Use of turkey meal as partial and total replacement of fish meal in practical diets for sunshine bass (Morone chrysops × Morone saxatilis) grown in tanks

Economical, nutritious diets for hybrid striped bass (HSTB) are required for the continued expansion and sustainability of this industry. Turkey meal (TM) is a by‐product of the US turkey industry and is a potentially‐valuable local, alternative protein source for use in aquaculture diets because of its excellent nutritional composition and quality. TM may substitute for more expensive fish meal (FM)‐based diets; however, there are no published data with regard to using this ingredient in sunshine bass diets. Therefore, a 16‐week feeding trial was conducted with juvenile (36 g) sunshine bass (Morone chrysops × Morone saxatilis) to evaluate growth, feed conversion and body composition when fed diets with decreasing levels of FM (300, 200, 100 and 0 g kg^?1) and increasing levels of turkey meal (0, 97, 175 and 264 g kg^?1). Four practical diets were formulated to contain 400 g kg^?1 protein and similar energy levels. Twenty fish were stocked into each of the 12, 1200‐L circular tanks and were fed twice daily ad libitum. At the conclusion of the feeding trial, there were no significant (P > 0.05) differences in final mean weight, percentage weight gain, specific growth rate and feed conversion ratio among treatments, which averaged 363.7 g, 904.3%, 2.02% day^?1 and 1.73, respectively. Percentage survival of fish fed diet 4 (0 g kg^?1 FM and 264 g kg^?1 TM) was significantly (P > 0.05) lower (survival = 88.3%) than fish fed diet 3 (100 g kg^?1 FM and 175 g kg^?1 TM; survival = 95%), but not different from fish fed diet 1 (survival = 92.5%) and fish fed diet 2 (survival = 93.3%). Fillet weight and amount of abdominal fat were not significantly different among all treatments and averaged 258 and 58 g kg^?1, respectively. Fish fed diet 1 (300 g kg^?1 FM, 0 g kg^?1 TM) and diet 2 (200 g kg^?1 FM and 970 g kg^?1 TM) had a significantly (P < 0.05) lower hepatosomatic index (2.83 and 3.01, respectively) than fish fed diet 4 (3.33), but not different (P > 0.05) compared to fish fed diet 3 (3.14). Lipid in the fillet of fish fed diet 2 (197 g kg^?1) was significantly (P < 0.05) higher than fish fed all other diets; and the percentage lipid in the fillet of fish fed diet 1 (126 g kg^?1) was significantly lower than fish fed diets 2 and 4, but not different (P >0.05) compared to fish fed diet 3. Fillet moisture, protein and ash were similar among fish fed all diets and averaged 748, 798 g kg^?1 and 51.0 g kg^?1 (dry‐matter basis), respectively. The amino acid composition of fillets was similar among all treatments with a few slight significant differences. Results from the present study indicate that tank‐grown sunshine bass can be fed a diet containing 264 g kg^?1 TM with 0 g kg^?1 FM, compared to diets containing up to 300 g kg^?1 FM, without adverse effects on weight gain, growth rate, feed conversion and body composition. Further research should be conducted using lower‐protein diets to determine minimum protein level for tank‐grown sunshine bass.     

Selenium nutrition of hybrid striped bass (Morone chrysops × M. saxatilis) bioavailability, toxicity and interaction with vitamin E

Two concurrent 12-week feeding trials were conducted to evaluate the bioavailability of inorganic sodium selenite and organic seleno-DL-methionine and to investigate the potential interaction between selenium and vitamin E in juvenile hybrid striped bass. In experiment 1, purified diets utilizing casein, gelatin and an amino acid premix as protein sources with a basal selenium concentration of 0.11 mg Se   kg⁻¹ were supplemented with either Na₂SeO₃ to provide selenium concentrations of 1.19, 2.00, 5.17 and 21.23 mg Se kg⁻¹ or with seleno-DL-methionine to provide 0.90, 1.26 and 2.55 mg Se kg⁻¹ and fed to juvenile hybrid striped bass in aquaria. A second experiment evaluated potential interactions by feeding these purified diets with or without supplemental vitamin E or sodium selenite, singularly or in combination. No overt selenium deficiency signs were exhibited by fish in either of the experiments; however, signs of selenium toxicity including retarded weight gain (WG), reduced feed intake and feed efficiency ratio (FER) as well as increased mortality, were observed in fish fed the diet containing more than 20 mg Se kg⁻¹. Whole-body selenium and whole-body selenium retention were linearly influenced by sodium selenite and selenomethionine. However, there was no significant effect of dietary selenium, vitamin E or their interaction on WG, FER and survival. Slope-ratio analysis showed that bioavailability of seleno-DL-methionine as a selenium source for juvenile hybrid striped bass was significantly ( P  < 0.01) higher (3.3-fold) than sodium selenite.     

