Second-degree Polynomial Regression Analysis Research Articles

Diet with optimal glutathione supplement improves growth, nonspecific immunity, intestinal microbiota, and antioxidant ability in Micropterus salmoides.

In this study, Micropterus salmoides were fed with dietary glutathione (GSH, 0, 100, 300, and 500 mg/kg) for 56 days to investigate its effects on growth performance, serum nonspecific immunity, liver antioxidant capacity, tissue morphology, and intestinal microbiota. The results showed that the survival rate, weight gain rate, and specific growth rate and condition factor increased, whereas the feed conversion ratio, hepato-somatic index, and viscerosomatic index decreased in the GSH groups. Compared with the control group, the serum total protein content significantly increased, whereas the triglyceride and total cholesterol significantly decreased in the 300-mg/kg dietary GSH group. The activities of lysozyme, alkaline phosphatase, and acid phosphatase were significantly higher in GSH-supplemented groups, peaking at 300-mg/kg GSH. GSH supplementation significantly increased total antioxidant capacity and decreased malondialdehyde content, with the most pronounced effects at 300-mg/kg GSH. Further antioxidant indicators showed that a dietary supplement of 300-mg/kg GSH significantly increased the activities of superoxide dismutase, glutathione transferase, endogenous glutathione, glutathione reductase, and catalase. At 300-mg/kg GSH, the liver exhibited improved characteristics with alleviated vacuolation and hepatocyte nuclear shift, and intestine showed enhanced structure with increased villus height and intestinal wall thickness. Additionally, a 300-mg/kg GSH supplementation improved the diversity of intestinal microbiota, increased the abundance of probiotics such as Bacillus, and inhibited the development of pathogenic bacteria such as Plesiomonas. Overall, the results suggest that the effect of GSH addition on improving growth performance, nonspecific immunity, antioxidant capacity, and intestinal microbiota of M. salmoides is best in the 300-mg/kg addition group. Based on second-degree polynomial regression analysis of weight gain, the optimum requirement of dietary GSH in M. salmoides is a 336.84-mg/kg diet.

Dietary Supplementation with Chromium DL-Methionine Enhances Growth Performance of African Catfish (Clarias gariepinus).

Sustainable aqua feeds have become an urgent necessity for future-oriented aquaculture sector development, and especially mineral supply could be limited when diets are being prepared with low amounts of animal-based sources. Since knowledge about the efficiency of organic trace mineral supplementation in different species of fish is limited, the effects of chromium DL-methionine in African catfish nutrition were evaluated. Four commercially based diets with increasing chromium DL-methionine supplementation (0, 0.2, 0.4, and 0.6 mg Cr kg-1) in the form of Availa-Cr 1000 were fed to African catfish (Clarias gariepinus B., 1822) in quadruplicate groups for 84 days. Growth performance parameters (final body weight, feed conversion ratio, specific growth rate, daily feed intake, protein efficiency ratio, and protein retention efficiency), biometric indices (mortality, hepatosomatic index, spleen somatic index, and hematocrit), and mineral retention efficiency were assessed at the end of the feeding trial. The specific growth rate was significantly increased in fish-fed diets with 0.2 mg Cr kg-1 and 0.4 mg Cr kg-1 supplementation in comparison with control and based on the second-degree polynomial regression analysis; supplementation with 0.33 mg Cr kg-1 was optimal in commercially based diets for African catfish. Chromium retention efficiency was reduced with increasing supplementation levels; however, the chromium content of the whole body was comparable to literature. The results suggest that organic chromium supplementation is a viable and safe supplement for diets to increase the growth performance of African catfish.

