Utilisation of diets supplemented with microbial phytase by seabass (Dicentrarchus labrax) juveniles

A trial was carried out to compare the growth performance, body composition and apparent digestibility coefficients (ADC) of diets by seabass, with an initial weight of 13.5 g, fed diets including fish meal (68.6 % of the dietary protein) or soybean meal (65.6 % of the dietary protein) as the main protein sources. Microbial phytase was added to the soybean meal based diet (1 000 and 2 000 IU·kg⁻¹) and to the fish meal based diet (2 000 IU·kg⁻¹) in order to study its effect on phosphorus utilisation. Results of this trial showed that growth rate, feed conversion and nitrogen retention were significantly better in fish fed the fish meal based diet. Energy retention was similar in both groups. ADC of protein were similar among groups. ADC of phosphorus was significantly higher in the fish meal based diet (63 %) than in the soybean meal based diet (25 %). Supplementation of the fish meal based diet with microbial phytase did not improve the ADC of phosphorus, while in the soybean meal based diet the inclusion of 1 000 and 2 000 IU·kg⁻¹ of microbial phytase significantly increased the ADC of phosphorus to 71.5 % and 79.8 %, respectively. It is concluded that for practical purposes supplementation of diets with microbial phytase may prove valuable in diets including high levels of plant feedstuffs.     

Top-spraying soybean meal-based diets with phytase improves protein and mineral digestibilities but not lysine utilization in rainbow trout, Oncorhynchus mykiss (Walbaum)

Two digestibility trials and two growth trials were carried out to evaluate the influence of top‐sprayed phytase on apparent digestibility coefficients (ADCs) of protein and mineral and utilization in rainbow trout fed with soybean meal‐based diets. In Trial 1, a semi‐purified diet containing 50% soybean meal was supplemented with graded levels of phytase (0, 500, 1000, 2000 and 4000 U kg^?1 diet), and fed to triplicate groups of fish. In Trial 2, commercial‐type extruded feeds containing 36% soybean meal with either 0 or 2000 U phytase kg^?1 were fed to five replicate groups of fish. Phytase clearly decreased phytic acid content of feces from 35 to 5 mg and from 34 to 14 mg phytic acid per g faecal dry matter in Trials 1 and 2 respectively. Apparent digestibility coefficient of P improved from 23% to 83% in Trial 1 and from 35% to 54% in Trial 2 by phytase. Apparent protein increased by 1.2% and 3.2%‐units by phytase in Trials 1 and 2. Zinc digestibility was significantly increased in Trial 1, but not in Trial 2. Trials 3 and 4 were conducted to evaluate the influence of phytase on dietary P (Trial 3) and lysine (Trial 4) utilization. Three diets were prepared for each trial: P (Trial 3)‐ or lysine (Trial 4)‐deficient basal diets, basal diets with phytase supplementation (2000 U kg^?1) and P (Trial 3)‐ or lysine (Trial 4)‐fortified diets. Rainbow trout (initial weight 20 g) were fed for 10 weeks using four and six replicates for Trials 3 and 4 respectively. Phytase increased P utilization in Trial 3 as demonstrated by an increase in vertebra ash from 24.1% to 45.4%, and by an increase in weight gain from 243% to 459% of the initial weight. Phytase did not increase lysine utilization, since neither protein retention nor weight gain were enhanced by phytase. Supplemental lysine increased protein retention and weight gain to 43.1% and 514%, respectively, and also decreased whole‐body lipid contents significantly from 120 to 123 g kg^?1 in fish fed the basal diet and phytase‐supplemented diet to 106 g kg^?1 in fish fed with lysine‐fortified diet.     

