Vol.:(0123456789)1 3

Amino Acids (2020) 52:523–542 https://doi.org/10.1007/s00726-020-02833-4

ORIGINAL ARTICLE

Composition of amino acids and related nitrogenous nutrients in feedstuffs for animal diets

Peng Li1 · Guoyao Wu2

Received: 6 January 2020 / Accepted: 19 February 2020 / Published online: 11 March 2020 © The Author(s) 2020

AbstractWe analyzed the composition of amino acids (AAs) in oligopeptides, proteins, and the free pool, as well as creatine, agmatine, polyamines, carnosine, anserine, and glutathione, in animal- and plant-derived feedstuffs. Ingredients of animal origins were black soldier fly larvae meal (BSFM), chicken by-product meal, chicken visceral digest, feather meal, Menhaden fishmeal, Peruvian anchovy fishmeal, Southeast Asian fishmeal, spray-dried peptone from enzymes-treated porcine mucosal tissues, poultry by-product meal (pet-food grade), spray-dried poultry plasma, and spray-dried egg product. Ingredients of plant origins were algae spirulina meal, soybean meal, and soy protein concentrate. All animal-derived feedstuffs contained large amounts of all proteinogenic AAs (particularly glycine, proline, glutamate, leucine, lysine, and arginine) and key nonpro-teinogenic AAs (taurine and 4-hydroxyproline), as well as significant amounts of agmatine, polyamines, creatine, creatinine, creatine phosphate, and glutathione. These nitrogenous substances are essential to either DNA and protein syntheses in cells or energy metabolism in tissues (particularly the brain and skeletal muscle). Of note, chicken by-product meal, poultry by-product meal, and spray-dried poultry plasma contained large amounts of carnosine and anserine (potent antioxidants). Compared with most of the animal-derived feedstuffs, plant-derived feedstuffs contained much lower contents of glycine and proline, little 4-hydroxyproline, and no creatine, creatinine, creatine phosphate, carnosine or anserine. These results indicate the unique importance of animal-source feedstuffs in improving the feed efficiency, growth and health of animals (including fish and companion animals). Because soy protein concentrate is consumed by infants, children and adults, as are BSFM and algae for children and adults, our findings also have important implications for human nutrition.

Keywords Animal · Feeding · Nutrition · Peptides · Protein · Rendered products

AbbreviationsAA Amino acidBSFM Black soldier fly larvae mealCBPM Chicken by-product mealCVD Chicken visceral digestDM Dry matterEAA Nutritionally essential amino acid

FM-M Fishmeal (United States Menhaden)FM-P Fishmeal (Peruvian anchovy)FM-SE Fishmeal (Southeast Asian miscellaneous

marine fishes)HPLC High-performance liquid chromatographyHyp 4-HydroxyprolineNEAA Nutritionally nonessential amino acidPCA Perchloric acidPFG Pet-food gradeSBM Soybean mealSDEP Spray-dried egg productSDPM Spray-dried peptone from enzymes-treated por-

cine mucosal tissuesSDPP Spray-dried poultry plasmaSPC Soy protein concentrate

Handling Editor: F. Blachier.

Electronic supplementary material The online version of this article (https ://doi.org/10.1007/s0072 6-020-02833 -4) contains supplementary material, which is available to authorized users.

* Guoyao Wu g-wu@tamu.edu

1 North American Renderers Association, Alexandria, VA 22314, USA

2 Department of Animal Science, Texas A&M University, College Station, TX 77843, USA

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524 P. Li, G. Wu

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Introduction

Animal-source feedstuffs are generally superior to plant-source ones for the growth and health of livestock, poultry, and fish (Wu 2018). This is due, in part, to the greater quantity of proteinogenic amino acids (AAs) and higher quality (the ratios and digestibilities of AAs) of the for-mer than the latter. Traditionally, extensive research has focused on AAs that are not synthesized by animal cells and are known as nutritionally essential AAs (EAAs), including leucine, lysine, methionine, threonine, and tryptophan (Hou and Wu 2018a). However, little atten-tion has been directed to AAs that are synthesizable in animal cells [so-called nutritionally nonessential AAs (NEAAs), such as glutamate, glutamine, glycine, proline, and 4-hydroxyproline] (e.g., Cummins et al. 2017; Dust et al. 2005; Myers et al. 2014). However, NEAAs have versatile nutritional and physiological functions and are generally more abundant in animal- than plant feedstuffs (Hou et al. 2015a). The high abundance of NEAAs in ani-mal protein can cut the energetic and EAA costs of their de novo syntheses in animal cells and leads to improved feed efficiency in the production of animals, especially carnivorous species (Li and Wu 2018). In addition, ani-mal-source feedstuffs contain taurine, creatine and creatine phosphate that are important anti-oxidants and participate in energy metabolism in tissues [particularly the brain, skeletal muscle, heart, and gonads of animals (Wu 2013)]. In contrast, plant-source feedstuffs lack these nitrogenous nutrients (Hou et al. 2019). Furthermore, animal-derived feedstuffs may contain polyamines that are essential for DNA and protein syntheses in mammals, birds, and other vertebrates (Kerr et al. 2017). Finally, the presence of oligopeptides [small peptides (containing 2–10 AA resi-dues) and large peptides (containing 11–20 AA residues)] in animal-source feedstuffs may enhance their efficiency in promoting animal growth.

At present, little is known about the content of creatine, polyamines, and oligopeptides in animal-source feedstuffs, most of which are produced by the rendering and animal protein industries to convert wastes into high-quality pro-tein sources, protect the global environment (Meeker and Hamilton 2006), and reduce carbon emissions from animal production (Wu 2018). In addition, the literature shows large variations of these substances and AAs in feedstuffs among different laboratories (e.g., Bryan 2018; Donadelli et al. 2019; Frikha  et al. 2014; Kerr et al. 2017; Kim et al. 2000; Norberg et al. 2004; Renna et al. 2017; Shumo et al. 2019). These salient variations in published values might be attributable to the raw materials used (e.g., their sources, freshness and microbial contamination), process-ing technologies for ingredient production, and errors in

AA analyses. A database on the composition of AAs and related nutrients in a variety of protein ingredients derived from terrestrial animals and fishes is much needed to guide the formulation of diets for feeding livestock, poultry, fish, shrimp and companion animals (Turchini et al. 2019; Wu 2018). To achieve this goal, we analyzed eleven common animal-source feedstuffs and, for comparison, three com-mon plant-source feedstuffs for AAs in oligopeptides, pro-tein, and the free pool as well as creatine, creatine phos-phate, creatinine, agmatine, polyamines, and glutathione.

Materials and methods

Materials

Chicken by-product meal (CBPM), chicken visceral digest (CVD), hydrolyzed feather meal, poultry by-product meal (pet-food grade), and spray-dried poultry plasma (SDPP) were obtained from North American Renderers Asso-ciation (Alexandria, VA, USA). Black soldier fly larvae meal (BSFM) was manufactured by Dr. Jeffery Tomberlin (Department of Entomology, Texas A&M University, Col-lege Station, TX, USA). Fishmeal (US Menhaden), fish-meal (Peruvian anchovy), and fishmeal (Southeast Asian miscellaneous marine fishes) were obtained from Tongwei Research Institute (Chengdu, China). Spray-dried peptone from enzymes-treated porcine mucosal tissues (SDPM; Pro-Pep WD) was obtained from International Nutrition Inc. (Omaha, NE, USA). SDPM was a by-product of heparin extraction under salt solution and was dried by a spray-dried technology without the presence of plant protein carriers. Spray-dried egg product was obtained from IsoNova Tech-nologies LLC (Springfield, MO, USA). Plant-source feed-stuffs [algae spirulina meal, soybean meal (SBM), and soy protein concentrate (SPC)] were obtained from Aquaculture Research and Teaching Facility of Texas A&M University (College Station, TX, USA).

High-performance liquid chromatography (HPLC)-grade water and methanol were purchased from Fisher Scientific (Houston, TX, USA). Balenine (β-alanyl-3-methylhistidine; ophidine), which has been reported to be present in the skeletal muscles of snakes, whales and pigs (Boldyrev et al. 2013; Carnegie et al. 1982; Wolff et al. 1968), was a gift of Dr. J. Wolff (National Institute of Health, Bethesda, MD, USA). Other materials, including proteases, HPLC columns, AA standards, agmatine, carnosine (β-alanyl-L-histidine), and anserine (β-alanyl-1-methylhistidine) were products of Sigma Chemicals (St. Louis, MO, USA).

525Composition of amino acids and related nitrogenous nutrients in feedstuffs for animal diets

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Chemical analyses

Each food was finely ground to 0.5 mm in size before use for analysis. Dry matter (DM) content was determined by drying approximately 100 mg samples to a constant mass in a 105 °C oven. The content of crude protein, crude fat, ash (minerals), and carbohydrate in feedstuffs was determined as described by Wu et al. (2016a). Creatine and creatinine were analyzed by HPLC, as previously described by Kai et al. (1983). Creatine phosphate was converted into creatine by creatine kinase (Lamprecht and Stein 1965), followed by the HPLC analysis of creatine. The detection limits for creatine, creatinine and creatine phosphate were 3.5, 3.5, and 7 ng/g feed (as-fed basis), respectively.

For the determination of polyamines, agmatine, small peptides (carnosine, anserine and balenine), and free AAs, each feed sample (~ 200 mg) was homogenized in 2 ml of 1.5 M HClO4 (perchloric acid, PCA). The homogenate was neutralized with 1 ml of 2 M K2CO3, followed by addition of 2 ml HPLC-grade water. The whole solution was centrifuged at 600 g for 10 min, and the supernatant fluid was analyzed for polyamines and agmatine (Dai et al. 2014b), free AAs (Hou et al. 2019; Wu and Meininger 2008), carnosine and anserine (Wu et al. 2016a), and balenine (Hou et al. 2015b) using HPLC methods involving precolumn derivatization with o-phthaldialdehyde. Polyamines, agmatine, carnosine, anserine, balenine, and free AAs in samples were quanti-fied on the basis of known amounts of standards using the Millenium-32 Software (Waters, Milford, MA, USA). The detection limits for carnosine, anserine and balenine were 0.35 ng/g feed (as-fed basis).