The effect of different dietary protein levels on growth performance and nutrient utilization of snarpsnout sea bream ( Diplodus puntazzo )

This study evaluated the effects of different dietary protein levels on growth performance and nutrient utilization of snarpsnout sea bream (Diplodus puntazzo) juveniles. Five isoenergetic diets were formulated to contain a dietary protein level at 30% (P30), 35% (P35), 40% (P40), 45% (P45) and 50% (P50). Each diet was randomly assigned to triplicate groups of fish (IBW 2.80 g) and fed to apparent satiation for 100 days. The dietary protein to energy ratio significantly affected the feed intake with the lower ratios leading to a higher feed consumption. The growth performance of D. puntazzo was gradually increased as the dietary protein level increased up to 40% and then gradually reduced as the dietary protein increased further to 45% and 50%. The feed efficiency got improved as dietary protein levels increased up to 45% but slightly decreased at 50% protein level. A second-degree polynomial regression analysis estimated that a dietary protein level at 41.4% and 43.8% delivered the maximum weight gain and the higher feed efficiency, respectively. The increased dietary carbohydrate and lipid levels in fish fed a low protein diet (P30) resulted in a significant deterioration of feed conversion and growth rates showing also reduced nutrient retentions and causing severe mortalities.

Culture salinity modulates Nrf2 antioxidant signaling pathway and immune response of juvenile Genetically Improved Farmed Tilapia (GIFT) (Oreochromis niloticus) under different dietary protein levels

This study aimed to evaluate that dietary protein levels and culture salinity levels affect the health status of juvenile genetically improved farmed tilapia (GIFT, Oreochromis niloticus). Graded protein levels of six diets were prepared, ranging from 18.20% to 49.49% (dry basis), and were used in cultured GIFT at two salinity levels (0‰ and 8‰) for 8 weeks. The results suggested that appropriate protein levels reduced pro-inflammatory gene expressions in the intestine including interleukin 1β (IL-1β), interleukin 8 (IL-8) and tumour necrosis factor-α (TNF-α) mRNA levels at two salinity levels (P < 0.05). 8‰ salinity significantly decreased the expression levels of IL-1β, TNF-α and nuclear factor-kappa B (NF-κB) (P < 0.05). The anti-inflammatory factor interleukin 10 (IL-10) was significantly increased by 36.42% protein level (P < 0.05). Regarding antioxidant capacity, appropriate protein levels and 8‰ salinity significantly improved the antioxidant capacity of fish by regulating the activities of intestinal total superoxide dismutase (T-SOD), glutathione peroxidase (GPx), and the levels of glutathione (GSH) and malondialdehyde (MDA). Furthermore, appropriate protein levels and 8‰ salinity also significantly enhanced the antioxidant gene expressions associated with the Nrf2/keap1 signaling pathway by regulating the expression levels of heme oxygenase-1 (HO-1), GPx, catalase (CAT) and superoxide dismutase (SOD). According to GPx activities and the mRNA levels of IL-10, the optimum dietary protein levels for GIFT juveniles were 31.12%–32.18% (0‰) and 34.25–35.38% (8‰) based on second-degree polynomial regression analysis. The present study found that appropriate protein levels and 8‰ culture salinity are critical in maintaining the health of GIFT juveniles by improving antioxidant and immune capacity.

Dietary tryptophan requirement of northern snakehead, Channa argus (Cantor, 1842)

The optimum dietary tryptophan requirement has not been estimated for northern snakehead (Channa argus Cantor, 1842) despite being considered the main limiting essential amino acid in many cereal grain ingredients. A 70-day feeding trial was carried out to determine the dietary tryptophan requirement using 540 juvenile fish (10.21 ± 0.11 g) randomly distributed into 18 net cages with six treatments and three replicates. Six extruded isonitrogenous (48.56% protein) and isoenergetic (19.72 KJ of gross energy g−1) diets containing 0.19%, 0.30%, 0.39%, 0.48%, 0.59% and 0.68% L-tryptophan were prepared. Fish were hand-fed twice daily at apparent satiation level. The results indicated that final weight, weight gain (WG), specific growth rate (SGR), feed efficiency (FE), protein efficiency ratio (PER), the crude protein content in dorsal muscle, glutamate dehydrogenase activity and glutamate oxaloacetate transaminase activity in liver were significantly improved, with increases in dietary tryptophan up to 0.48%. The content of Methionine, Histidine, Threonine, Glycine, Phenylalanine and Glutamic acid in dorsal muscle of fish was also markedly affected by the dietary tryptophan levels. On the other hand, fish fed with 0.39% dietary tryptophan had the highest pepsin activity, which was significantly higher than that in fish fed with 0.59% and 0.68% dietary tryptophan, however, the glutamate pyruvate transaminase activity significantly increased until the dietary tryptophan level increased to 0.68%. Based on the second-degree polynomial regression analysis of SGR and FE against dietary tryptophan levels, the optimum dietary tryptophan requirement for C. argus was respectively estimated to be 0.46% and 0.45% of the diet, corresponding to 0.95% and 0.93% of dietary protein.