A comparison of two faecal collection methods for protein and amino acid digestibility coefficients of menhaden fish meal and two grades of poultry by-product meals for market-size sunshine bass (Morone chrysops × M. saxatilis)

Apparent digestibility and availability coefficients for protein and amino acids in menhaden fish meal (MEN), pet‐food grade (PBM‐pet,) and feed‐grade poultry by‐product meal (PBM‐feed) were determined for market‐size (500 g) sunshine bass in two consecutive trials using passive netting (1.6 mm mesh) followed by manual stripping of faeces. A reference diet resembling a commercial feed was formulated to meet or exceed all known nutritional requirements of hybrid striped bass. Test diets were formulated to contain a 70 : 30 mixture of reference diet to test ingredient with chromic oxide (1%) serving as the inert marker. Diets were extruded under commercial conditions and the reference diet was fed for two weeks in order to acclimate fish to experimental conditions. Each diet was randomly assigned to triplicate tanks containing 30 fish each. Fish were fed their respective diet twice daily to apparent satiation for two weeks, with faecal collections being conducted on the 7th and 14th day, in each trial. ADC values determined in the net method were highly variable and generally lower than ADCs obtained by stripping. Consistently lower and highly variable chromium concentrations were found in the net method faecal samples and suggest that marker loss relative to nutrient content, or dilution of marker with non‐faecal matter, on the net collectors influenced results in that trial. In contrast, the standard errors of ADCs determined in the strip method were less than 5 percentage points in most cases. Protein digestibility ranged from a low of 51% (PBM‐feed) to a high of 87% (PBM‐pet) in the net method, and from a low of 80% (PBM‐feed) to a high of 99% (MEN) in the strip method. With the exception of Lys, no differences in amino acid availabilities among diets were found in the net method. In the strip method, protein digestibility and amino acid availabilities in MEN were generally greater than those found in PBM‐pet or PBM‐feed, whereas ADCs were not significantly different between the two poultry by‐products. Based on the conditions of the present study, net collection of faecal matter can not be recommended for determining the digestibility of nutrients in feed ingredients for market‐size sunshine bass. Digestibility coefficients obtained by the strip method for feed and petfood grades poultry by‐product were higher than those previously reported and will be facilitate more efficient and economical diet formulations for larger sunshine bass.     

Amino acid availability from selected animal‐ and plant‐ derived feedstuffs for market‐size sunshine bass (Morone chrysops × Morone saxatilis)