For determining peptide-bound plus free AAs (i.e., total AAs) in feeds (except for peptide-bound tryptophan), approximately 200 mg samples were hydrolyzed in 10 mL of 6 N HCl at 110 °C for 24 h under N2 (Dai et al. 2014a). For tryptophan analysis, approximately 100 mg samples were hydrolyzed at 110 °C for 20 h in 10 mL of 4.2 M NaOH plus 0.1 mL of 25% thiodiglycol (an antioxidant), as previ-ously described (Dai et al. 2014a). Free AAs were extracted from each feed as described previously for the determination of polyamines. The differences in AA content between the acid or alkaline hydrolysis and the free AA fraction were taken to indicate the content of peptide-bound AAs (i.e., AAs in proteins and small plus large peptides). The PCA-soluble fraction (containing small plus large peptides and free AA) was neutralized with 1 M NaOH and the super-natant fluid (0.5 ml) was hydrolyzed in 10 mL of 6 N HCl at 110 °C for 24 h under N2. The differences in AA content before and after the acid hydrolysis were used to calculate the content of small plus large peptides. Glutamine, gluta-mate, asparagine, and aspartate in the proteins and peptides of feedstuffs were determined using proteases after samples were dried in an oven (105 °C) for 20 h, as we described

previously (Hou et al. 2019; Li et al. 2011). Briefly, the working solution of enzymes contained the following per 1 ml of phosphate-buffered saline (pH 7.5): 2 mg pronase E (from Streptomyces griseus; Sigma Cat #P5147), 2 mg prolidase (from porcine kidney; Sigma Cat #P6675), 2 mg pyroglutamate aminopeptidase (from Bacillus amyloliquefa-ciens; Sigma Cat #P4669), 2 mg carboxypeptidase A (from bovine pancreas; Sigma Cat #C0261), and 2 mg aminopepti-dase M (from porcine kidney; Sigma Cat #L0632). A finely-grounded feed sample (~ 50 mg) was incubated at 25 °C for 6 h with 250 µl of phosphate-buffered saline (pH 7.5) and 50 µl of the enzyme solution. At the end of the incubation, 50 µl of 1.5 M HClO4 was added to the solution, followed by the addition of 25 µl of 2 M K2CO3 and 5 ml of HLPC water. Blanks were prepared by adding 50 µl of 1.5 M HClO4 to the assay mixture before the addition of 50 µl of the enzyme solution. All analyses of AAs were performed in triplicate for each sample using HPLC methods involving precolumn derivatization with o-phthaldialdehyde (Dai et al. 2014a). Amino acids in samples were quantified on the basis of known amounts of standards (Sigma Chemicals, St. Louis, MO, USA) using the Waters Millenium-32 Software (Zhang et al. 2019). Peptide-bound AAs were calculated as total AAs minus free AAs. The content of true proteins plus pep-tides was calculated on the basis of the molecular weights of AA residues (i.e., the molecular weight of an intact AA–18; Hou et al. 2019).

Statistical analysis

Values (means ± SEM) are expressed on the as-fed basis, because animal diets are generally formulated on this basis. Sample size (n = 6/feed) was chosen on the basis of known variations of AAs among feeds (Li et al. 2011) and statisti-cal power calculation with a probability of 0.9 (Jobgen et al. 2008). Log transformation of variables was performed when the variance of data was not homogenous among treatment groups, as assessed by the Levene’s test (Fu et al. 2010). Data on AA composition were analyzed by one-way analysis of variance and the Student–Newman–Keuls multiple com-parison (Assaad et al. 2014). Probability values < 0.05 were taken to indicate statistical significance.

Results

Content of nutrients in animal‑ and plant‑derived feedstuffs

Results of the approximate analyses of nutrients in animal- and plant-derived feedstuffs (as-fed basis) are summarized in (Table 1). The DM content of the feedstuffs varied from 88.7% for SDPM to 98.0% for chicken by-product meal.

526 P. Li, G. Wu

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The content of crude protein was the highest in feather meal (91.3%; P < 0.05) and the lowest in BSFM (42.0%; P < 0.05). Spray-dried egg product had the highest content of crude fat (33.5%; P < 0.05) but algae spirulina meal contained only 0.25% crude fat. The content of minerals was the highest in Southeast Asian fishmeal (21.9%; P < 0.05), followed by SDPM, Menhaden fishmeal, spray-dried poultry plasma, Peruvian fishmeal, chicken visceral digest, and poultry by-product meal (pet-food grade) in descending order. The content of carbohydrate was the highest in soybean meal (36.2%; P < 0.05) and the lowest in feather meal (0.15%; P < 0.05).

Content of total AAs, total  free AAs, total peptides, and total proteins in feedstuffs

Data on the content of total AAs (peptide-bound plus free AAs), total free AAs, total peptides, total small plus large peptides, and total proteins in feedstuffs are summarized in Table 2. Feather meal and BSFM contained the highest and lowest content of total AAs, respectively. Among animal-source feedstuffs, the content of total AAs was the second-highest in spray-dried poultry plasma, followed by chicken visceral digest, Southeast Asian fishmeal, chicken by-prod-uct meal, and Peruvian fishmeal in descending order. Algae spirulina meal and soy protein concentrate also contained

high content of total AAs, whereas soybean meal contained the lowest content of total AAs.

SDPM and spray-dried egg product contained the high-est and lowest content of free AAs, respectively, which accounted for 39.4% and 0.37% of total AAs, respectively. The content of free AAs was the second-highest in chicken visceral digest (7.6% of total AAs), followed by Southeast Asian fishmeal (6.8% of total AAs), Peruvian fishmeal (4.9% of total AAs), BSFM (2.9% of total AAs), and Menhaden fishmeal (2.2%) in descending order. All the plant-source feedstuffs contained a low content of free AAs.

Feather meal and SDPM contained the highest and low-est content of peptide-bound AAs (i.e., AAs in proteins and small plus large peptides), respectively, which accounted for 99.5% and 60.6% of total AAs, respectively. The con-tent of peptide-bound AAs was the second-highest in spray-dried poultry plasma (85.4%), followed by chicken visceral digest (73.7%), chicken by-product meal (67.8%), Southeast Asian fishmeal (65.6%), and Peruvian fishmeal (63.3%) in descending order. The content of peptide-bound AAs accounted for 99.0%, 98.6%, 99.1%, and 99.7% of total AAs in algae spirulina meal, soybean meal, and soy protein concentrate, respectively.

Chicken visceral digest and feather meal contained the highest and lowest content of AAs in PCA-soluble pep-tides (i.e., small plus large peptides), respectively, which accounted for 62.4% and 4.3% of AAs in total peptides,

Table 1 Content of nutrients in animal- and plant-derived feedstuffs (%, as-fed basis)

Values are means ± SEM, n = 6.BSFM black soldier fly larvae meal; CBPM chicken by-product meal; CVD chicken visceral digest; FM-M fishmeal (United States Menhaden); FM-P fishmeal (Peruvian anchovy); FM-SE fishmeal (Southeast Asian miscellaneous marine fishes); Hyp 4-hydroxyproline; PBM (PFG) poultry by-product meal (pet-food grade); PCA perchloric acid; SBM soybean meal; SDEP spray-dried egg product; SDPM spray-dried peptone from enzymes-treated porcine mucosal tissues; SDPP spray-dried poultry plasma; SM spirulina meal; SPC soy protein concentrate.a −m:Withinacolumn,meansnotsharingthesamesuperscriptletterdiffers(P < 0.05)

Sample Water Dry matter Crude protein Crude fat Minerals Carbohydrates

Animal-source feedstuffs BSFM 4.70 ± 0.11h 95.30 ± 0.11e 42.00 ± 0.07m 33.52 ± 0.22b 6.22 ± 0.06i 13.57 ± 0.16d

 CBPM 1.97 ± 0.02l 98.03 ± 0.02a 68.07 ± 0.11e 13.38 ± 0.05c 12.38 ± 0.17f 4.20 ± 0.11h

 CVD 6.78 ± 0.13f 93.22 ± 0.13g 67.18 ± 0.06g 8.57 ± 0.11e 12.03 ± 0.22f 5.44 ± 0.26g

 Feather meal 4.20 ± 0.03i 95.80 ± 0.03d 91.27 ± 0.03a 3.52 ± 0.02j 0.87 ± 0.01l 0.15 ± 0.01l

 FM-M 7.23 ± 0.05e 92.77 ± 0.05h 62.40 ± 0.07i 11.13 ± 0.08d 18.86 ± 0.03c 0.38 ± 0.02k

 FM-P 8.41 ± 0.05c 91.59 ± 0.05j 68.77 ± 0.10d 7.32 ± 0.03f 15.13 ± 0.05e 0.37 ± 0.02j

 FM-SE 7.95 ± 0.03d 92.05 ± 0.03i 64.70 ± 0.07h 5.07 ± 0.03g 21.89 ± 0.05a 0.39 ± 0.01j

 SDPM 11.26 ± 0.03a 88.74 ± 0.03l 55.18 ± 0.06j 4.63 ± 0.07h 19.78 ± 0.24b 9.14 ± 0.18e

 PBM  (PFG) 3.19 ± 0.08k 96.81 ± 0.08b 70.20 ± 0.10b 11.50 ± 0.07d 11.20 ± 0.06g 3.91 ± 0.15i

 SDPP 4.58 ± 0.03h 95.42 ± 0.03e 69.77 ± 0.06c 4.02 ± 0.09i 18.28 ± 0.05d 3.35 ± 0.08j

 SDEP 4.87 ± 0.05g 95.13 ± 0.05f 48.90 ± 0.05k 35.01 ± 0.07a 4.88 ± 0.03k 6.34 ± 0.13f

Plant-source feedstuffs Algae SM 3.47 ± 0.11j 96.53 ± 0.11c 68.80 ± 0.06d 0.25 ± 0.01m 7.18 ± 0.03h 20.30 ± 0.12c

 SBM 10.83 ± 0.07b 89.17 ± 0.07k 46.33 ± 0.09l 0.94 ± 0.02k 5.68 ± 0.03j 36.22 ± 0.07a

 SPC 4.64 ± 0.02h 95.36 ± 0.02e 67.47 ± 0.05f 0.47 ± 0.01l 5.53 ± 0.04j 21.89 ± 0.06b

527Composition of amino acids and related nitrogenous nutrients in feedstuffs for animal diets

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respectively. The content of AAs in PCA-soluble peptides was the second-highest in SDPM (50.3% of total pep-tide-bound AAs), followed by Southeast Asian fishmeal (20.1% of total peptide-bound AAs), chicken by-product meal (14.2% of total peptide-bound AAs), and Menhaden fishmeal (13.2% of total peptide-bound AAs) in descend-ing order. The content of AAs in PCA-soluble peptides accounted for 7.1%, 11.0%, 7.3%, and 2.8% of total pep-tide-bound AAs in algae spirulina meal, soybean meal, and soy protein concentrate, respectively.

