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Amino Acid Digestibility in Soybean Products, Rapeseed Expellers and a Fermented Mixture of Co-products for Weaner Pigs

21 March 2014

A study at the Hans H Stein Monogastric Nutrition Laboratory at the University of Illinois shows similar digestibility of crude protein and amino acids for all processed soy products tested and these were generally higher than for the rapeseed products tested. A fermented mixed product based on rapeseed had the lowest digestible amino acid content.

Soybean meal is the most common source of protein in swine diets in the United States. However, conventional soybean meal contains antinutritional factors such as antigenic proteins, oligosaccharides, lectins and trypsin inhibitors that limit its use in diets fed to weanling pigs.

Methods of processing soybean meal to remove antinutritional factors have been developed. These include enzyme treatment, fermentation, and the removal of soluble carbohydrates.

Like soybean meal, rapeseed products are usually not fed to weanling pigs due to the presence of glucosinolates and relatively high concentrations of fibre in these products.

Previous research has shown that fermentation of soybean meal can reduce antinutritional factors and fiber concentrations. It is possible that fermentation can make double-zero (00)-rapeseed meals and 00-rapeseed expellers suitable for feeding to weanling pigs, but no research has been conducted to confirm this hypothesis.

An experiment was conducted to determine the standardised ileal digestibility (SID) by weanling pigs of crude protein and amino acids in four sources of processed soybean products, conventional soybean meal, conventional 00-rapeseed expellers, and in a fermented mixture of co-products including 00-rapeseed expellers, wheat bran, potato peel, and soy molasses.

Experimental Design

Twenty-seven weanling barrows with an average initial body weight of 9.29kg were surgically equipped with a T-cannula in the distal ileum and fed one of eight diets.

The four processed soybean products were two sources of enzyme-treated soybean meal (ESBM-1 and ESBM-2), extruded soybean meal (SBM-EX), and soy protein concentrate (SPC). Another diet contained conventional soybean meal (SBM-CV).

Two rapeseed products were also tested: conventional 00-rapeseed expellers (RSE), and a fermented co-product mixture (FCM) containing 00-rapeseed meal, wheat, soy molasses and potato peel.

Seven of the diets each contained one of the seven test ingredients as the sole source of amino acids. In addition, a nitrogen-free diet was used to calculate basal endogenous losses of crude protein and amino acids.

Ileal digesta were collected and analyzed to determine amino acid digestibility.


The concentration of crude protein ranged from 47.81 per cent to 62.05 per cent in the soybean meal products and from 30.13 per cent to 32.00 per cent in the rapeseed products (Table 1).

Table 1. Analysed crude protein and amino acid composition of enzyme-treated soybean meal (ESBM-1 and ESBM-2), extruded soybean meal (SBM-EX), soy protein concentrate (SPC), conventional soybean meal (SBM-CV), conventional 00-rapeseed expellers (RSE), and a fermented 00-rapeseed coproduct mixture (FCM) fed to pigs
Crude protein, % 56.82 52.07 53.28 62.05 47.81 30.13 32.00
Indispensable AA, %              
 Arg 4.00 3.64 3.75 4.54 3.44 1.73 1.80
 His 1.43 1.31 1.30 1.57 1.22 0.79 0.75
 Ile 2.63 2.38 2.40 2.93 2.18 1.21 1.11
 Leu 4.31 3.89 4.02 4.85 3.60 1.96 2.12
 Lys 3.64 3.14 3.17 3.90 3.02 1.78 1.65
 Met 0.74 0.70 0.67 0.82 0.65 0.59 0.59
 Phe 2.86 2.57 2.71 3.22 2.37 1.16 1.27
 Thr 2.10 1.92 1.95 2.35 1.79 1.28 1.31
 Trp 0.74 0.65 0.70 0.77 0.66 0.39 0.37
 Val 2.82 2.57 2.49 3.08 2.35 1.47 1.58
Total Indispensable AA, % 25.27 22.77 23.16 28.03 21.28 12.36 12.55
Dispensable AA, %              
 Ala 2.43 2.22 2.20 2.66 2.03 1.26 1.43
 Asp 6.28 5.72 5.94 7.08 5.35 2.10 2.27
 Cys 0.74 0.70 0.65 0.77 0.62 0.65 0.68
 Glu 9.54 8.65 8.96 10.69 8.17 4.47 4.93
 Gly 2.33 2.13 2.12 2.54 1.96 1.43 1.52
 Pro 2.92 2.63 2.63 3.13 2.33 1.74 1.98
 Ser 2.45 2.22 2.40 2.81 2.10 1.17 1.19
 Tyr 1.99 1.81 1.88 2.19 1.68 0.85 0.93
Total AA, % 53.95 48.85 49.94 59.90 45.52 26.03 27.48