A study was conducted with market‐size (867 g) hybrid striped bass to determine the nutrient digestibility and apparent amino acid availability of six common feedstuffs. The animal‐protein feedstuffs tested were menhaden fish meal (MEN), anchovy fish meal (ANCH), pet‐food grade poultry by‐product meal (PBM‐pet), and feed‐grade poultry by‐product meal (PBM‐feed), while the plant‐protein feedstuffs were dehulled solvent extracted soybean meal (SBM) and distiller’s dried grains with solubles (DDGS). Test diets consisted of a 70 : 30 mixture of reference diet to test ingredient with chromic oxide (10 g kg^?1%) as the inert marker. Diets were randomly assigned to triplicate tanks of fish that were fed their respective diets for 7 days prior to fecal collection by stripping. Two feeding trials were conducted sequentially to determine the digestibility of the six test ingredients. In trial 1, the three ingredients evaluated were MEN, PBM‐feed, and PBM‐pet. In trial 2, the three ingredients evaluated were ANCH, SBM, and DDGS. Apparent digestibility coefficients of protein (ADC‐CP) were significantly (P < 0.05) different among test ingredients in trial 1 as protein digestibility of MEN (86%) was significantly higher (P < 0.05) than that of PBM‐feed (75%), but was not significantly different from that of PBM‐pet (78%). Protein digestibilities in trial 2 were not significantly different among test ingredients and averaged 76% for ANCH, SBM, and DDGS. Some apparent amino acid availability coefficients differed among feedstuffs for both trial 1 and trial 2. MEN provided higher amino acid availabilities for alanine, aspartic acid, glutamic acid, lysine, valine, and tryptophan (99%, 98%, 94%, 96%, 99%, and 108%, respectively) when compared to PBM‐feed (73%, 50%, 69%, 80%, 77%, and 91%, respectively) and PBM‐pet (79%, 66%, 81%, 81%, 78%, and 99% respectively). Glycine, histidine, leucine, and proline availabilities in MEN (95%, 96%, 100%, and 98%, respectively) were significantly (P < 0.05) higher than those of PBM‐feed (64%, 82%, 82%, and 57%, respectively), but were not significantly different from PBM‐pet (85%, 92%, 89%, and 80%, respectively). For trial 2, apparent amino acid availabilities for cystine, isoleucine, lysine, and tyrosine were significantly higher (P < 0.05) among treatments fed SBM (100%, 87%, 93%, and 97%, respectively) and ANCH (37%, 95%, 92%, and 84%, respectively) compared to treatments fed DDGS (?13%, 52%, 62% and 62%, respectively). Overall, amino acid availability in SBM and the two PBM’s appear comparable to MEN and ANCH and corroborate their high value as potential replacements for fish meal in sunshine bass diets. However, DDGS provided the lowest availabilities for several amino acids and should be used with caution.     

Dietary cholesterol and lecithin have limited effects on growth and body composition of hybrid striped bass (Morone chrysops × M. saxatilis)

The effects of cholesterol and lecithin on growth and body composition of juvenile hybrid striped bass ( Morone chrysops  ×  M. saxatilis ) were investigated by feeding juvenile hybrids (initial weight 5.0 g) diets containing cholesterol at either 0 or 1% and lecithin at either 0, 2, 4, or 6% in a 2 × 4 factorial design. Each of the eight diets was fed to fish in triplicate 38-L aquaria maintained as a brackish water recirculating system for 8 weeks. Weight gain, feed efficiency, muscle ratio and hepatosomatic index were not significantly ( P  > 0.05) affected by dietary supplementation of cholesterol or lecithin. Supplementation of the diet with lecithin at 4 and 6% significantly ( P  < 0.05) decreased intraperitoneal fat accumulation regardless of dietary cholesterol level. Neither muscle nor liver lipid levels were significantly altered by dietary supplementation of cholesterol or lecithin although both liver and plasma lipid classes were affected. Dietary cholesterol decreased concentrations of liver and plasma free fatty acids and liver phospholipids while increasing concentrations of liver triglycerides and plasma phospholipids. Dietary lecithin did not consistently affect plasma and liver lipid classes although changes in phospholipid levels approaching significance ( P =0.0502 and P =0.0513, respectively) were observed. Thus it is concluded that dietary supplementation with cholesterol or lecithin had no substantial beneficial effects on growth or body composition of juvenile hybrid striped bass.     

Hypoxia affects performance traits and body composition of juvenile hybrid striped bass (Morone chrysops × M. saxatilis)

Performance traits and body composition of juvenile hybrid striped bass (Morone chrysops × M. saxatilis) in response to hypoxia were evaluated in replicate tanks maintained at constant dissolved oxygen concentrations that averaged 23.0 ± 2.3%, 39.7 ± 3.0% and 105.5 ± 9.5% dissolved oxygen saturation. Fish were fed a commercially formulated feed daily to apparent satiation. Total feed intake and fish growth and yield increased linearly in response to increased dissolved oxygen concentration. Nutrient utilization was reduced significantly only at the greatest level of hypoxia. With the exception of whole body protein content, whole body compositional indices and nutrient retention efficiencies were linearly related to dissolved oxygen concentration. Results demonstrate that as hypoxia becomes more severe, juvenile hybrid striped bass feed intake is reduced, which affects growth and nutrient retention.     

