatch. Myofiber cross-sectional area was only smaller (P<0.05) in the starved compared to the fed birds at 3 days posthatch. TUNEL-positive nuclei were present at all days for the fed and starved groups. The proportion of TUNEL-positive nuclei was higher (P<0.05) for the starved group at day 2 and day 3 posthatch compared to the fed group at 3 days posthatch. Apoptosis is a mechanism that contributes to the smaller myofiber size observed at 3 days posthatch.     

Effect of nutrition on subcellular localization of rat fat-cell lipoprotein lipase.

This study supports the possibility for multiple subcellular forms of lipoprotein lipase. 1. The total activity of lipoprotein lipase per g of intact epididymal adipose tissue from fed rats is much higher than that from starved rats. 2. The isolated fat-cells of fed and of starved rats have lipoprotein lipase of almost the same activity per g of fat-pads. The isolated fat-cells of starved rats have a much higher proportion of total activity per g of the intact tissue than do those of fed rats. 3. Under the conditions of homogenization used, only a small proportion of the total activity per g of intact tissue from fed rats was associated with the fat layer which floated to the top of the homogenate during low-speed centrifugation. The different proportions of the specific enzyme activity found in each subcellular fraction are described. 4. Lipoprotein lipase from plasma membranes and microsomal fractions from starved and fed rats was purified by affinity chromatography. 5. The total activity of microsomal lipoprotein lipase per g of intact adipose tissue is enhanced by a normal diet. 6. In intact epididymal adipose tissue from fed rats, the activity per g of tissue of lipoprotein lipase of plasma membranes is much higher than that in the same fraction from starved rats. By contrast, the activities per g of tissue in plasma membranes obtained from starved or from fed rats by collagenase treatment were similar.     

Polymorphisms of the apolipoprotein B and E genes and their relationship to plasma lipid variables in healthy Chinese men

In this study we have analysed the apolipoprotein (Apo) E polymorphism and polymorphisms of the ApoB gene, including the ApoB/Xba I and ApoB/4311 diallelic polymorphisms and a hypervariable region (HVR) situated in the 3 region of the gene (ApoB/3HVR), in a sample of healthy male subjects from Taiyuan (northern People's Republic of China). In comparison to Caucasian populations, in the Chinese sample, the Xba I2 allele (presence of cutting site; frequency 6.1%; and 95% confidence interval, 3.3–8.9) and the long HVR alleles (9.4%; 6.0–12.8) were rare, whereas the ApoB/4311 (Ser) allele (70.8%; 65.4–76.2) and the 34-repeat allele of the HVR (HVR34; 62.4%; 56.8–68.0) were frequent. In subjects having none, one, or two HVR34 alleles, the mean levels of plasma triglycerides were 2.32±1.44 (SD), 1.45+0.74, and 1.75±1.07 g/l, respectively (P < 0.007). Similar trends were observed for very low density lipoprotein (VLDL) cholesterol, LpE:B, and LpCIII:B. The frequencies of the ApoE alleles were similar to those reported in other populations of Asian origin; E2 (7.4%; 4.2–10.6), E3 (84.4%; 80.2–88.6), and E4 (8.2%; 5.0–11.4). Individuals carrying the E2 allele had a lower mean level of ApoB than E33 individuals: 0.87±0.16 and 1.00±0.22 g/l, respectively (P < 0.007). Individuals carrying the E4 allele had higher levels of ApoE than E33 individuals: 0.140±0.084 and 0.094±0.052 g/l, respectively (P < 0.004); similar trends were observed for VLDL cholesterol, triglycerides, LpE:B, and LpCIII:B. The ApoB/ HVR34 and ApoE/E4 polymorphisms accounted for 10% to 15% of the variability of the plasma levels of VLDL cholesterol, ApoE, triglycerides, LpE:B, and LpCIII:B. Several lipid variables appeared to be favourably affected by specific forms of ApoB and ApoE that are particularly frequent in this Chinese population.     

