Broken-line Regression Analysis Research Articles

A preliminary study of dietary protein requirement of juvenile marbled flounder (Pseudopleuronectes yokohamae)

An 8-week feeding trial was conducted to determine the optimal dietary protein level for juvenile marbled flounder. Five semi-purified test diets were formulated to contain different protein levels (CP) including 42.7%, 47.4%, 53.3%, 58.8%, and 64.5% (dry matter), named as CP42.7, CP47.4, CP53.3, CP58.8, and CP64.5, respectively. Five hundred and twenty-five juveniles (6.0 ± 0.1 g) were randomly distributed into 15 tanks (300 L tanks), resulting in 35 fish per tank (n = 3 tanks). Fish were fed the test diets 5 times per day until satiation. The CP58.8 resulted in the highest gain in weight and the best efficiency in feed utilization among the tested protein levels (P < 0.05). Fish fed the CP58.8 diet showed significantly higher whole-body protein and lipid contents than the fish that were fed the other diets (P < 0.05). Fish fed the CP53.3, CP58.8, and CP64.5 diets showed a significantly higher dorsal-muscle lipid content than the fish that were fed the CP42.7 and CP47.4 diets (P < 0.05). The one-slope straight broken-line regression analysis on the results of the thermal growth coefficient and feed conversion ratio indicated that the estimated optimum dietary protein level was 58.8%. Taken together, it is suggested that the dietary protein level of 58.8% is optimal for better growth and high efficiency in feed utilization for the juvenile marbled flounder.

Effect of dietary vitamin C on the growth performance, nonspecific immunity and antioxidant ability of red swamp crayfish (Procambarus clarkii)

The dietary vitamin C (VC) requirement of red swamp crayfish (Procambarus clarkii) has not been determined. The aim of this study was to investigate the effects of dietary VC level on growth performance, body composition, nonspecific immunity, and antioxidant capacity of red swamp crayfish and to determine its VC requirement. Six experimental diets (control, VC3, VC6, VC9, VC12 and VC15) with different levels of VC (0.00, 60.13, 126.93, 192.06, 250.12 and 321.38 mg/kg diet, respectively) were fed to juvenile crayfish (average weight: 7.00 ± 0.01 g) for 70 d. At the end of the growth trial, the highest final body weight, specific growth rate (SGR), and muscle rate all occurred in the VC12 group (P < 0.05). Hepatosomatic index and serum superoxide dismutase activity were the highest in the VC9 group. Compared with the control group, crayfish fed with VC supplemented diets showed significantly higher contents of crude protein and crude lipid in whole-body, and the higher activities of catalase and glutathione peroxidase as well as the glutathione content in the hepatopancreas (P < 0.05). Conversely, the feed conversion ratio and hepatopancreatic malondialdehyde value of crayfish in the VC supplemented groups were significantly reduced relative to that of the control group (P < 0.05). The VC3 to VC15 diets significantly increased the serum activities of phenoloxidase, lysozyme, nitric oxide synthase, acid phosphatase, anti-superoxide anion and nitric oxide concentration, and the total hemocyte count and blood cell respiratory burst activity (P < 0.05). After the crayfish were subjected to the challenge of the white spot syndrome virus, the cumulated mortality rate in the VC supplemented groups was significantly lower than the control (P < 0.05), which was the lowest in the VC12 and VC15 groups. To conclude, VC can be used as a supplement in crayfish feed to increase growth, immunity, and antioxidant capacity. Broken-line regression analysis on SGR indicated that the optimal dietary VC requirement of P. clarkii was estimated to be 265.67 mg/kg diet.

Dietary manganese requirement of fingerling Indian major carp, Labeo rohita (Hamilton) estimated by growth, tissue manganese concentration and hepatic manganese-superoxide dismutase activity