Feather meal and chicken visceral digest contained the highest and lowest content of AAs in PCA-insoluble polypeptides (i.e., proteins), respectively, which accounted for 95.7% and 37.83% of AAs in total peptides, respec-tively. The content of AAs in proteins was the second-highest in spray-dried poultry plasma (94.2% of total peptide-bound AAs), spray-dried egg product (91.6% of total peptide-bound AAs), Peruvian fishmeal (88.7% of

total peptide-bound AAs), and chicken by-product meal (85.8% of total peptide-bound AAs) in descending order. The content of AAs in protein accounted for 92.9%, 89.0%, 92.7%, and 97.3% of total peptide-bound AAs in algae spirulina meal, soybean meal, and soy protein concentrate, respectively.

Content of total individual AAs (peptide‑bound plus free AAs) in feedstuffs

Data on the content of total individual AAs (peptide-bound plus free AAs) in feedstuffs are summarized in Table 3. Tyrosine was the most abundant AA in the peptides plus the free AA pool in BSFM; glutamate in Menhaden fish-meal, Southeast Asian fishmeal, SDPM, and spray-dried egg product; glycine in chicken by-product meal, chicken vis-ceral digest, and poultry by-product meal (pet-food grade); leucine in Peruvian fishmeal and spray-dried poultry plasma;

Table 2 Content of total amino acids, total free amino acids, total peptides, total small plus large peptides, total proteins, and total glutathione in animal- and plant-derived feedstuffs (as-fed basis)1

BSFM black soldier fly larvae meal; CBPM chicken by-product meal; CVD chicken visceral digest; FM-M fishmeal (United States Menhaden); FM-P fishmeal (Peruvian anchovy); FM-SE fishmeal (Southeast Asian miscellaneous marine fishes); Hyp 4-hydroxyproline; PBM (PFG) poultry by-product meal (pet-food grade); PCA perchloric acid; SBM soybean meal; SDEP spray-dried egg product; SDPM spray-dried peptone from enzymes-treated porcine mucosal tissues; SDPP spray-dried poultry plasma; SM spirulina meal; SPC soy protein concentrate1 Values are means ± SEM, n = 6. The amounts of amino acids were calculated on the basis of their intact molecular weights2 Small plus large peptides3 Proteinsa −n: Within a column, means not sharing the same superscript letter differs (P < 0.05)

Sample Total amino acids (g/kg feed)

Total free amino acids (g/kg feed)

Amino acids in peptides (g/kg feed) Total glutathione (mg/kg feed)

Total PCA-soluble peptides2 PCA-insoluble polypeptides3

(A) (B) (C = A–B) (D) (E = C–D)

Animal-source feedstuffsBSFM 503.8 ± 1.5l 15.8 ± 0.07e 487.9 ± 1.5j 39.6 ± 0.21j 448.3 ± 1.5k 154 ± 3.7c

CBPM 685.6 ± 2.4f 7.28 ± 0.05i 678.3 ± 2.4f 96.2 ± 0.44d 582.1 ± 2.6e 113 ± 4.8d

CVD 798.3 ± 1.5c 60.9 ± 0.35b 737.4 ± 1.4e 459.0 ± 1.6a 278.4 ± 1.9m 19.8 ± 0.6h

Feather meal 924.6 ± 1.0a 4.37 ± 0.04j 920.3 ± 1.0a 39.1 ± 0.15j 881.2 ± 1.1a 0.71 ± 0.02i

FM-M 601.8 ± 0.7j 13.2 ± 0.08f 588.6 ± 0.7i 77.4 ± 0.25e 511.1 ± 0.6j 35.0 ± 1.4f

FM-P 665.2 ± 1.9g 32.5 ± 0.50d 632.7 ± 2.1h 71.4 ± 0.33f 561.3 ± 2.4g 23.8 ± 0.31g

FM-SE 703.6 ± 1.0e 48.1 ± 0.32c 655.5 ± 1.2g 131.6 ± 0.8c 523.8 ± 1.9i 225 ± 5.4a

SDPM 590.0 ± 0.9k 232.2 ± 0.9a 357.8 ± 1.5l 180.1 ± 0.6b 177.7 ± 2.0n 175 ± 3.2b

PBM (PFG) 642.0 ± 1.4h 14.7 ± 0.08e 627.3 ± 1.4h 78.7 ± 0.52e 548.6 ± 1.3h 73.2 ± 1.6c

SDPP 864.0 ± 3.3b 10.3 ± 0.09g 853.7 ± 3.3b 49.7 ± 0.41i 804.0 ± 3.1b 48.0 ± 1.3e

SDEP 630.1 ± 0.6i 2.35 ± 0.01l 627.7 ± 0.6h 52.5 ± 0.39h 575.2 ± 0.6f 34.2 ± 0.9f

Plant-source feedstuffsAlgae SM 775.1 ± 1.2d 8.01 ± 0.10h 767.1 ± 1.2d 54.1 ± 0.20g 712.9 ± 1.3d 33.9 ± 0.4f

SBM 443.9 ± 1.2m 4.25 ± 0.04j 439.7 ± 1.2k 32.3 ± 0.10k 407.4 ± 1.2l 174 ± 4.1b

SPC 800.6 ± 1.9c 2.81 ± 0.02k 797.8 ± 1.9c 21.9 ± 0.10l 775.9 ± 1.9c 172 ± 4.5b

528 P. Li, G. Wu

1 3

Tabl

e 3

Con

tent

of t

otal

indi

vidu

al a

min

o ac

ids (

tota

l pep

tide-

boun

d am

ino

acid

s plu

s tot

al fr

ee a

min

o ac

ids)

in a

nim

al- a

nd p

lant

-der

ived

feed

stuffs

Valu

es e

xpre

ssed

as

g/kg

feed

(as-

fed

basi

s), a

re m

eans

± S

EM, n

= 6.

Tot

al p

eptid

e-bo

und

amin

o ac

ids

are

thos

e in

all

pept

ides

[per

chlo

ric a

cid-

solu

ble

pept

ides

(olig

opep

tides

) plu

s pe

rchl

oric

ac

id-in

solu

ble

poly

pept

ides

(pro

tein

s)].

The

mol

ecul

ar w

eigh

ts o

f int

act a

min

o ac

ids w

ere

used

for t

he c

alcu

latio

n. T

he fr

ee a

min

o ac

ids i

n th

is ta

ble

did

not i

nclu

de β

-ala

nine

, citr

ullin

e, o

rnith

-in

e or

taur

ine

BSFM

bla

ck s

oldi

er fl

y la

rvae

mea

l; C

BPM

chi

cken

by-

prod

uct m

eal;

CVD

chi

cken

vis

cera

l dig

est;

FM-M

fish

mea

l (U

nite

d St

ates

Men

hade

n); F

M-P

fish

mea

l (Pe

ruvi

an a

ncho

vy);

FM-S

E fis

h-m

eal (

Sout

heas

t Asi

an m

isce

llane

ous

mar

ine

fishe

s); H

yp 4

-hyd

roxy

prol

ine;

Orn

orn

ithin

e; P

BM (

PFG

) po

ultry

by-

prod

uct m

eal (

pet-f

ood

grad

e); P

CA p

erch

loric

aci

d; S

BM s

oybe

an m

eal;

SDEP

spra

y-dr

ied

egg

prod

uct;

SDPM

spra

y-dr

ied

pept

one

from

enz

ymes

-trea

ted

porc

ine

muc

osal

tiss

ues;

SD

PP sp

ray-

drie

d po

ultry

pla

sma;

SM

spiru

lina

mea

l; SP

C so

y pr

otei

n co

ncen

trate

A C

yste

ine +

½ c

ystin

ea −

l : W

ithin

a ro

w, m

eans

not

shar

ing

the

sam

e su

pers

crip

t let

ter d

iffer

(P <

0.05

)

Am

ino

acid

Ani

mal

-sou

rce

feed

stuffs

Plan

t-sou

rce

feed

stuffs

BSF

MC

BPM

CV

DFe

athe

r mea

lFM

-MFM

-PFM

-SE

SDPM

PBM

(PFG

)SD

PPSD

EPA

lgae

SM

SBM

SPC

Ala

31.4

0j ±

0.17

45.3

6d ±

0.18

41.2

4e ±

0.38

41.2

0e ±

0.28

36.2

8g ±

0.27

47.3

9c ±

0.33

45.9

0d ±

0.36

35.0

9h ±

0.21

39.8

3f ±

0.41

49.8

0b ±

0.12

34.3

1i ±

0.26

58.5

1a ±

0.33

19.7

3k ±

0.21

34.4

3i ±

0.28

Arg

26.4

0j ±

0.21

47.5

0d ±

0.37

40.2

2f ±

0.25

58.3

0a ±

0.30

36.7

0h ±

0.21

35.7

8h ±

0.35

41.4

7e ±

0.23

35.9

2h ±

0.24

41.4

8e ±

0.52

49.4

0c ±

0.19

38.2

0g ±

0.31

51.8

2b ±

0.25

32.0

3i ±

0.20

57.9

6a ±

0.00

1A

sn19

.26h

± 0.

0826

.05d

± 0.

2225

.02e

± 0.

1417

.85i

± 0.

1322

.62f

± 0.

1322

.83f

± 0.

2025

.99d

± 0.

3115

.18j

± 0.

0625

.63d

e ± 0.

1325

.72d

e ± 0.

3226

.92c

± 0.

1133

.41b

± 0.

1420

.98g

± 0.

1436

.07a

± 0.

06A

sp30

.37h

± 0.

1339

.34d

± 0.

3436

.60e

f ± 0.

2130

.65h

± 0.

2333

.30g

± 0.

2034

.10g

± 0.

2938

.66d

± 0.

4737

.17e

± 0.

1538

.60d

± 0.

1951

.70b

± 0.

6335

.98f

± 0.

1442

.87c

± 0.

1831

.22h

± 0.

2155

.95a

± 0.

10C

ysA

6.89

h ± 0.

0410

.68e

± 0.

1612

.17d

± 0.

1841

.70a

± 0.

216.

74h ±

0.09

7.15

h ± 0.

036.

85h ±

0.05

9.85

f ± 0.

0910

.41e

± 0.

