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Liu, Li, Zeng, Li, Xu, Wang, Zhang, and Piao: Determination and Prediction of the Amino Acid Digestibility of Sunflower Seed Meals in Growing Pigs


This experiment was conducted to evaluate the chemical composition and amino acid (AA) digestibility of sunflower seed meal (SFSM) and to use this data to develop prediction equations for estimating AA digestibility for growing pigs. Ten SFSM were collected from five provinces in China. Twelve barrows (38.8±4.6 kg), fitted with ileal T-cannula were allotted into two 6×6 Latin square designs. Each of six experimental periods comprised a 5-d adaption period followed by a 2-d collection of ileal digesta. The ten test diets contained 50% SFSM as the sole source of AA. Another nitrogen-free diet was used to measure the basal endogenous losses of crude protein (CP) and AA. Chromic oxide (0.3%) was used as an inert marker in each diet. There was considerable variation (CV>10%) among the ten SFSM in chemical composition (dry matter [DM]). The concentration of CP and ether extract (EE) ranged from 29.33% to 39.09% and 0.88% to 11.33%, respectively. Crude fibre (CF), neutral detergent fibre and acid detergent fibre ranged from 21.46% to 36.42%, 38.15% to 55.40%, and 24.59% to 37.34%, respectively. There was variation among the ten SFSM in apparent ileal digestibility (AID) and standardized ileal digestibility (SID) for lysine and threonine, which ranged from 63.16 to 79.21 and 55.19% to 72.04% for AID and 67.03% to 82.07% and 61.97% to 77.01% for SID, respectively. The variation in CP and methionine ranged from 60.13% to 74.72% and 74.79% to 88.60% for AID and 66.70% to 79.31% and 77.16% to 90.27% for SID, respectively. Methionine was a good indicator to predict AA digestibility. These results indicate that conventional chemical composition of SFSM was variable (CV>10%) among the ten SFSM (DM). The results of AID, SID and prediction equations could be used to evaluate the digestibility of SFSM in growing pigs.


Sunflower (Helianthus annuus, Asteraceae) is one of the most widely cultivated oil crops in the world (Flagella et al., 2002). The world-wild production of sunflower seed reached 37.08 million tonnes and subsequently produced 15.22 million tonne of oil (FAO, 2012). Together with soybeans, cottonseeds and canola (rapeseed), sunflower seeds are one of the major oilseeds produced in the world (Salunkhe et al., 1992).
Oilseed by-products play an important role in supplying plant protein (Church and Kellems, 1998). Soybean meal (SBM) is often referred to as the gold standard compared with other protein sources (Cromwell, 2000; Zhang et al., 2013). The demand for soybean is increasing due to its inclusion in livestock feed and also its use for human consumption (Sasipriya and Siddhuraju, 2013). In order to satisfy the need for protein resources, other materials such as rapeseed meal (Baidoo et al., 1987; Brand et al., 2001; Opalkal et al., 2001; Zhang et al., 2012), cottonseed meal (Noland et al., 1968; Tanksley et al., 1981) and peanut meal (Batal et al., 2005; Sulabo et al., 2013) have been used to replace SBM in the feed industry.
Sunflower seed meal (SFSM) is a by-product of the oil extraction of sunflowers and could be an important protein resource for use in animal diets. Solvent extracted sunflower seed meal has an average concentration of crude protein (CP) of 30.7% and a higher concentration of Methionine (Met) than solvent extracted SBM, but has less lysine (Lys) than SBM (NRC, 2012). Another characteristic of SFSM is that it is not known to have antinutritional factors such as those found in soyabean, cottonseed and rapeseed meals. Although sunflower seed contains 1.56% chlorogenic acid (Milic et al., 1968), its concentration in SFSM does not lead to toxicity effects (Senkoylu and Dale, 1999). Sunflower seed meal diets supplemented with Lys can be used as a replacement for SBM in growing pigs (Seerley et al., 1974). However, the digestibility of these nutrients may vary considerably resulting in rather inaccurate measures for the nutritional value of actual batches of feed (Just et al., 1983). Therefore, the objective of this study was to compare the chemical composition of different SFSM and determine the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and amino acid (AA) of SFSM fed to growing pigs. In addition, the results of the chemical analysis were used to establish prediction equations for AID and SID that could be applied in future commercial practice.