Dietary manganese requirement of Labeo rohita fingerlings (6.4 ± 0.12 cm; 2.3 ± 0.07 g) was estimated by feeding seven isonitrogenous and isoenergetic (350 g kg−1 crude protein; 16.7 kJ g−1 gross energy) test diets with different manganese concentrations (1.6, 2.6, 5.1, 11.1, 20.3, 40.2 and 80.1 mg kg−1 diet). The test diets were hand-fed to triplicate groups of fish at 08:00, 12:00 and 16:00 h to apparent satiation for 8-week. Live weight gain (LWG), protein efficiency ratio, specific growth rate, feed conversion ratio, protein gain, manganese concentration in the scales, vertebrae and whole body, and hepatic manganese-superoxide dismutase (Mn-SOD), total superoxide dismutase, catalase, glutathione peroxidise and lipase activities improved significantly (P < .05) in fish fed diets containing increasing manganese concentrations up to 11.1 mg kg−1 and then stabilized. Maximum apparent manganese retention (P < .05) was recorded in groups fed with 1.6 and 2.6 mg kg−1 dietary manganese levels followed by a significant decrease in fish fed higher levels of dietary manganese. Dietary manganese supplementation exerted no significant effects (P > .05) on the body moisture and ash contents, but showed a significant influence (P < .05) on the protein and fat contents, viscerosomatic index, hepatosomatic index, and condition factor. Increase in dietary manganese levels significantly affected (P < .05) whole body, vertebrae, scales and liver mineralization, except copper concentration. Hepatic malondialdehyde (MDA) concentration and lactate dehydrogenase (LDH) activity significantly decreased with increment in manganese levels up to 11.1 mg kg−1 diet. Broken-line regression analysis of LWG, scales, whole body and vertebrae manganese concentration, and hepatic Mn-SOD activity against dietary manganese concentrations, indicated the manganese requirement of L. rohita fingerlings in the range of 9.4–10.9 mg kg−1 of diet.

Autochthonous probiotics Lactococcus lactis and Weissella confusa in the diet of fingerlings great sturgeon, Huso huso : effects on growth performance, feed efficiency, haematological parameters, immune status and intestinal morphology

This research evaluated the influences of two autochthonous probiotics Lactococcus lactis and Weissella confusa, on growth performance, feed conversion efficiency, haematological parameters, immune status and intestinal morphology of Huso huso fingerlings. Fingerlings (N: 480; initial weight, 2.92 ± 0.01 g) were randomly dispersed in four treatments (three replicates) and fed with the diet (crude protein 47%) that fortified by autochthonous probiotics Lactococcus lactis and Weissella ciberia (PB0: control; PB1.5: 1.5 × 107; PB3: 3 × 107; PB4.5: 4.5 × 107) for 56 days. The results revealed that growth in fish fed probiotics diets were increased compared with the control group. Haematological and blood biochemistry indices did not show any differences between groups (p > 0.05). The highest value of complement 3 was observed in the PBP4.5 group (p < 0.05), while other immunological indices were not significant between treatments (p > 0.05). Foregut villi height of fish fed with PB4.5 diet revealed notable differences compared with those of other groups (p < 0.05). The villi height of PB3 and PB4.5 groups were significantly higher than that of the other treatments (p < 0.05). Taken together, the results of this study showed that the optimum range of autochthonous probiotics were 2.5–2.61 × 107 CFU/g in H. huso fingerlings based on broken-line regression analysis.

Optimal dietary lipid requirement for juvenile Asian red-tailed catfish (Hemibagrus wyckioides): Dietary lipid level for Hemibagrus wyckioides

This study investigated the effects of dietary lipid content on growth rate, feed utilization, digestive enzyme activity, and antioxidant capacity of juvenile Asian red-tailed catfish (Hemibagrus wyckioides), and thereby to evaluate the optimal dietary lipid requirement. Five isoproteic diets were prepared to contain varied levels of dietary lipid (3 %, 5.5 %, 8 %, 10.5 %, and 13 %). Each diet was fed to triplicate groups of juveniles (average body weight 3.20 g) in a recirculating farming system maintained at 28 ± 1 °C. Daily gain coefficient (DGC) and protein efficiency ratio improved steadily with the dietary lipid content up to 10.5 %, and then reached a plateau. Similarly, protein retention increased gradually with the dietary lipid content up to 13 %. Conversely, lipid retention decreased linearly with increasing dietary lipid content, but no significant difference was found among juveniles fed diets with 8 %, 10.5 %, and 13 % lipid. The optimum feed conversion ratio (FCR) was observed in juveniles fed diets with 10.5 % or 13 % lipid. Plasma insulin-like growth factor 1 level increased steadily with the dietary lipid content up to 8 %. However, plasma amino methyl propanediol, aspartate aminotransferase and alanine aminotransferase activities depressed generally with increasing dietary lipid content. Besides, the highest hepatic peroxidase, catalase, glutathione peroxidase, and alkaline phosphatase activities were found in juveniles fed diet with 10.5 % lipid. Single-slope broken-line regression analysis of DGC or FCR response to varied levels of dietary lipid showed that the optimal dietary lipid requirement of juvenile H. wyckioides was 11.1 % or 9.4 % of diet containing 42 % protein, respectively.