Optimizing dietary protein sources for Japanese sea bass (Lateolabrax japonicus) with an emphasis on using poultry by‐product meal to substitute fish meal

This study evaluated the potential of using poultry by‐product meal (PBM) to replace fish meal in diets for Japanese sea bass, Lateolabrax japonicus. Fish (initial body weight 8.5 g fish^?1) were fed six isoproteic and isoenergetic diets in which fish meal level was reduced from 400 g kg^?1 (diet C) to 320 (diet PM1), 240 (diet PM2), 160 (diet PM3), 80 (diet PM4) or 0 g kg^?1 (diet PM5), using PBM as the fish meal substitute. The weight gain (WG), specific growth rate, nitrogen retention efficiency, energy retention efficiency and retention efficiency of indispensable amino acids were higher in fish fed PM1, PM2, PM3 and PM4 diets than in fish fed diets C or PM5. The phosphorus retention efficiency was lower in fish fed PM3, PM4 and PM5 diets than in fish fed C, PM1 or PM2 diets. Fish fed diet PM5 had the highest feed conversion ratio, total nitrogen waste output (TNW) and total phosphorus waste output (TPW) among the treatments. No significant differences were found in the hepatosomatic index or body contents of moisture, lipid and ash among the treatments. Fish fed diet C had lower condition factor and viscerosomatic index than those of fish fed PM1, PM3, PM4 and PM5 diets. The results of this study indicate that using fish meal and PBM in combination as the dietary protein source produced more benefits in the growth and feed utilization of Japanese sea bass than did using fish meal or PBM alone as the dietary protein source. The dietary fish meal level for Japanese sea bass can be reduced to 80 g kg^?1 if PBM is used as a fish meal substitute.     

The effect of exogenously administered recombinant bovine somatotropin on intestinal phytase activity and in vivo phytate hydrolysis in hybrid striped bass Morone chrysops × M. saxatilis

It has been recently demonstrated that hybrid striped bass Morone chrysops × M. saxatilis exhibit intestinal phytase activity, an enzyme capable of liberating inorganic orthophosphate from the phytate molecule, thereby making phytate phosphorus (PP) available for absorption and utilization by the fish. However, it was also determined that hybrid bass were able to digest only 1–2% of dietary PP. Therefore, an experiment was conducted to determine if exogenously administered recombinant bovine somatotropin (rbST) would increase intestinal phytase activity in hybrid striped bass to a level that would improve PP availability. The results indicate that exogenous rbST treatment, administered either through intraperitoneal injection or orally, does increase intestinal brush border membrane protein concentration. While injection with rbST led to significant increases in both specific brush border membrane and total intestinal phytase activity, oral rbST administration did not cause similar increases. Total P and PP digestibility were not influenced by rbST administration. While treatment with rbST does have the potential to enhance intestinal phytase activity in hybrid striped bass, it does not appear to increase PP digestibility. This observation limits the hormone's utility as an effective technique for improving PP bioavailability to this species.     

Apparent digestibility of Asian carp‐ and common carp‐derived fish meals in feeds for hybrid striped bass Morone saxatilis ♀ × M. chrysops ♂ and rainbow trout Oncorhynchus mykiss

Apparent digestibility coefficients (ADCs) of nutrients (crude protein, amino acids, crude lipid, fatty acids, and minerals) were determined for fish meals derived from menhaden, Asian carp (combination of silver and bighead carps), and common carp in feeds for hybrid striped bass and rainbow trout. Extruded test diets were formulated to contain a 70 : 30 mixture of reference diet and test ingredient with yttrium oxide (1 g kg^?1) serving as the inert marker. Diets were randomly assigned to triplicate tanks and fish were fed once per day at 2% body weight. Fecal samples were collected by manual stripping. The ADCs were calculated according to standard procedures. The composition and digestibility of Asian carp and common carp meals was broadly similar to menhaden meal. Protein digestibility ranged from 86.5% (Asian carp meal) to 93.1% (common carp meal). Lipid was highly digestible with ADCs >100% for all ingredients. Although the Asian carp meal was less digestible than the other two fish meals, it was still a highly digestible ingredient. Our data suggest that fish meals derived from Asian or common carp would be valuable feedstuffs in diets for hybrid striped bass, rainbow trout, and possibly other cultured fishes.     

