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Determination and prediction of the energy content and amino acid digestibility of peanut meals fed to growing pigs a
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Qingyun Li , Xiangshu Piao , Jundi Liu , Zhikai Zeng , Sai Zhang & b
Xinjian Lei a
State Key Laboratory of Animal Nutrition, Ministry of Agriculture Feed Industry Centre, China Agricultural University, Beijing, China b
Faculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China Published online: 29 May 2014.
To cite this article: Qingyun Li, Xiangshu Piao, Jundi Liu, Zhikai Zeng, Sai Zhang & Xinjian Lei (2014) Determination and prediction of the energy content and amino acid digestibility of peanut meals fed to growing pigs, Archives of Animal Nutrition, 68:3, 196-210, DOI: 10.1080/1745039X.2014.910970 To link to this article: http://dx.doi.org/10.1080/1745039X.2014.910970
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Archives of Animal Nutrition, 2014 Vol. 68, No. 3, 196–210, http://dx.doi.org/10.1080/1745039X.2014.910970
Determination and prediction of the energy content and amino acid digestibility of peanut meals fed to growing pigs Qingyun Lia, Xiangshu Piaoa*, Jundi Liua, Zhikai Zenga, Sai Zhanga and Xinjian Leib
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State Key Laboratory of Animal Nutrition, Ministry of Agriculture Feed Industry Centre, China Agricultural University, Beijing, China; bFaculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China (Received 17 January 2014; accepted 24 March 2014) Two experiments were conducted to determine the content of digestible energy (DE) and metabolisable energy (ME) as well as the apparent ileal digestibility (AID) and standardised ileal digestibility (SID) of amino acids in peanut meal (PNM) for growing pigs. In Experiment 1, 78 growing pigs (46.8 ± 2.6 kg) were randomly allotted to 1 of 13 diets, including a corn–soya bean meal basal diet and 12 PNM test diets. In Experiment 2, 12 growing barrows (48.7 ± 2.8 kg) were allotted to one of two 6 × 6 Latin squares. The treatments include a N-free diet and 10 PNM test diets. The results of Experiment 1 showed that the DE and ME differed (p < 0.05) among the 12 PNM samples. On a dry matter basis, the DE and ME content ranged from 14.5 to 16.4 MJ/ kg (mean 15.6 MJ/kg) and from 12.7 to 15.5 MJ/kg (mean 13.9 MJ/kg), respectively. The apparent total tract digestibility (ATTD) of gross energy (GE) was 82.2%. The DE of PNM could be precisely predicted by equations including NDF combined with GE or crude protein (CP) with an R2 value of 0.91 and 0.92, respectively. For the AID and SID for lysine, the results of Experiment 2 indicated variations among PNM sources ranging from 59.6% to 76.7% and 64.8% to 80.9%, respectively. However, for CP, variations for AID and SID were lower and ranged from 70.2% to 81.9% and 75.7% to 85.6%, respectively. The results indicate that the concentration of lysine was the best single predictor to estimate the digestibility of amino acids. However, further work is needed to investigate the reason for the variation in the digestibility of lysine and avoid processing procedures that are detrimental to lysine digestibility. Keywords: amino acids; digestibility; energy content; equations; peanut oilmeal; pigs; prediction
1. Introduction Peanut meal (PNM) is a by-product of oil extraction from whole or broken peanuts and the solvent-extracted PNM is increasingly being used as an animal feed (Dale and Batal 2005), since the tight supply of protein sources drives feed manufacturers to pay more attention to more economical protein ingredients in place of soya bean meal (Sulabo et al. 2013). Annual global production of peanuts has been on the increase, reaching 35 million tons in recent years, while 12 million tons were generated in China alone, accounting for 34% of world production (Revoredo and Fletcher 2002). As a result, 3.5 million tons of PNM is being produced each year (Revoredo and Fletcher 2002), which provides a considerable amount of protein for the feed industry. *Corresponding author. Email: [email protected] © 2014 Taylor & Francis
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The use of PNM as an alternative protein source has been evaluated in poultry (Costa et al. 2001; Pesti et al. 2003), pigs (Orok et al. 1975; Balogun and Koch 1979; Adeola 2009) and shrimp (Liu et al. 2012). The variable effects of PNM on performance may be the result of limited data on the energy content and amino acid digestibility of PNM to allow more accurate feed formulation. Since PNM has gone through heat treatment (Hou et al. 2004), there is a risk of reduced digestibility of amino acids caused by Maillard reactions (Stein et al. 2006). Dale and Batal (2005) also reported a considerable variation in N-corrected metabolisable energy (ME) for chickens among 17 PNM samples, which ranged from 2273 to 3009 kcal/kg (9.5–12.6 MJ/kg). To include PNM in feed formulation, for the swine industry, it is important to understand the variation of nutrient digestibility and to estimate its value accurately. Therefore, the objectives of this study were to determine the chemical composition and the contents of digestible energy (DE) and ME as well as the amino acid digestibility in PNM and to develop equations to predict the energy content and digestibility of amino acids based on its chemical composition.
2. Materials and methods 2.1. General The Institutional Animal Care and Use Committee at China Agricultural University (Beijing, China) reviewed and approved the protocols used in this study. Twelve commercial PNM samples were obtained from eight peanut oil plants in three provinces (Hebei, Shandong and Henan), which are the main peanut-producing areas located in the east coast and midland of China. All PNM samples were produced from peanut kernels by the pre-press extraction method. Their chemical composition is shown in Table 1.