The feasibility of partial replacement fish meal with poultry by‐products in practical diets of juvenile great sturgeon, Huso huso : Effects on growth performance, body composition, physiometabolic indices, digestibility and digestive enzymes

To characterize the effects of a poultry by-product (PBM) on the gonadosomatic, physiometabolic indices, digestibility and digestive enzymes of juvenile Huso huso (28.42 ± 0.17 g), we procured six experimental diets with 0 (control), 20%, 40%, 60%, 80% and 100% PBM to replace fishmeal. After an 8-week feeding trial, results confirmed that the weight gain, the specific growth rate of fish fed the 80% and 100% diets were markedly inferior to other groups (p < 0.05). Also, the highest feed conversion ratio and the lowest protein efficiency ratio were observed in dietary of full replacement of fishmeal by PBM (p < 0.05). Triglyceride and cholesterol significantly increased in the PBM100 than the control and PBM20 (p < 0.05). Gastrointestinal enzyme activities were notably decreased in fish fed the diets of more than 60% substitution of fishmeal by PBM (p < 0.05). No statistical difference was observed in the digestibility of protein, dry matter, lipid and gross energy in fish fed up to 300 g/kg (PBM60) of PBM, while beyond this level, all of ADCs value reduced (p < 0.05). Taken together, the optimum range replacement by PBM was 235.9–251.8 g/kg in juvenile Huso huso diet based on the broken-line regression analysis.

Effects of dietary carbohydrate-to-lipid ratio on growth performance, plasma parameters and hepatic antioxidant status in ide (Leuciscus idus, Linnaeus, 1758)

A 60-day feeding trial was carried out to investigate the effects of the dietary carbohydrate-to-lipid ratio (CHO:L) on growth performance, plasma parameters and hepatic antioxidant status in ide (Leuciscus idus). Six isonitrogenous and isoenergetic diets were formulated to contain various CHO:L ratios from 0.79 to 15.29. The final weight, weight gain (WG) and feed conversion ratio (FCR) were affected by the dietary CHO:L ratio, and the optimal values were found in fish fed a diet with a 3.66 ratio (P < 0.05). The hepatosomatic index and glycogen content were positively related to the dietary CHO:L ratio, and the whole body lipid content decreased with the increasing dietary CHO:L ratio (P < 0.05). Plasma alanine aminotransferase and aspartic transaminase activities and total protein, albumin, total triglyceride and glucose contents were similar among dietary treatment groups (P> 0.05). The lowest total cholesterol content was observed in fish fed with highest dietary CHO:L ratio (P < 0.05). Significantly lower malondialdehyde contents were observed in fish fed diets with 2.23 and 3.66 CHO: L ratios than in those fed diets with 0.79 or 15.29 CHO:L ratios. The highest values of superoxide dismutase, glutathione peroxidase and catalase activities, total antioxidant capacity and glutathione content were found in fish fed a diet with a 2.23 CHO:L ratio. The present results indicated that diets with a CHO:L ratio 2.23 is optimal for juvenile ide antioxidant status, and the optimal dietary CHO：L ratio was calculated to be 2.96 and 2.79, respectively, based on the broken-line regression analysis of WG or FCR.

Effects of dietary magnesium supplementation on growth, feed utilization, nucleic acid ratio and antioxidant status of fingerling Heteropneustes fossilis

To investigate the effects of dietary magnesium on growth, feed utilization, nucleic acid ratio and antioxidant status of Heteropneustes fossilis and determine the optimum dietary magnesium requirement, basal diet (400 g/kg crude protein and 17.89 MJ/kg gross energy) supplemented with magnesium sulfate at 0, 2.02, 4.05, 6.08, 8.11 and 10.14 g/kg diet, yielding 0, 0.20, 0.40, 0.60, 0.80 and 1.0 g magnesium per kg of the diet were fed to triplicate groups of fishes. Analyzed values of dietary magnesium were found to be 0.06, 0.28, 0.45, 0.68, 0.88 and 1.05 g/kg. Increasing dietary magnesium levels significantly (P < 0.05) enhanced the absolute weight gain (AWG), specific growth rate (SGR), RNA-DNA ratio, protein retention efficiency (PRE) and protein gain (PG) up to 0.68 g/kg. Biometric indices were also found to improve up to 0.68 g/kg magnesium and then remained static. Antioxidant status in terms of superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) also exhibited significant improvement (P < 0.05) in response to incremental levels of dietary magnesium up to 0.68 g/kg. The whole-body composition also reflected significant changes up to magnesium level of 0.68 g/kg diet. Serum alkaline phosphatase (ALP) activity and magnesium concentration improved with the increasing magnesium level up to 0.88 g/kg diet. Improvement in whole-body and vertebrae mineralization in response to increasing dietary magnesium levels was also noted up to 0.88 g/kg diet. Broken-line regression analysis of SGR, PG, RNA-DNA ratio, serum SOD activity and vertebrae magnesium data against increasing levels of dietary magnesium indicated the optimum requirement of H. fossilis in the range of 0.65−0.79 g/kg diet.