Plasma Markers of Cholesterol Homeostasis and Apolipoprotein B‐100 Kinetics in the Metabolic Syndrome

Objective: The metabolic syndrome is characterized by defective hepatic apolipoprotein B‐100 (apoB) metabolism. Hepato‐intestinal cholesterol metabolism may contribute to this abnormality. Research Methods and Procedures: We examined the association of cholesterol absorption and synthesis with the kinetics of apoB in 35 obese subjects with the metabolic syndrome. Plasma ratios of campesterol and lathosterol to cholesterol were used to estimate cholesterol absorption and synthesis, respectively. Very‐low‐density lipoprotein (VLDL), intermediate‐density lipoprotein (IDL), and low‐density lipoprotein apoB kinetics were studied using stable isotopy and mass spectrometry. Kinetic parameters were derived using multicompartmental modeling. Results: Compared with controls, the obese subjects had significantly lower plasma ratios of campesterol, but higher plasma ratios of lathosterol (p < 0.05 in both). This was associated with elevated VLDL‐apoB secretion rate (p < 0.05) and delayed fractional catabolism of IDL and low‐density lipoprotein‐apoB (p < 0.01). In the obese group, plasma ratios of campesterol correlated inversely with VLDL‐apoB secretion (r = ?0.359, p < 0.05), VLDL‐apoB (r = ?0.513, p < 0.01) and IDL‐apoB (r = ?0.511, p < 0.01) pool size, and plasma lathosterol ratio (r = ?0.366, p < 0.05). Subjects with low cholesterol absorption had significantly higher VLDL‐apoB secretion, VLDL‐apoB and IDL‐apoB pool size, and plasma lathosterol ratio (p < 0.05 in both) than those with high cholesterol absorption. Discussion: Subjects with the metabolic syndrome have oversecretion of VLDL‐apoB and decreased catabolism of apoB‐containing particles and low absorption and high synthesis rates of cholesterol. These changes in cholesterol homeostasis may contribute to the kinetic defects in apoB metabolism in the metabolic syndrome.     

Effects of feeding,starvation, and refeeding on the fatty acid composition of channel catfish,ICtalurus punctatus,tissues

• 1.1. The effects of feeding, food deprivation (14 and 28 days) and refeeding (starved 14 then fed 14 days) on the fatty acid composition of white muscle, liver and brain of pond-raised channel catfish (Ictalurus punctatus) were investigated.
• 2.2. Levels of n-3 fatty acids were significantly higher (P < 0.05) in white muscle of fish starved 28 days (10.7%) than in fish fed throughout the study (8.0%), due primarily to an increase in 22:6(n-3) docosahexaenoic acid or DHA.
• 3.3. Significantly higher levels of 20:5(n-3) (eicosapentaenoic acid or EPA) were found in livers offish starved 28 days (P < 0.05) compared to fish fed throughout the study.
• 4.4. Results suggest that the fatty acid compositions of channel catfish white muscle and liver are subject to only limited perturbation during periods of starvation and refeeding and that the brain is extremely well protected.

     

Increased Whole‐Body Adiposity Without a Concomitant Increase in Liver Fat is Not Associated With Augmented Metabolic Dysfunction

Aim of this study was to determine whether an increase in adiposity, without a concomitant increase in intrahepatic triglyceride (IHTG) content, is associated with a deterioration in metabolic function. To this end, multiorgan insulin sensitivity, assessed by using a two‐stage hyperinsulinemic–euglycemic clamp procedure in conjunction with stable isotopically labeled tracer infusion, and very low‐density lipoprotein (VLDL) kinetics, assessed by using stable isotopically labeled tracer infusion and mathematical modeling, were determined in 10 subjects with class I obesity (BMI: 31.6 ± 0.3 kg/m²; 37 ± 2% body fat; visceral adipose tissue (VAT): 1,225 ± 144 cm³) and 10 subjects with class III obesity (BMI: 41.5 ± 0.5 kg/m²; 43 ± 2% body fat; VAT: 2,121 ± 378 cm³), matched on age, sex, and IHTG content (14 ± 4 and 14 ± 3%, respectively). No differences between class I and class III obese groups were detected in insulin‐mediated suppression of palmitate (67 ± 3 and 65 ± 3%, respectively; P = 0.635) and glucose (67 ± 3 and 73 ± 5%, respectively; P = 0.348) rates of appearance in plasma, and the insulin‐mediated increase in glucose disposal (218 ± 18 and 193 ± 30%, respectively; P = 0.489). In addition, no differences between class I and class III obese groups were detected in secretion rates of VLDL‐triglyceride (6.5 ± 1.0 and 6.0 ± 1.4 µmol/l·min, respectively; P = 0.787) and VLDL‐apolipoprotein B‐100 (0.40 ± 0.05 and 0.41 ± 0.04 nmol/l·min, respectively; P = 0.866), and plasma clearance rates of VLDL‐triglyceride (31 (16–59) and 29 (18–46) ml/min, respectively; P = 0.888) and VLDL‐apolipoprotein B‐100 (15 (11–19) and 17 (11–25) ml/min, respectively; P = 0.608). We conclude that increased adiposity without a concomitant increase in IHTG content does not cause additional abnormalities in adipose tissue, skeletal muscle, and hepatic insulin sensitivity, or VLDL metabolism.     