2.2. Experiment 1 Experiment 1 was conducted to determine the DE and ME contents of PNM and to develop prediction equations based on the chemical composition of PNM. Seventy-eight cross-bred barrows (Duroc × Landrace × Yorkshire), weighing 46.8 ± 2.6 kg, were allotted to 13 diets according to a completely randomised design, including one corn– soya bean meal basal diet and 12 PNM test diets (Table 2). Each diet was fed to six replicate pigs. The basal diet contained 89.7% corn and 6.05% dehulled soya bean meal. Crystalline amino acids were added to balance the dietary amino acid composition (Ji et al. 2012). The test diets were formulated to contain 19.4% PNM at the expense of corn, soya bean meal and amino acids. This value was chosen on the basis of a preliminary experiment, which was conducted to determine the inclusion level of PNM in Experiment 1. Because Ilori et al. (1984) reported that PNM comprised between 20% and 25% of the diet in most swine formulations, in this preliminary experiment, 9.70%, 14.55%, 19.40% or 24.25% of PNM were included in the diets. The results revealed that the optimal inclusion rate was 19.4% (data are not shown). Furthermore, vitamins and minerals were supplemented to all diets to meet or exceed the estimated nutrient requirements for growing pigs, as recommended by NRC (1998). All ingredients were ground through a 2.5-mm screen (hammer mill). All pigs were individually housed in stainless steel metabolism cages (1.44 × 0.66 × 1.22 m3) with a feeder and a nipple drinker placed in an environmentally controlled room with a temperature maintained at 22 ± 2°C. Two equal-sized meals were
5.9 1.3 3.3 1.7 1.8 0.6 2.5 1.4 0.5 2.1
2.2 6.0 0.6 9.1 3.1 2.3 2.4 1.6
Indispensable amino acids Arginine Histidine Leucine Isoleucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine
Dispensable amino acids Alanine Aspartic acid Cystine Glutamic acid Glycine Proline Serine Tyrosine 2.2 6.2 0.6 9.3 3.1 2.3 2.5 1.6
5.8 1.3 3.4 1.8 1.6 0.6 2.6 1.4 0.5 2.2
89.1 58.0 1.8 23.7 8.8 7.0 0.28 0.80 19.3
2
2.3 6.5 0.6 9.8 3.3 2.4 2.6 1.7
6.0 1.3 3.5 1.8 1.6 0.5 2.7 1.5 0.5 2.3
89.9 57.8 0.4 18.6 8.2 6.6 0.24 0.83 19.2
3
2.0 5.7 0.6 8.5 2.8 2.1 2.3 1.8
5.7 1.2 3.1 1.6 1.8 0.5 2.4 1.4 0.5 2.0
89.3 52.0 0.9 14.8 6.7 7.0 0.25 0.73 19.4
4
2.3 6.6 0.6 10.0 3.4 2.4 2.7 1.6
6.3 1.3 3.6 1.9 1.8 0.6 2.7 1.5 0.6 2.3
89.9 59.2 0.3 21.9 7.9 6.4 0.24 0.88 18.9
5
2.1 6.0 0.6 9.0 3.1 2.2 2.4 1.6
5.7 1.2 3.2 1.7 1.7 0.6 2.5 1.4 0.5 2.1
89.3 57.1 0.4 23.1 7.0 6.5 0.22 0.86 19.5
6
2.2 6.5 0.6 9.8 3.3 2.4 2.6 1.6
5.9 1.3 3.5 1.8 1.7 0.6 2.7 1.5 0.5 2.3
90.3 57.8 1.1 25.1 8.9 6.4 0.25 0.83 18.9
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Peanut meal number*
2.2 6.3 0.6 9.5 3.2 2.3 2.6 1.6
5.8 1.7 3.4 1.8 1.7 0.5 2.6 1.5 0.5 2.2
90.3 55.1 0.9 25.0 8.2 7.2 0.13 0.78 18.7
8
2.2 6.4 0.7 9.6 3.2 2.4 2.6 1.7
6.2 1.3 3.4 1.8 1.8 0.5 2.7 1.5 0.5 2.2
90.5 57.5 0.8 23.8 9.1 7.4 0.26 0.79 19.1
9
2.2 6.4 0.6 9.5 3.1 2.4 2.6 1.6
6.2 1.3 3.4 1.8 1.9 0.5 2.7 1.5 0.5 2.2
89.6 57.6 1.4 21.0 8.2 8.2 0.33 0.78 19.4
10
2.1 6.2 0.7 9.4 3.1 2.3 2.5 1.5
6.0 1.3 3.4 1.7 1.9 0.6 2.6 1.4 0.5 2.1
87.5 53.7 0.7 28.2 9.6 8.1 0.38 0.69 19.0
11
2.1 5.9 0.6 8.8 2.9 2.1 2.4 1.6
5.8 1.2 3.2 1.7 1.8 0.5 2.5 1.4 0.5 2.1
90.6 53.4 0.8 22.7 8.3 5.7 0.21 0.77 18.7
12
2.2 6.2 0.6 9.4 3.1 2.3 2.5 1.6
5.9 1.3 3.4 1.8 1.8 0.6 2.6 1.5 0.5 2.2
89.8 56.3 0.9 22.7 8.3 7.1 0.25 0.79 19.1
Mean
4.0 4.4 6.3 4.7 5.3 4.9 4.7 4.6
3.4 10.0 4.3 4.5 5.7 9.5 4.0 3.6 5.7 4.4
1.1 4.0 49.5 15.1 10.3 11.2 24.2 6.7 1.6
CV‡
Notes: *Origin of peanut meals 1–4, 5–8 and 9–12 were Hebei, Shandong and Henan Provinces of China, respectively; ‡CV, Coefficient of variation; #NDF, Neutral detergent fibre; † ADF, Acid detergent fibre.
91.4 56.2 1.3 24.3 9.2 8.1 0.25 0.76 18.6
1
Analysed nutrient contents of the 12 sources of peanut meal.
Dry matter [%] Crude protein [% of DM] Ether extract [% of DM] NDF# [% of DM] ADF† [% of DM] Ash [% of DM] Calcium [% of DM] Phosphorus [% of DM] Gross energy [MJ/kg]
Table 1.
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Archives of Animal Nutrition Table 2.