Effects of dietary protein levels on growth, muscle composition, digestive enzymes activities, hemolymph biochemical indices and ovary development of pre-adult red swamp crayfish (Procambarus clarkii)

This study was conducted to evaluate the effect of dietary protein levels on growth performance, muscle composition, digestive enzymes activities, hemolymph biochemical indices and ovary development of pre-adult red swamp crayfish Procambarus clarkii (initial weight = 12.86 ± 0.10 g). Six isoenergetic diets (fish meal, soybean meal, gluten, and shrimp powder as main protein sources) were formulated to contain graded levels of 20.70 %, 24.70 %, 30.56 %, 35.77 %, 41.12 % and 44.64 % crude protein. Each diet was assigned to triplicate groups of 15 experimental crayfish (10 female and 5 male) for 8 weeks. Our results showed that weight gain (WG) increased with dietary protein supplementation from 20.7% to 35.77%, and then decreased with further increases in dietary protein. Broken-line regression analysis based on WG showed that the optimal dietary protein level for maximum growth performance of crayfish was 39.60 %. Feed conversion ratio (FCR) exhibited an opposite trend as observed in WG, with the lowest in crayfish fed the 30.56 % or 35.77 % protein diet. Protein efficiency ratio (PER) in crayfish fed the 41.12 % or 44.64 % protein diet was significantly lower than that in crayfish fed the 20.70–30.56 % protein diet. Hepatosomatic index (HSI) value of crayfish decreased with dietary protein supplementation and achieved minimum values at 35.77 % or 41.12 % protein diet. The highest crude protein content of tail muscle was found in crayfish fed the diet containing 35.77 % or 41.12 % protein. Activities of protease and lipase in both hepatopancreas and intestine were significantly affected by dietary protein levels, while amylase activity showed no significant difference. Dietary protein also significantly induced the contents of hemolymph total protein, albumin, globulin, glucose, total cholesterol and low-density lipoprotein, along with aspartate transaminase and alanine transaminase activities. Moreover, histological analysis revealed that the ovary development of most female crayfish fed the 35.77–41.12 % protein diet were at stage V, which had a higher frequency of mature oocytes than that of females fed other protein diets. Thus, these results provide the theoretical basis for feed formulation to determine the appropriate protein requirement of pre-adult red swamp crayfish.

Dietary choline requirement of juvenile Chinese sucker (Myxocyprinus asiaticus)

An 8-week growth experiment was conducted to quantify the appropriate dietary choline requirement of juvenile Chinese sucker (Myxocyprinus asiaticus). Each of seven semi-purified diets containing choline at a level of 44.79 (basal), 164.95, 278.70, 574.29, 1076.52, 2124.29 or 4477.72 mg/kg diet was fed to three replicates with 30 fish (5.52 g per fish). The results showed that weight gain and specific growth rate increased significantly with the increase of dietary choline levels from 44.79–574.29 mg/kg, and then decreased above these levels. Fish fed the basal diet had the lowest survival rate and feed efficiency. Choline contents in whole body and muscle tissues showed an increasing trend and then stabilized with increasing dietary choline supplementation. Dietary choline had no significant effects on whole-body moisture, crude protein, crude lipid and ash contents, but had a significant effect on muscle crude lipid content. Liver aspartate aminotransferase and alanine aminotransferase activities increased firstly and then decreased with the increase in dietary choline levels, whereas the changes in liver triglyceride content exhibited an opposite trend. Broken-line regression analysis showed that dietary choline requirement for juvenile Chinese sucker was 493.8 and 549.7 mg/kg based on specific growth rate and muscle choline content, respectively.

Evaluation of a Bacterial Single-Cell Protein in Compound Diets for Rainbow Trout (Oncorhynchus mykiss) Fry as an Alternative Protein Source.