The effect of dietary methionine levels on growth, feed conversion and protein retention efficiency of Nile Tilapia (Oreochromis niloticus) fingerlings

Abstract. Mohammed FA, Yousif RA, Hilal FM, Adam RA, Ahmed TK. 2020. The effect of dietary methionine levels on growth, feed conversion and protein retention efficiency of Nile Tilapia (Oreochromis niloticus) fingerlings. Nusantara Bioscience 12: 21-27. A 49 days feeding trial was conducted to evaluate growth, feed utilization and body composition of Nile tilapia Oreochromis niloticus (4.30±0.01 g), fed five isonitrogenous (32 g 100 g-1 crude protein) and isoenergetic (14.51 kJ g-1 Gross energy) practical diets and five levels of methionine supplementation (0.5, 1, 1.5, 2 and 2.5 g 100 g-1). The experimental design was completely randomized with five treatments and three replicates. Fish were stocked in triplicate groups of 20 fish held in 70 L flow-through tanks (water volume 55 L) and fed twice daily (08:00 am and 04:30 pm) to apparent satiation. When absolute weight gain (AWG; g fish-1), feed conversion ratio, protein deposition (g fish-1) and protein retention efficiency (%) data were subjected to second-degree polynomial regression analysis 95% of the plateau of the above parameters was achieved at dietary methionine concentrations between 1.4-1.5 g 100 g-1 dry diet or 0.09-0.10 g methionine kJ-1 GE. Corresponding to 4.4-4.7 g 100 g-1 of the dietary protein. Based on these results, dietary methionine requirement for Nile tilapia Oreochromis niloticus is recommended 1.4-1.5 g 100 g-1 diet.

The effects of feeding rates on growth performance, feed conversion efficiency and body composition of juvenile snow trout, Schizothorax zarudnyi.

This study was performed to investigate the effects of feeding rates on growth performance, feed conversion and body composition of juvenile snow trout (Schizothorax zarudnyi). For this purpose, fish with an initial body weight of 2.17± 0.1 g were fed a commercial diet (40% protein, 3.8 Kcal/g diet) at five ration sizes 2%, 4%, 6%, 8% and 10% of their body weight per day, for 60 days. Feeding trial was conducted in triplicate. Maximum weight gain, best feed conversion ratio (FCR), best specific growth rate (SGR %), highest energy retention (ERE %) and protein efficiency ratio (PER %) were evident for rations of 4–6% body weight. Second-degree polynomial regression analysis for PER, FCR and ERE indicated the break-points occurred at 4.9, 5.1 and 5.2% BW day−1, respectively. Maximum body protein content was obtained for 4% and 6% rations. Body moisture, fat and ash content remained unchanged. Based on the above results, it may be concluded that 4.9-5.2% body weight per day ration is optimal for the growth, conversion efficiencies and body composition of juvenile S. zarudnyi and it entails favorable economic benefits.

Effect ofl-ascorbyl-2-polyphosphate supplementation on growth performance, body composition, antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp,Litopenaeus vannamei