This experiment was conducted at the China Agricultural University (Beijing, China). The Institutional Animal Care and Use Commitee at China Agricultural University approved the protocol for the experiment. All the pigs had been used in another experiment before being placed in this experiment.

Animals and housing

The experiment was conducted in the Metabolism Laboratory of the Ministry of Agriculture Feed Industry Centre, Beijing. Temperature and humidity of the room were automatically controlled at 18°C to 21°C and 50% to 65%.
Twelve barrows (Duroc×Landrace×Yorkshire) with an initial body body weight (BW) 38.8±4.6 kg were fitted with a simple T-cannula in the distal ileum (Stein et al., 1998). The barrows were individually placed in stainless-steel metabolism crates (1.4×0.45×0.6 m3). Each crate was installed with a one-hole feeder and a nipple drinker.

Source of sunflower seed meal and experiment design

Ten sunflower seed meals were collected from five provinces in China which are representative of more than 80% of the output of China. The chemical composition of ten SFSM differed from each other (Tables 1 and 2).
The 12 barrows were allocated into two 6×6 Latin square designs according to their initial BW with 6 pigs for each Latin square. Each Latin square contained 5 SFSM which were the only source of AA and one nitrogen-free diet which was used to estimate basal ileal endogenous losses of CP and AA. The diets used in this experiment were prepared based on the chemical composition of the feed ingredients (Tables 3 and 4). All diets were fed in mash form.

Sample collection

The daily feed intake at the beginning of each period was set at 4% of BW (Adeola, 2001). During each of the 6 experimental periods, the first 5 d were for adaptation to the diet. On d 6 and 7, ileal digesta samples were collected from 8:00 to 16:00 h. Cannulas were opened and plastic bags were fastened with the help of a rubber band in order to collect the digesta flowing into the bags. Every 30 minutes, the plastic bags were replaced and digesta samples were taken and stored at −20°C. Ileal digesta samples were thawed and mixed at the end of every two day collection period. All the samples were mixed and lyophilised in a Vacuum-Freeze Dryer (Tofflon Freezing Drying Systems, Minhang District, Shanghai, China) and passed a 1 mm screen before a sub-sample was obtained for chemical analysis.

Chemical analyses

All analyses in the experiment were performed in duplicate and the chemical analyses were repeated if the difference between duplicates were over 5%. The methods used to analyze the chemical composition were similar to the description by Ji et al. (2012).The ten SFSM, diets and digesta samples were analyzed for dry matter (DM) (AOAC procedure 4.1.06, 2000), CP (AOAC procedure 990.03, 2000), Kjeldahl N (Thiex et al., 2002) and CP was calculated as N×6.25. The AA were analyzed after being hydrolysed with 6 N HCl for 24 h at 110°C. Fifteen AA were analyzed using an AA Analyzer (Hitachi L-8900, Tokyo, Japan). Tryptophan was determined after LiOH hydrolysis for 22 h at 110°C using High Performance Liquid Chromatography (Agilent 1200 series, Santa Clara, CA, USA). Methionine and cystine were determined as methionine sulfone and cysteic acid after cold performic acid oxidation overnight and hydrolysing with 7.5 N HCl for 24 h at 110°C using an AA Analyzer (Hitachi L-8800, Tokyo, Japan).
The 10 SFSM were also analyzed for crude fiber (CF), ether extract (EE) (Thiex et al., 2003), ash, calcium (Ca) (AOAC procedure 4.8.03, 2000) and total phosphorus (AOAC procedure 3.4.11, 2000). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were determined using fibre bags and an analyser (Fibre Analyzer, Ankom Technology, Macedon, NY, USA) following an adaptation procedure described by Van Soest et al. (1991). Diets and ileal digesta samples were analyzed for chromium concentration. A Polarized Zeeman Atomic Absorption Spectrometer (Hitachi Z2000, Tokyo, Japan) was used after the samples were prepared by nitric acid-perchloric acid.


Values for AID and SID of CP and each AA were determined according to the method of Stein et al. (2007) described previously.

Statistical analyses

Simple and multiple regression analyses (stepwise regression analysis) were conducted to determine the relationships among chemical components and AA digestibility. For prediction equations, the residual standard deviation (RSD) was used as the selection criterion. A smaller RSD was proposed to indicate a better fit. Data for AID and SID were analyzed using the Proc-Mixed procedure of SAS (SAS Institute; Cary, NC, USA). Means were calculated using the LSMEANS statement, and when a significant F-test for treatment was observed, means were separated using the PDIFF option. The value of 5% (p<0.05) was used to determine significance.