Partial replacement of fish meal by soybean meal with or without methionine and phytase supplement in diets for juvenile Chinese sucker,Myxocyprinus asiaticus

This study was designed to evaluate the effects of using soybean meal supplemented with or without methionine (M) and graded levels of phytase (P) to replace high‐level (60%) fish meal in the diets for juvenile Chinese sucker. Seven experimental diets (about 430 g kg^?1 crude protein on dry matter basis) were formulated from practical ingredients. The control diet (FM) was formulated to contain 400 g kg^?1 white fish meal (FM), whereas in the other six diets (diets 2–7), soybean meal (SBM) was used to replace 60% fish meal with or without methionine (3 g kg ^?1) and 0,500, 1000, 1500 and 2000 U kg^?1 phytase (designated as SBM, SM, SMP500, SMP1000, SMP1500 and SMP2000, respectively). Results from the feeding trial indicated that SBM without any methionine or phytase supplement replacing about 60% FM significantly affected the growth of fish (P < 0.05). Weight gain of fish fed diet SM was significantly higher than the fish fed diet SBM, but still much lower than fish fed the control diet (P < 0.05). SBM with methionine and phytase supplement significantly improved the growth of fish and apparent digestibility coefficients of phosphorus compared with the groups which fed diet SBM and diet SM (P < 0.05). Weight gain of fish fed SMP1000, SMP1500 and SMP2000 had no significant difference than fish fed control diet. Furthermore, fish fed SMP1500 showed optimum weight gain and ADC of phosphorus between these three groups. This suggested that soybean meal with 3 g kg^?1 methionine and 1500 U kg^?1 phytase supplement could successfully replace 60% fish meal in the diet for juvenile Chinese sucker without affecting growth and enhanced the apparent digestibility coefficient of phosphorus.     

Balance trials with African catfish Clarias gariepinus fed phytase-treated soybean meal-based diets

Balance trials were conducted with African catfish Clarias gariepinus to assess the effect of phytase treatment of soybean meal-based diets on growth, feed utilization and nutrient budgets. Isocaloric (20–22 kJ g⁻¹) and isonitrogenous (47–50% protein) diets were tested. In a first experiment the control diet (58% fish meal and 18% soybean meal) was compared with two diets containing 6% fish meal and 69% soybean meal, and two diets containing 29% fish meal and 41% soybean meal. One of each of these two diets had been pretreated with phytase (1000 units per kg dry diet). In the second experiment, the control diet (6% fish meal and 69% soybean meal, pretreated with 1000 units phytase kg⁻¹ dry diet) was compared with four diets that were similar in composition but supplemented with increasing amounts of phytase (15, 380, 750, 1000 units kg⁻¹ dry diet). Replacement of fish meal by soybean meal in the first experiment led to a depression in growth rate and feed utilization parameters. Results of both experiments clearly indicated a positive effect of phytase treatment, particularly on phosphorus digestibility and retention, and consequently the phosphorus conversion efficiency and the phosphorus budget. No differences in these parameters were found between addition of equal amounts of phytase by pretreatment or supplementation.     

Effects of supplementing methionine hydroxy analogue in soybean meal and distiller's dried grain-based diets on the performance and nutrient retention of rainbow trout [Oncorhynchus mykiss (Walbaum)]

Two experiments were conducted to evaluate the effects of supplementing methionine hydroxy analogue (MHA) on the performance, body composition, and nutrition retention of rainbow trout. In experiment 1, a 2×4 factorial arrangement with two MHA supplemental levels (with and without) and four fish meal replacement levels (25%, 50%, 75%, and 100%, replaced with soybean meal (SBM) and wheat gluten) was used. A fish meal diet was included as a control. Results showed that fish meal replacement levels had significant effects on fish weight gain (WG), feed conversion ratio (FCR), body moisture, crude protein, crude fat, and ash (P<0.05). In experiment 2, a fish meal reference diet and seven other diets were made using SBM and distiller's dried grain with solubles supplemented with 0, 0, 0.55, 1.1, 1.65, 2.2, and 2.75 g MHA kg^?1 diet to replace 50% of fish meal. WG, FCR, and apparent retention of crude protein and phosphorus were significantly improved in rainbow trout fed the diet containing 1.65 g MHA kg^?1 diet compared with fish fed an equivalent diet without MHA.     