Ingredients and nutrient contents of experimental diets [% as-fed]. Experiment 1
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Ingredients Corn Soya bean meal Peanut meal Cornstarch Soya bean oil Sucrose Cellulose acetate* Dicalcium phosphate Limestone Sodium chloride Chromic oxide Potassium carbonate Magnesium oxide L-lysine · HCl DL-methionine L-threonine L-tryptophan Mineral and vitamin premix# Analysed nutrient contents Dry matter Crude protein Calcium Phosphorus
Experiment 2
Basal diet
Peanut meal diets
N-free diet
Peanut meal diets
89.70 6.05 – – – – – 1.70 0.50 0.30 – – – 0.75 0.10 0.30 0.10 0.50
71.76 4.84 19.40 – – – – 1.70 0.50 0.30 – – – 0.60 0.08 0.24 0.08 0.50
– – – 73.35 3.00 15.00 4.00 2.50 0.50 0.45 0.30 0.30 0.10 – – – – 0.50
– – 35.00 47.00 – 15.00 – 1.50 0.40 0.30 0.30 – – – – – – 0.50
86.1 11.0 0.66 0.56
87.3 18.3 0.62 0.53
90.3 0.32 0.67 0.48
90.9 18.0 0.61 0.51
Notes: *Provided by Chemical Reagents Company, Beijing, China; #Provided per kg of complete diet for growing pigs: vitamin A, 5512 IU; vitamin D3, 2200 IU; vitamin E, 30 mg; vitamin K3, 2.2 mg; vitamin B12, 27.6 μg; riboflavin, 4 mg; pantothenic acid, 14 mg; niacin, 30 mg; choline chloride, 400 mg; folic acid, 0.7 mg; vitamin B1, 1.5 mg; vitamin B6, 3 mg; biotin, 44 μg; Mn, 40 mg (MnO); Fe, 75 mg (FeSO4 · H2O); Zn, 75 mg (ZnO); Cu, 10 mg (CuSO4 · 5H2O); I, 0.3 mg (KI); Se, 0.3 mg (Na2SeO3).
fed twice a day at 08:00 and 15:30 h at a rate of 4% of individual body weight. Water was freely available from a drinking nipple. The diets were provided in mash form. The experiment lasted 12 d, consisting of a 7-d adaptation to the diets followed by a 5-d total collection of faeces and urine using the methods described by Song et al. (2003) and Ren et al. (2011). Feed refusals and spillage were collected twice daily to be dried and weighed. Faeces that appeared in the metabolism crates were collected immediately in the plastic bags and stored at –20°C. Urine was collected in buckets located under the metabolism crates. The buckets contained 10 ml of 6 N HCl for every 1000 ml of urine and were emptied whenever they were full. The volume of collected urine was measured and 10% of the daily urine collection was stored at –20°C. At the end of the collection period, faeces and urine, pooled over the 5-d period, were separately thawed and mixed within animal, and then a representative subsample was obtained for chemical analysis. Before analysis, faecal subsamples were dried at 65°C in a drying oven for 72 h and ground through a 1-mm screen.
2.3. Experiment 2 Experiment 2 was designed to determine the apparent ileal digestibility (AID) and standardised ileal digestibility (SID) of crude protein (CP) and amino acids in 10 PNM
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samples. Only 10 of the 12 PNM samples were used in Experiment 2, since the PNM Sources 1 and 3 were removed due to their similar amino acid composition to that of Sources 6 and 7. Twelve cross-bred (Duroc × Landrace × Yorkshire) growing barrows (48.7 ± 2.8 kg) were randomly allotted to one of two 6 × 6 Latin square designs with 6 periods and 12 diets. Each Latin square contained one N-free diet and five PNM test diets (Table 2). Pigs were equipped with a simple T-cannula near the distal ileum using the procedures described by Stein et al. (1998). The PNM test diets contained corn starch (47%), sucrose (15%) and PNM (35%) as the sole source of amino acids. The N-free diet was used to measure basal endogenous losses of CP and amino acids. All diets contained 0.3% chromic oxide as an indigestible marker and vitamins and minerals were included to meet or exceed the estimated nutrient requirements for growing pigs, as recommended by NRC (1998). All pigs were provided daily feed equivalent to 4% of body weight, and two equal-sized meals were provided every day at 08:00 and 17:00 h. Pigs had free access to water throughout the experiment. Pig body weights were recorded at the beginning of the experiment and at the end of each period. Each period lasted 7 d, with the initial 5 d to adapt to the diet, and days 6 and 7 to collect ileal digesta from 08:00 to 17:00 h. The procedures used to collect digesta followed the description provided by Stein et al. (1998). Briefly, digesta was collected in plastic bags attached to simple T-cannula until the bags were full and immediately stored in a -20°C freezer after each collection. Ileal digesta samples were thawed, mixed within animal and diet, and a subsample was taken. The digesta samples were lyophilised in a vacuum-freeze dryer (Tofflon Freezing Drying Systems, Minhang District, Shanghai, China) and ground through a 1-mm screen for further chemical analysis.
2.4. Chemical analysis All PNM samples and diets used in this experiment were analysed for dry matter (DM) (AOAC 2007, procedure 930.15), CP (AOAC 2007, 984.13), ash (AOAC 2007, 942.05), calcium (AOAC 2007, 927.02), phosphorus (AOAC 2007, 984.27) and ether extract (EE) (Thiex et al. 2003). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were determined using filter bags and fibre analyser equipment (Fibre Analyzer, Ankom Technology, Macedon, NY, USA) following a modification of the procedure of Van Soest et al. (1991). The GE in PNM, diets, faecal and urine samples were measured using an Automatic Adiabatic Oxygen Bomb Calorimeter (Parr 6300 Calorimeter, Moline, IL, USA). Samples of PNM, diets and ileal digesta were also analysed for the concentration of amino acids. With the exception of methionine, cystine and tryptophan, the amino acid content was determined after hydrolysis with 6 N HCl at 110°C for 24 h using an amino acid analyser (Hitachi L-8900, Tokyo, Japan). Methionine and cystine were determined as methionine sulphone and cysteic acid after cold performic acid oxidation overnight and hydrolysing with 7.5 N HCl at 110°C for 24 h using an amino acid analyser. Tryptophan was determined after LiOH hydrolysis for 22 h at 110°C using high performance liquid chromatography (HPLC) (Agilent 1200 Series, Santa Clara, CA, USA). The chromium concentration of diets and ileal digesta samples were determined after nitric acid–perchloric acid wet ash sample preparation using polarized Zeeman atomic absorption spectrometer (Hitachi Z2000, Tokyo, Japan).