Composition of ingredients

The chemical composition for 10 SFSM are shown in Table 1. Among all the ingredients, the CP, EE, NDF, ADF, CF, Ash, Ca and P obviously differed with a coefficient of variation (CV) higher than 10%. The concentration of EE, CF, Ca and P showed the greatest difference with a CV higher than 15%. On DM basis, the content of CP, NDF, ADF and CF ranged from 29.33% to 39.09%, 38.15% to 55.40%, 24.59% to 37.34% and 21.46% to 36.42%, respectively.
The AA composition for SFSM is shown in Table 2. The results showed that most AA were variable (CV>10%) except proline, alanine, and Lys (CV<10%). The average concentration of AA in SFSM were lower than those published by NRC (2012). The level of the four commonly limiting AA were 1.48%, 0.75%, 1.25%, and 0.37% for Lys, Met, threonine (Thr) and tryptophan (Trp), respectively.

Ileal digestibility of crude protein and amino acid

The results of AID and SID are shown in Table 5 and 6. The AID for CP varied from 60.13% to 74.72% among the 10 sources of SFSM. Sunflower seed meal with a high concentration of CP (sources 2 and 9) had higher AID values than SFSM with a lower concentration of CP (sources 3, 6, and 10) (p<0.05). The SFSM with the highest concentration of CP (source 9) had greater digestibility coefficients than the other SFSM for most AA (p<0.05). The results of SID for CP among 10 SFSM were similar to the values for AID. Sources 2 and 9 SFSM had relatively higher SID for CP than the other sources (p<0.05). However, the SID value of one sample with a lower concentration of CP (source 5) was higher than another sample with a higher concentration of CP (source 1) (p<0.05) which was a bit different compared with the result of AID.
Among indispensable AA of SFSM, the AID of Lys, Met, Thr, and Trp in the sample with the highest concentration of CP (source 9) was the highest at 79.21%, 88.60%, 72.04%, and 77.40%, respectively. Also, the SID of most AA in sources 2, 7, and 9 were the highest among all SFSM. Source 2 had relatively higher AID and SID values for leucine and isoleucine than other SFSM (p<0.05). The AID of phenylalanine in source 5 was 80.54% which was beyond the average level (p<0.05). Additionally, SFSM (sources 3 and 10) with lower concentrations of indispensable AA had lower AID and SID than other SFSM (p<0.05).

Correlations and prediction equations for nitrogen and amino acid digestibility

Several factors affected the prediction equations for N and AA. Among the representative chemical constituents (% of DM), EE had a negative correlation with Lys and Met (p<0.05). The best single predictor for AID and SID was Met according to a linear stepwise regression. The best fit equations were obtained for AID N and SID N, which were: AID N = 22.97+(0.74×CP)+(25.44×Met) with R2 = 0.96, RSD = 0.87, p<0.05; and SID N = 35.22+(0.54×CP)+(25.38 ×Met) with R2 = 0.96, RSD = 0.83, p<0.05. In addition, CP, Trp and Ca were also used to estimate the digestibility in different equations (Table 7).


Composition of ingredient

According to the reports, SFSM is a valuable ingredient for swine because of its high energy concentration and ease of handing in feed mills (Thacker, 1998). It is also a good ingredient because it is free of most antinutritional factors (Wahlstrom, 1990).
The results of the chemical analysis of SFSM conducted in this experiment varied greatly. The CV of CP, NDF, ADF, CF, Ash, Ca, and P was higher (CV>10%) due to the selection of samples before the official experiment. Preparations for collecting samples from the major provinces which cultivate SFSM in China involved contacting the representative plants, acquiring basic information on the chemical concentration of SFSM in each plant and collecting typical samples in person. In addition, the variation of SFSM might result from different growth conditions, such as climate and soil conditions (Alpaslan and Gündüz, 2000). Although, most SFSM underwent a similar production process of a pre-pressing extraction method (Fick and Miller, 1997). The differences, such as temperature, pressure and time during the production process might lead to the changes in chemical concentration in SFSM (Clandinin and Robblee, 1950; Parrado et al., 1991). The large variation of EE (0.88% to 11.33%) was mainly related to the different extraction process.
The average concentration of CP (sources 1, 2, 7, 8, and 9) were higher than other sources and NRC (2012) probably because of genetic improvement (Robertson, 1972). The concentrations of EE among the ten SFSM sources varied from 0.88% to 11.33% depending on the extraction process and the amount of residual oil left after extraction (Dinusson, 1990). The EE in source 4 and 8 SFSM were lower than the others which means the oil had been extracted according to the Association of American Feed Control Officials (AAFCO, 2011). The 10 SFSM had an higher average value of NDF but lower ADF than González-Vega et al. (2012) which was similar to the value reported in NRC (2012).

