Apparent protein and energy digestibility of common and alternative feed ingredients by Atlantic cod, Gadus morhua (Linnaeus, 1758)

Studies were conducted with Atlantic cod, Gadus morhua (L.), to determine the apparent digestibility coefficients (ADCs) of protein and energy and the digestible energy (DE) content in feed ingredients widely available in Canada. We also tested the assumption of “independency” used in digestibility studies. The feed ingredients included two fish meals (herring, anchovy), three crustacean by-product meals (whole krill, crab, shrimp), two animal by-product meals (poultry by-product, hydrolyzed feather), six oilseed meals (soybean, soy protein concentrate, soy protein isolate, canola, canola protein concentrate, flaxseed), two pulse meals (white lupin, pea protein concentrate) and two cereal grain meals (corn gluten, wheat gluten). Protein ADCs were high for wheat gluten meal (99.9%), soy protein concentrate (98.6%), soy protein isolate (97.4%), whole krill meal (96.3%), herring meal (93.3%), soybean meal (92.3%), anchovy meal (92.2%), pea protein concentrate (89.8%), white lupin meal (89.7%), crab meal (89.4%), canola protein concentrate (88.8%) and corn gluten meal (86.3%); mid-range for poultry by-product meal (80.2%) and canola meal (76.0%); and low for shrimp meal (66.7%), hydrolyzed feather meal (62.4%) and flaxseed meal (50.2-55.0%). Energy ADC was high for whole krill meal (96.3%), wheat gluten meal (95.4%), soy protein concentrate (94.9%), herring meal (92.8%), soy protein isolate (92.1%), soybean meal (88.1%) and anchovy meal (86.4%); mid-range for canola protein concentrate (83.3%), corn gluten meal (82.7%), crab meal (82.4%), pea protein concentrate (76.7%) and white lupin meal (75.3%); and low for poultry by-product meal (71.0%), canola meal (60.6%), hydrolyzed feather meal (58.9%), shrimp meal (41.4%) and flaxseed meal (21.2-37.4%). From the protein ADC data, results clearly showed that the basal diet and test feed ingredients were digested independently of one another in nearly all cases, the only exceptions being for those diets containing test ingredients of very high (> 99%, wheat gluten) or very low (< 67%, hydrolyzed feather and flaxseed) protein ADCs. In the case of DE, the basal diet and test feed ingredients were digested independently in all test diets without exception.     

海水养殖花鲈对几种饲料蛋白原料的表观消化率

测定了在室内海水流水系统中养殖的花鲈对7种常用饲料原料,宠物级鸡肉粉(P-PBM)、饲料级鸡肉粉(F-PBM)、血粉(BM)、羽毛粉(FEM)、蚕蛹粉(SWP)、豆粕(SBM)和菜粕(RSM)以及1种混合动物蛋白粉(MM=50%P-PBM+20%F-PBM+20%BM+10%FEM)的干物质、蛋白质和能量表观消化率(ADC)。实验饲料由70%基础饲料(蛋白质含量为42.0%,能量含量为18.9MJ/kg)和30%的待测原料组成。基础饲料和实验饲料中均添加1%(质量分数)的Cr2O3作为外源标记物。饲养实验共进行4周。实验期间每天投饵两次,采用虹吸方法收集粪便。实验结果显示:花鲈对P-PBM、F-PBM、BM、FEM、MM、SWP、SBM和RSM干物质ADC分别为61%～87%,蛋白质ADC为80%～96%,能量ADC为75%～93%。其中,花鲈对SBM的蛋白质ADC最高,对MM的蛋白质ADC最低,对BM的干物质和能量ADC最高,对RSM的干物质和能量ADC最低。     

The effect of dietary protein level on the apparent digestibility coefficient of two selected feed ingredients for Nile tilapia,Oreochromis niloticus L.