1826

.50b

± 0.

2413

.69c

± 0.

278.

81g ±

0.07

7.01

h ± 0.

0613

.62c

± 0.

13G

ln25

.10l

± 0.

0738

.84e

± 0.

2237

.25f

± 0.

2629

.13i

± 0.

1736

.02g

± 0.

1533

.90h

± 0.

1539

.57d

± 0.

2327

.84k

± 0.

3234

.12h

± 0.

1744

.93b

± 0.

4929

.00j

± 0.

1542

.47c

± 0.

2637

.77f

± 0.

2669

.21a

± 0.

35G

lu34

.43l

± 0.

0753

.38g

± 0.

3163

.42c

± 0.

4449

.17i

± 0.

2953

.20g

± 0.

2351

.28h

± 0.

2359

.73d

± 0.

3557

.68e

± 0.

2247

.50j

± 0.

2467

.67b

± 0.

7454

.81f

± 0.

2868

.12b

± 0.

4142

.15k

± 0.

2983

.58a

± 0.

42G

ly29

.08j

± 0.

2359

.40d

± 0.

3982

.47b

± 0.

2789

.72a

± 0.

4042

.62g

± 0.

3150

.85e

± 0.

5558

.69d

± 0.

3549

.50f

± 0.

3368

.60c

± 0.

3434

.04i

± 0.

3924

.52k

± 0.

1541

.92g

± 0.

3122

.99l

± 0.

2335

.90h

± 0.

30H

is17

.08c

± 0.

1913

.58e

± 0.

147.

45i ±

0.04

8.95

h ± 0.

0514

.10d

± 0.

1614

.31d

± 0.

2214

.58d

± 0.

2012

.85f

± 0.

1113

.12e

f ± 0.

1436

.60a

± 0.

7014

.47d

± 0.

1412

.91f

± 0.

1611

.48g

± 0.

2620

.81b

± 0.

23H

yp12

.72g

± 0.

1118

.51d

± 0.

4817

.30e

± 0.

1949

.70a

± 0.

4315

.65f

± 0.

2918

.24d

± 0.

2219

.84c

± 0.

347.

89h ±

0.10

22.4

5b ±

0.24

0.21

i ± 0.

010.

23i ±

0.01

0.14

j ± 0.

010.

089k

± 0.

002

0.13

j ± 0.

002

Ile20

.21f

± 0.

1627

.19d

± 0.

2938

.37b

± 0.

4637

.80b

± 0.

3724

.19e

± 0.

1527

.52d

± 0.

3227

.90d

± 0.

3624

.43e

± 0.

3123

.78e

± 0.

2627

.73d

± 0.

1429

.74c

± 0.

2940

.87a

± 0.

2420

.30f

± 0.

2737

.72b

± 0.

26Le

u32

.54k

± 0.

2052

.75f

± 0.

2861

.03d

± 0.

3269

.17b

± 0.

3645

.01h

± 0.

2552

.73f

± 0.

3445

.92g

± 0.

2743

.01i

± 0.

1943

.32i

± 0.

3875

.59a

± 0.

3546

.11g

± 0.

3763

.22c

± 0.

2834

.52j

± 0.

4057

.91e

± 0.

22Ly

s32

.13i

± 0.

2745

.19d

e ± 0.

3750

.20c

± 0.

5421

.52k

± 0.

1844

.59e

± 0.

2552

.52b

± 0.

2445

.67d

± 0.

2440

.67g

± 0.

2735

.43h

± 0.

3668

.53a

± 0.

2840

.87g

± 0.

3141

.78f

± 0.

3128

.10j

± 0.

2650

.42c

± 0.

31M

et12

.01e

± 0.

0814

.28d

± 0.

1615

.81c

± 0.

207.

53f ±

0.05

19.7

0b ±

0.35

21.6

2a ±

0.21

20.3

1b ±

0.18

12.0

1e ±

0.13

13.8

3d ±

0.16

19.6

8b ±

0.19

20.1

3b ±

0.16

21.6

7a ±

0.22

6.02

g ± 0.

0511

.73e

± 0.

32Ph

e21

.77h

± 0.

1926

.97f

± 0.

1936

.99d

± 0.

1639

.60b

c ± 0.

2323

.12g

± 0.

2023

.13g

± 0.

2526

.52f

± 0.

2623

.31g

± 0.

2223

.19g

± 0.

2047

.42a

± 0.

2530

.41e

± 0.

3038

.79c

± 0.

2222

.03h

± 0.

2940

.40b

± 0.

64Pr

o29

.18i

± 0.

2642

.99e

± 0.

6455

.30b

± 0.

4811

6.4a

± 0.

937

.23f

± 0.

3842

.72e

± 0.

2448

.02d

± 0.

4431

.63h

± 0.

2750

.74c

± 0.

3143

.20e

± 0.

3433

.93g

± 0.

3431

.22h

± 0.

2924

.40j

± 0.

2434

.80g

± 0.

34Se

r23

.40l

± 0.

1830

.51h

± 0.

4364

.49b

± 0.

3689

.22a

± 0.

3825

.18k

± 0.

1629

.14i

± 0.

3432

.82g

± 0.

3133

.72g

± 0.

3626

.22j

± 0.

2049

.91d

± 0.

3753

.91c

± 0.

2743

.51f

± 0.

2921

.43m

± 0.

2248

.31e

± 0.

26Th

r25

.51h

± 0.

2727

.71g

± 0.

3119

.91i

± 0.

2239

.22c

± 0.

1925

.03h

± 0.

2528

.50g

± 0.

4431

.43e

± 0.

2428

.52g

± 0.

2125

.58h

± 0.

2144

.49a

± 0.

1931

.01f

± 0.

3241

.31b

± 0.

1917

.82j

± 0.

0932

.69d

± 0.

18Tr

p7.

06g ±

0.07

7.59

f ± 0.

1010

.26c

± 0.

108.

02e ±

0.07

7.02

g ± 0.

046.

82g ±

0.09

7.04

g ± 0.

046.

28h ±

0.07

6.29

h ± 0.

0513

.62a

± 0.

179.

66d ±

0.08

10.2

1c ±

0.12

6.23

h ± 0.

0612

.12b

± 0.

20Ty

r38

.47a

± 0.

1922

.86e

f ± 0.

2025

.62d

± 0.

1421

.40g

± 0.

3518

.88i

± 0.

2720

.11h

± 0.

3923

.61e

± 0.

2622

.37f

± 0.

1618

.81i

± 0.

2435

.14b

± 0.

2126

.06d

± 0.

2737

.89a

± 0.

2316

.78j

± 0.

1128

.66c

± 0.

12Va

l28

.65i

± 0.

2333

.21g

± 0.

2055

.68b

± 0.

3758

.13a

± 0.

3530

.20h

± 0.

2536

.53f

± 0.

1832

.53g

± 0.

2430

.48h

± 0.

2529

.10i

± 0.

2849

.62c

± 0.

2535

.71f

± 0.

2743

.61d

± 0.

2720

.78j

± 0.

4538

.21e

± 0.

28

529Composition of amino acids and related nitrogenous nutrients in feedstuffs for animal diets

1 3

and proline in feather. Glutamate was the second most abun-dant AA in the peptides plus the free AA pool in BSFM and chicken by-product meal; glycine in feather meal, Southeast Asian fishmeal, and SDPM; leucine in Menhaden fishmeal; lysine in Peruvian fishmeal and spray-dried poultry plasma; and serine in chicken visceral digest, and spray-dried egg product. Glutamate was the third most abundant AA in the peptides plus the free AA pool in chicken visceral digest, Peruvian fishmeal, poultry by-product meal, and spray-dried poultry plasma; leucine in BSFM, chicken by-product meal, SDPM, and spray-dried egg product; lysine in Menhaden fishmeal; proline in Southeast Asian fishmeal; and serine in feather meal. Alanine was the fourth most abundant AA in the peptides plus the free AA pool in BSFM; arginine in chicken by-product meal; aspartate in spray-dried poul-try plasma; glycine in Menhaden fishmeal and Peruvian fishmeal; leucine in chicken visceral digest, feather meal, Southeast Asian fishmeal, and poultry by-product meal; and lysine in SDPM and spray-dried egg product. In all animal-source feedstuffs except for BSFM and Southeast Asian fishmeal, tryptophan and cysteine were the least and second least abundant AA, respectively, but the opposite was true for BSFM and Southeast Asian fishmeal, whereas 4-hydroxyproline, histidine and methionine were among the third, fourth or fifth least abundant AAs depending on feedstuffs. Similar results were obtained when values were calculated as the percentage of total AAs in the feedstuffs (Supplemental Table 1).

Glutamate was the most abundant AA in the peptides plus the free AA pool in algae spirulina meal, soybean meal, and soy protein concentrate. In algae spirulina meal, leucine was the second most abundant AA in the peptides plus the free AA pool, followed by alanine, arginine, valine and serine in descending order. In both soybean meal and soy protein concentrate, glutamine was the second most abundant AA in the peptides plus the free AA pool, followed by either leucine or arginine as the third or fourth most abundant AA.

Content of free AAs in feedstuffs

Data on the Content of free AAs in feedstuffs are summa-rized in Table 4. The first, second, third, fourth, and fifth most abundant free AAs in descending order were as fol-lows: tyrosine, glutamate, glutamine, leucine, and proline in BSFM; taurine, alanine, glycine, aspartate, and leucine in chicken by-product meal; leucine, serine, proline, alanine, and arginine in chicken visceral digest; cysteine, proline, alanine, leucine, and glutamate in feather meal; taurine, ala-nine, leucine, lysine, and glutamate in Menhaden fishmeal; taurine, histidine, alanine, leucine, and arginine in Peruvian fishmeal; taurine, alanine, leucine, valine, and proline in Southeast Asian fishmeal; leucine, lysine, alanine, valine, and aspartate in SDPM; taurine, alanine, glycine, glutamate,

and aspartate in poultry by-product meal (pet-food grade); glutamate, taurine, alanine, arginine, and glycine in spray-dried poultry plasma; and alanine, taurine, glutamate, argi-nine, and aspartate in spray-dried egg product.

Glutamate was the most abundant free AA in algae spirulina meal and arginine in both soybean meal and soy protein concentrate. Alanine was the second most abun-dant free AA in algae spirulina meal and glutamate in both soybean meal and soy protein concentrate. The content of other free AAs in plant-derived feedstuffs was very low, compared with animal-derived feedstuffs.