Simple SummaryFish meal (FM), as the main protein source, is used in aquafeeds due to its good nutritional profile and palatability. In recent years, because of the high cost and uncertainty in FM supply, studies have been focused to identify and evaluate alternative protein ingredients to minimize FM and reducethe cost of formulated feeds. Currently, plant protein ingredients and animal by-products are used as alternative protein sources to FM, but these components have some nutritional limitations, such as beingrich in anti-nutritional elements and deficient in certain essential amino acids. Among alternative protein sources, single-cell protein (SCP) such as bacteria, yeasts and microalgae, is considered a promising substitute for animal- or plant-derived ingredients. In this work, we aimed to evaluate the replacement of FM with a bacterial SCP, a by-product of the monosodium L-glutamic acid produced by microbial fermentation of vegetal raw materials, in diets for rainbow trout (Oncorhynchus mykiss) fry. Results indicated that the maximum replacement of FM by SCP in terms of growth and feed efficiency performance was up to 50%, while the broken-line regression analyses using DHA muscle content and weight gain showed that this value ranged between 46.9 to 52% SCP depending on the parameter considered.A 60-day trial was conducted in rainbow trout (Oncorhynchus mykiss) fry (initial weight = 2.5 ± 0.6 g) to evaluate the potential use of a bacterial single-cell protein (SCP) as an alternative protein source. Five experimental diets with different levels of fishmeal replacement (0, 25, 50, 75 and 100%) and no amino acid supplementation were tested. At the end of the trial, we found that fry fed diets, replacing 25 and 50% of fishmeal with bacterial SCP, were 9.1 and 21.8% heavier, respectively, than those fed the control diet (p < 0.05), while Feed Conversion Ratio (FCR) values were also lower in comparison to the reference group. These results were also supported by Protein Efficiency Ratio (PER) and Lipid Efficiency Ratio (LER) values that improved in fish fed diets replacing 50% fishmeal by bacterial SCP. The inclusion of SCP enhanced Feed intake (FI) (p < 0.05), although FI was reduced at higher inclusion levels (>50%), which was associated to feed palatability. High levels of bacterial SCP (>50%) affected the muscular amino acid and fatty acid profiles, imbalances that were associated to their dietary content. The broken-line regression analysis using muscle DHA content and weight gain data showed that the maximum levels of fishmeal replacement by bacterial SCP were 46.9 and 52%, respectively.

Partial replacement of fishmeal with corn protein concentrate in diets for rainbow trout (Oncorhynchus mykiss): Effects on growth performance, physiometabolic responses, and fillet quality

An 8-week feeding trial was run to investigate the replacement of fishmeal with corn protein concentrate (CPC; Empyreal®) in rainbow trou (100.5 ± 2.3 g) diet. Fishmeal was increasingly replaced with 0 (Control), 30 (CPC3), 60 (CPC6), 90 (CPC9) and 120 (CPC12) g/kg CPC. The results showed that the substitution of fishmeal with CPC up to 90 g/kg did not cause significant differences in the growth indices as compared to the control group, while further replacement resulted in the reduction of the growth performance. The fillet crude protein showed no significant difference between the control diet and diets containing up to 90 g/kg CPC (p > .05). Serum biochemical parameters such as albumin and glucose did not change notably, while the highest levels of alanine aminotransferase and lactate dehydrogenase were seen in the CPC12 group (p < .05). Also, serum lysozyme activity was increased with the elevation of dietary CPC up to 90 g/kg (p < .05). The redness and yellowness of the fillet were markedly elevated with the dietary incorporation of CPC (p < .05). Taken together, the optimum range of fishmeal substitution with CPC was 81.0–82.2 g/kg CPC in rainbow diet based on the broken-line regression analysis.

Effects of dietary lysine levels on growth performance, whole body composition and gene expression related to glycometabolism and lipid metabolism in grass carp, Ctenopharyngodon idellus fry