Effects of dietary supplements on the availability of minerals in fish meal; preliminary observations

Preliminary studies were conducted to determine if several feed supplements with the potential to improve dietary mineral availabilities in fish meal had any measurable effect in fish feeds. In the first study with rainbow trout, 11 supplements were tested: citric acid; sodium citrate; potassium chloride; sodium chloride; histamine dihydrochloride; EDTA disodium salt; sodium bicarbonate; a mixture of amino acids; ascorbic acid; a mixture of inositol and choline; and cholecalciferol. Apparent availability of calcium, phosphorus, magnesium, sodium, iron, manganese and strontium in fish meal-based diets was determined using both yttrium oxide (Y₂O₃) and chromium oxide (Cr₂O₃) as inert dietary markers. Apparent availability was expressed as the fractional net absorption (%) of minerals from diets. After a 7-day acclimation period with test diets, fecal samples were collected for five consecutive days using passive collection systems. Apparent availability of calcium, phosphorus, magnesium, iron, manganese and strontium was increased by citric acid supplementation. Apparent availability of manganese also was increased by EDTA and sodium citrate. The other supplements had no measurable effect on the apparent availability of minerals in fish meal. In the second study, the effect of supplemental citric acid was further investigated using monogastric (rainbow trout) and agastric fish (goldfish). Fish were fed for 5 weeks (rainbow trout) or 3 weeks (goldfish) with fish meal-based diets containing either 0% (control), 2% or 5% citric acid on a dry basis. Feces were collected by settling and by stripping. Apparent availabilities of calcium and phosphorus were greatly affected by citric acid supplementation in rainbow trout but not in goldfish. Phosphorus levels in feces of fish fed a diet with 5% citric acid were approximately half of that of fish fed the control diet (0% citric acid) in the rainbow trout trial. This pattern was consistent during the 5-week feeding trial. A dietary supplement of citric acid as high as 5% did not reduce feed intake or appetite of rainbow trout. Conversely, this level of dietary acidification led to a marked reduction of feed intake in goldfish. Dietary supplementation of citric acid at 2% level did not reduce feed intake of goldfish; however, this level of dietary acidification had little effect on the apparent availability of major minerals in fish meal-based diet. Levels of non-fecal excretion of calcium and phosphorus, inorganic phosphorus in urine, and citric acid in feces were increased in rainbow trout fed 5% citric acid. The pH values of the feces and urine were decreased in rainbow trout fed citric acid. Plasma bicarbonate, plasma calcium and phosphorus, and blood pH of rainbow trout tended to increase by a 5% dietary supplementation of citric acid. The soluble inorganic phosphorus content increased in the diets and decreased in the feces of rainbow trout by supplementing the diet with 5% citric acid. Feces samples of rainbow trout collected by stripping provided similar availability values to data collected by settling for most elements except sodium, which had negative values in all dietary treatments.     

A comparison of the effect of dietary fungal phytase and dicalcium phosphate supplementation on growth performances,feed and phosphorus utilization of tra catfish juveniles (Pangasianodon hypophthalmus Sauvage, 1878)

Six isonitrogenous (320 g kg^?1) and isolipidic (60 g kg^?1) diets were formulated with graded levels (0, 5, 10 and 15 g kg^?1) of dicalcium phosphate (DCP) and fungal phytase (750 and 1500 FTU kg^?1 diet). Tra catfish (Pangasianodon hypophthalmus), 9.6 g, were fed the diets for 12 weeks. Each experimental diet was fed to eight replicates of fish to apparent satiation. At the end of the trial, fish fed the diets containing 15 g kg^?1 DCP, 750 and 1500 FTU kg^?1 phytase had higher growth performances, protein efficiency ratio and phosphorus retention than those fed the control diet, 5 g kg^?1 DCP and 10 g kg^?1 DCP diets (P < 0.05). Whole body ash and phosphorus concentration of fish fed the 10 g kg^?1 DCP and 15 g kg^?1 DCP diets were significantly higher than those of fish fed the control diet. Higher apparent digestibility coefficient of phosphorus was observed in fish fed the phytase supplemented diets. The present results indicate that supplementation of phytase at 750 FTU kg^?1 and 1500 FTU kg^?1 improves growth performances, feed and phosphorus utilization. The supplementation can completely replace dicalcium phosphate or other phosphorus sources in tra catfish feed and reduce the phosphorus discharge into environment.     