Content of peptide‑bound AAs in feedstuffs

Data on the content of peptide-bound AAs (i.e., AAs in proteins plus small and large peptides) in feedstuffs are summarized in Table 5. Tyrosine was the most abundant peptide-bound AA in BSFM; glutamate in Menhaden fishmeal, SDPM, and spray-dried egg product; glycine in chicken by-product meal, chicken visceral digest, South-east Asian fishmeal, and poultry by-product meal (pet-food grade); leucine in spray-dried poultry plasma; lysine in Peruvian fishmeal; and proline in feather. Glutamate was the second most abundant peptide-bound AA in BSFM, chicken by-product meal, Menhaden fishmeal, Southeast Asian fishmeal, and spray-dried egg product; glycine in feather meal and SDPM; leucine in Menhaden fish-meal, and Peruvian fishmeal; lysine in spray-dried poul-try plasma; proline in poultry by-product meal (pet-food grade); and serine in chicken visceral digest and egg prod-uct. Lysine was the third most abundant peptide-bound AA in BSFM and Menhaden fishmeal; glutamine in SDPM; glutamate in chicken visceral digest, Peruvian fishmeal, SDPM, poultry by-product meal, and spray-dried poul-try plasma; leucine in chicken by-product meal and egg product; lysine in BSFM and Menhaden fishmeal; proline in Southeast Asian fishmeal. Leucine was the fourth most abundant peptide-bound AA in BSFM, chicken visceral digest, and poultry by-product meal (pet-food grade); arginine in chicken by-product meal, feather meal, and SDPM; glycine in Menhaden fishmeal and Peruvian fish-meal; lysine in Southeast Asian fishmeal and egg product; and valine in spray-dried poultry plasma. In all animal-source feedstuffs except for BSFM and Menhaden fish-meal, tryptophan and cysteine were the least and second least abundant AA, respectively, but the opposite was true for BSFM and Menhaden fishmeal, whereas 4-hydroxypro-line, histidine and methionine were among the third, fourth or fifth least abundant peptide-bound AAs depending on feedstuffs.

Leucine was the most abundant peptide-bound AA in algae spirulina meal and glutamate in soybean meal and soy

530 P. Li, G. Wu

1 3

Tabl

e 4

Con

tent

of f

ree

amin

o ac

ids i

n an

imal

- and

pla

nt-d

eriv

ed fe

edstu

ffs

Valu

es, e

xpre

ssed

as m

g/kg

feed

(as-

fed

basi

s), a

re m

eans

± S

EM, n

= 6

BSFM

bla

ck so

ldie

r fly

larv

ae m

eal;

CBP

M c

hick

en b

y-pr

oduc

t mea

l; C

it ci

trulli

ne; C

VD c

hick

en v

isce

ral d

iges

t; FM

-M fi

shm

eal (

Uni

ted

Stat

es M

enha

den)

; FM

-P fi

shm

eal (

Peru

vian

anc

hovy

); FM

-SE

fishm

eal (

Sout

heas

t Asi

an m

isce

llane

ous

mar

ine

fishe

s); H

yp 4

-hyd

roxy

prol

ine;

Orn

orn

ithin

e; P

BM (P

FG) p

oultr

y by

-pro

duct

mea

l (pe

t-foo

d gr

ade)

; PCA

per

chlo

ric a

cid;

SBM

soy

-be

an m

eal;

SDEP

spr

ay-d

ried

egg

prod

uct;

SDPM

spr

ay-d

ried

pept

one

from

enz

ymes

-trea

ted

porc

ine

muc

osal

tiss

ues;

SD

PP s

pray

-drie

d po

ultry

pla

sma;

SM

spi

rulin

a m

eal;

SPC

soy

pro

tein

co

ncen

trate

A C

yste

ine +

½ c

ystin

ea −

m: W

ithin

a ro

w, m

eans

not

shar

ing

the

sam

e su

pers

crip

t let

ter d

iffer

(P <

0.05

)

Am

ino

 aci

dA

nim

al-s

ourc

e fe

edstu

ffsPl

ant-s

ourc

e fe

edstu

ffs

BSF

MC

BPM

CV

DFe

athe

r mea

lFM

-MFM

-PFM

-SE

SDPM

PBM

(PFG

)SD

PPSD

EPA

lgae

SM

SBM

SPC

Ala

1341

ef ±

1710

11h ±

1746

59c ±

8234

3k ±

1011

34g ±

3028

21d ±

8851

15b ±

3916

955a

± 82

1382

e ± 14

1290

f ± 15

718i

± 3.

139

6j ±

6.1

244l

± 4.

247

.3m

± 1.

5β-

Ala

25.6

f ± 0.

351

.0e ±

0.9

120b

± 4.

284

.0c ±

1.2

26.9

f ± 0.

511

8b ±

2.1

142a

± 2.

381

.2c ±

1.3

53.5

e ± 0.

816

.0g ±

0.4

59.6

d ± 1.

03.

6j ±

0.1

8.2h

± 0.

16.

3i ±

0.3

Arg

1613

d ± 20

277j

± 4.

146

13b ±

8721

7k ±

4.7

662i

± 5.

815

70d ±

6513

46e ±

2712

816a

± 18

571

9h ±

7.9

814g

± 27

166l

± 2.

117

4l ±

4.6

1249

f ± 33

2097

c ± 22

Asn

622c

± 19

141f

± 1.

711

51b ±

1590

.7g ±

1.4

61.5

h ± 0.

815

6f ±

2.8

145f

± 2.

133

62a ±

3021

9e ±

2.3

93.8

g ± 1.

58.

1j ±

0.3

35.7

i ± 0.

933

7d ±

1365

.7h ±

0.7

Asp

519f

± 1.

035

4g ±

4.5

3860

b ± 38

182h

± 3.

734

8g ±

3.5

610e

± 6.

287

4d ±

9.1

1521

0a ±

7789

2c ±

5.1

75.7

k ± 0.

913

2i ±

2.9

316g

± 5.

660

5e ±

1488

.7j ±

1.0

Cit

9.4g

± 0.

11.

1k ±

0.1

13.6

f ± 0.

41.

1k ±

0.1

64.7

d ± 1.

821

3c ±

3.5

327b

± 3.

914

00a ±

391.

3k ±

0.1

3.1i

± 0.

11.

8j ±

0.1

4.7h

± 0.

222

.7e ±

1.2

21.2

e ± 0.

7C

ysA

102g

± 2.

861

.2i ±

1.4

630b

± 27

547c

± 13

51.8

j ± 0.

918

4e ±

3.3

373d

± 7.

041

40a ±

3511

9f ±

3.8

82.3

h ± 2.

421

.5m

± 1.

026

.0l ±

0.6

47.3

k ± 1.

421

.9m

± 0.

4G

ln11

46a ±

3319

.0g ±

0.9

346b

± 3.

320

.0h ±

0.6

78.6

d ± 0.

512

.3i ±

0.4

7.9l

± 0.

211

.4jk

± 0.

410

.5k ±

0.4

69.8

e ± 1.

430

.2f ±

0.6

135c

± 1.

618

.0g ±

0.3

6.3m

± 0.

1G

lu17

02f ±

5923

2k ±

5.4

4599

c ± 52

200l

± 3.

670

9j ±

7.8

1502

g ± 82

2278

e ± 24

1457

8a ±

250

937h

± 7.

933

84d ±

6419

0l ±

3.3

6232

b ± 93

810i

± 13

106m

± 1.

2G

ly65

4d ±

2361

6e ±

3.6

2127

b ± 40

234g

± 5.

942

3f ±

5.7

1156

c ± 49

1177

c ± 32

7123

a ± 53

1152

c ± 8.

864

6d ±

5.2

78.2

i ± 1.

164

.5j ±

0.8

163h

± 3.

637

.5k ±

0.6

His

1110

c ± 12

67.8

g ± 1.

010

46c ±

7.5

38.8

h ± 0.

656

1d ±

5.2

5632

b ± 48

1062

c ± 20

5796

a ± 27

129f

± 1.

923

8e ±

2.4

9.3k

± 0.

320

.8i ±

0.7

75.9

g ± 2.

815

.9j ±

0.3

Hyp

588d

± 17

89.3

g ± 1.

817

64b ±

1962

.4h ±

1.7

112f

± 2.

349

5e ±

2112

97c ±

1625

43a ±

3267

.0h ±

1.6

35.5

i ± 0.

35.

5j ±

0.1

0.12

l ± 0.

010.

20k ±

0.01

0.15

l ± 0.

01Ile

253f

± 5.

324

5f ±

4.1

3073

b ± 46

117g

± 3.

137

8e ±

5.4

828c

± 21

2910

b ± 41

1242

3a ±

116

419d

± 6.

250

.5i ±

1.8

58.3

h ± 1.

243

.8j ±

0.6

48.0

i ± 1.

023

.5k ±

0.8

Leu

804e

± 15

347g

± 9.

054

16b ±

7026

5h ±

4.7

822e

± 21

1806

d ± 61

4559

c ± 55

2215

6a ±

276

739f

± 5.

419

2i ±

2.9

96.0

j ± 0.

991

.3k ±

1.1

86.2

l ± 1.

143

.0m

± 0.

9Ly

s22

9h ±

4.1

256g

± 5.

634

12b ±

4510

9j ±

3.0

808e

± 21

1219

d ± 31

1603

c ± 19

1949

6a ±

110

588f

± 7.

614

3i ±

2.6

24.6

m ±

0.5

24.8

m ±

0.4

76.8

k ± 1.

830

.8l ±

0.5

Met

132g

± 5.

270

.2i ±

1.4

880c

± 10

101h

± 2.

415

6f ±

2.4

519d

± 16

1171

b ± 26

5449

a ± 25

168e

± 3.

452

.5j ±

1.0

25.2

l ± 0.

934

.5k ±

0.4

36.8

k ± 0.

519

.2m

± 0.

5O

rn3.

8j ±

0.1

109d

± 3.

993

.0e ±

0.9

14.7

h ± 0.

322

3b ±

4.9

218b

± 6.

617

7c ±

2.4

1539

a ± 68

27.3

f ± 1.

55.

5i ±

0.2

2.8k

± 0.

13.

8j ±

0.1

18.0

g ± 0.

61.

6l ±

0.1

Phe

164g

± 3.

615

1g ±

1.8

2881

b ± 13

165g

± 3.

041

9e ±

3.0

807d

± 33

2423

c ± 29

1279

4a ±

160

387f

± 7.