Supplementations of poultry by‐product meal and selenium yeast increase fish meal replacement by soybean meal in golden pompano (Trachinotus ovatus) diet

The effects of poultry by‐product meal (PBM) and selenium yeast (Se‐yeast) supplementations on fish meal replacement by soybean meal (SBM) in the diet of golden pompano (Trachinotus ovatus) were examined. In trial I, a 2 × 3 layout including two PBM levels (100 and 170 g kg^?1) and three levels of fish meal replacement (0, 40 or 60%) was used. At 100 g kg^?1 PBM, fish fed the basal diet exhibited the highest weight gain (WG) and nitrogen retention efficiency (NRE) and the lowest feed conversion ratio (FCR). At 170 g kg^?1 PBM, no significant differences were found in WG and NRE between fish fed the basal diet and diet with 40% of fish meal replaced by SBM. In trial II, the basal diet containing 170 g kg^?1 PBM (trial I) served as a reference. A 2 × 2 layout included two levels of fish meal replacement (40 or 60%) and two levels of Se‐yeast addition (0 and 1 g kg^?1). No significant differences were found in WG, feed intake, FCR and NRE between fish fed the reference diet and diet with 40 or 60% fish meal replacement plus 1 g kg^?1 Se‐yeast addition. This study indicates that supplementations of PBM and Se‐yeast can enhance the level of fish meal replacement by SBM in golden pompano diet. Dietary fish meal level can be reduced to 140 g kg^?1 by optimizing inclusion of SBM, PBM and Se‐yeast.     

Immunomodulatory effects of β‐glucans derived from Euglena gracilis or Saccharomyces cerevisiae for hybrid striped bass (Morone chrysops × M. saxatilis)

Beta‐glucans (BGs) can activate the animal's innate immune system, enhancing the primary defence lines against pathogenic insults. The objective of this study was to assess the immune responses of hybrid striped bass (HSB) when exposed to paramylon, derived from Euglena gracilis, or zymosan, derived from Saccharomyces cerevisiae. Two separate trials were conducted to evaluate the efficacy of these immunostimulants as a feed additive or injected intraperitoneally. Five diets were formulated to contain either paramylon or zymosan at two different levels (50 or 100 mg/kg), and no supplementation serving as the control. Blood and head kidney were sampled, and an elevated production of anion superoxide from isolated phagocytes was observed for all supplemented groups when compared to the control. Dietary paramylon at 50 mg/kg increased immunoglobulin levels in the plasma. The second trial was conducted by injecting a BG solution (10 mg of β‐glucan kg^‐1 of body weight) and phosphate buffer solution serving as the control. Seven days after injection, blood samples were collected and immunological profiles from whole blood and plasma were significantly (p < .05) affected by the treatments. The results from this study indicate that both dietary and injected paramylon and zymosan modulated the immunological responses of HSB.     

Effect of DL‐methionine supplementation on the success of almost total replacement of fish meal with soybean meal in diets for hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus)