The effect of dietary protein level on the apparent digestibility coefficient (ADC) of meat and bone meal and rapeseed meal for Nile tilapia Oreochromis niloticus L. was examined. Three reference diets were formulated to contain 240 (RD24), 350 (RD35) and 450 (RD45) g kg^?1 crude protein, and chromic oxide was added at 10 g kg^?1 in the reference diets as an inert indicator. Six test diets were formulated by mixing one of the reference diets with each test ingredient at a ratio of 70:30. Fish (initial body weight 101.0 ± 0.6 g) were fed reference diets for 3 days and then fed test diets in the following 4 days cyclically for 4 weeks. Faeces of fish fed each reference diet or test diet was collected from the third day of each diet conversion. Dietary protein level significantly affected the ADC of protein and energy of reference diets, test diets and test ingredients. The ADC of protein and energy of meat and bone meal and rapeseed meal was the highest when these ingredients were mixed with diet RD35. The scope of variation in the ADC of protein and energy of meat and bone meal was 8% (from 69.9% to 78.3%) and 8% (from 70.2% to 78.0%), and the scope of variation in the ADC of protein and energy of rapeseed meal was 4% (from 79.8% to 83.3%) and 5% (from 56.0% to 60.7%) when the dietary protein level was increased from 300 to 480 g kg^?1. This indicates that the ADC of protein and energy of meat and bone meal and rapeseed meal for Nile tilapia varied considerably at different dietary protein levels.     

Digestibility of Alternative Protein‐Rich Feedstuffs for Channel Catfish,Ictalurus punctatus

Apparent digestibility coefficients (ADCs) of amino acids, crude protein, gross energy, and dry matter of canola meal, corn gluten feed, fish offal meal, shrimp and fish offal meal, poultry by‐product meal, and hydrolyzed feather meal were determined for channel catfish, Ictalurus punctatus. Experimental diets contained 30% test ingredient, 69.5% casein‐based reference diet, and 0.5% chromic oxide. Groups of 20 fish (102.45 g) were fed the experimental diets twice a day at 3.5% body weight. Fecal samples were collected in triplicate daily at 0000 h and 0600 h after settlement into collection devices. Shrimp and fish offal meal and corn gluten feed presented significantly lower (P < 0.05) ADC for dry matter (59.5 and 39.3%) suggesting their low value as feedstuffs for catfish feeds. Although ADC values for crude protein were above 80% for all the test ingredients, amino acid digestibility varied significantly, except for histidine whose ADC remained constant regardless of the protein source. Lysine was the first limiting amino acid in most of the test ingredients, except in fish offal meal and poultry by‐product meal. Among the protein sources tested, only fish offal meal and poultry by‐product meal met channel catfish amino acid requirements for a 28% digestible protein grow‐out diet.     

The Apparent Digestibility Coefficients of 13 Selected Animal Feedstuff for Cobia,Rachycentron canadum

The apparent digestibility coefficients (ADCs) of crude protein, lipid, phosphorous, and amino acids, as well as energy, of 13 animal feedstuffs were determined for cobia, Rachycentron canadum (initial weight 130.0 g). The feedstuffs tested included five types of fishmeal, two of blood meal, one of poultry meat meal, two of meat‐and‐bone meal, two of feather meal, and one type of shrimp meal. A reference diet was formulated and the test diets contained 70% of the reference diet and 30% of each feedstuff. The ADCs of crude protein, lipid, energy, phosphorous, and amino acids of the test ingredients ranged from 68.97 to 92.5%, 69.3 to 95.7%, 77.5 to 98.3%, 58.2 to 80.1%, and 72.5 to 97.0%, respectively. The ADCs of crude protein of white fishmeal, steam‐dried brown fishmeal, imported flame‐dried fishmeal, spray‐dried blood cells, poultry byproduct meal, meat‐bone meal, and meat meal were significantly higher than those of dried blood meal, fermented feather meal, and hydrolyzed feather meal (P < 0.05). The ADCs of lipid of dried blood meal and hydrolyzed feather meal were significantly lower than those of other feedstuffs (P < 0.05). The ADCs of energy of fermented feather meal and hydrolyzed feather meal were significantly lower than those of other feedstuffs (P < 0.05) and the ADCs of phosphorus of white fishmeal, steam‐dried brown fishmeal, and imported flame‐dried fishmeal were significantly higher than those of the other ingredients (P < 0.05).     