Digestibility of crude protein and amino acid

Waldroup et al. (1970) reported that SFSM can be effectively used to replace up to 50% of SBM in broiler diets. The AID and SID values for CP in this experiment were lower than NRC (2012) because of the lower concentration of CP in the 10 SFSM. The results of AID and SID of CP and AA in source 3 SFSM resulted from the highest concentration of NDF, ADF, and CF which had depressive effect on AA digestibility (Sauer et al., 1980; Lenis et al., 1996).
The SFSM with relatively higher concentration of EE associated with lower NDF and ADF (source 2) had higher AID and SID values (p<0.05). The different content of EE in the diets also affected the digestibility of ten sunflower seed meal (Noblet and Perez, 1993). The relatively higher concentration of NDF and CF may contribute to a decreased AA digestibility (Sauer et al., 1980; Lenis et al., 1996).
Jørgensen et al. (1984) reported that the digestibility of sunflower seed products is lower than SBM. Sunflower seed meal has a lower content of Lys than SBM (Smith, 1968; Sosulski and Sarwar, 1973). Sources 2 and 9 SFSM had a higher concentration of Lys. However, the average AID and SID values of Lys among all SFSM were lower than NRC (2012). Differences in heating temperature probably also caused the variation of AID and SID value of CP resulting in Maillard reaction which decreased the concentration and digestibility of Lys in corn distillers dried grains with solubles (Pahm et al., 2008). In addition, the concentration of Met was relatively higher in SFSM than SBM (Olvera-Novoa et al., 2002).
For most indispensable AA, the AID was lower than the value shown in NRC (2012). However, the SID of those AA had less variation. This means that endogenous loss of AA can not be ignored for evaluation of AA. In addition, the SID value had greater accuracy than AID (González-Vega et al., 2012).

Correlations and prediction equation of nitrogen and amino acid digestibility

The results of the study indicated that the variability of chemical composition in SFSM could contribute to the difference of AID and SID values. The AID and SID of CP could be accurately predicted by Met which means that Met was highly correlated with CP. The concentration of reactive Lys was a good predictor for the concentration of Lys in distillers dried grains with solubles and canola meal, respectively (Almeida et al., 2014). The Lys concentration per unit CP could be an acceptable predictor of Lys SID in wheat distillers dried grains with solubles (Cozannet et al., 2010). Other factors, such as CP, Trp, and Ca were also essential for estimating the digestibility of AA.
In conclusion, the digestibility of SFSM has great variation resulting from differences in chemical composition. The concentration of Met was the major factor affected in the equations established in this experiment. In order to improve SFSM as an alternative to SBM for use in diets for swine, more SFSM samples should be collected and further research should be conducted to increase the accuracy of the equations.


This research was financially supported by the Special Public Sector Fund in Agriculture (200903006) and National Natural Science Foundation of China (31372316).

Table 1
Analyzed chemical composition of sunflower seed meal (% DM)
Item Sunflower seed meal number1

1 2 3 4 5 6 7 8 9 10 Min Max Mean CV
DM 90.91 91.37 92.51 90.76 92.15 92.91 91.27 91.85 90.79 90.31 90.31 92.91 91.48 0.92
 CP 34.91 38.00 29.33 32.02 31.68 29.47 35.19 34.63 39.09 30.87 29.33 39.09 33.52 10.13
 Ether extract 2.19 2.08 5.23 0.93 1.23 3.47 2.02 0.88 1.73 11.33 0.88 11.33 3.11 101.99
 NDF 41.65 38.15 55.40 45.93 47.32 43.97 40.96 42.67 40.72 51.90 38.15 55.40 44.87 12.01
 ADF 25.85 24.59 37.34 31.31 31.42 28.04 25.89 27.99 26.07 30.52 24.59 37.34 28.90 13.28
 Crude fibre 21.83 23.11 36.42 30.54 29.87 27.25 21.46 25.66 22.47 33.69 21.46 36.42 27.23 19.31
 Ash 6.86 7.15 5.45 6.32 6.82 7.75 8.30 6.40 6.76 6.71 5.45 8.30 6.85 11.37
 Calcium 0.27 0.32 0.17 0.34 0.33 0.45 0.44 0.30 0.30 0.31 0.17 0.45 0.32 25.07
 Phosphorus 1.04 1.15 0.63 0.81 0.94 0.84 1.02 0.98 1.06 0.92 0.63 1.15 0.94 15.89

DM, dry matter; Min, minimum; Max, maximum; CV, coefficient of variation; CP, crude protein; NDF, neutral detergent fibre; ADF, acid detergent fibre.