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2.5. Calculations
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In Experiment 1, the energy lost in faeces and urine was calculated for each diet, and the DE and ME in each of the 13 diets were calculated. By subtracting the DE and ME contributed by the corn–soya bean meal basal diet to the PNM test diets, the DE and ME contributed by each source of PNM were calculated by difference (Adeola 2001). The apparent total tract digestibility (ATTD) of GE in each diet was calculated by the method of Stein et al. (2007). In Experiment 2, the AID for each amino acid in the diets containing PNM was calculated using the equations described by Stein et al. (2007): AID ¼ ½1 AAd=AAf ÞðCrf =CrdÞ 100% where AAd is the concentration of amino acids in the ileal digesta [g/kg of DM], AAf is the concentration of amino acids in the diets [g/kg of DM], Crf represents chromium concentration in the diet [g/kg of DM], and Crd represents chromium concentration in the digesta [g/kg of DM]. The AID for CP was also calculated using this equation, where amino acids are replaced by the concentration of the CP in the digesta and diets. The basal endogenous loss of each amino acid (IAAend, g/kg of DMI) at the distal ileum was determined based on the outflow obtained when pigs were fed the N-free diet using the equation of Stein et al. (2007): IAAend ¼ AAdðCrf =CrdÞ where AAd is the concentration of each amino acid in the ileal digesta collected from pigs fed the N-free diet. The endogenous outflow of CP was determined using the same equation, where AAd is replaced by the concentration of the CP in the digesta. By correcting the AID of each amino acid that was calculated for each sample for the IAAend of each amino acid, the SID of each amino acid was calculated using the equation of Stein et al. (2007): SID ¼ AID þ ðIAAend =AAdiet Þ 100%
2.6. Statistical analysis All data were processed using SAS (SAS Inst. Inc., Cary, NC). CORR procedure was adopted for correlation coefficients analyses in Experiment 1. Simple and multiple regression analyses (stepwise regression analysis) were conducted to study the relationship among chemical composition and energy content as well as amino acid digestibility. For selecting the energy and amino acid digestibility prediction equations, the residual standard deviation (RSD) was used as the selection criterion. A smaller RSD was proposed to indicate a better fit. In Experiment 2, data were analysed using the ProcMixed procedure of SAS. The statistical model for the digestibility values had treatment and period as fixed effects and pig as a random effect. When the ANOVA was significant, differences between treatments were tested using least square means (t-tests). In all analyses, the differences were considered significant if p < 0.05.
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3. Results 3.1. Chemical composition of peanut meal The proximate chemical composition and amino acid content of the 12 PNM sources are shown in Table 1, which demonstrated that the collected PNM samples were quite variable. The coefficient of variation (CV) of EE, NDF, ADF, ash and calcium was greater than 10%. On a DM basis, the concentration of CP ranged from 52.0% to 59.2% and the concentration of GE ranged from 18.6 to 19.5 MJ/kg. The content of EE (DM basis) was low in all samples but ranged from 0.32% to 1.85%. The average concentrations (DM basis) of NDF, ADF, ash, calcium and phosphorus were 22.7% (14.7–28.2%), 8.3% (6.7–9.6%), 7.1% (5.7–8.2%), 0.25% (0.13–0.38%) and 0.79% (0.69–0.88%), respectively. The concentration of all amino acids, except histidine, was fairly similar among the 12 PNM sources with a CV less than 7%. However, the average concentrations of all amino acids were greater than the values published in the NRC (2012). On a DM basis, the average content of lysine, methionine, threonine, tryptophan and arginine was 1.8%, 0.6%, 1.5%, 0.5% and 5.9%, respectively.
3.2. Energy concentration and energy digestibility The DE and ME values and ATTD of GE for the 12 PNM samples were significantly different (Table 3). The concentration of DE (mean 15.6 MJ/kg) and ME (mean 13.9 MJ/ kg) ranged from 14.5 to 16.4 MJ/kg and 12.7 to 15.5 MJ/kg of DM, respectively. The difference between the highest and lowest values for DE and ME was 1.9 MJ/kg and 2.8 MJ/kg of DM, respectively. The ATTD of GE ranged from 76.4% to 85.7% with a mean value of 82.2%.
3.3. Digestibility of crude protein and amino acids The AID of CP and all amino acids, except isoleucine, showed significant differences among the PNM sources (Table 4). The AID for CP varied between 70.2% and 81.9% with an average value of 77.1%. The variation of AID for lysine among samples (59.6–76.7%) was higher than that for the AID of the other amino acids. The AID of arginine (mean 92.5%) was the highest among all amino acids and ranged from 90.8% to 94.5%. The SID of methionine and alanine differed by trend (p < 0.1), while the SID of CP and the other amino acids showed significant differences. Regarding SID, for all dispensable amino acids, the variability among samples ranged between 6.6% and 9.2% (i.e., from 79.4% to 86.0% and 75.2% to 84.4%, for tyrosine and serine, respectively), which was lower than that for the essential amino acids lysine (16.0%) and tryptophan (13.7%) (range from 64.8% to 80.9% and 69.7% to 83.4% for lysine and tryptophan, respectively).
3.4. Correlations and prediction equations of energy values and amino acids digestibility The NDF content showed a negative correlation with DE and ME (p < 0.05). The ADF content correlated negatively with DE, while the GE content correlated positively with the content of DE (p < 0.05) (Table 5). The best single predictor for DE was the NDF content (R2 = 0.67) (Table 6). The accuracy of the equations was improved with the inclusion of
14.1ab 13.1abc 15.8abc 14.7ab 82.2ab
2 14.8a 13.2ab 16.4a 14.7ab 85.7a
3 14.4ab 13.9a 16.1abc 15.5a 85.3a
4 14.4ab 12.5abcd 16.0abc 13.9bc 83.1a
5 14.5ab 12.1bcd 16.2ab 13.5bc 85.5a
6 13.9ab 12.4bcd 15.4abcd 13.7bc 80.7ab
7 13.5bc 11.4d 15.0cd 12.7c 79.8ab
8
a–d
14.0ab 12.8abcd 15.5abcd 13.9bc 81.2ab
9
Notes: #DE, Digestible energy; *ME, Metabolisable energy; †SEM, Standard error of the mean; ‡GE, Gross energy; significantly (p > 0.05).