An 8-week feeding trial was conducted to evaluate the effects of ascorbic acid (AsA), in the form of l-ascorbyl-2-polyphosphate (LAPP) on growth performance, body composition, antioxidative capacity and salinity stress tolerance of juvenile Pacific white shrimp, Litopenaeus vannamei. Five practical diets (46% crude protein and 7.6% lipid) supplemented with graded levels of AsA (14.64, 48.55, 84.98, 308.36 and 639.27 mg kg−1 diet) were fed to five replicate groups of L. vannamei (mean initial wet weight 0.57 g). No significant differences were found on growth performance among all treatments. However, whole body lipid content significantly decreased with dietary AsA levels increasing. Activities of total antioxidant capacity, glutathione reductase and glutathione peroxidase were significantly affected by dietary AsA levels. Shrimp fed LAPP-free diet had higher malondialdehyde content than those fed the diets supplemented with LAPP. Dietary AsA levels higher than 308.36 mg kg−1 diet increased the survival of shrimps after 1, 2 and 3 h of acute salinity change. Broken-line regression analysis on survival after 3 h of salinity stress and second-degree polynomial regression analysis on glutathione reductase data indicated that the optimal dietary AsA requirement of L. vannamei was estimated to be 306.39, 319.75 mg kg−1 diet respectively.

Effect of dietary fructooligosaccharide supplementation on growth, body composition, hematological and immunological parameters of Asian seabass (Lates calcarifer)

A feeding trial to study the effect of addition of prebiotic fructooligosaccharide (FOS) on feeds for juvenile Asian seabass (Lates calcarifer) (12.2 ± 0.4 g) was carried out. Five isonitrogenous and isocaloric experimental diets were formulated that contained 400 g kg−1 protein and 90 g kg−1 lipid. The FOS was supplemented at 2.5, 5, 7.5 and 10 g kg−1 in the diet of L. calcarifer with a control that was devoid of FOS. The trial was carried out in 1000-L fiber reinforced polymer (FRP) tanks with three replicates (each containing 20 fish) for each treatment. After 45 days of feeding, it was observed that FOS supplementation at 10 g kg−1 in the diet resulted in significantly (P 0.05) differences in biological indices of fish fed with the experimental and control diets. Whole body chemical composition of animals post-feeding revealed significantly (P < 0.05) higher crude protein, crude lipid and total ash content in 5 g kg−1 FOS-supplemented diet. The analysis of hematological parameters revealed that red blood cells (RBC), white blood cells, hemoglobin, packed cell volume, mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration levels increased significantly (P < 0.05) with dietary FOS supplementation up to 5 g kg−1.The second-degree polynomial regression analysis of RBC (4.06 ± 0.05 × 106 mm−3) showed that FOS 5 g kg−1 is an optimal level in seabass diet. Significantly (P < 0.05) higher lysozyme (77.4 ± 0.5 U mL−1) and superoxide dismutase (75.2 ± 0.3 U mL−1) activity was recorded at 10 g kg−1 FOS supplementation. It could therefore be concluded that 10 g kg−1 FOS supplementation has a beneficial effect in improving the survival rate and immunological parameters in L. calcarifer juveniles.

Dietary protein requirement of juvenile obscure puffer,Takifugu obscurus

A 10-week feeding experiment was conducted to determine the optimum dietary protein requirement of juvenile obscure puffer (Takifugu obscurus). Six isoenergetic (20 MJ kg−1 gross energy) diets were formulated to contain graded levels of 34%, 38%, 42%, 46%, 50% or 54% crude protein (as dry matter basis). The results showed final body weight, weight gain and specific growth rate (SGR) increased significantly with increasing protein levels up to 42% and then decreased thereafer. Second-order polynomial regression analysis (y = −0.0024x2 + 0.1788x − 1.3196, R2 = 0.9032) indicated a maximum SGR at protein level of 37%. Feed conversion ratio (FCR) decreased with increasing levels of dietary protein up to 42% and increased thereafter. Second-order polynomial regression analysis (y = 0.0054x2 − 0.4351x + 10.391, R2 = 0.753) indicated a minimum FCR at protein level of 40%. Protein efficiency ratio (PER) of fish fed the 34%, 38% and 42% diets was significantly higher than that of fish fed the 46%, 50% and 54% diets, and broken-line analysis indicated PER tended to decrease when dietary protein level was higher than 40%. Generally, whole body lipid content, total cholesterol, low-density lipoprotein cholesterol and triacylglycerol decreased with increasing levels of dietary protein. Fish fed the 42% protein diet showed the highest essential amino acids (histidine, isoleucine, leucine, lysine and threonine) and non-essential amino acids (aspartic acid and glutamic acid) in muscle. Based on the second-degree polynomial regression analysis of SGR and FCR and broken-line analysis of PER, the optimal dietary protein level of obscure puffer is estimated to be between 37% and 40% (% as dry matter basis).