This study evaluated the effects of increasing levels of methionine (Met) supplementation on the success of almost total replacement of fish meal (FM) with soybean meal (SBM) in diets for hybrid tilapia (Oreochromis niloticus × Oreochromis mossambicus). Fish were fed for 70 days a FM‐based diet (Diet1‐positive control) or SBM‐based diets supplemented with graded levels of DL‐methionine (Diet2 to Diet7). Contrast in dietary Met, concentration was created by supplementing Diet2‐negative control with 1.2 (Diet3), 2.4 (Diet4), 3.6 (Diet5), 4.8 (Diet6) or 6.0 g kg^?1 (Diet7) of DL‐Met. Specific growth rate (SGR), feed conversion ratio (FCR), and protein gain and retention efficiency (PER) improved significantly with increasing levels of dietary DL‐Met supplementation. Moreover, nonlinear regression analysis of the effects of supplementing SBM‐based diet with graded levels of DL‐Met indicated that a dietary Met + Cys level of 15.7 and 12.5 g kg^?1 diet (as fed) was required to reach 95% of maximum weight and protein gain, respectively. Supplementation of SBM‐based diet with graded levels of DL‐Met proved an effective strategy in reducing FM content in practical diets for hybrid tilapia. Data also indicate that adjustment of dietary formulas according to currently recommended Met or Met + Cys dietary concentrations is probably limiting maximum growth potential of hybrid tilapia.     

Incorporation of a mixture of meat and bone meal,poultry by‐product meal,blood meal and corn gluten meal as a replacement for fish meal in practical diets of Pacific white shrimp Litopenaeus vannamei at two dietary protein levels

A 6‐week feeding trial was carried out in glass tanks to determine the effects of partial replacement of fish meal (FM) with a combination of meat and bone meal (MBM), poultry by‐product meal (PBM), blood meal (BM) and corn gluten meal (CGM) in practical diets on the growth, nutrient digestibility and body composition of Pacific white shrimp. Six practical diets were formulated, containing two levels of crude protein (CP) (330 and 380 g kg^?1) and similar crude lipid (CL) levels. For the 330 g kg^?1 dietary protein level, 0, 357 and 714 g kg^?1 FM were replaced by the mixture in Diets 1–3, respectively; while 0, 514 and 784 g kg^?1 FM were replaced in Diets 4–6, respectively, for 380 g kg^?1 dietary protein level. White shrimp‐fed diets containing 330 g kg^?1 CP had significantly lower weight gain compared with white shrimp fed diets containing 380 g kg^?1 CP. Increasing the mixture and dietary protein level significantly raised the body ash content of white shrimp. White shrimp fed a low‐protein diet obtained better nutrient digestibility compared with those fed a high‐protein diet.     

Effects of totally replacing dietary fish oil by linseed oil or soybean oil on juvenile hybrid sturgeon,Acipenser baeri Brandt♀×A. schrenckii Brandt♂

The growth performance, body composition, fillet fatty acid content, serum hepatic enzymes and postprandial changes in serum lipid metabolism of hybrid sturgeon (70.8 ± 0.5 g) were investigated to determine the effects of total replacement of 80 g kg^‐1 fish oil (diet A) with linseed oil (diet B) and soybean oil (diet C), respectively. No significant differences in weight gain rate and specific growth ratio were observed among all fish groups (p > .05). Diet A fish group had the highest, but diet B fish group had the lowest feed intake (p < .05). Feed efficiency of fish fed diet A was significantly lower than the other two fish groups (p < .05). Fish fed diet A had the lowest fillet and liver lipid contents (p < .05). Serum lactate dehydrogenase, alanine aminotransferase and aspartate aminotransferase activities of fish fed diet A were significantly lower than those of fish fed diets B and C (p < .05). The contents of linoleic acid (C18:2n6) and linolenic acid (C18:3n3) in fillets showed a significantly positive linear correlation with the diets. Serum glucose and non‐esterified fatty acid were just affected by the time point (p < .05). The lipid source, time point and interaction of both factors had significant effects on serum triglyceride, high‐density lipoprotein cholesterol and low‐density lipoprotein cholesterol (p < .05). Serum total cholesterol was only affected by interaction of time point and lipid source (p < .05), and ketone body was not affected by lipid source, time point or interaction of both factors (p > .05). In summary, total replacement of fish oil with linseed oil or soybean oil had no significant adverse effects on hybrid sturgeon growth during 84‐day period, and linoleic acid and linolenic acid in fillet were modified by dietary treatments.     