13.8ab 12.3bcd 15.1bcd 13.4bc 81.0ab
1
Peanut meal number
12.7c 11.6cd 14.5d 13.3bc 76.4b
11
14.0ab 12.1bcd 15.4abcd 13.3bc 81.8ab
12
14.1 12.5 15.6 13.9 82.2
0.32 0.43 0.36 0.48 1.90
Archives of Animal Nutrition Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/gaan20
Determination and prediction of the energy content and amino acid digestibility of peanut meals fed to growing pigs a
a
a
a
a
Qingyun Li , Xiangshu Piao , Jundi Liu , Zhikai Zeng , Sai Zhang & b
Xinjian Lei a
State Key Laboratory of Animal Nutrition, Ministry of Agriculture Feed Industry Centre, China Agricultural University, Beijing, China b
Faculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China Published online: 29 May 2014.
To cite this article: Qingyun Li, Xiangshu Piao, Jundi Liu, Zhikai Zeng, Sai Zhang & Xinjian Lei (2014) Determination and prediction of the energy content and amino acid digestibility of peanut meals fed to growing pigs, Archives of Animal Nutrition, 68:3, 196-210, DOI: 10.1080/1745039X.2014.910970 To link to this article: http://dx.doi.org/10.1080/1745039X.2014.910970
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Archives of Animal Nutrition, 2014 Vol. 68, No. 3, 196–210, http://dx.doi.org/10.1080/1745039X.2014.910970
Determination and prediction of the energy content and amino acid digestibility of peanut meals fed to growing pigs Qingyun Lia, Xiangshu Piaoa*, Jundi Liua, Zhikai Zenga, Sai Zhanga and Xinjian Leib
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a
State Key Laboratory of Animal Nutrition, Ministry of Agriculture Feed Industry Centre, China Agricultural University, Beijing, China; bFaculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou, China (Received 17 January 2014; accepted 24 March 2014) Two experiments were conducted to determine the content of digestible energy (DE) and metabolisable energy (ME) as well as the apparent ileal digestibility (AID) and standardised ileal digestibility (SID) of amino acids in peanut meal (PNM) for growing pigs. In Experiment 1, 78 growing pigs (46.8 ± 2.6 kg) were randomly allotted to 1 of 13 diets, including a corn–soya bean meal basal diet and 12 PNM test diets. In Experiment 2, 12 growing barrows (48.7 ± 2.8 kg) were allotted to one of two 6 × 6 Latin squares. The treatments include a N-free diet and 10 PNM test diets. The results of Experiment 1 showed that the DE and ME differed (p < 0.05) among the 12 PNM samples. On a dry matter basis, the DE and ME content ranged from 14.5 to 16.4 MJ/ kg (mean 15.6 MJ/kg) and from 12.7 to 15.5 MJ/kg (mean 13.9 MJ/kg), respectively. The apparent total tract digestibility (ATTD) of gross energy (GE) was 82.2%. The DE of PNM could be precisely predicted by equations including NDF combined with GE or crude protein (CP) with an R2 value of 0.91 and 0.92, respectively. For the AID and SID for lysine, the results of Experiment 2 indicated variations among PNM sources ranging from 59.6% to 76.7% and 64.8% to 80.9%, respectively. However, for CP, variations for AID and SID were lower and ranged from 70.2% to 81.9% and 75.7% to 85.6%, respectively. The results indicate that the concentration of lysine was the best single predictor to estimate the digestibility of amino acids. However, further work is needed to investigate the reason for the variation in the digestibility of lysine and avoid processing procedures that are detrimental to lysine digestibility. Keywords: amino acids; digestibility; energy content; equations; peanut oilmeal; pigs; prediction
1. Introduction Peanut meal (PNM) is a by-product of oil extraction from whole or broken peanuts and the solvent-extracted PNM is increasingly being used as an animal feed (Dale and Batal 2005), since the tight supply of protein sources drives feed manufacturers to pay more attention to more economical protein ingredients in place of soya bean meal (Sulabo et al. 2013). Annual global production of peanuts has been on the increase, reaching 35 million tons in recent years, while 12 million tons were generated in China alone, accounting for 34% of world production (Revoredo and Fletcher 2002). As a result, 3.5 million tons of PNM is being produced each year (Revoredo and Fletcher 2002), which provides a considerable amount of protein for the feed industry. *Corresponding author. Email: [email protected] © 2014 Taylor & Francis
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The use of PNM as an alternative protein source has been evaluated in poultry (Costa et al. 2001; Pesti et al. 2003), pigs (Orok et al. 1975; Balogun and Koch 1979; Adeola 2009) and shrimp (Liu et al. 2012). The variable effects of PNM on performance may be the result of limited data on the energy content and amino acid digestibility of PNM to allow more accurate feed formulation. Since PNM has gone through heat treatment (Hou et al. 2004), there is a risk of reduced digestibility of amino acids caused by Maillard reactions (Stein et al. 2006). Dale and Batal (2005) also reported a considerable variation in N-corrected metabolisable energy (ME) for chickens among 17 PNM samples, which ranged from 2273 to 3009 kcal/kg (9.5–12.6 MJ/kg). To include PNM in feed formulation, for the swine industry, it is important to understand the variation of nutrient digestibility and to estimate its value accurately. Therefore, the objectives of this study were to determine the chemical composition and the contents of digestible energy (DE) and ME as well as the amino acid digestibility in PNM and to develop equations to predict the energy content and digestibility of amino acids based on its chemical composition.
2. Materials and methods 2.1. General The Institutional Animal Care and Use Committee at China Agricultural University (Beijing, China) reviewed and approved the protocols used in this study. Twelve commercial PNM samples were obtained from eight peanut oil plants in three provinces (Hebei, Shandong and Henan), which are the main peanut-producing areas located in the east coast and midland of China. All PNM samples were produced from peanut kernels by the pre-press extraction method. Their chemical composition is shown in Table 1.