Effects of graded levels of histidine on growth performance, digested enzymes activities, erythrocyte osmotic fragility and hypoxia-tolerance of juvenile grass carp Ctenopharyngodon idella

A 10-week experiment was conducted to estimate the effects of graded levels of histidine on growth performance, digested enzymes activities, erythrocyte osmotic fragility and hypoxia-tolerance of juvenile grass carp Ctenopharyngodon idella. Six isonitrogenous (38%) and isoenergetic semi-purified diets containing casein and gelatin with graded levels of histidine (0.45, 0.72, 1.02, 1.28, 1.55, 1.78g100g−1DM) were formulated. Each diet was assigned to triplicate groups of 30 fish (3.68±0.01) for each tank. The highest weight gain (WG, %), final body weight (FBW, g) and specific growth rate (SGR) were recorded when histidine level was 1.02% of the diet. Whole body protein and muscle protein were not significantly affected by the histidine level (P>0.05). Muscle histidine content was linearly increased along with the dietary histidine increasing (P<0.05). Fish fed histidine deficient diet (0.45g100g−1) exhibited highest erythrocyte osmotic fragility (P<0.05). Meanwhile, the shortest survival time and lowest catalase (CAT) activity and total antioxidant capacity were also recorded in fish fed histidine deficient diet (P<0.05). Second-degree polynomial regression analysis of final body weight data indicated that the minimum recommended dietary histidine requirement for grass carp was 1.21% of the diet, corresponding to 3.2% of dietary protein. Statement of relevanceThe present study determined optimum dietary histidine requirement for juvenile grass carp and the data goes to 1.21% of the diet, corresponding to 3.2% of dietary protein. We also found that juvenile grass carp fed with histidine deficiency diet not only limited their growth performance, but also exhibited higher erythrocyte osmotic fragility, lower hypoxia-tolerance and antioxidant enzyme activities. Digested enzyme activities were also significantly affected by the dietary histidine levels. Thus, it is important to meet histidine requirement when commercial diets are formulated for this species.

Effects of graded levels of threonine on growth performance, biochemical parameters and intestine morphology of juvenile grass carp Ctenopharyngodon idella

This experiment was conducted to investigate the effects of threonine on growth performance, biochemical parameters and intestine morphology of juvenile grass carp Ctenopharyngodon idella. Six isonitrogenous and isoenergetic semi-purified diets containing casein and gelatin with graded level of threonine (0.73, 1.03, 1.33, 1.63, 1.93, 2.23 g 100 g− 1 DM) were formulated. Each diet was randomly assigned to triplicate groups of 30 fishes (4.02 ± 0.004 g, mean ± S.E.M.) each tank for 10 weeks. The highest weight gain (WG, %), final body weight (FBW, g) and specific growth rate (SGR) were recorded when threonine level was 1.33% of the diet. Second-degree polynomial regression analysis of SGR data indicated that the optimum requirement of threonine is to be at 1.37%, corresponding to 3.61% of dietary protein. Whole body protein, muscle protein, aspartate aminotransferase and cholesterol were significantly affected by the threonine level (P < 0.05). Threonine retention was significantly affected by dietary threonine level (P < 0.05). Fish fed threonine deficiency diets (0.73%, 1.03%) exhibited intestinal villus exfoliation, twist, severely fusion, lower anterior intestinal villus height and serosa thickness. The present results indicated that dietary threonine level not only affected grass carp growth, feed intake and body protein synthesis, but also influenced anterior intestinal development and integrity.