Digestibility Characteristics of Selected Feed Ingredients for Developing Bespoke Diets for Nile Tilapia Culture in Europe and North America

The apparent digestibility coefficients of dry matter (ADC DM), protein (ADCp), essential amino acids (ADC EAA), and energy (ADCe) for Nile tilapia of a selected range of animal and plant feed ingredients found in Western European and North American markets were determined. The investigation was able to provide useful data and information as a prelude for effective diet formulation for this fish species. A reference diet was used for the basis of assessing hydrolyzed fish protein concentrate (CPSP), full‐fat soybean meal (FFSBM), solvent‐extracted soybean meal (SESBM), maize gluten meal (MGM), poultry meat meal (PMM), hydrolyzed feather meal (HFM), and spray‐dried hemoglobin meal (SDHM) by substitution. For each major commercial test ingredient, the ADC were as follows: for plant proteins – FFSBM (ADCp 86.99% and ADCe 74.84%), SESBM (ADCp 93.46% and ADCe 82.16), and MGM which was also utilized well by Nile tilapia (ADCp 83.03% and ADCe 82.36%); for animal proteins – PMM (ADCp 69.30% and ADCe 73.47%), HFM (ADCp 45.53% and ADCe 49.11%), and SDHM was highly digested (ADCp 85.79% and ADCe 75.96%). The ADC EAA reflected the same trends as ADCp, and these varied from >87% on average for the EEA in fish meal, >88% for CPSP, >84% for FFSBM, >63% for SESBM, >83% for MGM, and only 61% for PMM, >63% for HFM, and >77% for SDHM. Highest ADC were obtained with SDHM and SESBM among the animal and plant by‐products tested, respectively. These are discussed in the context of practical diets for tilapia.     

Apparent Digestibility of Different Ingredients in Diets for Bullfrog Rana catesbeiana Tadpoles

The objective of this study was to determine apparent digestibility of protein and energy of ingredients commonly present in rations fed to bullfrog tadpoles Rana catesbeiana such as corn, soybean meal, wheat meal, rice bran, poultry by-product meal, blood meal, fish meal, corn starch and soybean oil.
A completely randomized design was used to test ten experimental diets with four replicates. About 30% of the reference diet was replaced by the test ingredients, except for soybean oil that was used at 10% ratio and 0.5% of chromium oxide as inert marker. The values of apparent digestibility coefficient of crude protein (ADC_CP) and gross energy (ADC_GE) of the protein ingredients were, respectively: fish meal, 81 and 95%; poultry byproduct meal, 82 and 87%; blood meal, 64 and 53%; and soybean meal, 93 and 90%. While for the energetic ingredients, ADC_CP and ADC_GE, were, respectively: wheat meal, 100 and 72%; rice bran, 57 and 24%; and corn, 84 and 92%. Soybean oil and cornstarch ADC_GE values were 70 and 96%, respectively; cornstarch digestibility is highly dependent on feed processing technique.
The results showed that the ingredients of plant origin, except for rice bran, had good digestibility, thus indicating that tadpoles can effectively use plant protein. In this trial, the least digestible ingredients were blood meal and rice bran, thus indicating that the use of such ingredients in bullfrog tadpole diets should be limited.     

Apparent digestibility coefficients of four feed ingredients for Synechogobius hasta

Apparent digestibility coefficients (ADCs) of dry matter, crude protein, lipid, energy, phosphorus and amino acids in white fish meal, soybean meal, rapeseed meal and peanut meal were determined for Synechogobius hasta (28.65 ± 0.43 g, mean ± SD), using a reference diet with chromic oxide indicator and test diets that contained 70% reference diet, by weight, and 30% of feed ingredients. The juvenile S. hasta were held in 300 L tanks at a density of 30 fish per tank respectively. Faeces were collected from three replicate groups of fish by siphoning. The ADCs of dry matter and energy were the highest in white fish meal and the lowest in rapeseed meal ( P <0.05). Crude protein ADC was the lowest in rapeseed meal ( P <0.05) and showed no significant differences among other treatments ( P >0.05). The highest phosphorus ADC was observed in white fish meal and differences were not marked for other treatments ( P >0.05). Lipid ADC were above 90% and showed no significant differences among the treatments ( P >0.05). Amino acid availability values for the test ingredients followed similar trend to values of protein digestibility. All amino acids were more available from fish meal than from plant protein ingredients. Among three plant meals, the availability of amino acids was higher in peanut meal and lower in rapeseed meal.     