2.2. Experiment 1 Experiment 1 was conducted to determine the DE and ME contents of PNM and to develop prediction equations based on the chemical composition of PNM. Seventy-eight cross-bred barrows (Duroc × Landrace × Yorkshire), weighing 46.8 ± 2.6 kg, were allotted to 13 diets according to a completely randomised design, including one corn– soya bean meal basal diet and 12 PNM test diets (Table 2). Each diet was fed to six replicate pigs. The basal diet contained 89.7% corn and 6.05% dehulled soya bean meal. Crystalline amino acids were added to balance the dietary amino acid composition (Ji et al. 2012). The test diets were formulated to contain 19.4% PNM at the expense of corn, soya bean meal and amino acids. This value was chosen on the basis of a preliminary experiment, which was conducted to determine the inclusion level of PNM in Experiment 1. Because Ilori et al. (1984) reported that PNM comprised between 20% and 25% of the diet in most swine formulations, in this preliminary experiment, 9.70%, 14.55%, 19.40% or 24.25% of PNM were included in the diets. The results revealed that the optimal inclusion rate was 19.4% (data are not shown). Furthermore, vitamins and minerals were supplemented to all diets to meet or exceed the estimated nutrient requirements for growing pigs, as recommended by NRC (1998). All ingredients were ground through a 2.5-mm screen (hammer mill). All pigs were individually housed in stainless steel metabolism cages (1.44 × 0.66 × 1.22 m3) with a feeder and a nipple drinker placed in an environmentally controlled room with a temperature maintained at 22 ± 2°C. Two equal-sized meals were
5.9 1.3 3.3 1.7 1.8 0.6 2.5 1.4 0.5 2.1
2.2 6.0 0.6 9.1 3.1 2.3 2.4 1.6
Indispensable amino acids Arginine Histidine Leucine Isoleucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine
Dispensable amino acids Alanine Aspartic acid Cystine Glutamic acid Glycine Proline Serine Tyrosine 2.2 6.2 0.6 9.3 3.1 2.3 2.5 1.6
5.8 1.3 3.4 1.8 1.6 0.6 2.6 1.4 0.5 2.2
89.1 58.0 1.8 23.7 8.8 7.0 0.28 0.80 19.3
2
2.3 6.5 0.6 9.8 3.3 2.4 2.6 1.7
6.0 1.3 3.5 1.8 1.6 0.5 2.7 1.5 0.5 2.3
89.9 57.8 0.4 18.6 8.2 6.6 0.24 0.83 19.2
3
2.0 5.7 0.6 8.5 2.8 2.1 2.3 1.8
5.7 1.2 3.1 1.6 1.8 0.5 2.4 1.4 0.5 2.0
89.3 52.0 0.9 14.8 6.7 7.0 0.25 0.73 19.4
4
2.3 6.6 0.6 10.0 3.4 2.4 2.7 1.6
6.3 1.3 3.6 1.9 1.8 0.6 2.7 1.5 0.6 2.3
89.9 59.2 0.3 21.9 7.9 6.4 0.24 0.88 18.9
5
2.1 6.0 0.6 9.0 3.1 2.2 2.4 1.6
5.7 1.2 3.2 1.7 1.7 0.6 2.5 1.4 0.5 2.1
89.3 57.1 0.4 23.1 7.0 6.5 0.22 0.86 19.5
6
2.2 6.5 0.6 9.8 3.3 2.4 2.6 1.6
5.9 1.3 3.5 1.8 1.7 0.6 2.7 1.5 0.5 2.3
90.3 57.8 1.1 25.1 8.9 6.4 0.25 0.83 18.9
7
Peanut meal number*
2.2 6.3 0.6 9.5 3.2 2.3 2.6 1.6
5.8 1.7 3.4 1.8 1.7 0.5 2.6 1.5 0.5 2.2
90.3 55.1 0.9 25.0 8.2 7.2 0.13 0.78 18.7
8
2.2 6.4 0.7 9.6 3.2 2.4 2.6 1.7
6.2 1.3 3.4 1.8 1.8 0.5 2.7 1.5 0.5 2.2
90.5 57.5 0.8 23.8 9.1 7.4 0.26 0.79 19.1
9
2.2 6.4 0.6 9.5 3.1 2.4 2.6 1.6
6.2 1.3 3.4 1.8 1.9 0.5 2.7 1.5 0.5 2.2
89.6 57.6 1.4 21.0 8.2 8.2 0.33 0.78 19.4
10
2.1 6.2 0.7 9.4 3.1 2.3 2.5 1.5
6.0 1.3 3.4 1.7 1.9 0.6 2.6 1.4 0.5 2.1
87.5 53.7 0.7 28.2 9.6 8.1 0.38 0.69 19.0
11
2.1 5.9 0.6 8.8 2.9 2.1 2.4 1.6
5.8 1.2 3.2 1.7 1.8 0.5 2.5 1.4 0.5 2.1
90.6 53.4 0.8 22.7 8.3 5.7 0.21 0.77 18.7
12
2.2 6.2 0.6 9.4 3.1 2.3 2.5 1.6
5.9 1.3 3.4 1.8 1.8 0.6 2.6 1.5 0.5 2.2
89.8 56.3 0.9 22.7 8.3 7.1 0.25 0.79 19.1
Mean
4.0 4.4 6.3 4.7 5.3 4.9 4.7 4.6
3.4 10.0 4.3 4.5 5.7 9.5 4.0 3.6 5.7 4.4
1.1 4.0 49.5 15.1 10.3 11.2 24.2 6.7 1.6
CV‡
Notes: *Origin of peanut meals 1–4, 5–8 and 9–12 were Hebei, Shandong and Henan Provinces of China, respectively; ‡CV, Coefficient of variation; #NDF, Neutral detergent fibre; † ADF, Acid detergent fibre.
91.4 56.2 1.3 24.3 9.2 8.1 0.25 0.76 18.6
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Analysed nutrient contents of the 12 sources of peanut meal.
Dry matter [%] Crude protein [% of DM] Ether extract [% of DM] NDF# [% of DM] ADF† [% of DM] Ash [% of DM] Calcium [% of DM] Phosphorus [% of DM] Gross energy [MJ/kg]
Table 1.
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Archives of Animal Nutrition Table 2.