697

.8h ±

0.9

55.7

i ± 0.

742

.8j ±

0.9

52.3

i ± 0.

822

.0k ±

0.6

Pro

711e

± 11

236h

± 7.

448

35b ±

106

469f

± 10

444f

± 10

1255

d ± 30

3774

c ± 30

1441

5a ±

425

368g

± 10

118i

± 2.

549

.0k ±

0.9

53.7

k ± 0.

771

.4j ±

1.4

26.3

l ± 0.

5Se

r59

6d ±

1221

5h ±

1.4

4846

b ± 30

243h

± 4.

027

4g ±

4.1

514e

± 22

467f

± 5.

512

063a

± 55

666c

± 8.

050

.4l ±

2.1

90.5

j ± 1.

111

4i ±

1.7

63.2

k ± 1.

338

.8m

± 1.

1Ta

urin

e90

.0k ±

1.3

2096

f ± 37

1317

h ± 9.

214

2j ±

2.8

4089

c ± 29

7486

b ± 12

798

64a ±

6416

38g ±

2738

84d ±

4724

55e ±

3832

6i ±

6.0

0.00

± 0.

000.

00 ±

0.00

0.00

± 0.

00Th

r36

2f ±

4.3

181h

± 1.

824

57b ±

4010

3i ±

1.7

341g

± 4.

799

0d ±

5411

07c ±

3412

763a

± 93

542e

± 8.

010

3i ±

3.8

83.5

j ± 1.

047

.8k ±

0.8

36.7

l ± 1.

933

.2l ±

0.7

Trp

75.0

f ± 1.

249

.2h ±

0.9

581c

± 7.

710

5e ±

2.3

110e

± 2.

143

4d ±

2085

0b ±

9.3

4193

a ± 24

56.3

g ± 0.

921

.2k ±

0.6

20.0

k ± 0.

628

.0j ±

0.6

34.5

i ± 0.

416

.2l ±

0.3

Tyr

2528

c ± 22

118j

± 5.

130

81b ±

3117

8h ±

4.1

353g

± 4.

683

0e ±

3111

88d ±

2212

467a

± 14

745

9f ±

4.3

142i

± 2.

432

.8m

± 0.

545

.5l ±

0.8

90.1

k ± 2.

434

.3m

± 1.

1Va

l44

5g ±

4.2

317h

± 17

3151

c ± 46

198i

± 3.

956

5f ±

7.3

1079

d ± 39

3847

b ± 47

1682

1a ±

121

732e

± 5.

312

4j ±

1.4

68.0

k ± 0.

973

.8k ±

0.7

76.0

k ± 2.

430

.2l ±

0.6

531Composition of amino acids and related nitrogenous nutrients in feedstuffs for animal diets

1 3

Tabl

e 5

Con

tent

of p

eptid

e-bo

und

amin

o ac

ids i

n an

imal

- and

pla

nt-d

eriv

ed fe

edstu

ffs

Valu

es e

xpre

ssed

as

g/kg

feed

(as-

fed

basi

s), a

re m

eans

± S

EM, n

= 6.

Pep

tide-

boun

d am

ino

acid

s ar

e th

ose

in a

ll pe

ptid

es [p

erch

loric

aci

d-so

lubl

e pe

ptid

es (o

ligop

eptid

es) p

lus

perc

hlor

ic a

cid-

inso

lubl

e po

lype

ptid

es (p

rote

ins)

]. Th

e m

olec

ular

wei

ghts

of i

ntac

t am

ino

acid

s wer

e us

ed fo

r the

cal

cula

tion

BSFM

bla

ck s

oldi

er fl

y la

rvae

mea

l; C

BPM

chi

cken

by-

prod

uct m

eal;

CVD

chi

cken

vis

cera

l dig

est;

FM-M

fish

mea

l (U

nite

d St

ates

Men

hade

n); F

M-P

fish

mea

l (Pe

ruvi

an a

ncho

vy);

FM-S

E fis

h-m

eal (

Sout

heas

t Asi

an m

isce

llane

ous m

arin

e fis

hes)

; Hyp

4-h

ydro

xypr

olin

e; P

BM (P

FG) p

oultr

y by

-pro

duct

mea

l (pe

t-foo

d gr

ade)

; PCA

per

chlo

ric a

cid;

SBM

soy

bean

mea

l; SD

EP s

pray

-drie

d eg

g pr

oduc

t; SD

PM sp

ray-

drie

d pe

pton

e fro

m e

nzym

es-tr

eate

d po

rcin

e m

ucos

al ti

ssue

s; S

DPP

spra

y-dr

ied

poul

try p

lasm

a; S

M sp

irulin

a m

eal;

SPC

soy

prot

ein

conc

entra

teA

Cys

tein

e + ½

cys

tine

a −n :

With

in a

row

, mea

ns n

ot sh

arin

g th

e sa

me

supe

rscr

ipt l

ette

r diff

er (P

< 0.

05)

Am

ino

acid

Ani

mal

-sou

rce

feed

stuffs

Plan

t-sou

rce

feed

stuffs

BSF

MC

BPM

CV

DFe

athe

r mea

lFM

-MFM

-PFM

-SE

SDPM

PBM

(PFG

)SD

PPSD

EPA

lgae

SM

SBM

SPC

Ala

30.0

6j ±

0.17

44.3

5c ±

0.37

36.5

8f ±

0.38

40.8

6d ±

0.28

35.1

5g ±

0.27

44.5

7c ±

0.33

40.7

8d ±

0.36

18.1

3l ±

0.21

38.4

5e ±

0.41

48.5

1b ±

0.12

33.5

9i ±

0.26

58.1

2a ±

0.33

19.4

8k ±

0.21

34.3

8h ±

0.28

Arg

24.7

9k ±

0.21

47.2

2e ±

0.37

35.6

1h ±

0.25

58.0

8a ±

0.30

36.0

4h ±

0.21

34.2

0i ±

0.35

40.1

3f ±

0.23

23.1

0l ±

0.24

40.7

6f ±

0.52

48.5

8d ±

0.19

38.0

3g ±

0.31

51.6

5c ±

0.25

30.7

8j ±

0.20

55.8

6b ±

0.29

Asn

18.6

3h ±

0.08

25.9

1d ±

0.22

23.8

7e ±

0.14

17.7

6i ±

0.13

22.5

6f ±

0.13

22.6

7f ±

0.20

25.8

4d ±

0.31

11.8

2j ±

0.06

25.4

1d ±

0.13

25.6

3d ±

0.32

26.9

1c ±

0.11

33.3

8b ±

0.14

20.6

5g ±

0.14

36.1

0a ±

0.06

Asp

29.8

5j ±

0.13

38.9

8d ±

0.34

32.7

5h ±

0.21

30.4

7i ±

0.23

32.9

5h ±

0.20

33.4

9g ±

0.29

37.7

9e ±

0.47

21.9

6k ±

0.15

37.7

1e ±

0.19

51.6

2b ±

0.63

35.8

5f ±

0.14

42.5

6c ±

0.18

30.6

1i ±

0.21

55.7

6a ±

0.10

Cys

A6.

78g ±

0.04

10.6

1e ±

0.16

11.5

4d ±

0.18

41.1

5a ±

0.21

6.68

gh ±

0.09

6.97

g ± 0.

036.

47h ±

0.05

5.71

i ± 0.

0910

.29e

± 0.

1826

.42b

± 0.

2413

.67c

± 0.

278.

78f ±

0.07

6.96

g ± 0.

0613

.59c

± 0.

13G

ln23

.95l

± 0.

0738

.32e

± 0.

2236

.90g

± 0.

2629

.11j

± 0.

1735

.94h

± 0.

1533

.89i

± 0.

1539

.56d

± 0.

2327

.83k

± 0.

3234

.11i

± 0.

1744

.86b

± 0.

4928

.97j

± 0.

1542

.33c

± 0.

2637

.75f

± 0.

2669

.21a

± 0.

35G

lu32

.73n

± 0.

0753

.15g

± 0.

3158

.82d

± 0.

4448

.97j

± 0.

2952

.49h

± 0.

2349

.78i

± 0.

2357

.46e

± 0.

3543

.11l

± 0.

2246

.56k

± 0.

2464

.29b

± 0.

7454

.62f

± 0.

2861

.89c

± 0.

4141

.34m

± 0.

2983

.47a

± 0.

42G

ly28

.42j

± 0.

2358

.78d

± 0.

3980

.34b

± 0.

2789

.48a

± 0.

4042

.20g

± 0.

3149

.69f

± 0.

5557

.51e

± 0.

3542

.37g

± 0.

3367

.45c

± 0.

3433

.39i

± 0.

3924

.44k

± 0.

1541

.85g

± 0.

3122

.83l

± 0.

2335

.86h

± 0.

30H

is15

.97c

± 0.

1913

.51e

± 0.

146.

40l ±

0.04

8.91

h ± 0.

0513

.54e

± 0.

168.

68h ±

0.22

13.5

2e ±

0.20

7.05

i ± 0.

1112

.99f

± 0.

1436

.36a

± 0.

7014

.46d

± 0.

1412

.89f

± 0.

1611

.41g

± 0.

2620

.79b

± 0.

23H

yp12

.13e

± 0.

1118

.42c

± 0.

4815

.54d

± 0.

1949

.64a

± 0.

4315

.54d

± 0.

2917

.75c

± 0.

2218

.54c

± 0.

445.

35f ±

0.10

22.3

8b ±

0.24

0.17

h ± 0.

010.

22g ±

0.01

0.14

hi ±

0.01

0.08

9j ±

0.00

30.

13i ±

0.01

Ile19

.95i

± 0.

1626

.94f

± 0.

2935

.30c

± 0.

4637

.68b

± 0.

3723

.81h

± 0.

1526

.69f

± 0.

3224

.99g

± 0.

3612

.01j

± 0.

3123

.36h

± 0.

2627

.68e

± 0.

1429

.68d

± 0.

2940

.82a

± 0.

2420

.25i

± 0.

2737

.70b

± 0.

26Le

u31

.73m

± 0.

2052

.40f

± 0.

2855

.61e

± 0.

3268

.90b

± 0.

3644

.19i

± 0.

1850

.92g

± 0.

3441

.36k

± 0.

2720

.86n

± 0.

1942

.58j

± 0.

3875

.40a

± 0.

3546

.02h

± 0.

3763

.13c

± 0.

2834

.43l

± 0.

4057

.87d

± 0.

22Ly

s31

.90j

± 0.