Apparent digestibility coefficients of selected feed ingredients for juvenile snakehead,Ophiocephalus argus

Apparent digestibility coefficients (ADCs) of dry matter, crude protein, crude lipid, gross energy, phosphorus and amino acids in Peruvian fish meal, poultry by‐product meal, meat and bone meal, spray‐dried blood meal, hydrolysed feather meal, corn gluten meal, soybean meal, peanut meal, cottonseed meal and rapeseed meal were determined for juvenile snakehead (Ophiocephalus argus) with initial mean body weight of 78.1 g. A reference diet and test diets that consisted of a 70 : 30 mixture of the reference diet to test ingredient were used with 5 g kg^?1 Cr₂O₃ as an external indicator. Fish meal, poultry by‐product meal and corn gluten meal had higher ADCs of dry matter, crude protein, and gross energy among ingredients tested. Dry matter ADCs ranged 61.9–81.5% for animal ingredients and corn gluten meal and ranged 52.2–68.0% for soybean meal, peanut meal, cottonseed meal and rapeseed meal. Energy ADCs of ingredients followed similar trends to differences in dry matter digestibility. Protein ADCs of animal and plant ingredients ranged 73.6–92.8% and 75.3–85.6%, respectively. Amino acid ADCs generally reflected protein digestibility. Lipid ADCs were relatively high for the ingredients tested. Phosphorus ADCs of animal and plant ingredients ranged 39.5–65.2% and 38.7–57.1%, respectively.     

Apparent Digestibility of Gross Nutrients from Feedstuffs in Extruded Feeds for Rainbow Trout,Oncorhynchus mykiss

Abstract.— The current experiment was performed to determine apparent protein and energy digestibility coefficients of feed ingredients by the fecal stripping technique using extruded diets. The ingredients tested included five fish meals, three terrestrial animal by‐products, five plant protein concentrates, four plant meals, and seven low‐protein plant ingredients. Protein digestibility differed among fish meals and ranged from 90% for fair and average quality menhaden meal to 97% for anchovy meal. Protein apparent digestibility coefficients (ADCs) in plant concentrates ranged from a low of 89% for rice protein concentrate to a high of 100% for wheat gluten meal. Apparent protein digestibility was lower in plant meals than fish meals with a low of 70% for flaxseed meal to a high of 89% for soybean meal. Low‐protein plant meals had generally lower protein ADC from 64% for rice bran to 85% for whole wheat. A similar pattern for energy ADCs was observed; ADCs ranged from 106% for anchovy meal to 32% for whole wheat. In the current trial, divergent protein and energy ADC values were obtained most notably in ingredients known to be high in fiber or have very high starch content. The comparability of ingredients/diets processed by cold pelleting or extrusion thus appears questionable at this juncture.     

Availability of protein and energy from three protein sources in hybrid sturgeon Acipenser guldenstadti × A. bester

The apparent digestibility coefficient (ADC) of three diet ingredients serving as protein sources for adult sturgeon Acipenser guldenstadti × A. bester was studied using an inert marker in the feed and collecting the faeces by stripping. Each experimental diet contained a different protein source, fishmeal, soybean meal and poultry meal, making up 50% of the total, the other 50% being reference diet (28% fishmeal, 9% poultry meal, 24% soybean meal, 26% wheat flour, 8% poultry oil plus 0.5% vitamins, egg yolk, guar and chromic oxide). The digestibility of protein from fishmeal was 81.0%, from soybean meal 81.9% and from poultry meal 64.6%. Energy digestibility tests gave the following results: fishmeal 13.0 kJ g^?1; soybean meal 12.1 kJ g^?1; and poultry meal 10.2 kJ g^?1. The differences in the ADC of various protein and carbohydrate sources are discussed.     