Combined and Singular Effects of Dietary PrimaLac® and Potassium Diformate (KDF) on Growth Performance and Some Physiological Parameters of Rainbow Trout (Oncorhynchus mykiss)

The present study was conducted to assess the effects of combined and singular dietary administration of PrimaLac® and potassium diformate (KDF) on growth performance, feed utilization, digestive enzymes activity, and some physiological parameters of rainbow trout (Oncorhynchus mykiss) juvenile. Three hundred sixty rainbow trout juveniles (25 ± 1.8 g) were randomly stocked in 300-L tanks (30 fish/tank), and fed three times daily on a basal diet (control), diets incorporated with 12 g kg⁻¹ KDF (FT₁), 1.5 g kg⁻¹ PrimaLac® (FT₂), and combination of 1.5 g kg⁻¹ probiotic and 12 g kg⁻¹ KDF (FT₃) in triplicates, for 8 weeks. At the end of feeding trial, growth performance, body composition, digestive enzymes, liver enzymes, and biochemical parameters were measured. Our results revealed that combined administration of PrimaLac® and KDF (FT₃) exhibited significantly higher weight gain and specific growth rate (SGR) compared to other groups (P < 0.05). Glucose and cortisol levels showed no significant differences between fish fed different test diets (P > 0.05). The highest lipase, protease and amylase activity were observed in group of fish fed FT₃ followed by FT₂ and FT₁. Besides, the diets FT₂ and FT₃ led to significantly lower of ALP, ALT, and AST compared to control group. The present results indicated that combined administration of PrimaLac® and KDF can be considered as a beneficial feed additive and growth promotor for O. mykiss juvenile.

     

An experimental study of ontogenetic and seasonal changes in the temperature preferences of unfed and fed brown trout,Salmo trutta

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Fumagillin Reduces Adipose Tissue Formation in Murine Models of Nutritionally Induced Obesity

The effect of fumagillin (a methionine aminopeptidase‐type 2 (Met‐AP2) inhibitor, with antiangiogenic properties) was investigated in murine models of diet‐induced obesity. Eleven‐week‐old male C57Bl/6 mice (group 1) were given fumagillin by oral gavage at a dose of 1 mg/kg/day during 4 weeks while fed a high‐fat diet (HFD) (20.1 kJ/g), and control mice (group 2) received solvent and were pair‐fed. At the end of the experiment, body weights in group 1 were significantly lower as compared to group 2 (P < 0.0005). The subcutaneous (SC) and gonadal (GON) fat mass was also significantly lower in group 1 (P < 0.005 and P < 0.05, respectively). Adipocytes were smaller in adipose tissues of mice in group 1, associated with higher adipocyte density. Blood vessel density normalized to adipocyte density was lower in group 1 adipose tissues. However, in mice with established obesity monitored to maintain the same body weight and fat mass as controls, short‐term fumagillin administration was also associated with adipocyte hypotrophy (P = 0.01) without affecting blood vessel size or density. Thus, treatment with fumagillin impaired diet‐induced obesity in mice, associated with adipocyte hypotrophy but without marked effect on adipose tissue angiogenesis.     