8 weeks rearing trial was designed to estimate the dietary lysine requirement, and evaluate the effects of dietary lysine on glycometabolism and lipid metabolism of grass carp fry. Six practical diets were prepared to feed 720 fish (initial weight 0.36 ± 0.00 g) with graded lysine levels (1.44%, 1.79%, 1.97%, 2.44%, 2.56% and 2.87%, dry diet). The results displayed that the final body weight (FBW), weight gain rate (WGR) and specific growth rate (SGR) were significantly improved by 2.44% dietary lysine, the same as feed intake (FI) and feed conversion ratio (FCR), compared with those of the control group (1.44% dietary lysine). Whole-body lipid contents diminished with raising dietary lysine levels from 1.44% to 2.44% and thereafter the content increased. Regarding glycometabolism, compared to the control diet, the 2.44% dietary lysine level significantly improved glycolysis by increasing glucokinase (GK) and pyruvate kinase (PK) mRNA levels, meanwhile the 2.87% dietary lysine level promoted gluconeogenesis by significantly increasing phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) mRNA levels. Glycogen synthase (GS) mRNA levels were independent of dietary treatment. For the lipolysis pathway, the 2.44% dietary lysine level caused the upregulation of hormone sensitive lipase (HSL), adipose triglyceride lipase (ATGL) and carnitine palmitoyl transferase-1 (CPT1) mRNA levels in the PPAR signaling pathway. Like the fatty acid synthase (FAS), acetyl-CoA carboxylase-1 (ACC1) and stearyl-CoA desaturase (SCD), the relative mRNA expression of peroxisome proliferator-activated receptor-γ (PPAR-γ) related to lipid synthesis in the PPAR signaling pathway, was not remarkably influenced by dietary lysine levels. Furthermore, sterol-regulatory element binding protein-1 (SREBP1) mRNA levels in the intestine were not clearly affected among all the treatments. According to the broken-line regression analysis, based on the SGR and FCR, the optimum requirements of grass carp fry for dietary lysine were 2.39% and 2.13% of diet (6.34% and 5.65% of dietary protein), respectively. Overall, appropriate dietary lysine levels (2.44%) could improve the growth performance, reduce the whole-body lipid, promote glycolysis and lipolysis.

Effects of dietary carbohydrate levels on growth, body composition, and gene expression of key enzymes involved in hepatopancreas metabolism in mud crab Scylla paramamosain

This study estimated the effects of different dietary carbohydrate levels on growth performance, feed utilization, body composition, and the gene expression of key enzymes involved in hepatopancreas lipogenesis and glucose metabolism in mud crab Scylla paramamosain. Crabs with an initial mean weight of 1.84 ± 0.06 g were used in an 8-week experiment to test five diets (C6, C12, C18, C24, C30) formulated to contain increasing levels of carbohydrate, measured as 8.55%, 13.36%, 17.76%, 25.64% and 32.50%, respectively. The results showed that the levels 25.64% and 32.50% improved growth performance, with the best gains at 25.64%. The highest dietary carbohydrate level led to higher hemolymph glucose concentrations and more fat deposition in the body. Furthermore, real-time quantitative PCR analysis revealed that the mRNA expression of key enzymes in glycolytic and lipogenic metabolism (i.e. glucokinase, fructose-2,6-diphosphatase, and fatty acid synthetase) were significantly affected by the dietary carbohydrate level. The mRNA expression of glucokinase was lowest in the group fed the carbohydrate-rich C30 diet, and the mRNA of fructose-2 and 6-diphosphatase were remarkably expressed in the C24 group (P < .05). The mRNA expression of fatty acid synthase at the dietary carbohydrate levels 32.50% and 25.64% were respectively 10-fold and 5-fold greater than with 8.55% dietary carbohydrate. The overall data suggest that S. paramamosain can be fed 25.64%–32.50% carbohydrate to achieve satisfactory growth performance. A two-slope broken-line regression analysis of weight gain showed that 24.08% dietary carbohydrate would be optimal for this species reared under similar conditions.

Effects of Dietary Carbohydrate to Lipid Ratios on Growth Performance, Muscle Fatty Acid Composition, and Intermediary Metabolism in Juvenile Black Seabream (Acanthopagrus schlegelii).

An 8-week feeding trial was conducted to evaluate the effects of dietary carbohydrate to lipid (CHO:L) ratios on growth performance, muscle fatty acid composition, and intermediary metabolism in juvenile black seabream (Acanthopagrus schlegelii). Five isonitrogenous and isoenergetic diets (48.0% crude protein and 18.0 MJ kg–1 gross energy) were formulated to contain different CHO:L ratios ranging from 0.33 to 3.75. Triplicate groups of 20 fish averaging 0.51 ± 0.01 g were fed with experimental diets twice daily to apparent satiation. The results indicated that final body weight (FBW), percentage weight gain (PWG), specific growth rate (SGR), and protein efficiency ratio (PER) were significantly influenced by the dietary CHO:L ratios (p < 0.05). The highest FBW, PWG, and SGR were observed in fish fed the diet with a CHO:L ratio of 1.36 (p < 0.05). A two-slope broken-line regression analysis based on PWG indicated that the optimal dietary CHO:L is 1.08. Lipid content in the whole body decreased, and glycogen concentration in the liver increased with the increase of dietary CHO:L ratios from 0.33 to 3.75 (p < 0.05). Moreover, there was a positive correlation between muscle fatty acid composition and dietary fatty acid composition. The relative expression levels of genes involved in glucose metabolism, such as gk, pepck, and glut2 were upregulated by increasing the dietary CHO:L ratio. Also, the mRNA expression level of genes related to lipid synthesis, such as fas and accα were significantly upregulated with dietary CHO:L ratios increasing from 0.33 to 3.75. The highest expression of genes involved in fatty acid β-oxidation, such as cpt1 and acox1, were observed in fish fed the 1.36 CHO:L ratio diet. The gene expression of Δ6 fatty acyl desaturase (fads2) in the liver significantly increased with increase of dietary CHO:L ratios from 0.33 to 3.75. Fish fed the diet with CHO:L ratios of 2.26 and 3.75 had lower expression levels of elovl5 than those fed the other diets. These results demonstrate that dietary optimal CHO:L ratios could improve PWG and SGR but also influence expression of genes involved in glucose and lipid metabolism. Based on the overall results, the optimal dietary CHO:L ratio is 1.08 for black seabream.