1 Sources of sunflower seed meal: 1, 4, and 8 were from Xinjiang; 2, 7, and 9 were from Hebei; 3 was from Liaoning; 5 was from Shanxi; 6 and 10 were from Inner Mongolia.

Table 2
Analyzed AA composition of sunflower seed meal (% DM)
Item Sunflower seed meal number1

1 2 3 4 5 6 7 8 9 10 Min2 Max3 Mean CV4
Indispensable AA
 Arginine 2.70 3.03 2.22 2.52 2.48 2.35 2.91 2.60 3.06 2.34 2.22 3.06 2.62 11.36
 Histidine 0.89 1.11 0.87 0.86 0.85 0.80 0.97 0.88 1.18 0.83 0.80 1.18 0.93 13.67
 Isoleucine 1.36 1.55 1.20 1.29 1.25 1.15 1.45 1.34 1.62 1.23 1.15 1.62 1.34 11.45
 Leucine 2.18 2.38 1.78 2.04 1.99 1.92 2.29 2.07 2.46 1.81 1.78 2.46 2.09 11.06
 Lysine 1.56 1.63 1.22 1.52 1.45 1.31 1.56 1.51 1.67 1.36 1.22 1.67 1.48 9.61
 Methionine 0.80 0.86 0.61 0.74 0.76 0.65 0.80 0.77 0.89 0.66 0.61 0.89 0.75 12.00
 Phenylalanine 1.45 1.67 1.22 1.23 1.30 1.17 1.45 1.42 1.71 1.28 1.17 1.71 1.39 13.39
 Threonine 1.33 1.42 1.09 1.15 1.14 1.08 1.35 1.29 1.45 1.17 1.08 1.45 1.25 11.04
 Tryptophan 0.37 0.43 0.33 0.34 0.35 0.32 0.40 0.34 0.44 0.35 0.32 0.44 0.37 11.64
 Valine 1.85 2.02 1.57 1.60 1.62 1.52 1.83 1.76 2.05 1.80 1.52 2.05 1.76 10.47
Dispensable AA
 Alanine 1.70 1.76 1.41 1.55 1.54 1.49 1.74 1.66 1.79 1.52 1.41 1.79 1.62 8.10
 Aspartate 3.08 3.50 2.66 2.88 2.68 2.71 3.23 3.03 3.56 2.77 2.66 3.56 3.01 11.04
 Cystine 0.64 0.62 0.39 0.52 0.53 0.47 0.60 0.60 0.71 0.48 0.39 0.71 0.56 17.15
 Glutamine 7.02 7.62 5.97 6.56 6.28 6.20 7.51 6.89 7.86 6.12 5.97 7.86 6.80 10.05
 Glycine 2.05 2.32 1.70 1.93 1.91 1.69 2.12 2.01 2.35 1.92 1.69 2.35 2.00 11.22
 Proline 1.19 1.30 1.12 1.16 1.17 1.11 1.28 1.17 1.33 1.16 1.11 1.33 1.20 6.58
 Serine 1.45 1.64 1.14 1.38 1.37 1.29 1.53 1.41 1.66 1.36 1.14 1.66 1.42 11.00
 Tyrosine 0.78 0.93 0.66 0.68 0.63 0.70 0.88 0.75 0.97 0.59 0.59 0.97 0.76 17.58

DM, dry matter; Min, minimum; Max, maximum; CV, coefficient of variation; AA, amino acid.

1 Sources of sunflower seed meal: 1, 4, and 8 were from Xinjiang; 2, 7, and 9 were from Hebei; 3 was from Liaoning; 5 was from Shanxi; 6 and 10 were from Inner Mongolia.