Utilization of fish and animal by-product meals in low-pollution feeds for rainbow trout Oncorhynchus mykiss (Walbaum)

The apparent digestibilities (availabilities) of dry matter, protein, phosphorus and selected minerals in fish and animal by‐products were determined using rainbow trout Oncorhynchus mykiss (Walbaum). Blood meal (ring‐dried), feather meal and deboned fish meal had relatively high concentrations of protein, low concentrations of phosphorus and many minerals, and high digestibilities (availabilities) of these nutrients. Other animal by‐products, however, had high concentrations of minerals, including phosphorus, which are associated with the bone fraction. Availabilities of manganese and zinc in the diet were reduced by the inclusion of high‐ash animal by‐products in the diet, whereas availabilities of potassium, sodium and copper were relatively unaffected. Dietary concentrations of bone minerals (calcium, phosphorus) and ash were inversely correlated with availabilities (% of intake) of most minerals except copper in the diet. Also, dietary concentrations of bone minerals correlated inversely with the net absorption (mg g^?1 diet) of zinc, manganese and magnesium in the diet. When rainbow trout were fed diets containing incremental concentrations of fish bones, the apparent availabilities of phosphorus, calcium, magnesium and iron decreased as fish bone content in the diet increased. Reducing the bone fraction of high‐ash (high‐phosphorus) by‐product meals is therefore an essential approach to using such ingredients in low‐pollution fish feeds.     

Corn‐expressed dietary phytase augments vertebral and scale mineral content in juvenile rainbow trout (Oncorhynchus mykiss)

Fishmeal (FM) is increasingly being replaced by plant proteins which are a relatively poor phosphorous source for mineralized tissues. To promote P availability plant‐based feedstuffs are supplemented with exogenous phytase. However, the effect of phytase on skeletal development in juvenile rainbow trout (Oncorhynchus mykiss) which have distinct mineral requirements is poorly understood. To address this juvenile trout were fed FM diet, a replacement feed (soybean meal, SBM) in which 50% (460 g kg^?1) of crude protein (from FM) was substituted with soybean‐meal or SBM supplemented with microbial or corn‐expressed phytase. Vertebral and scale morphology, remodelling and mineralization were then assessed by histomorphometric and colorimetric assays. Body weight and SGR of trout fed SBM was lower than FM fed fish with no improvement noted with any phytase supplement. Vertebral mineral content and autocentrum morphology were similar in trout fed SBM or FM and supplementation with microbial‐phytase did not enhance these parameters at any concentration. However, scale and vertebral mineral content were significantly enhanced in trout fed SBM supplemented with corn‐expressed phytase 1500 FTU kg^?1 (vertebral phosphorus P = 0.014, Ca P = 0.026; scale phosphorus P = 0.012). Thus, SBM feeds supplemented with corn‐expressed phytase could help reduce FM usage and generate a more robust skeleton less prone to deformity.     

Dietary microbial phytase increased the phosphorus digestibility in juvenile Korean rockfish Sebastes schlegeli fed diets containing soybean meal

This study was conducted to evaluate the effects of dietary microbial phytase supplementation on nutrient digestibility, growth performance and body composition in juvenile Korean rockfish fed soybean meal-based diets.Nine experimental diets were formulated to be isonitrogenous and isocaloric to contain 48.6% crude protein (CP) and 15.9 kJ of available energy/g with or without dietary phytase (Natuphos-5000™, BASF, NJ, USA) supplementation. White fish meal (FM) provided 89.1% of the total protein in the basal diet (S₀), in the other eight diets, 30 or 40% FM protein was replaced by soybean meal: 70% FM+30% soybean meal (S₃₀); 70% FM+30% 1000 U phytase pretreated SM (S₃₀PP₁₀₀₀); 70% FM+30% SM+1000 U phytase/kg diet (S₃₀P₁₀₀₀); 70% FM+30% SM+2000 U phytase/kg diet (S₃₀P₂₀₀₀); 60% FM+40% SM (S₄₀); 60% FM+40% 1000 U P_tre SM (S₄₀PP₁₀₀₀); 60% FM+40% SM+1000 U phytase/kg diet (S₄₀P₁₀₀₀); and 60% FM+40% SM+2000 U phytase/kg diet (S₄₀P₂₀₀₀). After 2 weeks of the adaptation, triplicate groups of 20 fish initially averaging 7.25±0.04 g (mean±S.D.) were randomly distributed into the aquarium and were fed one of the experimental diets for 8 weeks.By the end of the 8-week feeding trial, supplementation of phytase significantly improved the apparent digestibility coefficient (ADC) of phosphorus in rockfish diets (P<0.05) containing 30% and 40% soybean meal regardless of the level and method of phytase supplementation. Supplementation of phytase significantly increased the ADC of dry matter in diets containing 30% soybean meal (P<0.05). However, phytase had no influence on growth performance and whole body composition of fish. The pretreatment of soybean meal with 1000 U phytase improved weight gain (WG) when 30% fish meal protein was replaced by soybean meal. Based on the experimental results, we conclude that supplementation of phytase can improve the apparent digestibility coefficient of phosphorus in Korean rockfish.     