Apparent digestibility of various feedstuffs for bluntnose black bream Megalobrama amblycephala Yih

The apparent digestibility of 66 different feedstuffs by the bluntnose black bream Megalobrama amblycephala Yih was determined in digestibility trials in a recirculation aquaculture system. The ingredients consisted of 26 distinct energy feedstuffs, 18 nonanimal protein feedstuffs and 22 animal protein feedstuffs. In each of three trials, a reference diet was mixed with various test ingredients in a 70 : 30 ratio; reference and test diets were fed to the fish, and faecal samples were collected using a hand‐held screen system. Energy availability for the 26 energy feedstuffs varied between ?23.0% (silkworm manure) and 89.5% (millet grain), protein digestibility for the 18 nonanimal protein ingredients varied from 58.0% (pea protein meal) to 98.1% (soybean meal), and protein digestibility for the 22 animal protein feedstuffs varied between ?5.7% (feather meal) and 99.1% (fermented dried blood meal). The average protein digestibility of 85.9% for the nonanimal protein feedstuffs was significantly higher than that for the animal feedstuffs (P < 0.05), partly validating the assumption that herbivorous bluntnose black bream would digest proteinic nutrients in nonanimal feedstuffs better than in animal ingredients under intensive aquaculture. Finally, the energy availability of nonanimal protein feedstuffs was significantly lower than that of animal feedstuffs (P < 0.05).     

花鲈对七种蛋白质原料的表观消化率

为了解花鲈(Lateolabrax maculatus)对水解羽毛粉、喷雾干燥血球蛋白粉、鸡肉粉、黄粉虫粉、大豆分离蛋白、大豆浓缩蛋白和脱酚棉籽蛋白等七种蛋白质原料的干物质、钙、磷、粗蛋白和氨基酸的表观消化率,实验选取平均体重为(54.3±1.5)g的花鲈240尾,随机分成8组,每组3个平行,对照组投喂基础饲料,试验组分别投喂试验饲料,试验饲料由70%基础饲料和30%实验原料组成,以0.1%的三氧化二钇(Y2O3)为外源指示剂。结果显示:花鲈对七种蛋白质原料的干物质和粗蛋白表观消化率以血球蛋白粉、鸡肉粉、大豆分离蛋白和大豆浓缩蛋白较高,脱酚棉籽蛋白和黄粉虫粉次之,水解羽毛粉最低。其中,花鲈对血球蛋白粉的粗蛋白消化率最高,为95.64%,显著高于其他六种原料;鸡肉粉次之,为90.61%,与大豆分离蛋白和大豆浓缩蛋白之间差异不显著;水解羽毛粉最低,为71.18%,与黄粉虫粉和脱酚棉籽蛋白之间差异不显著,与其他蛋白原料之间差异显著。花鲈对鸡肉粉和黄粉虫粉的总钙的表观消化率分别为30.39%和42.65%。花鲈对总磷的表观消化率从高到低依次为大豆分离蛋白(76.04%)、脱酚棉籽蛋白(67.49%)、大豆浓缩蛋白(51.24%)、鸡肉粉(42.88%)、黄粉虫粉(38.40%)。花鲈对各蛋白质原料中氨基酸的表观消化率与粗蛋白质的表观消化率变化趋势基本一致。结果表明,喷雾干燥血球蛋白粉、鸡肉粉、大豆分离蛋白和大豆浓缩蛋白可作为花鲈优质的蛋白源,脱酚棉籽蛋白、黄粉虫粉和水解羽毛粉在花鲈饲料中添加量不宜过高。     

Apparent Digestibility Coefficients of Nutrients and Nutritional Value of Poultry By-product Meals for Rainbow Trout Oncorhynchus mykiss Measured in vivo Using Settlement