Table 3
Ingredient composition of experimental diets (% as-fed)
Ingredients Sunflower seed meal diets Nitrogen-free diet
Sunflower seed meal 50.00 -
Corn starch 35.00 73.35
Soybean oil 2.00 3.00
Sucrose 10.00 15.00
Cellulose acetate1 - 4.00
Limestone 0.40 0.50
Dicalcium phosphate 1.50 2.50
Sodium chloride 0.30 0.45
Chromic oxide 0.30 0.30
Potassium carbonate - 0.30
Magnesium oxide - 0.10
Micromineral and vitamin premix2 0.50 0.50

1 Made by Chemical Reagents Company, Beijing, China.

2 Premix provided the following per kg of complete diet: vitamin A, 5,512 IU; vitamin D3, 2,200 IU; vitamin E, 30 IU; vitamin K3, 2.2 mg; vitamin B12, 27.6 μg; riboflavin, 4 mg; pantothenic acid, 13.8 mg; niacin, 30 mg; choline chloride, 400 mg; folacin, 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).

Table 4
Analyzed composition of experiment diets (% DM)
Item Sunflower seed meal number

1 2 3 4 5 6 7 8 9 10
DM 85.67 84.16 85.87 85.19 83.49 85.92 83.98 84.13 83.54 84.76
CP 18.94 22.77 16.09 17.84 17.49 16.80 20.38 19.20 23.06 17.16
Indispensable AA
 Arginine 1.41 1.64 1.18 1.32 1.37 1.27 1.56 1.38 1.66 1.31
 Histidine 0.55 0.61 0.45 0.47 0.45 0.43 0.58 0.51 0.67 0.46
 Leucine 0.73 0.90 0.65 0.66 0.68 0.63 0.81 0.69 0.92 0.65
 Isoleucine 1.06 1.24 0.96 1.04 1.12 1.05 1.20 1.00 1.33 0.97
 Lysine 0.80 0.86 0.66 0.80 0.81 0.70 0.79 0.79 0.89 0.72
 Methionine 0.41 0.43 0.31 0.38 0.39 0.35 0.41 0.39 0.48 0.36
 Phenylalanine 0.77 0.95 0.65 0.70 0.83 0.66 0.80 0.76 0.97 0.70
 Threonine 0.74 0.78 0.58 0.61 0.63 0.58 0.75 0.70 0.80 0.64
 Tryptophan 0.19 0.24 0.18 0.18 0.19 0.17 0.23 0.18 0.25 0.19
 Valine 0.99 1.10 0.86 0.84 0.88 0.84 1.02 1.03 1.09 0.97
Dispensable AA
 Alanine 0.82 0.96 0.76 0.80 0.88 0.79 0.94 0.74 0.96 0.81
 Aspartate 1.61 2.14 1.41 1.53 1.50 1.44 1.89 1.61 2.21 1.50
 Cystine 0.32 0.35 0.21 0.29 0.29 0.25 0.33 0.30 0.36 0.24
 Glutamine 3.60 4.15 3.22 3.36 3.47 3.29 4.14 3.55 4.30 3.23
 Glycine 1.05 1.29 0.90 1.00 1.07 0.92 1.24 1.01 1.32 1.01
 Proline 0.64 0.61 0.60 0.62 0.68 0.59 0.61 0.60 0.67 0.54
 Serine 0.77 0.91 0.62 0.70 0.77 0.72 0.81 0.76 0.93 0.67
 Tyrosine 0.41 0.49 0.38 0.37 0.33 0.33 0.47 0.39 0.52 0.33

DM, dry matter; CP, crude protein; AA, amino acid.

Table 5
Apparent ileal digestibility (%) of CP and AA in sunflower seed meal fed to growing pigs
Item Sunflower seed meal number Mean1 SEM p-value