The Efficacy of a Novel Microbial 6‐Phytase Expressed in Aspergillus oryzae on the Performance and Phosphorus Utilization of Cold‐ and Warm‐Water Fish: Rainbow Trout,Oncorhynchus mykiss,and Nile Tilapia,Oreochromis niloticus

The efficacy and tolerance of a novel microbial 6‐phytase were investigated in rainbow trout, Oncorhynchus mykiss, and Nile tilapia, Oreochromis niloticus. Reference diets were sufficient in available phosphorus (P). The test diet limiting in available P was supplemented with phytase at 500, 1000, or 2000 phytase units/kg feed. The enzyme was effective in increasing total P apparent digestibility coefficient in relation to increasing the dose of phytase in rainbow trout and Nile tilapia. Zinc apparent digestibility improved in relation to phytase supplementation in rainbow trout. P release due to phytase supplementation ranged from 0.06 to 0.18% P/kg feed in rainbow trout and from 0.13 to 0.26% P/kg feed in Nile tilapia. A 58‐d performance trial was conducted to evaluate tolerance of fish to phytase supplementation. Dietary treatments consisted of a basal diet without phytase or supplemented with 2000 and 200,000 phytase units/kg feed. Results indicate that this novel microbial 6‐phytase is well tolerated by fish. Significant improvements for growth as well as feed conversion ratio were observed when the phytase was fed at 2000 phytase units/kg feed. This phytase is proven efficient in releasing P from phytate and could be added when plants are used for fish meal replacement in diets for salmonid and omnivorous fish.     

Effect of supplemented fungal phytase on performance and phosphorus availability by phosphorus-depleted juvenile rainbow trout (Oncorhynchus mykiss), and on the magnitude and composition of phosphorus waste output

The effect of a supplemental fungal phytase on performance and phosphorus availability by juvenile rainbow trout fed diets with a high inclusion of plant based protein and on the magnitude and composition of the waste phosphorus production was tested in a 2 × 3 factorial design at a temperature of 11 °C. Two factors comprised of two dietary fungal phytase levels (0 or 1400 U kg^? 1 feed^? 1), and three dietary total phosphorus levels (0.89, 0.97 or 1.12%). All fish were acclimated to the lowest total phosphorus diet for 16 days, which included 0.29% phytate-phosphorus and no supplemental fungal phytase, to ensure that they were depleted of phosphorus prior to the feeding trial.Growth and feed conversion ratios were not significantly affected by the increasing dietary phosphorus level or supplemental fungal phytase. Phosphorus availability increased significantly as a result of phytase supplementation, reaching an upper level of 74% at an available dietary phosphorus concentration of 0.71%. Adding fungal phytase to the diets improved the availability of phytate-phosphorus from an average of 6 to 64%. The fish retained 53–79% of the ingested phosphorus, while 24–44% was recovered in the faeces. The particulate phosphorus waste output was significantly higher in faeces from fish fed diets without fungal phytase compared to fish fed phytase supplemented diets. The dissolved/suspended phosphorus waste output represented 2–13% of the ingested phosphorus, and there was a significant increase in the dissolved/suspended phosphorus waste output from fish fed the phytase supplemented diet containing 0.71% available phosphorus, suggesting that the phosphorus requirement was reached at this phosphorus level. Consistent with this, there was a substantial increase in the dissolved/suspended phosphorus waste output from fish fed the phytase supplemented diet containing 0.81% available phosphorus, suggesting that the phosphorus requirement was exceeded in this group.This study demonstrated that phytase supplementation will be advantageous to the fish and the environment if supplemented to low-phosphorus diets containing a large share of plant-derived protein. Conversely, the results demonstrated that fungal phytase should not be supplemented to diets in which the available phosphorus level already meets the requirement of the fish, as this will lead to a significant increase in the dissolved/suspended phosphorus waste output.     