Dietary calcium requirement of fingerling Indian major carp, Labeo rohita (Hamilton) based on growth performance, tissue mineralization, whole body, and serum biochemical composition

The dietary calcium requirement of fingerling Labeo rohita (6.0 ± 0.11 cm; 1.94 ± 0.07 g) was examined using seven iso-nitrogenous and iso-caloric purified diets (350 g kg−1 crude protein; 16.72 kJ g−1 gross energy) with incremental levels of calcium (2.14, 3.12, 4.23, 5.11, 6.14, 8.23, and 11.24 g kg−1) that were hand-fed to triplicate groups of fish (20 fish per tank) to apparent satiation for 8 weeks. At the end of the feeding trial, ten fish from each replicate tank (n = 10 × 3) were sampled to obtain serum, scales, and vertebrae. The remaining fish in each tank were sampled to determine proximate chemical body composition. Live weight gain (LWG; 637.6%), protein gain (PG; 2.19 g fish−1), protein retention efficiency (29.89%), and feed conversion ratio (1.69) improved with increased dietary calcium up to 5.11 g kg−1 and then stabilized. Dietary calcium up to 5.11 g kg−1 significantly increased calcium and phosphorus concentrations of whole body, vertebrae, and scales. Fish fed a diet with calcium higher than 5.11 g kg−1 had a significant decrease (P < 0.05) in magnesium and zinc, while potassium was unaffected. Serum alkaline phosphatase activity increased (P < 0.05) with increased dietary calcium up to 5.11 g kg−1, but serum calcium and phosphorus concentrations remained unchanged. Based on broken-line regression analysis of LWG, PG, whole body, vertebrae, and scale calcium content against dietary calcium concentration, dietary calcium in the range of 5.16–5.48 g kg−1 is recommended for fingerling L. rohita.

Optimal dietary protein concentrations for largemouth bass (Micropterus salmoides) of different sizes (10–500 g)

Three feeding trials were conducted to determine the optimal dietary protein levels for largemouth bass (Micropterus salmoides) of different sizes. Six isolipidic (12%) diets with different protein levels (46%, 48%, 50%, 52%, 54% and 56%) were tested to feed three size groups of fish for 56 days (Trial 1 and Trial 2) or 84 days (Trial 3). The initial body weights were approximately 10 g in Trial 1, 100 g in Trial 2, and 200 g in Trial 3, respectively. The fish in each size class were randomly distributed into 18 cages (1 m × 1 m × 1 m) in six groups (three replicates) and fed by hand to apparent satiation two times per day. At the end of the feeding trials, the fish grew to an average size of 26–36 g, 276–320 g, and 434–526 g, respectively. The weight gain (WG) showed an increasing trend with increasing dietary protein level up to 52%, 50%, and 48%, respectively, and then plateaued in all the three trials, which indicated that the minimum dietary protein requirements for largemouth bass decrease with increasing fish size. The feed efficiency (FE) in the three trials showed a similar trend to growth performance. Protein efficiency ratio (PER) tended to decline when dietary protein levels exceeded 48%, 50%, and 48% in the three trails, respectively. Broken-line regression analysis showed that the optimal dietary protein levels based on SGR for largemouth bass of different sizes (initial size 10, 100, and 200 g) were 51.6%, 50.5%, and 47.8%, respectively.