1 2 3 4 5 6 7 8 9 10
CP 67.13bcd 73.38a 60.13f 64.69cde 66.91bcd 61.00ef 69.31b 68.66bc 74.72a 63.09def 66.90 1.35 <0.01
Indispensable AA
 Arginine 89.19a 88.19a 84.93bc 85.39bc 87.37ab 84.40c 86.68abc 84.98bc 88.60a 86.41abc 86.61 0.88 <0.01
 Histidine 79.25abc 80.83ab 67.47e 75.26bcd 77.95bcd 73.56d 79.82abc 78.56abcd 83.65a 75.00cd 77.14 1.77 <0.01
 Leucine 68.16b 75.21a 63.42c 69.42b 74.77a 69.53b 75.35a 67.47bc 74.95a 66.61bc 70.49 1.53 <0.01
 Isoleucine 73.02c 80.11a 70.38c 72.02c 73.89bc 71.13c 73.95bc 68.92c 78.66ab 68.47c 73.06 1.82 <0.01
 Lysine 76.45a 78.49a 63.16c 75.97a 75.79a 67.35b 76.15a 76.80a 79.21a 65.49bc 73.49 1.09 <0.01
 Methionine 84.24bc 87.78ab 74.79d 83.41c 84.22bc 80.71c 84.32bc 83.11c 88.60a 74.92d 82.61 1.19 <0.01
 Phenylalanine 72.25bc 81.99a 69.80c 78.01ab 80.54a 70.34c 78.79ab 78.04ab 79.39a 74.98abc 76.41 2.21 <0.01
 Threonine 67.90abc 70.93a 55.58d 62.63bc 66.72abc 55.19d 70.47a 69.47ab 72.04a 61.74cd 65.27 2.30 <0.01
 Tryptophan 69.53bc 75.68a 62.53d 68.95bc 69.22bc 64.64cd 73.56ab 68.20c 77.40a 65.42cd 69.51 1.69 <0.01
 Valine 62.91de 75.39a 62.00e 66.79cde 69.04abcd 65.56de 72.89abc 73.98ab 75.54a 68.32bcde 69.24 2.08 <0.01
Dispensable AA
 Alanine 68.21bcd 73.56a 61.55ef 65.22de 70.20abc 66.19cd 72.06ab 64.03de 74.02a 59.64f 67.47 1.43 <0.01
 Aspartate 69.61bc 79.59a 59.63d 70.36bc 71.37b 66.85c 75.71a 71.36b 76.66a 69.59bc 71.07 1.34 <0.01
 Cystine 62.76de 71.26ab 39.76g 63.82cd 67.27bcd 57.80ef 68.65abc 64.20cd 74.06a 55.70f 62.53 1.83 <0.01
 Glutamine 79.28b 84.04a 75.13c 79.71b 80.94b 79.34b 83.84a 80.38b 83.78a 79.32b 80.58 0.80 <0.01
 Glycine 55.89d 60.93c 44.94e 47.17e 55.34d 48.60e 66.19b 58.20cd 70.02a 47.88e 55.52 1.34 <0.01
 Proline 71.86b 71.58b 42.80f 67.28c 51.50e 61.20d 70.22bc 67.43c 77.54a 62.28d 64.37 1.03 <0.01
 Serine 67.00bc 74.50a 49.40e 67.50cd 63.53bc 61.66d 69.19b 69.73b 75.36a 60.14d 65.78 1.59 <0.01
 Tyrosine 83.93b 86.34a 76.35e 78.59d 78.07de 67.19f 84.46ab 80.54c 84.90ab 64.38g 78.48 0.67 <0.01

CP, crude protein; AA, amino acid; SEM, standard error of the mean.

1 The average value of 10 sunflower seed meal.

a–g Values within the same row with no common superscript differ significantly (p<0.05).

Table 6
Standardized ilea digestibility (%) of CP and AA in sunflower seed meal fed to growing pigs
Item Sunflower seed meal number Mean1 SEM p-value