A comparison of the growth performance of rainbow trout (Oncorhynchus mykiss) when fed soybean,narrow‐leaf or yellow lupin meals in extruded diets

This study compared the effect of increasing dietary inclusion of soybean, narrow‐leaf lupin or yellow lupin kernel meals when fed to rainbow trout. Each meal was formulated into a test diet to create a series of inclusion levels of 0, 100, 200, 300 and 400 g kg^?1. Each diet was formulated to the same digestible protein and energy specifications. The diets were fed to apparent satiety to 30.0 ± 0.71 g rainbow trout for 28 days. After this period, fish in the reference (0 g kg^?1) treatment attained a weight of 93.2 g. Growth of the fish among the treatments was observed to be improved by the addition of either variety of lupin meal. In contrast, growth of fish fed the soybean meal was equivalent to that of the 0 g kg^?1 fish meal reference, but was poorer at the 400 g kg^?1 inclusion level. Feed intake with the lupin meals was marginally improved with lupin inclusion, but at the higher soybean meal inclusions, feed intake was reduced relative to the fish meal reference diet. The inclusion of the different grains also had significant effects on the physical properties of the pellets.     

Evaluation of fish-meal free diets for rainbow trout, Oncorhynchus mykiss

Eight experimental diets were formulated for rainbow trout using agricultural byproducts as major ingredients. Each experimental diet contained varying amounts of corn grain, corn gluten meal, corn gluten feed and one of the following: 200 g kg^?1 peanut meal, 200 or 400 g kg^?1 soybean meal (SBM), 390 g kg^?1 low-allergen soy flour, 310 g kg^?1 soy protein concentrate, 300 g kg^?1 low-allergen soy protein concentrate or 200 g kg^?1 SBM + 110 g kg^?1 blood meal. One diet contained 200 g kg^?1 SBM and canola oil as the main lipid source. The remaining diets contained 95 g kg^?1 menhaden oil. Fish fed a commercial trout diet exhibited significantly greater weight gain (322%), and a lower feed conversion ratio (0.89) but significantly lower protein efficiency ratio (2.18) than fish fed the experimental diets. Within the experimental diets, fish fed the 400 g kg^?1 soy flour diet and the 400 g kg^?1 soybean meal diet had significantly higher weight gains (276% and 268%) and protein efficiency ratios (2.58 and 2.52), and lower feed conversion ratios (1.02 and 1.03) than fish fed other experimental diets. Fillet flavour varied between treatments. Most notable was the lower fishy flavour and higher chicken flavour of fish fed the diet that contained canola oil rather than menhaden oil. Microscopic evaluation of the liver and five sections of the gastrointestinal tract failed to demonstrate any differences between treatment groups. The ingredient costs of several experimental diets were lower than the estimated cost of a standard commercial trout diet. However, the superior feed conversion ratios of fish fed the control diet resulted in lower feed costs per unit of fish produced.     

Microbial Phytase Can Replace Inorganic Phosphorus Supplements in Channel Catfish Ictalurus punctatus Diets1

Abstract.– Juvenile channel catfish Ictalurus punctatus (initial weight: 6.8 g/fish) were fed four practical diets containing 0, 250, 500, and 750 units of microbial phytase/kg and a diet containing 1% feed grade dicalcium phosphate (but no microbial phytase) under laboratory conditions for 12 wk. Fish fed the diets containing 250 units of microbial phytase/kg and above consumed more feed, gained more weight, and had a lower feed conversion ratio (FCR) in comparison to fish fed the basal diet containing no microbial phytase. Fish fed the diet containing dicalcium phosphate had intermediate weight gain and feed conversion ratio as compared to fish fed the basal diet and diets containing microbial phytase. Bone ash and phosphorus concentrations were lower for fish fed the basal diet than for fish fed other diets. No differences in weight gain, feed consumption, FCR, bone ash and bone phosphorus were observed among fish fed the diets containing various levels of microbial phytase. Fish fed the diet containing dicalcium phosphate had a lower bone phosphorus concentration than fish fed diets containing microbial phytase. Fecal phosphorus concentrations were lower for fish fed the diets containing microbial phytase than for fish fed the basal diet and the diet containing dicalcium phosphate. Results from the present study indicated that addition of 250 units of microbial phytase/kg to practical diets can effectively improve bioavailability of phytate phosphorus to channel catfish and may possibly eliminate the use of an inorganic phosphorus supplement in channel catfish diets. However, these data must be verified in trials conducted in ponds, prior to recommending removal of supplemental phosphorus from channel catfish diets.     