Changes in plasma thyroxine,triiodothyronine and cortisol associated with starvation in rainbow trout (Salmo gairdneri)

Synopsis Chronically starved rainbow trout (Salmo gairdneri) showed a significant fall in liver size, total liver glycogen, liver glycogen concentration and plasma glucose levels. Liver lipid concentration did not differ significantly from controls although total liver lipid reserves fell during the first 40 days of starvation but had partly recovered after 65 days of starvation. Plasma cortisol and T3 levels did not show consistent changes concomitant with food deprivation over the 65 day period of the experiment. However, plasma T4 levels in fish starved for 40 or 65 days were significantly lower than comparably fed animals. The involvement of T4 in intermediate metabolic processes in salmonids is discussed.     

Effect of carbohydrate on age-related feeding behaviors and longevity in adult black cutworm,Agrotis ipsilon (Lepidoptera: Noctuidae)

Age-related consumption and longevity were monitored in the laboratory for adultA. ipsilon fed either a 1M sucrose solution or water. An additional group was completely starved. Adults consumed sucrose solution and water just after eclosion; the percentage feeding daily and the mean daily consumption for females and males fed sucrose solution declined with time, whereas the percentage feeding daily and the mean daily consumption of those fed water increased with time. Total consumption was significantly higher for those fed sucrose solution (P<0.01) because they lived longer, but consumption per day averaged over the entire adult stage was not significantly different between those fed sucrose solution and those fed water (P>0.05). Mean longevity was significantly extended for females and males fed sucrose solution over those fed water or starved (P<0.01). Moreover, consumption of either fluid was significantly correlated with extended longevity in all groups (P<0.05). These data on fluid consumption by adultA. ipsilon are discussed relative to posteclosion migratory activities.     

Effect of conjugated linoleic acid on dietary lipids utilization, liver morphology and selected immune parameters in sea bass juveniles (Dicentrarchus labrax)

Increased energy content in fish feeds has led to an enhanced fat deposition, particularly in European sea bass, concerning fish farmers. Inclusion of conjugated linoleic acid (CLA) could reduce fat deposition as in other vertebrates. To determine if dietary CLA affects fat deposition, lipid metabolism, lipid composition and morphology of different tissues, growth and selected immune parameters, European sea bass juveniles were fed 4 graded levels of CLA (0, 0.5, 1 and 2%). Growth and feed conversion were not affected by CLA, whereas feed intake was reduced (P < 0.05) by feeding 2% CLA. In these fish perivisceral fat was also reduced (P < 0.05), particularly reducing (P < 0.05) monounsaturated fatty acids. CLA has not affected tissue proximal composition, but reduced (P < 0.05) saturated and monounsaturated fatty acids and increased (P < 0.05) the n−3 and n−3 highly unsaturated fatty acids in muscle and increase (P < 0.05) CLA content in muscle, liver and perivisceral fat. A progressive reduction in lipid vacuolization of hepatocytes cytoplasm and regular-shaped morphology was found in fish fed increased CLA levels, together with a progressive increase in malic enzyme activity (only significant in fish fed 1% CLA). Finally, inclusion of CLA up to 1% increased (P < 0.05) plasma lysozyme activity and was positively correlated with alternative complement pathway.     

The Effect of Lactococcus lactis subsp. lactis PTCC 1403 on the Growth Performance,Digestive Enzymes Activity,Antioxidative Status,Immune Response,and Disease Resistance of Rainbow Trout (Oncorhynchus mykiss)

The effect of Lactococcus lactis subsp. lactis strain PTCC 1403 as a potential probiotic was investigated on the growth, hematobiochemical, immune responses, and resistance to Yersinia ruckeri infection in rainbow trout. A total of 240 fish were distributed into 12 fiberglass tanks representing four groups (× 3 replicates). Each tank was stocked with 20 fish (average initial weight: 11.81 ± 0.32 g) and fed L. lactis subsp. lactis PTCC 1403 at 0 (control, T0), 1 × 10⁹ (T1), 2 × 10⁹ (T2), and 3 × 10⁹ (T3) CFU/g feed for 8 weeks. The results showed enhanced protein efficiency ratio and reduced feed conversion ratio in the fish-fed T2 diet. Further, fish-fed T2 and T3 diets showed a significantly higher survival rate than the control (p < 0.05). Trypsin, lipase, and protease activities were increased in fish-fed L. lactis subsp. lactis PTCC 1403 compared to the control (p < 0.05). Fish fed with a T2 diet showed significantly (p < 0.05) lower glucose content than other groups. The blood lysozyme activity and IgM showed significantly (p < 0.05) higher values in fish-fed T2 and T3 diets than in other groups. The antioxidative responses were increased in fish-fed T2 and T3 diets (p < 0.05). After 7 days post-Y. ruckeri challenge, the cumulative mortality rate showed the lowest value in fish fed with T1 and T2 diets, while the highest value was recorded in the control group. In conclusion, the results revealed beneficial effects of L. lactis subsp. lactis PTCC 1403 on the feed efficiency, immune response, and resistance to Y. ruckeri infection in rainbow trout.