Impact of partial substitution of fish meal by methylated soy protein isolates on the nutritional, immunological, and health aspects of Nile tilapia, Oreochromis niloticus fingerlings

The impact of partial replacement of fish meal with methylated soy protein isolates (MSPI) on fish performance was assessed in 10 weeks feeding trial using Nile tilapia,Oreochromisniloticusfingerlings (n = 225) with average initial weight 18.51 ± 0.05 g/fish. The effects on the growth, histopathological condition of certain organs, economic efficiency, immune status, and disease resistance to Aeromonashydrophila were evaluated. The fingerlings were randomly segregated into five experimental groups with varying percentages of fish meal with substituted MSPI: 0%, 22%, 44%, 66%, and 88% (MSPI0, MSPI22, MSPI44, MSPI66, and MSPI88). The results of final body weight, body weight gain, daily body weight gain, protein efficiency ratio,and SGR were uniquely increased by the treatment MSP22, while increasing the level of MSPI more than 22% resulted in linearly proportional decreases in these parameters over the respective control. The broken-line regression analysis using feed conversion ratio and body weight gain data revealed that the maximum dietary replacement of fishmeal with MSPI was 66%. Alterations in the histomorphological structures of the liver and intestine were observed with an increased level of replacement.The total weight of surviving fish, phagocytic index, IgM level, and lysozyme activity post bacterial challenge were significantly increased by MSPI substitution in fish meal. The survival percentage after the bacterial challenge was increased by MSPI inclusion, the highest survival percentage was recorded in the MSPI66 group (95.55%) compared to MSPI0 (66.66%).MSPI22 increased the total return, net profit, and performance index %. It could be concluded that the maximum dietary replacement of fishmeal with MSPI Oreochromis niloticus fingerlings was 66%. The growth performance was decreased by increasing the substitution percentage of fish meal by MSPI. MSPI was shown to be a good immune-modulating substance and improved gut health. MSPI substitution at 88% is not recommended due to the bad effect on the hepatic and intestinal tissues.

Effects of dietary L‐lysine supplementation on growth, body composition and muscle‐growth‐related gene expression with an estimation of lysine requirement of GIFT tilapia

An 8-week feeding trial was conducted with extruded practical diets containing 320 g/kg of crude protein from plant-based sources to determine the effects of L-lysine on growth performances, muscle-growth-related gene (myoD, myogenine and myostatin) expression and haemato-biochemical responses in juvenile genetically improved farmed tilapia (GIFT). Five isonitrogenous and isoenergetic diets were formulated to contain graded levels of lysine (14.3, 16, 17.5, 19 and 20.5 g/kg of diet). Each diet was randomly assigned to triplicate groups of 30 juvenile fish (5.2 ± 0.1 g), which were fed thrice a day (9:00, 13:00 and 17:00 hr). Maximum growth performances were observed in fish fed with lysine at 19 g/kg of diet. There was no significant (p > .05) effect on whole-body composition and amino acids profile by dietary lysine supplementation. Significant (p < .05) changes were observed in relative expression of muscle-growth-related genes namely myoD and myogenine and in plasma metabolites by dietary lysine supplementation. In contrast, the relative expression of myostatin was not affected by dietary lysine supplementation. Broken-line regression analysis and second-order polynomial regression analysis of weight gain and N gain against dietary lysine levels showed that the dietary lysine requirement for juvenile GIFT tilapia was 18–18.3 g/kg of diet and 19.3–19.5 g/kg of diet, respectively.

Dietary Metabolizable Energy Responses in Yellow-Feathered Broiler Chickens from 29 to 56 d

SUMMARY In this study, the metabolizable energy (ME) requirements were determined for Chinese yellow-feathered chickens aged from 29 to 56 d. In total, 1,200 29-d-old male yellow-feathered broilers were randomly assigned to 5 dietary treatments with 6 replicates each of 40 birds. Birds were fed 5 levels of dietary ME (2,799, 2,897, 2,997, 3,098, and 3,198 kcal ME/kg diet). Broilers that received high-energy diets had a higher (P 0.05), whereas the abdominal fat percentage and thigh intramuscular fat percentage increased significantly. The retention of energy and protein increased (P 0.05) on the energy, protein, and fat contents in the whole body. The plasma concentrations of total cholesterol and total triglyceride were not (P > 0.05) affected by the dietary energy concentration but the plasma concentration of uric acid increased significantly. According to broken-line regression analysis, the recommended dietary ME levels that maximized ADG, optimized FCR, and minimized the deposition of abdominal fat (%) in yellow-feathered broiler chickens aged from 29 to 56 d were 3,198 kcal, 3,213 kcal, and 2,920 kcal ME/kg, respectively.