Effect of dietary replacement of fish meal by soybean protein concentrate on growth performance and phosphorus discharging of juvenile black sea bream,Acanthopagrus schlegelii

The 8‐week experiment was conducted to evaluate the effects of partial replacement of fish meal (FM) with soybean protein concentrate (SPC) on juvenile black sea bream, Acanthopagrus schlegelii (10.70 ± 0.04 g). Diets were formulated to replace FM protein by SPC at 0, 8, 16, 24, 32 or 40% (designated as T1, T2, T3, T4, T5 and T6, respectively). Diets except T1 were supplemented with phytase at 2000 phytase activity U kg^?1. The results showed that survival rate, growth performance and feed utilization were not significantly affected by increasing dietary SPC. Fish fed diet T3 had higher feed intake compared to those fed T1, T2 and T5 diets. Whole body compositions of black sea bream were significantly influenced by SPC replacing FM except for protein, ash and phosphorus content. Condition factor of fish was significantly lower in T2 than that of fish in T3 group. Apparent digestibility coefficients (ADCs) of dry matter was higher in fish fed T6 diet than those of fish fed T1 and T2 diets, ADCs of phosphorus increased with dietary SPC level up to T3 and then decreased. The results obtained in this study indicate that FM protein could be effectively replaced by SPC protein with phytase in diet of black sea bream.     

Efficacy of phytase on phosphorus utilization in practical diets fed to striped bass Morone saxatilis

Several experiments were conducted to determine the effects of phytase on dietary phosphorus (P) utilization by striped bass Morone saxatilis fed high phytate diets. The experiments were designed to determine the effectiveness of various dietary levels of a dry or liquid phytase concentrate incorporated in diets to improve the P utilization of striped bass. Fish were fed various basal diets containing over 700 g kg^?1 plant feed ingredients and 4.9–7.1 g kg^?1 P and 1.5–1.7 g kg^?1 non-phytin P. A diet supplemented with potassium monophosphate (PMP) and containing 9 g kg^?1 total P and 6 g kg^?1 non-phytin P with no added phytase was the positive control. The dietary treatments were assigned to duplicate tanks and diets were fed to juvenile striped bass for up to 14 weeks. The effectiveness of the phytase treatments was determined by measuring weight gain, feed conversion, serum, scale and vertebral calcium and P, as well as P absorption. Apparent P absorption was determined using 5 g kg^?1 chromic oxide as an indigestible marker in the diet. In experiment one, significant improvements (P < 0.05) were found in scale and vertebral phosphorus concentrations with 2400 Phytase Units (PU) kg^?1 (PU is the quantity of enzyme which liberates one micromole of inorganic P per minute from 0.015 tool L^?1 sodium phytate at 37°C and pH 5.5) added to the diet. In experiment two, significant differences were observed between serum phosphorus in the phytase and no-phytase groups, while there were no differences between the positive control (PMP supplemented) and the phytase-treated fish. It was concluded that 2400 PU kg^?1 of enzyme resulted in bone mineralization and serum phosphorus concentrations equal to that observed with 13 g kg^?1 dietary PMP addition (9 g kg^?1 total P).     

Incorporation of plant protein feedstuffs into fish meal diets for rainbow trout increases phosphorus availability

Individual plant protein feedstuffs were incorporated into a diet containing fish meal and fed to rainbow trout to determine apparent and true phosphorus availability (APA and TPA, respectively). The plant protein feedstuffs evaluated were soybean, canola and peanut meals; each was incorporated at 200 g kg^–1 of dry matter. The average initial weight of fish was 68 g and the water temperature was maintained at 15°C. Concentrations of macronutrients were constant in diets. Incorporation of plant protein feedstuffs significantly increased APA and TPA values. The APA values were 19.5% for fish meal and 39.5%, 40.2%, and 38.5% for the diets containing soybean meal, canola meal, and peanut meal, respectively. Similarly, the TPA values for the combination of fish meal and plant protein feedstuff were 43.4%, 42.1% and 40.6% for diets containing soybean, canola and peanut meals, respectively, which were significantly higher than values for fish meal (21.5%). Calculation of APA and TPA values for individual feedstuffs resulted in values for the plant protein ingredients of over 100%. We speculate that the increased APA and TPA values were the result of decreasing total dietary phosphorus concentrations or dilution of the calcium concentrations from bone in fish meal.     