Bio‐Ag reutilization of distiller's dried grains with solubles (DDGS) as a substrate for black soldier fly larvae,Hermetia illucens,along with poultry by‐product meal and soybean meal,as total replacement of fish meal in diets for Nile tilapia,Oreochromis niloticus

A feeding trial was conducted in a closed system with Nile tilapia, Oreochromis niloticus, juveniles (mean initial weight, 2.66 g) to examine total replacement of menhaden fish meal (FM) with distiller's dried grains with solubles (DDGS), which had been used as substrate for the production of black soldier fly larvae, Hermetia illucens, in combination with soybean meal (SBM) and poultry by‐product meal (PBM), with or without supplementation of the amino acids (AA) DL‐methionine (Met), L‐lysine (Lys) and a commercial non‐amylaceous polysaccharide enzyme (Enz) product. Fish were fed seven isoenergetic [available energy (AE) = 4.0 kcal g^?1 of diet] and isonitrogenous (350 g kg^?1 protein as‐fed basis) practical diets formulated with equivalent digestible protein levels. Diet 1 was formulated to be similar to a commercial, high‐quality, tilapia diet containing 200 g kg^?1 FM. Diets 2–5 were formulated as a 2 × 2 factorial to replace FM with similar contributions from DDGS (45%), PBM (25%) and SBM (2.1–2.9%), but to differ in supplementation of AA and/or Enz preparation. Diets 6 and 7 were formulated to investigate the effects of a 2/3 and 1/3 reduction, respectively, in DDGS contribution to the replacement protein mix, with concomitant increases in SBM, with respect to diet 3, and were balanced with Lys and Met. After 6 weeks, growth responses were slightly attenuated (P ≤ 0.05) and average daily intake (ADI) and feed conversion ratio (FCR) were slightly higher in tilapia fed DDGS diets 2–5 compared to those of fish fed the FM control diet 1. Growth responses were not significantly affected by the presence or absence of AA or Enz (diets 2–5), or the level of DDGS (diets 3, 7 and 6). Whole‐body proximate composition was not different among treatments. Amino acid profiles of fish fed DDGS diets were not significantly different from those of fish fed the FM control. Evidence of interaction between AA and Enz supplementation was detected in whole‐body amino acid concentrations such that AA content was higher with AA or Enz addition alone, but lower when both were added to the diet. Results suggest that DDGS replacement of FM in tilapia diets can be substantial when diets are formulated on a digestible protein basis and DDGS is combined with highly digestible animal (PBM) and plant proteins (SBM).     

Effects of dietary supplementation of probiotics on the growth,activities of digestive and non‐specific immune enzymes in hybrid grouper (Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀)

Effects of Bacillus cereus BC‐01, Lactobacillus acidophilus LAG01, Clostridium butyricum CBG01 and their combinations as supplementation on the growth performance, digestive enzyme activities and serum non‐specific immunity of hybrid grouper (Epinephelus lanceolatus ♂×E. fuscoguttatus ♀) were assessed. Seven different diets, that is one control diet (basal feed without any probiotics, CT) and six treatment diets containing single B. cereus (Bs), L. acidophilus (Ls) and C. butyricum (Cs) at 1.0 × 10⁹ cfu/kg feed, and also their combinations in equal proportion at 1.0, 2.0 and 3.0 × 10⁹ cfu/kg feed (BLC1, BLC2 and BLC3) were prepared respectively. After 60‐day feeding trial, the final weight, specific growth rate,food consumption, food conversion efficiency and apparent digestibility coefficient of fish in Ls and BLC3 were significantly higher compared with the control (p < .05). The activities of pepsin and trypsin in the intestine of fish for Ls and BLC3 were significantly higher relative to the control (p < .05). Relative to controls, significantly enhanced amylase and lipase activities in proximal intestine except for Cs and BLC1 and lipase activities in distal intestine except for Cs were observed (p < .05). Meanwhile, activities of superoxide dismutase in the serum of fish for all treatments, lysozyme and catalase in Ls and BLC3, and glutathione peroxidase except for Cs were significantly enhanced (p < .05). Based on the above, dietary supplementation of single L. acidophilus at 1.0 × 10⁹ cfu/kg or combination of three strains at 3.0 × 10⁹ cfu/kg for hybrid grouper is recommended.