1 2 3 4 5 6 7 8 9 10
CP 72.71cd 78.03ab 66.70e 70.62cde 72.95cd 67.30e 74.49bc 74.16bc 79.31a 69.25de 72.55 1.35 <0.01
Indispensable AA
 Arginine 91.75a 90.39abc 88.00bcd 88.11bcd 90.02abcd 87.25d 88.99abcd 87.60cd 90.77ab 89.18abcd 89.21 0.88 <0.01
 Histidine 81.83abc 83.16ab 70.66d 78.31bc 81.10abc 76.84c 82.29abc 81.36abc 85.79a 78.11bc 79.94 1.77 <0.01
 Leucine 72.01bc 78.51a 67.66c 73.37b 78.41a 73.44b 78.75a 71.57bc 78.03a 70.83bc 74.26 1.53 <0.01
 Isoleucine 75.81bc 82.37a 73.47c 75.11c 76.88bc 74.35c 76.46bc 71.85c 80.87ab 71.58c 75.87 1.82 <0.01
 Lysine 79.63a 81.46a 67.03c 79.17a 78.96a 70.99b 79.40a 80.04a 82.07a 69.02bc 76.78 1.09 <0.01
 Methionine 86.17bc 89.63ab 77.39d 85.54c 86.26bc 82.99c 86.25bc 85.14c 90.27a 77.16d 84.68 1.19 <0.01
 Phenylalanine 74.46bc 83.78a 72.42c 80.45ab 82.58a 72.93c 80.90ab 80.27ab 81.15ab 77.41abc 78.64 2.21 <0.01
 Threonine 73.29abc 76.04ab 62.39de 69.18bcd 72.97abc 61.97e 75.75ab 75.10abc 77.01a 67.93cde 71.16 2.30 <0.01
 Tryptophan 75.41bcd 80.15ab 68.70e 75.11bcd 74.92bcd 71.02de 78.21abc 74.41cd 81.80a 71.06de 75.08 1.69 <0.01
 Valine 66.69d 78.79a 66.36d 71.20bcd 73.26abc 69.99cd 76.56ab 77.58ab 78.94a 72.16bcd 73.15 2.08 <0.01
Dispensable AA
 Alanine 73.41bcd 78.04a 67.16ef 70.55de 75.06abc 71.61cd 76.59ab 69.78de 78.48a 64.90f 72.56 1.43 <0.01
 Aspartate 72.78cd 81.98a 63.24e 73.70cd 74.77bc 70.39d 78.42ab 74.52bcd 78.97a 73.00cd 74.18 1.34 <0.01
 Cystine 68.64bcd 76.64a 48.56e 70.24bc 73.65ab 65.27cd 74.30ab 70.35bc 79.27a 63.43d 69.03 1.83 <0.01
 Glutamine 81.31b 85.79a 77.39c 81.88b 83.04b 81.56b 85.60a 82.43b 85.48a 81.58b 82.61 0.80 <0.01
 Glycine 63.72bc 67.32b 54.15d 55.43d 63.07c 57.54d 72.82a 66.39bc 76.29a 56.08d 63.28 1.34 <0.01
 Proline 79.79b 79.84b 51.24f 75.44c 58.96e 69.75d 78.48bc 75.94c 85.06a 71.73d 72.62 1.03 <0.01
 Serine 72.21bc 78.94a 55.91e 69.08cd 72.75bc 67.30d 74.15b 75.02ab 79.70a 66.14d 71.12 1.59 <0.01
 Tyrosine 93.01a 93.93a 86.20c 88.58b 89.45b 78.53d 92.40a 90.13b 92.15a 75.74e 88.01 0.67 <0.01

CP, crude protein; AA, amino acid; SEM, standard error of the mean.

1 The average value of 10 sunflower seed meal.

a–f Values within the same row with no common superscript differ significantly (p<0.05).

Table 7
Linear regression equations for prediction of AA digestibility (%) based on the chemical composition (% of DM) of sunflower seed meal fed to growing pigs1
Number Linear regression equations RSD2 R2 p-value
1 AID N = 22.97+(0.74×CP)+(25.44×Met) 0.87 0.96 <0.01
2 AID Lys = 30.00−(0.62×EE)+(30.70×Lys) 0.78 0.97 <0.01
3 AID Lys = 34.04+(94.25×Met)−(86.16×Trp) 0.85 0.98 <0.01
4 AID Met = 53.56−(0.48×EE)+(8.52×Ca)+(36.86×Met) 0.77 0.97 <0.01
5 AID Thr = 17.22+(63.72×Met) 2.17 0.87 <0.01
6 SID N = 35.22+(0.54×CP)+(25.38×Met) 0.83 0.96 <0.01
7 SID Lys = 36.24−(0.61×EE)+(28.70×Lys) 0.93 0.97 <0.01
8 SID Lys = 39.65+(90.30×Met)−(84.36×Trp) 0.84 0.98 <0.01
9 SID Met = 58.02−(0.49×EE)+(7.96×Ca)+(33.98×Met) 0.77 0.97 <0.01
10 SID Thr = 28.39+(56.73×Met) 2.04 0.87 <0.01

AA, amino acid; DM, dry matter; RSD, residual standard deviation; AID, apparent ileal digestibility; CP, crude protein; Met, methionine; Lys, lysine; EE, ether extract; Trp, tryptophan; Thr, threonine; SID, standardized ileal digestibility.

1 Regression equations were developed based on stepwise regression analyses.

2 RSD = The root mean square of the error that applies to the whole model.


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