3044

.93e

± 0.

3746

.78d

± 0.

5421

.41l

± 0.

1843

.78f

± 0.

2551

.30b

± 0.

2444

.07f

± 0.

2421

.17l

± 0.

2734

.84i

± 0.

3668

.39a

± 0.

2840

.85h

± 0.

3141

.76g

± 0.

3128

.02k

± 0.

2650

.39c

± 0.

31M

et11

.87h

± 0.

0814

.20f

± 0.

1614

.93e

± 0.

207.

43i ±

0.05

19.5

4d ±

0.35

21.1

0b ±

0.21

19.1

4d ±

0.18

6.56

j ± 0.

1313

.66g

± 0.

1619

.62d

± 0.

1920

.10c

± 0.

1621

.64a

± 0.

225.

98k ±

0.05

11.7

1h ±

0.32

Phe

21.6

1h ±

0.19

26.8

1f ±

0.19

34.1

1d ±

0.16

39.4

3bc ±

0.23

22.7

0h ±

0.20

22.3

3h ±

0.25

24.1

0g ±

0.26

10.5

2i ±

0.22

22.8

0h ±

0.26

47.3

2a ±

0.25

30.3

6e ±

0.30

38.7

4c ±

0.22

21.9

8h ±

0.29

40.3

8b ±

0.64

Pro

28.4

7i ±

0.26

42.7

5d ±

0.64

50.4

7b ±

0.48

115.

9a ±

0.89

36.7

9f ±

0.38

41.4

6e ±

0.24

44.2

5c ±

0.44

17.2

2k ±

0.27

50.3

7b ±

0.31

43.0

8d ±

0.34

33.8

8g ±

0.34

31.1

6h ±

0.29

24.3

3j ±

0.24

34.7

7g ±

0.34

Ser

22.8

1l ±

0.18

30.3

0h ±

0.43

59.6

5b ±

0.36

88.9

7a ±

0.38

24.9

1k ±

0.16

28.6

3i ±

0.34

32.3

5g ±

0.31

21.6

5m ±

0.36

25.5

5j ±

0.20

49.8

5d ±

0.37

53.8

2c ±

0.27

43.3

9f ±

0.29

21.3

7m ±

0.22

48.2

7e ±

0.26

Thr

25.1

4g ±

0.27

27.5

3f ±

0.31

17.4

5h ±

0.22

39.1

1c ±

0.19

24.6

9g ±

0.25

27.5

1f ±

0.44

30.3

2e ±

0.24

15.7

5i ±

0.21

25.0

4g ±

0.21

44.3

9a ±

0.19

30.9

3e ±

0.32

41.2

6b ±

0.19

17.7

8h ±

0.09

32.6

6d ±

0.18

Trp

6.98

g ± 0.

077.

54f ±

0.10

9.68

d ± 0.

107.

92e ±

0.07

6.91

g ± 0.

046.

38h ±

0.09

6.19

h ± 0.

042.

09i ±

0.07

6.23

h ± 0.

0513

.60a

± 0.

179.

64d ±

0.08

10.1

8c ±

0.12

6.20

h ± 0.

0612

.10b

± 0.

20Ty

r35

.94b

± 0.

1922

.74f

± 0.

2022

.54f

± 0.

1421

.22g

± 0.

3518

.53i

± 0.

2719

.28h

± 0.

3922

.42f

± 0.

269.

90k ±

0.16

18.3

5i ±

0.24

35.0

0c ±

0.21

26.0

3e ±

0.27

37.8

5a ±

0.23

16.6

9j ±

0.11

28.6

3d ±

0.12

Val

28.2

1i ±

0.23

32.8

9g ±

0.20

52.5

3b ±

0.37

57.9

4a ±

0.35

29.6

3h ±

0.25

35.4

5f ±

0.18

28.6

9i ±

0.24

13.6

5k ±

0.25

28.3

7i ±

0.28

49.4

9c ±

0.30

35.6

4f ±

0.27

43.5

3d ±

0.27

20.7

1j ±

0.45

38.1

8e ±

0.28

532 P. Li, G. Wu

1 3

protein concentrate. In algae spirulina meal, glutamate was the second most abundant AA in their peptide-bound AA, followed by alanine, arginine, valine, serine, aspartate and glutamine in descending order. In both soybean meal and soy protein concentrate, glutamine was the second most abun-dant AA in their peptide-bound AA, followed by leucine, arginine, aspartate, and lysine in descending order.

Content of AAs in the PCA‑soluble peptides of feedstuffs

Data on the content of AAs in the PCA-soluble peptides (i.e., AAs in small and large peptides called oligopeptides) of feedstuffs are summarized in Table 6. The patterns of AAs in oligopeptides were very different from those in total pep-tides (i.e., oligopeptides plus proteins, Table 7). The most noticeable differences were that, in contrast to total peptides (oligo- plus poly-peptides), (a) phenylalanine and tyrosine were the first and second least abundant AA in the oligo-peptides of BSFM; (b) the content of 4-hydroxyproline was greater than that of proline in the oligopeptides of chicken by-product meal; (c) 4-hydroxyproline was barely detectable in the oligopeptides of both spray-dried poultry plasma and egg product; (d) methionine was the least abundant AA in the oligopeptides of feather meal and SDPM and was the third least abundant AA in the oligopeptides of chicken vis-ceral digest, father meal, Southeast Asian fishmeal, SDPM, poultry by-product meal (pet-food grade), and spray-dried poultry plasma; (e) histidine was the second least abundant AA in the oligopeptides of feather meal; and (f) methionine was the least abundant AA in the oligopeptides of soybean meal and soy protein concentrate and was the fourth least abundant proteinogenic AA in the oligopeptides of algae spirulina meal.

The PCA-soluble fraction in all of the animal-source feedstuffs contained various amounts of carnosine (Table 8). Except for the three fishmeal feedstuffs and BSFM, all of the analyzed animal-source feedstuffs contained various amounts of anserine (Table 8). Among the ten animal-source feedstuffs, the content of carnosine was the highest (P < 0.05) in chicken by-product meal, followed by spray-dried poultry plasma, SDPM, Peruvian fishmeal, and poultry by-product meal (pet-food grade) in descending order. The content of anserine was the highest (P < 0.05) in chicken by-product meal, followed by poultry by-product meal (pet-food grade), spray-dried poultry plasma, SDPM, and chicken visceral digest in descending order. Carnosine and anserine were absent from the plant-source feedstuffs (Table 8). All of the animal- and plant-source feedstuffs analyzed in the present study did not contain balenine.

Alanine was the most abundant AA in the oligopeptides of Menhaden fishmeal; glutamate in the oligopeptides of BSFM and SDPM; glycine in chicken by-product meal,

chicken visceral digest, Peruvian fishmeal, Southeast Asian fishmeal, poultry by-product meal (pet-food grade), and egg product; and serine in feather meal and spray-dried poultry plasma. Glutamine was the second most abundant AA in the oligopeptides of BSFM; glutamate in the oligopeptides of chicken by-product meal, chicken visceral digest, Peruvian fishmeal, Southeast Asian fishmeal, poultry by-product meal (pet-food grade), and spray-dried poultry plasma; and gly-cine and proline in the oligopeptides of SDPM and feather meal, respectively. Glycine was the third most abundant AA in the oligopeptides of BSFM, feather meal and Menhaden fishmeal; serine in the oligopeptides of chicken visceral digest and Peruvian fishmeal; as well as alanine, arginine, glutamate, leucine, and proline in the oligopeptides of chicken by-product meal, poultry by-product meal (pet-food grade), egg product, spray-dried poultry plasma, and South-east Asian fishmeal, respectively. Serine was the fourth most abundant AA in the oligopeptides of BSFM and Menhaden fishmeal; arginine in the oligopeptides of chicken by-product meal and feather meal; alanine in the oligopeptides of Peru-vian fishmeal, Southeast Asian fishmeal, poultry by-product meal (pet-food grade), and spray-dried poultry plasma; leu-cine in the oligopeptides of chicken visceral digest and egg product; and aspartate in the oligopeptides of SDPM. In all animal-source feedstuffs except for Southeast Asian fishmeal and poultry by-product meal (pet-food grade), the content of tryptophan in the oligopeptides was lower (P < 0.05) than the content of cysteine, but the opposite was true for South-east Asian fishmeal and poultry by-product meal (pet-food grade).

Glutamate was the most abundant AA in the oligopep-tides of algae spirulina meal, and serine in the oligopeptides of soybean meal and soy protein concentrate. In algae spir-ulina meal, serine was the second most abundant AA in their oligopeptides, followed by aspartate, alanine, glutamine, threonine, asparagine, and leucine in descending order. In both soybean meal and soy protein concentrate, glutamate was the second most abundant AA in their oligopeptides, followed by glutamine, glycine, and aspartate in descend-ing order.

Content of AAs in the PCA‑insoluble peptides of feedstuffs

Data on the content of AAs in the PCA-insoluble polypep-tides (i.e., proteins) of feedstuffs are summarized in Table 7. For all animal-source feedstuffs except for BSFM, chicken by-product meal, chicken visceral digest, and SDPM, the patterns of AA in proteins of the analyzed feedstuffs were generally similar to those in the total peptides (i.e., oligo-peptides plus proteins, Table 7). Tyrosine was still the most abundant AA in the proteins of BSFM, lysine, leucine, ala-nine, and valine were the second, third, fourth, and fifth most

533Composition of amino acids and related nitrogenous nutrients in feedstuffs for animal diets

1 3

Tabl

e 6

Con

tent

of a

min

o ac

ids i

n th

e PC

A-s

olub

le p

eptid

es (s

mal

l and

larg

e pe

ptid

es) o

f ani

mal

- and

pla

nt-d

eriv

ed fe

edstu

ffs

Valu

es, e

xpre

ssed

as g

/kg

feed

(as-

fed

basi

s), a

re m

eans

± S

EM, n

= 6

A C

yste

ine +

½ c

ystin

ea −

l : W

ithin

a ro

w, m

eans

not

shar

ing

the

sam

e su

pers

crip

t let

ter d

iffer

(P <

0.05

)BS

FM b

lack

sol

dier

fly

larv

ae m

eal;

CBP

M c

hick

en b

y-pr

oduc

t mea

l; C

VD c

hick

en v

isce

ral d

iges

t; FM

-M fi

shm

eal (

Uni

ted

Stat

es M

enha

den)

; FM

-P fi

shm

eal (

Peru

vian

anc

hovy

); FM

-SE

fish-

mea

l (So

uthe

ast A

sian

mis

cella

neou

s mar

ine

fishe

s); H

yp 4

-hyd

roxy

prol

ine;

PBM

(PFG

) pou

ltry

by-p

rodu

ct m

eal (

pet-f

ood

grad

e); P

CA p

erch

loric

aci

d; S

BM s

oybe

an m

eal;

SDEP

spr

ay-d

ried

egg

prod

uct;

SDPM

spra

y-dr

ied

pept

one

from

enz

ymes

-trea

ted

porc

ine

muc

osal

tiss

ues;

SD

PP sp

ray-

drie

d po

ultry

pla

sma;

SM

spiru

lina

mea

l; SP

C so

y pr

otei

n co

ncen

trate

Am

ino

acid

Ani

mal

-sou

rce

feed

stuffs

Plan

t-sou

rce

feed

stuffs

BSF

MC

BPM

CV

DFe

athe

r m

eal

FM-M

FM-P

FM-S

ESD

PMPB

M (P

FG)

SDPP

SDEP

Alg

ae S

MSB

MSP

C

Ala

2.39

h ± 0.