     

Fenofibrate Increases Very Low Density Lipoprotein Triglyceride Production Despite Reducing Plasma Triglyceride Levels in APOE*3-Leiden.CETP Mice

The peroxisome proliferator-activated receptor alpha (PPARα) activator fenofibrate efficiently decreases plasma triglycerides (TG), which is generally attributed to enhanced very low density lipoprotein (VLDL)-TG clearance and decreased VLDL-TG production. However, because data on the effect of fenofibrate on VLDL production are controversial, we aimed to investigate in (more) detail the mechanism underlying the TG-lowering effect by studying VLDL-TG production and clearance using APOE*3-Leiden.CETP mice, a unique mouse model for human-like lipoprotein metabolism. Male mice were fed a Western-type diet for 4 weeks, followed by the same diet without or with fenofibrate (30 mg/kg bodyweight/day) for 4 weeks. Fenofibrate strongly lowered plasma cholesterol (−38%) and TG (−60%) caused by reduction of VLDL. Fenofibrate markedly accelerated VLDL-TG clearance, as judged from a reduced plasma half-life of glycerol tri[³H]oleate-labeled VLDL-like emulsion particles (−68%). This was associated with an increased post-heparin lipoprotein lipase (LPL) activity (+110%) and an increased uptake of VLDL-derived fatty acids by skeletal muscle, white adipose tissue, and liver. Concomitantly, fenofibrate markedly increased the VLDL-TG production rate (+73%) but not the VLDL-apolipoprotein B (apoB) production rate. Kinetic studies using [³H]palmitic acid showed that fenofibrate increased VLDL-TG production by equally increasing incorporation of re-esterified plasma fatty acids and liver TG into VLDL, which was supported by hepatic gene expression profiling data. We conclude that fenofibrate decreases plasma TG by enhancing LPL-mediated VLDL-TG clearance, which results in a compensatory increase in VLDL-TG production by the liver.     

Lipoprotein lipase activity and its relationship to high milk fat transfer during lactation in grey seals

Lipoprotein lipase regulates the hydrolysis of circulating triglyceride and the uptake of fatty acids by most tissues, including the mammary gland and adipose tissue. Thus, lipoprotein lipase is critical for the uptake and secretion of the long-chain fatty acids in milk and for the assimilation of a high-fat milk diet by suckling young. In the lactating female, lipoprotein lipase appears to be regulated such that levels in adipose tissue are almost completely depressed while those in the mammary gland are high. Thus, circulating fatty acids are directed to the mammary gland for milk fat production. Phocid seals serve as excellent models in the study of lipoprotein lipase and fat transfer during lactation because mothers may fast completely while secreting large quantities of high fat milks and pups deposit large amounts of fat as blubber. We measured pup body composition and milk fat intake by isotope (deuterium oxide) dilution and plasma post-heparin lipoprotein lipase activity in six grey seal (Halichoerus grypus) mother-pup pairs at birth and again late in the 16-day laction period. Maternal post-heparin lipoprotein lipase activity increased by an average of four-fold by late lactation (P=0.027), which paralleled an increase in milk fat concentration (from 38 to 56%; P=0.043). Increasing lipoprotein lipase activity was correlated with increasing milk fat output (1.3–2.1 kg fat per day) over lactation (P=0.019). Maternal plasma triglyceride (during fasting) was inversely correlated to lipoprotein lipase activity (P=0.027) and may be associated with the direct incorporation of longchain fatty acids from blubber into milk. In pups, post-heparin lipoprotein lipase activity was already high at birth and increased as total body fat content (P=0.028) and the ratio of body fat: protein incrased (P=0.036) during lactation. Although pup plasma triglyceride increased with increasing daily milk fat intake (P=0.023), pups effectively cleared lipid from the circulation and deposited 70% of milk fat consumed throughout lactation. Lipoprotein lipase may play an important role in the mechanisms involved with the extraordinary rates of fat transfer in phocid seals.Abbreviations FFA free fatty acid - HL hepatic lipase - LPL lipoprotein lipase - PH-HL post-heparin hepatic lipase - PH-LPL post-heparin lipoprotein lipase - VLDL very low density lipoprotein     