Ingredients and nutrient contents of experimental diets [% as-fed]. Experiment 1
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Ingredients Corn Soya bean meal Peanut meal Cornstarch Soya bean oil Sucrose Cellulose acetate* Dicalcium phosphate Limestone Sodium chloride Chromic oxide Potassium carbonate Magnesium oxide L-lysine · HCl DL-methionine L-threonine L-tryptophan Mineral and vitamin premix# Analysed nutrient contents Dry matter Crude protein Calcium Phosphorus
Experiment 2
Basal diet
Peanut meal diets
N-free diet
Peanut meal diets
89.70 6.05 – – – – – 1.70 0.50 0.30 – – – 0.75 0.10 0.30 0.10 0.50
71.76 4.84 19.40 – – – – 1.70 0.50 0.30 – – – 0.60 0.08 0.24 0.08 0.50
– – – 73.35 3.00 15.00 4.00 2.50 0.50 0.45 0.30 0.30 0.10 – – – – 0.50
– – 35.00 47.00 – 15.00 – 1.50 0.40 0.30 0.30 – – – – – – 0.50
86.1 11.0 0.66 0.56
87.3 18.3 0.62 0.53
90.3 0.32 0.67 0.48
90.9 18.0 0.61 0.51
Notes: *Provided by Chemical Reagents Company, Beijing, China; #Provided per kg of complete diet for growing pigs: vitamin A, 5512 IU; vitamin D3, 2200 IU; vitamin E, 30 mg; vitamin K3, 2.2 mg; vitamin B12, 27.6 μg; riboflavin, 4 mg; pantothenic acid, 14 mg; niacin, 30 mg; choline chloride, 400 mg; folic acid, 0.7 mg; vitamin B1, 1.5 mg; vitamin B6, 3 mg; biotin, 44 μg; Mn, 40 mg (MnO); Fe, 75 mg (FeSO4 · H2O); Zn, 75 mg (ZnO); Cu, 10 mg (CuSO4 · 5H2O); I, 0.3 mg (KI); Se, 0.3 mg (Na2SeO3).
fed twice a day at 08:00 and 15:30 h at a rate of 4% of individual body weight. Water was freely available from a drinking nipple. The diets were provided in mash form. The experiment lasted 12 d, consisting of a 7-d adaptation to the diets followed by a 5-d total collection of faeces and urine using the methods described by Song et al. (2003) and Ren et al. (2011). Feed refusals and spillage were collected twice daily to be dried and weighed. Faeces that appeared in the metabolism crates were collected immediately in the plastic bags and stored at –20°C. Urine was collected in buckets located under the metabolism crates. The buckets contained 10 ml of 6 N HCl for every 1000 ml of urine and were emptied whenever they were full. The volume of collected urine was measured and 10% of the daily urine collection was stored at –20°C. At the end of the collection period, faeces and urine, pooled over the 5-d period, were separately thawed and mixed within animal, and then a representative subsample was obtained for chemical analysis. Before analysis, faecal subsamples were dried at 65°C in a drying oven for 72 h and ground through a 1-mm screen.
2.3. Experiment 2 Experiment 2 was designed to determine the apparent ileal digestibility (AID) and standardised ileal digestibility (SID) of crude protein (CP) and amino acids in 10 PNM
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samples. Only 10 of the 12 PNM samples were used in Experiment 2, since the PNM Sources 1 and 3 were removed due to their similar amino acid composition to that of Sources 6 and 7. Twelve cross-bred (Duroc × Landrace × Yorkshire) growing barrows (48.7 ± 2.8 kg) were randomly allotted to one of two 6 × 6 Latin square designs with 6 periods and 12 diets. Each Latin square contained one N-free diet and five PNM test diets (Table 2). Pigs were equipped with a simple T-cannula near the distal ileum using the procedures described by Stein et al. (1998). The PNM test diets contained corn starch (47%), sucrose (15%) and PNM (35%) as the sole source of amino acids. The N-free diet was used to measure basal endogenous losses of CP and amino acids. All diets contained 0.3% chromic oxide as an indigestible marker and vitamins and minerals were included to meet or exceed the estimated nutrient requirements for growing pigs, as recommended by NRC (1998). All pigs were provided daily feed equivalent to 4% of body weight, and two equal-sized meals were provided every day at 08:00 and 17:00 h. Pigs had free access to water throughout the experiment. Pig body weights were recorded at the beginning of the experiment and at the end of each period. Each period lasted 7 d, with the initial 5 d to adapt to the diet, and days 6 and 7 to collect ileal digesta from 08:00 to 17:00 h. The procedures used to collect digesta followed the description provided by Stein et al. (1998). Briefly, digesta was collected in plastic bags attached to simple T-cannula until the bags were full and immediately stored in a -20°C freezer after each collection. Ileal digesta samples were thawed, mixed within animal and diet, and a subsample was taken. The digesta samples were lyophilised in a vacuum-freeze dryer (Tofflon Freezing Drying Systems, Minhang District, Shanghai, China) and ground through a 1-mm screen for further chemical analysis.
2.4. Chemical analysis All PNM samples and diets used in this experiment were analysed for dry matter (DM) (AOAC 2007, procedure 930.15), CP (AOAC 2007, 984.13), ash (AOAC 2007, 942.05), calcium (AOAC 2007, 927.02), phosphorus (AOAC 2007, 984.27) and ether extract (EE) (Thiex et al. 2003). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were determined using filter bags and fibre analyser equipment (Fibre Analyzer, Ankom Technology, Macedon, NY, USA) following a modification of the procedure of Van Soest et al. (1991). The GE in PNM, diets, faecal and urine samples were measured using an Automatic Adiabatic Oxygen Bomb Calorimeter (Parr 6300 Calorimeter, Moline, IL, USA). Samples of PNM, diets and ileal digesta were also analysed for the concentration of amino acids. With the exception of methionine, cystine and tryptophan, the amino acid content was determined after hydrolysis with 6 N HCl at 110°C for 24 h using an amino acid analyser (Hitachi L-8900, Tokyo, Japan). Methionine and cystine were determined as methionine sulphone and cysteic acid after cold performic acid oxidation overnight and hydrolysing with 7.5 N HCl at 110°C for 24 h using an amino acid analyser. Tryptophan was determined after LiOH hydrolysis for 22 h at 110°C using high performance liquid chromatography (HPLC) (Agilent 1200 Series, Santa Clara, CA, USA). The chromium concentration of diets and ileal digesta samples were determined after nitric acid–perchloric acid wet ash sample preparation using polarized Zeeman atomic absorption spectrometer (Hitachi Z2000, Tokyo, Japan).