Fish meal production is not growing worldwide, therefore, it is important to search for alternative protein sources. Three types of poultry by-product meals (feed grade, prime, and refined) and two fish meals (herring and menhaden) were mixed into a casein-gelatin purified reference diet at 30% to measure apparent digestibility coefficients (ADCs) for rainbow trout Oncorhynchus mykiss . A total of 90 fish (initial mean body weight 294.6 ± 10.7 g) were stocked into six 140-L fiberglass digestibility tanks at 15 fish per tank. Individual tanks were assigned randomly to each of the five experimental diets and the reference diet. Fecal collection by settlement lasted for 2 wk. Feces collected in each week represented a replicate, and they were analyzed separately. The ADCs of nutrients for herring meal, menhaden meal, feed grade poultry by-product meal, prime poultry by-product meal, and refined poultry by-product meal were: dry matter, 81.3, 70.9, 70.9, 71.5, and 74.5%, respectively ( P = 0.0168); crude protein, 89.8, 85.8, 83.1, 84.8, and 87.1%, respectively ( P = 0.0032); crude fat, 91.5, 90.7, 79.7, 82.7, and 79.9%, respectively ( P = 0.0004); ash, 76.6, 66.2, 74.1, 77.4, and 79.6%, respectively ( P = 0.2880); phosphorus, 58.2, 46.9, 49.4, 45.8, and 56.0%, respectively ( P = 0.0143); gross energy, 88.2, 84.0, 81.9, 83.4, and 79.8%, respectively ( P = 0.2466). Significant differences in ADCs of essential amino acid existed only for arginine, leucine, and tryptophan when comparing refined poultry by-product meal with herring meal. Results showed that refined poultry by-product meal had similar ADC values to herring meal, thus, it has a similar nutritional value and can replace portions of herring meal in rainbow trout feeds. Furthermore, differences exist in ADC values among grades of poultry by-product meals that should dictate appropriate use levels in rainbow trout feeds.     

Apparent digestibility coefficients of feed ingredients and their predictability in compound diets for gilthead seabream, Sparus aurata L.

Apparent digestibility of crude protein, amino acids, lipid, carbohydrate and energy was measured for a range of feed ingredients fed to gilthead seabream, Sparus aurata L. — fish meal, poultry meal, meat meal, blood meal, squid meal, extracted soyabean and wheat flour. Chromic oxide was used as a non-absorbed reference substance and faeces were collected by stripping. Diets compounded from mixtures of these ingredients were then used to examine the possibility of predicting the digestibility of formulated diets.
Apparent digestibility of crude protein ranged from 79% to 90%, lipids from 83% to 95% and energy from 72% to 88% in the different ingredients. Apparent digestibility of carbohydrates was lower and ranged from 49% to 77%. Apparent digestibility of amino acids was higher than that of crude protein and differences were found among digestibilities of individual amino acids.
Tests conducted using five compound diets indicated that ingredient digestibility was additive for protein, amino acids, lipids and energy, whereas the digestibility of carbohydrates in the compound feeds was slightly lower than predicted.
Diets for Sparus aurata may thus be formulated on the basis of digestibility of individual ingredients.     

Digestibility of microbial and mussel meal for Arctic charr (Salvelinus alpinus) and Eurasian perch (Perca fluviatilis)

Apparent digestibility coefficients (ADCs) for four protein‐rich alternative feed ingredients, intact baker's yeast (Saccharomyces cerevisiae), extracted baker's yeast (S. cerevisiae), zygomycetes (Rhizopus oryzae) and blue mussel (Mytilus edulis), were determined for Arctic charr (Salvelinus alpinus) and Eurasian perch (Perca fluviatilis). Diets contained 30% of test ingredients, and ADCs were compared to a reference diet containing fish meal. For Arctic charr, ADCs for dry matter (DM, 71–99%), sum of amino acids (SAA, 84–99%) and gross energy (70–99%) were significantly lower for intact S. cerevisiae than for extracted S. cerevisiae, R. oryzae and M. edulis. The ADCs for the indispensable amino acids (IAA) in Arctic charr varied between 84% and 99%. Significant differences were found in ADCs for IAA between the test ingredients for Arctic charr, with higher values for extracted S. cerevisiae and M. edulis. The ADCs in Eurasian perch varied between 83% and 95% for DM, 89% and 98% for CP, 92% and 100% for SAA, 81% and 96% for gross energy. No significant differences were found for ADCs between the test ingredients in Eurasian perch, indicating a species effect on digestibility. Furthermore, the absence of intact cell walls had a positive effect on digestibility of S. cerevisiae for Arctic charr.     