Effect of replacing fish meal with soybean meal on growth,feed utilization and nitrogen and phosphorus excretion on rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>)

The effect of replacing fish meal with soybean meal (SBM) pretreated with phytase on feeds of juvenile rainbow trout was evaluated in a 90-day feeding trial. The rainbow trout (initial body weight, 4.01 ± 0.02 g) were fed five isonitrogenous (crude protein, 44.97%) and isolipidic (crude lipid, 13.42%) feeds. Diets were formulated to contain phytase-pretreated SBM replacing 0, 20, 40, 60 and 80% of fish meal protein, respectively. The results showed that there was no significant difference in weight gain (WG) among fish fed S0, S20, S40 and S60 diets; however, a significant reduction of this variable occurred when 80% of fish meal protein was replaced by phytase-treated SBM (P < 0.05). Similarly, specific growth rate and protein efficiency ratio had a similar trend with WG. Apparent digestibility coefficient (ADC) of protein and lipid in the S80 diet was significantly lower than that of the other diets, and the ADC of phosphorus significantly increased with the increase of dietary phytase-treated SBM level. No significant differences among treatments were detected for moisture, protein, lipid and ash content in whole body and muscle samples. Nitrogen and phosphorus excretion indicated that fish meal replacement by phytase-treated SBM led to an increase in nitrogen excretion, but led to a reduction in total phosphorus excretion. The results of the present study show that 60% of fish meal could be replaced by phytase-treated SBM in diets of juvenile rainbow trout without compromising weight gain or feed efficiency. A quadratic equation according to regression analysis of weight gain against dietary phytase-treated SBM level indicated that the optimal level of dietary phytase-treated SBM replacement for maximum growth was 26.90%.     

Apparent digestibility coefficients of selected protein feed ingredients for loach Misgurnus anguillicaudatus

Apparent digestibility coefficients of dry matter, crude protein, lipid and energy, and amino acids availability in white fish meal, brown fish meal, meat meal, fermented soybean meal, soybean meal and rapeseed meal were determined for loach (Misgurnus anguillicaudatus) (12.05 ± 0.21 g), using a reference diet with 5 g kg^?1 chromic oxide and test diets that contained 700 g kg^?1 reference diet, by weight, and 300 g kg^?1 of the test feed ingredients. The juvenile loach was held in 300‐l tanks at a density of 30 fish per tank. White fish meal, brown fish meal, meat meal and fermented soybean meal had highest apparent digestibility coefficients (ADCs) of dry matter, crude protein and gross energy among ingredients tested, ranged from 50.4% to 60.9% for dry matter, from 64.6% to 88.4% for crude protein and from 57.9% to 79.0% for gross energy. The apparent digestibility coefficients of dry matter ranged from 61.0% to 66.9% for animal products and 50.4% to 60.7% for plant products. For crude protein, apparent digestibility coefficients of protein exceeding 80% were observed for white fish meal, brown fish meal, meat meal and fermented soybean meal, and the apparent digestibility coefficients of protein in rapeseed meal were the lowest among all the treatments. Lipids from both animal and plant feedstuffs were poorly digested by loach, ranging from 64.0% to 77.6%. The apparent digestibility coefficients of energy were similar to those of dry matter and protein, and the highest and lowest ADCs of energy were found in WFM and RM, respectively. The loach used dietary phosphorus from the animal feedstuffs more efficiently than from plant feedstuffs (soybean meal and rapeseed meal), with ADC‐values ranging from 42.3% to 53.1% and from 25.1% to 32.7%, respectively. For the animal products, the availabilities of amino acids in white fish meal and brown fish meal were higher than that in meat meal, expect for Met, Asp, Pro, Gly, and Cys. Among all the plant products, the availabilities of amino acids in fermented soybean meal were higher than in soybean meal and rapeseed meal, and thus had a greater potential to be used as a dietary replacement of fish meal in loach diets.