038.

83c ±

0.10

26.6

2a ±

0.43

2.36

h ± 0.

0310

.62b

± 0.

325.

29e ±

0.05

10.7

9b ±

0.46

8.81

c ± 0.

247.

05d ±

0.07

3.43

g ± 0.

052.

31h ±

0.08

4.15

f ± 0.

051.

67i ±

0.05

1.54

i ± 0.

03A

rg1.

43j ±

0.04

7.96

d ± 0.

0821

.63a

± 0.

363.

13g ±

0.04

10.3

2b ±

0.29

4.54

e ± 0.

037.

82d ±

0.12

8.54

c ± 0.

337.

82d ±

0.07

2.54

h ± 0.

051.

97i ±

0.03

3.79

f ± 0.

061.

82i ±

0.05

1.27

j ± 0.

05A

sn0.

88k ±

0.03

4.01

d ± 0.

0318

.34a

± 0.

291.

29i ±

0.02

2.10

g ± 0.

072.

47f ±

0.04

5.45

c ± 0.

049.

74b ±

0.24

3.09

e ± 0.

021.

53h ±

0.02

2.09

g ± 0.

023.

20e ±

0.05

1.65

h ± 0.

040.

98j ±

0.01

Asp

1.77

i ± 0.

045.

19d ±

0.03

25.1

3a ±

0.43

1.90

i ± 0.

032.

92g ±

0.10

3.46

f ± 0.

058.

59c ±

0.09

13.9

6b ±

0.54

4.20

e ± 0.

033.

37f ±

0.05

2.71

g ± 0.

034.

36e ±

0.07

2.35

h ± 0.

061.

24j ±

0.02

Cys

A0.

47h ±

0.01

1.42

b ± 0.

041.

24c ±

0.04

2.95

a ± 0.

080.

61f ±

0.01

0.62

f ± 0.

010.

24l ±

0.01

0.75

de ±

0.04

0.33

j ± 0.

010.

80d ±

0.03

0.52

g ± 0.

020.

27k ±

0.01

0.72

e ± 0.

010.

40i ±

0.01

Gln

4.69

f ± 0.

047.

02d ±

0.07

24.6

1a ±

0.18

1.66

j ± 0.

022.

90h ±

0.03

4.46

fg ±

0.04

9.37

c ± 0.

1312

.57b

± 0.

146.

31e ±

0.05

3.11

h ± 0.

062.

15i ±

0.03

4.14

g ± 0.

083.

03h ±

0.03

2.23

i ± 0.

03G

lu6.

40f ±

0.05

9.22

d ± 0.

0944

.29a

± 0.

322.

38k ±

0.04

4.17

hi ±

0.04

6.04

f ± 0.

0613

.50c

± 0.

2433

.30b

± 0.

278.

61e ±

0.08

4.55

h ± 0.

143.

90i ±

0.05

5.45

g ± 0.

223.

18j ±

0.04

2.44

k ± 0.

04G

ly3.

00j ±

0.03

16.8

2d ±

0.34

55.6

5a ±

0.40

3.36

i ± 0.

067.

56g ±

0.08

8.51

f ± 0.

0519

.79c

± 0.

1520

.57b

± 0.

4017

.18d

± 0.

373.

28i ±

0.06

15.0

2e ±

0.34

5.06

h ± 0.

062.

48k ±

0.04

2.18

l ± 0.

04H

is2.

54b ±

0.05

1.63

d ± 0.

023.

76a ±

0.02

0.54

h ± 0.

012.

56b ±

0.09

0.76

g ± 0.

021.

77d ±

0.03

2.15

c ± 0.

101.

28e ±

0.03

2.33

bc ±

0.02

0.84

f ± 0.

020.

54h ±

0.01

0.77

g ± 0.

010.

55h ±

0.01

Hyp

0.65

h ± 0.

011.

31g ±

0.02

13.6

9a ±

0.34

1.68

f ± 0.

022.

80d ±

0.07

1.54

e ± 0.

085.

64b ±

0.08

3.36

c ± 0.

081.

37g ±

0.03

0.00

2k ±

0.00

00.

001k

± 0.

000

0.00

7j ±

0.00

00.

029i

± 0.

003

0.02

0i ±

0.00

0Ile

1.11

e ± 0.

032.

59cd

± 0.

0421

.52a

± 0.

600.

82g ±

0.01

1.05

ef ±

0.02

2.72

c ± 0.

052.

53cd

± 0.

046.

50b ±

0.38

0.77

h ± 0.

020.

93f ±

0.01

1.11

e ± 0.

022.

32d ±

0.04

1.18

e ± 0.

050.

45i ±

0.01

Leu

2.29

g ± 0.

034.

38d ±

0.04

35.0

5a ±

0.37

2.09

h ± 0.

032.

51g ±

0.03

3.23

e ± 0.

034.

76c ±

0.05

5.34

b ± 0.

152.

00h ±

0.03

4.32

d ± 0.

053.

15e ±

0.03

2.85

f ± 0.

021.

87i ±

0.04

1.16

j ± 0.

02Ly

s2.

23f ±

0.03

3.94

d ± 0.

0421

.97a

± 0.

460.

64j ±

0.01

2.22

f ± 0.

053.

80d ±

0.03

7.24

c ± 0.

125.

58b ±

0.14

1.86

g ± 0.

022.

98e ±

0.06

2.92

e ± 0.

041.

60h ±

0.04

1.35

i ± 0.

020.

40k ±

0.01

Met

0.66

e ± 0.

011.

73a ±

0.03

1.53

c ± 0.

030.

52g ±

0.01

1.62

b ± 0.

031.

76a ±

0.02

0.57

f ± 0.

030.

44h ±

0.02

0.76

d ± 0.

010.

57f ±

0.01

0.60

f ± 0.

010.

65e ±

0.01

0.61

f ± 0.

010.

35i ±

0.01

Phe

0.31

j ± 0.

012.

20cd

± 0.

0316

.13a

± 0.

210.

96g ±

0.02

2.13

cd ±

0.03

2.37

c ± 0.

030.

71i ±

0.06

5.24

b ± 0.

221.

90e ±

0.04

2.05

de ±

0.06

0.90

g ± 0.

011.

40f ±

0.02

0.82

h ± 0.

010.

66i ±

0.01

Pro

2.14

h ± 0.

061.

06j ±

0.02

31.0

0a ±

0.78

3.56

e ± 0.

046.

45d ±

0.09

3.59

e ± 0.

0112

.69b

± 0.

1310

.68c

± 0.

462.

89f ±

0.09

2.67

g ± 0.

070.

86k ±

0.01

1.41

i ± 0.

021.

11j ±

0.02

0.73

l ± 0.

01Se

r2.

73i ±

0.02

5.85

e ± 0.

0742

.49a

± 0.

265.

59e ±

0.06

7.23

d ± 0.

055.

89e ±

0.06

8.16

c ± 0.

2011

.56b

± 0.

455.

54fg

± 0.

055.

98e ±

0.05

5.68

ef ±

0.05

5.35

g ± 0.

063.

71h ±

0.07

2.83

i ± 0.

04Th

r1.

31i ±

0.03

4.59

d ± 0.

0714

.02a

± 0.

331.

63h ±

0.05

3.35

f ± 0.

154.

43d ±

0.13

6.48

c ± 0.

059.

75b ±

0.47

3.15

f ± 0.

072.

72g ±

0.05

2.52

g ± 0.

103.

85e ±

0.04

1.48

hi ±

0.03

1.05

j ± 0.

02Tr

p0.

41g ±

0.01

0.93

a ± 0.

020.

82b ±

0.02

0.56

d ± 0.

010.

52e ±

0.01

0.29

i ± 0.

010.

36h ±

0.01

0.47

f ± 0.

030.

38gh

± 0.

010.

41g ±

0.01

0.28

i ± 0.

010.

30i ±

0.01

0.63

c ± 0.

010.

37h ±

0.01

Tyr

0.64

f ± 0.

042.

15c ±

0.02

7.32

a ± 0.

220.

56g ±

0.01

2.12

c ± 0.

042.

08c ±

0.03

1.22

d ± 0.

023.

79b ±

0.27

0.81

e ± 0.

030.

82e ±

0.01

0.67

f ± 0.

011.

03d ±

0.03

0.62

f ± 0.

010.

48h ±

0.01

Val

1.59

g ± 0.

033.

37e ±

0.05

32.2

0a ±

0.70

0.96

i ± 0.

031.

70g ±

0.03

3.60

d ± 0.

053.

95c ±

0.05

7.00

b ± 0.

281.

38h ±

0.04

1.34

h ± 0.

032.

34f ±

0.04

2.39

f ± 0.

051.

21i ±

0.03

0.60

k ± 0.

01

534 P. Li, G. Wu

1 3

Tabl

e 7

Con

tent

of a

min

o ac

ids i

n th

e PC

A-in

solu

ble

poly

pept

ides

(pro

tein

s) o

f ani

mal

- and

pla

nt-d

eriv

ed fe

edstu

ffs

Valu

es, e

xpre

ssed

as g

/kg

feed

(as-

fed

basi

s), a

re m

eans

± S

EM, n

= 6

BSFM

bla

ck s

oldi

er fl

y la

rvae

mea

l; C

BPM

chi

cken

by-

prod

uct m

eal;

CVD

chi

cken

vis

cera

l dig

est;