Nutrient digestibility profile of premium (category III grade) animal protein by-products for temperate marine fish species (European sea bass, gilthead sea bream and turbot)

Three trials, with classical experimental designs for in vivo digestibility studies, were conducted to determine the apparent digestibility coefficient (ADC) of protein (ADCp), lipid (ADCl), energy (ADCe) and amino acids (AA) in selected animal by-products fed to European sea bass, Dicentrarchus labrax (Trial 1), gilthead sea bream, Sparus aurata (Trial 2), and turbot, Psetta maxima (Trial 3). In each trial, five experimental diets [including a reference diet (RD)] where fish meal (FM) was used as the sole protein source were fed ad libitum to the fish for a period of 4 weeks. Test diets were based on the FM RD and obtained by replacing 30% of the RD with a category III designated European animal by-products (fit for human consumption), namely: steam hydrolysed feather meal (HFM), enzyme-treated feather meal (EFM), poultry meat meal (PMM) and spray-dried haemoglobin meal (SDHM). Faecal material was collected using the 'Guelph system', and nutrient and energy digestibility coefficients were related to the measurement of chromic oxide (Cr₂O₃) incorporated into the diet at a rate of 0.5%. Without any exception, FM diets yielded the best digestibility values for all macro-nutrients and by all fish. Among the test ingredients, ADCp was consistently higher for PMM and SDHM in the three species (85.5%, 91.1% in sea bass; 79.2%, 82.8% in sea bream; and 78.4%, 74.8% in turbot). Conversely, ADCp of HFM and EFM were less efficiently digested (67.2%, 68.2% in sea bass; 21.5%, 21.7% in sea bream; and 46.6%, 36.0% in turbot). However, the novel processing method applied to feather meal did not considerably influence the digestibility of most of the nutrients in this feedstuff. The current investigation yielded valuable numerical ADC for EAA considered to be of prime importance in generating balanced diet formulations.     

Digestibility of nutrients and energy in ingredients for bullfrogs during different phases of development

The ability of frogs to digest dietary nutrients changes with growth, with the animals becoming more or less demanding. The objective of this study was to determine the apparent digestibility coefficients of protein, energy and ether extract of 14 ingredients used in bullfrog diets (spray‐dried blood meal, hydrolysed feather meal, poultry by‐product meal, red blood cell concentrate, tilapia by‐product meal, sardine fishmeal, salmon fishmeal, meat and bone meal, corn gluten meal, soybean meal, corn, wheat bran, soy protein concentrate and soybean oil). A total of 2,325 bullfrogs (Lithobates catesbeianus) in different phases of development were used: early phase (mean weight of 30–50 g), growth phase (80–110 g) and finishing phase (150–200 g). Faeces were collected using the method of dissection. Marked differences in digestibility of the ingredients were observed between the different phases of frog development. Among the ingredients studied, salmon fishmeal and corn gluten meal showed good utilization of the protein (78.9% and 86.7%, respectively) and energy fraction (89.4% and 83.3%, respectively). The salmon fishmeal, poultry by‐product meal, sardine fishmeal, soy protein concentrate, wheat bran and soybean oil exhibited good ether extract utilization (81.2%–92.8%), recommending their use in bullfrog diets.     

Nutrients apparent digestibility coefficients of selected protein sources for juvenile Siberian sturgeon (Acipenser baerii Brandt), compared by two chromic oxide analyses methods

Apparent digestibility coefficients (ADCs) of dry matter (ADC_d), crude protein (ADC_p), energy (ADC_e) and amino acids in selected feedstuffs were determined for juvenile Siberian sturgeon (8.38 ± 0.20 g). The tested feedstuffs were fishmeal (FM), meat and bone meal (MBM), poultry by-product meal, hydrolysed feather meal, fermented feather meal solvent-extracted cottonseed meal and soybean meal. ADCs were determined using a reference diet and test diets at 7 : 3 ratios with 5 g kg⁻¹ chromic oxide (Cr₂O₃) as an inert marker. Fish were reared in a recirculating system and fed to apparent satiation five times daily. Cr₂O₃ in diets and faeces samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and acid-digestion colorimetry (AC) methods, respectively. The results showed that ICP-AES method was more accurate for Cr₂O₃ determination than AC method, and the results determined by ICP-AES method were used in this study. ADC_d and ADC_p of seven tested ingredients were lowest for MBM (59.1 and 84.5%) and highest for FM (79.9 and 94.5%); ADC_e of tested ingredients were from 71.8% for SECM to 93.2% for FM. ADCs of amino acid in test ingredients followed similar trend to the ADC_p. The ADCs of individual amino acids varied from 61.6% (histidine in MBM) to 98.8% (valine in FM).     

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.