Response of fingerling stinging catfish,Heteropneustes fossilis(Bloch) to varying levels of dietaryl-leucine in relation to growth, feed conversion, protein utilization, leucine retention and blood parameters

Growth response of fingerling Heteropneustes fossilis (6.8 ± 0.2 g; 11.2 ± 0.3 cm) to dietary l-leucine levels was assessed by conducting 8-week feeding trial in a flow-through system (1–1.5 L min−1) at 28 °C water temperature. Casein–gelatin-based isonitrogenous (380 g kg−1; crude protein) and isoenergetic [17.9 MJ kg−1; gross energy (GE)] basal diet was supplemented with different levels of l-leucine to achieve desired leucine levels ranging between 10 and 22.5 g kg−1 dry diet. Analysed values were 9.9 (Lc9.9), 12.4 (Lc12.4), 15.1 (Lc15.1), 17.4 (Lc17.4), 20.1 (Lc20.1) and 22.4 (Lc22.4) g leucine kg−1 diet. Fishes were stocked randomly in quadruplicates and fed to satiation at 07:00 and 17:30 h. Maximum absolute weight gain (AWG g fish−1), feed conversion ratio (FCR), protein utilization efficiency (PUE%), leucine retention efficiency (LRE%) and haematological parameters were found in fish fed diet Lc17.4. For precise determination of dietary leucine requirement of Singhi, AWG g fish−1, FCR, PUE% and LRE% were subjected to broken-line and second-degree polynomial regression analysis. Second-degree polynomial regression analysis fitted the data more accurately (P > 0.05) exhibiting high R2 values. Hence, based on this analysis, dietary leucine requirement of fingerling H. fossilis is recommended to be 16.5 g kg−1 of the diet, corresponding to 43.4 g kg−1 protein for developing leucine-balanced commercial feeds.

Suitable dietary chitosan improves the growth performance, survival and immune function of tiger shrimp,Penaeus monodon

Different levels of dietary chitosan on growth performance, survival and stress tolerance to air exposure was studied in tiger shrimp, Penaeus monodon. Shrimp (mean initial wet weight about 1.16 g) were fed with six different diets (C0, C0.05, C0.1, C0.2, C0.3 and C0.4) containing six level of chitosan (0%, 0.05%, 0.1%, 0.2%, 0.3% and 0.4% respectively) in triplicate for 60 days. Growth performance [final body wet weight (FBW); weight gain (WG); biomass gain (BG)] of shrimp fed chitosan-containing diets were higher (P 0.05) in shrimp fed C0.3 diet group. Whole body and muscle lipid contents decreased with increasing dietary chitosan levels. Plasma total cholesterol and triglyceride contents of shrimp fed C0 diet was significantly higher (P < 0.05) than that of shrimp fed chitosan-containing diets. Plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities of shrimp fed C0 diet were higher than those of shrimp fed chitosan-containing diets. Digestive gland malondialdehyde (MDA) and carbonyl protein contents of shrimp fed chitosan-containing diets were lower (P < 0.05) than that of shrimp fed C0 diet. Total haemocyte count of shrimp fed C0 diet was lower (P < 0.05) than that of shrimp fed chitosan-containing diets. On the contrary, the haemolymph clotting time of shrimp fed C0 diet was higher (P < 0.05) than that of shrimp fed chitosan-containing diets. In conclusion, all results suggested that dietary intake containing 0.1% and 0.2% chitosan enhanced the growth of shrimp, whereas a higher level than 0.3% and 0.4% decreased growth of shrimp. Second-degree polynomial regression analysis of WG and BG indicated that the optimum supplement of dietary chitosan level should be 0.19–0.21%.

Effects of graded replacement of fish meal by fish protein hydrolysate on growth performance of early post-larval Pacific white shrimp (Litopenaeus vannamei, Boone)

Five dietary concentrations of fish protein hydrolysate (0, 9, 18, 27 and 36%) were included in five isonitrogenous diets (H0, H9, H18, H27 and H36) replacing fish meal by 0, 15, 30, 46 and 61% and offered to triplicate groups of early white shrimp post-larvae (mean initial wet weight 2 mg). After the 30-day feeding trial, the highest values of survival were obtained with shrimp fed diets H18 and H27. Final mean body wet weights (FBW, mg) of shrimp fed diets H9, H18, H27 and H36 were significantly higher than that of shrimp fed diet H0. Biomass gain (BG, g) of shrimp fed diets H18 and H27 were significantly higher than that of shrimp fed diets H0, H9 and H36. Specific growth rate (SGR, % day−1) showed the same pattern as FBW. Weight gain (WG, %) of shrimp fed diets H18 and H27 were significantly higher than that of shrimp fed diets H0 and H9. The trypsin activities of shrimp fed diets H9, H18, H27 and H36 were significantly higher than that of shrimp fed diet H0. Second-degree polynomial regression analysis on BG and WG indicated the appropriate supplement of fish protein hydrolysate in the diet of early white shrimp post-larvae should be between 21.22 and 26.35% of diet.