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2.5. Calculations
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In Experiment 1, the energy lost in faeces and urine was calculated for each diet, and the DE and ME in each of the 13 diets were calculated. By subtracting the DE and ME contributed by the corn–soya bean meal basal diet to the PNM test diets, the DE and ME contributed by each source of PNM were calculated by difference (Adeola 2001). The apparent total tract digestibility (ATTD) of GE in each diet was calculated by the method of Stein et al. (2007). In Experiment 2, the AID for each amino acid in the diets containing PNM was calculated using the equations described by Stein et al. (2007): AID ¼ ½1 AAd=AAf ÞðCrf =CrdÞ 100% where AAd is the concentration of amino acids in the ileal digesta [g/kg of DM], AAf is the concentration of amino acids in the diets [g/kg of DM], Crf represents chromium concentration in the diet [g/kg of DM], and Crd represents chromium concentration in the digesta [g/kg of DM]. The AID for CP was also calculated using this equation, where amino acids are replaced by the concentration of the CP in the digesta and diets. The basal endogenous loss of each amino acid (IAAend, g/kg of DMI) at the distal ileum was determined based on the outflow obtained when pigs were fed the N-free diet using the equation of Stein et al. (2007): IAAend ¼ AAdðCrf =CrdÞ where AAd is the concentration of each amino acid in the ileal digesta collected from pigs fed the N-free diet. The endogenous outflow of CP was determined using the same equation, where AAd is replaced by the concentration of the CP in the digesta. By correcting the AID of each amino acid that was calculated for each sample for the IAAend of each amino acid, the SID of each amino acid was calculated using the equation of Stein et al. (2007): SID ¼ AID þ ðIAAend =AAdiet Þ 100%
2.6. Statistical analysis All data were processed using SAS (SAS Inst. Inc., Cary, NC). CORR procedure was adopted for correlation coefficients analyses in Experiment 1. Simple and multiple regression analyses (stepwise regression analysis) were conducted to study the relationship among chemical composition and energy content as well as amino acid digestibility. For selecting the energy and amino acid digestibility prediction equations, the residual standard deviation (RSD) was used as the selection criterion. A smaller RSD was proposed to indicate a better fit. In Experiment 2, data were analysed using the ProcMixed procedure of SAS. The statistical model for the digestibility values had treatment and period as fixed effects and pig as a random effect. When the ANOVA was significant, differences between treatments were tested using least square means (t-tests). In all analyses, the differences were considered significant if p < 0.05.
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3. Results 3.1. Chemical composition of peanut meal The proximate chemical composition and amino acid content of the 12 PNM sources are shown in Table 1, which demonstrated that the collected PNM samples were quite variable. The coefficient of variation (CV) of EE, NDF, ADF, ash and calcium was greater than 10%. On a DM basis, the concentration of CP ranged from 52.0% to 59.2% and the concentration of GE ranged from 18.6 to 19.5 MJ/kg. The content of EE (DM basis) was low in all samples but ranged from 0.32% to 1.85%. The average concentrations (DM basis) of NDF, ADF, ash, calcium and phosphorus were 22.7% (14.7–28.2%), 8.3% (6.7–9.6%), 7.1% (5.7–8.2%), 0.25% (0.13–0.38%) and 0.79% (0.69–0.88%), respectively. The concentration of all amino acids, except histidine, was fairly similar among the 12 PNM sources with a CV less than 7%. However, the average concentrations of all amino acids were greater than the values published in the NRC (2012). On a DM basis, the average content of lysine, methionine, threonine, tryptophan and arginine was 1.8%, 0.6%, 1.5%, 0.5% and 5.9%, respectively.
3.2. Energy concentration and energy digestibility The DE and ME values and ATTD of GE for the 12 PNM samples were significantly different (Table 3). The concentration of DE (mean 15.6 MJ/kg) and ME (mean 13.9 MJ/ kg) ranged from 14.5 to 16.4 MJ/kg and 12.7 to 15.5 MJ/kg of DM, respectively. The difference between the highest and lowest values for DE and ME was 1.9 MJ/kg and 2.8 MJ/kg of DM, respectively. The ATTD of GE ranged from 76.4% to 85.7% with a mean value of 82.2%.
3.3. Digestibility of crude protein and amino acids The AID of CP and all amino acids, except isoleucine, showed significant differences among the PNM sources (Table 4). The AID for CP varied between 70.2% and 81.9% with an average value of 77.1%. The variation of AID for lysine among samples (59.6–76.7%) was higher than that for the AID of the other amino acids. The AID of arginine (mean 92.5%) was the highest among all amino acids and ranged from 90.8% to 94.5%. The SID of methionine and alanine differed by trend (p < 0.1), while the SID of CP and the other amino acids showed significant differences. Regarding SID, for all dispensable amino acids, the variability among samples ranged between 6.6% and 9.2% (i.e., from 79.4% to 86.0% and 75.2% to 84.4%, for tyrosine and serine, respectively), which was lower than that for the essential amino acids lysine (16.0%) and tryptophan (13.7%) (range from 64.8% to 80.9% and 69.7% to 83.4% for lysine and tryptophan, respectively).
3.4. Correlations and prediction equations of energy values and amino acids digestibility The NDF content showed a negative correlation with DE and ME (p < 0.05). The ADF content correlated negatively with DE, while the GE content correlated positively with the content of DE (p < 0.05) (Table 5). The best single predictor for DE was the NDF content (R2 = 0.67) (Table 6). The accuracy of the equations was improved with the inclusion of
14.1ab 13.1abc 15.8abc 14.7ab 82.2ab
2 14.8a 13.2ab 16.4a 14.7ab 85.7a
3 14.4ab 13.9a 16.1abc 15.5a 85.3a
4 14.4ab 12.5abcd 16.0abc 13.9bc 83.1a
5 14.5ab 12.1bcd 16.2ab 13.5bc 85.5a
6 13.9ab 12.4bcd 15.4abcd 13.7bc 80.7ab
7 13.5bc 11.4d 15.0cd 12.7c 79.8ab
8
a–d
14.0ab 12.8abcd 15.5abcd 13.9bc 81.2ab
9
Notes: #DE, Digestible energy; *ME, Metabolisable energy; †SEM, Standard error of the mean; ‡GE, Gross energy; significantly (p > 0.05).
13.8ab 12.3bcd 15.1bcd 13.4bc 81.0ab
1
Peanut meal number
12.7c 11.6cd 14.5d 13.3bc 76.4b
11
14.0ab 12.1bcd 15.4abcd 13.3bc 81.8ab
12
14.1 12.5 15.6 13.9 82.2
0.32 0.43 0.36 0.48 1.90