Reevaluation of dietary methionine requirement by plasma methionine and ammonia concentrations in surgically modified rainbow trout,Oncorhynchus mykiss

This study aimed to reevaluate the dietary methionine requirement by means of the plasma methionine and ammonia concentrations in surgically modified rainbow trout, Oncorhynchus mykiss. A total of 35 rainbow trout averaging 505 ± 6.5 g (initial body weight, mean ± SD) were randomly distributed into seven groups with five fish in each group. After 48 h of food deprivation, each group was fed one of seven L‐amino acid‐based diets containing graded levels of methionine (0.25, 0.40, 0.50, 0.60, 0.70, 0.80 or 0.95% of diet, dry matter bases) by intubation at 1% bodyweight. Blood samples were taken at 0, 5 and 24 h after intubation. Post‐prandial plasma free methionine concentrations (PPmet, 5 h after intubation) and post‐absorptive plasma free methionine concentrations (PAmet, 24 h after intubation) of fish fed diets containing 0.60% or more methionine were significantly (P < 0.05) higher than those of fish fed diets containing 0.50% or less methionine. PPmet and PAmet in fish fed diets containing 0.60% or higher methionine were not significantly different except the PPmet of fish fed a diet containing 0.95% methionine. Post‐prandial plasma ammonia concentrations (PPA, 5 h after intubation) of fish fed diets containing 0.70% or more methionine were significantly higher than those of fish fed diets containing 0.60% or less methionine, and PPA of fish fed diets containing 0.25% and up to 0.60% methionine were not significantly different from each other. Broken‐line model analyses on PPmet, PAmet, and PPA indicated that the dietary methionine requirement of rainbow trout was between 0.59% (1.69) and 0.67% (1.91) of diets (% dietary protein bases) when the diets contained 0.5% cystine.     

The Effects of a Synbiotic Mixture of Galacto-Oligosaccharides and Bacillus Strains in Caspian Salmon,Salmo trutta caspius Fingerlings

The effect of dietary supplementation with a synbiotic mixture of galacto-oligosaccharides (GOS) and Bacillus spp. was examined in Caspian salmon, Salmo trutta caspius (Kessler, 1877) fingerlings. Caspian salmon fed with the synbiotic diet had significantly higher weight gain rate, protein efficiency ratio, and survival rate, as well as lower feed conversion ratio, compared to the control group (P < 0.05). The serum protein, albumin, globulin, and lactate dehydrogenase levels of the fish fed with the synbiotic diet were significantly higher than the control group (P < 0.05), while the serum alkaline phosphatase levels were significantly lower (P < 0.05). The activities of the innate immune response parameters, including lysozyme, superoxide dismutase, and catalase were significantly higher in the Caspian salmon fed with the synbiotic diet (P < 0.05). The gut microbiota of the Caspian salmon fed with the synbiotic diet contained significantly elevated total viable aerobic bacterial counts (TVABCs), lactic acid bacteria (LAB) levels, and LAB/TVABCs ratio (P < 0.05). Additionally, the gut activities of amylase, trypsin, and chymotrypsin in the gut, as well as the trypsin/chymotrypsin ratio, were significantly increased in the fish that received the synbiotic diet (P < 0.05). In conclusion, the combined GOS and Bacillus spp. supplement positively affected the growth, survival rate, immunobiochemical parameters, digestive activity, and beneficial microbial density in the gut of Caspian salmon fingerlings.