Dietary L-tryptophan requirement of fingerling stinging catfish,Heteropneustes fossilis(Bloch)

To quantify dietary L-tryptophan requirement of fingerling Heteropneustes fossilis (6.66 ± 0.08 g), casein–gelatin-based isonitrogenous (38% CP) and isoenergetic (14.72 kJ g−1 DE) purified diets with eight levels of L-tryptophan (0.12%, 0.16%, 0.20%, 0.24%, 0.28%, 0.32%, 0.36%, 0.40% dry diet) were fed to triplicate groups of fish twice daily to apparent satiation for 12 weeks. Incremental levels of dietary tryptophan from 0.12 to 0.28% significantly (P < 0.05) improved absolute weight gain (AWG; 14.3–65.9 g fish−1), feed conversion ratio (FCR; 5.9–1.5), protein retention efficiency (PRE; 6.2–32.2%), haemoglobin (Hb; 6.5 to 11.9 g dL−1) and haematocrit (Hct; 23.5–33.8%). To determine the precise information on tryptophan requirement, data were subjected to broken-line and second-degree polynomial regression analysis. Broken-line regression analysis reflected highest R2 values for AWG g fish−1 (0.999), PRE% (0.993), Hb g dL−1 (0.995) and Hct% (0.993) compared with R2 values obtained using second-degree polynomial regression analysis of AWG g fish−1(0.949), PRE% (0.890), Hb g dL−1(0.969) and Hct% (0.943), indicating that data were better fit to broken-line regression analysis. Hence, based on broken-line regression analysis at 95% maximum response, tryptophan requirement of fingerling H. fossilis is recommended between 0.24% and 0.27% dry diet (0.63–0.71% protein).

Dietary lysine requirement of fingerling Catla catla (Hamilton) based on growth, protein deposition, lysine retention efficiency, RNA/DNA ratio and carcass composition

A 12-week experiment was conducted to quantify dietary lysine requirement of fingerling Catla catla (3.65±0.05cm; 0.58±0.02g) by feeding casein-gelatine-based diets (33.0% crude protein; 14.3kJ/g digestible energy) with six levels of L-lysine (1.25, 1.50, 1.75, 2.00, 2.25 and 2.50% dry diet). The experiment was conducted in eighteen 70-L indoor polyvinyl circular troughs provided with a water flow-through system (1-1.5L/min). Live weight gain (LWG), feed conversion ratio (FCR), protein deposition (PD), lysine retention efficiency (LRE%) and RNA/DNA ratio were used as the response criteria. Second-degree polynomial regression analysis at 95% maximum and minimum response of LWG and FCR data exhibited the lysine requirement between 1.8 and 1.9% dry diet, corresponding to 5.5-5.7% dietary protein. Regression analysis of PD, LRE and RNA/DNA ratio yielded the requirement between 1.7 and 1.8% dry diet, corresponding to 5.2-5.5% dietary protein. Since live weight gain and protein deposition are the key parameters for estimating nutrient requirement, these tools were used to recommend the lysine requirement of fingerling C. catla which ranges between 1.7 and 1.8% dry diet. Data generated during this study will be useful to formulate lysine-balanced feed for intensive culture of this fish.

Effects of dietary arginine levels on growth, feed conversion, protein productive value and carcass composition of stinging catfish fingerling Heteropneustes fossilis (Bloch)

A 12-week feeding trial was conducted to evaluate the effects of varying levels of dietary arginine on growth, feed conversion, protein productive value and carcass composition of fingerling Heteropneustes fossilis (10.11 ± 0.14 cm; 5.87 ± 0.07 g). Casein and gelatin-based isonitrogenous (38% crude protein) and isocaloric (14.72 kJ g−1 digestible energy) amino acid test diets with varying levels of l-arginine (1.00, 1.25, 1.50, 1.75, 2.00 and 2.25 g 100 g−1 of dry diet) were fed to randomly assigned triplicate groups of fish to apparent satiation twice daily at two feeding schedules (08.00 and 17.30 h). Thermal growth coefficient (TGC; 0.86), feed conversion ratio (FCR; 1.97) and protein productive value (PPV; 0.25) were best attained by the group fed diet containing 1.75 g arginine 100 g−1 of dry diet (D4). Carcass protein content also peaked at the above level of dietary arginine whereas carcass lipid showed consistent drop with the increase in dietary arginine level up to 1.75 g 100 g−1 of dry diet. Second-degree polynomial regression analysis at 95% maximum and minimum response of thermal growth coefficient, feed conversion, protein productive value, carcass protein and lipid productive value against varying levels of dietary arginine yielded that dietary arginine in the range of 1.51–1.66 g 100 g−1 of dry diet, corresponding to 3.97–4.37 g 100 g−1 protein is adequate to optimize growth, feed conversion, protein productive value and improve carcass quality in fingerling H. fossilis.

Dietary methionine requirement of Indian major carp fry,Cirrhinus mrigala(Hamilton) based on growth, feed conversion and nitrogen retention efficiency

This study was aimed at quantifying methionine requirement of Indian major carp fry, Cirrhinus mrigala (2.2 ± 0.2 cm; 0.19 ± 0.02 g) by conducting a 12-week feeding trial. Casein–gelatine-based isonitrogenous (40 g 100 g−1 crude protein) and isoenergetic (15.42 kJ g−1 DE) amino acid test diets were prepared to contain six levels of l-methionine (1.1, 1.3, 1.5, 1.7, 1.9 and 2.1 g 100 g−1 dry diet) at a fixed level of cysteine (0.85 g 100 g−1 dry diet) and fed to apparent satiation thrice daily to triplicate groups of fish. When absolute weight gain (g per fish), feed conversion ratio, protein deposition (g per fish) and nitrogen retention efficiency data were subjected to broken-line and second-degree polynomial regression analysis, 95% of the plateau of above parameters was achieved at dietary methionine concentrations between 1.60 and 1.69 g 100 g−1 dry diet or 0.10 to 0.11 g methionine kJ−1 DE, corresponding to 4.1–4.22 g 100 g−1 protein or 0.44–0.47 g methionine kJ−1 DE. Based on these results, dietary methionine requirement of fry C. mrigala is recommended 1.60–1.69 g 100 g−1 diet or 0.10–0.11 g methionine kJ−1 DE.

Growth, Feed Conversion, and Nutrient Retention Efficiency of African Catfish, Clarias gariepinus, (Burchell) Fingerling Fed Diets with Varying Levels of Protein

Growth, feed conversion, and nutrient retention efficiencies of African catfish fingerling, Clarias gariepinus (5.22 ± .07 cm; 8.22 ± 0.03 g), fed diets with varying levels of protein were assessed by feeding seven casein/gelatin based isocaloric (17.62 kJ/g GE) experimental diets with graded levels of dietary protein (20%, 25%, 30%, 35%, 40%, 45%, and 50% of the diet) to triplicate groups of fish to apparent satiation for eight weeks. Effects of feeding these diets on live weight gain (LWG%), feed conversion ratio (FCR), protein efficiency ratio (PER), protein retention efficiency (PRE%), and energy retention efficiency (ERE%) were assessed. Maximum LWG% (867%), PER (2.01), highest PRE (32%), ERE (69%), best FCR (1.39), and maximum body protein were recorded in fish fed diet containing 35% protein. On the basis of the second-degree polynomial regression analysis of the above response variables, it is recommended that the inclusion of protein in the range of 34.4%–39.6% is optimum for maximizing growth potential, feed conversion, and nutrient retention in African catfish fingerling, Clarias gariepinus.