Among soy products, the SID of crude protein was the same in ESBM-1, ESBM-2, SBM-EX and conventional soybean meal (Table 2).

The SID of crude protein in SPC was less than that in ESBM-1.The SID for the mean of all indispensable amino acids did not differ among soy products.

The SID of lysine and the lysine:crude protein ratio in ESBM-2 was less than that in SBM-CV, indicating that this product may have been damaged by excessive heat during processing.

The SID of crude protein and most amino acids was greater in the processed soy products than in the rapeseed products. For crude protein and all amino acids, SID values in RSE were greater than in FCM.

Table 2. Standardised ileal digestibility (SID) of crude protein and amino acids in enzyme-treated soybean meal (ESBM-1 and ESBM-2), extruded soybean meal (SBM-EX), soy protein concentrate (SPC), conventional soybean meal (SBM-CV), conventional 00-rapeseed expellers (RSE), and a fermented 00-rapeseed coproduct mixture (FCM) fed to pigs
Crude protein, % 89.92a 85.20abc 86.19ab 82.19bc 87.99ab 79.50c 70.60d <0.01
Indispensable AA, %                
 Arg 96.88a 93.48abc 95.03ab 92.26bc 95.44ab 90.12c 81.06d <0.01
 His 93.41a 90.64ab 90.27ab 88.88b 91.51ab 87.93b 79.56c <0.01
 Ile 91.71a 88.90ab 89.90ab 87.34b 89.71ab 81.29c 74.35d <0.01
 Leu 91.65a 89.22ab 89.64ab 87.50bc 89.65ab 84.94c 78.36d <0.01
 Lys 87.34ab 82.51bc 86.39ab 86.52ab 89.15a 80.19c 64.17d <0.01
 Met 92.92a 90.47abc 90.63abc 88.82bc 92.06ab 87.77c 83.71d <0.01
 Phe 92.60a 90.07ab 90.80ab 88.78b 89.91ab 85.29c 79.93d <0.01
 Thr 87.51a 83.93a 85.28a 85.97a 87.25a 78.05b 70.55c <0.01
 Trp 93.33a 89.95ab 91.09ab 89.99ab 92.30ab 89.00b 85.29c <0.01
 Val 89.95a 86.18a 86.42a 86.40a 88.22a 78.85b 71.36c <0.01
Mean 91.42a 88.25a 89.93a 88.28a 90.32a 83.84b 75.23c <0.01
Dispensable AA, %                
 Ala 88.25a 83.92ab 85.40ab 81.30b 86.95ab 81.53b 73.22c <0.01
 Asp 88.53a 86.32a 85.28a 85.81a 87.77a 81.10b 69.72c <0.01
 Cys 82.26ab 77.30b 79.33ab 79.03ab 84.64a 80.54ab 70.20c <0.01
 Glu 90.05a 87.12a 87.89a 88.06a 90.15a 87.49a 81.78b <0.01
 Gly 86.59a 77.67a 81.07a 74.47ab 86.22a 80.22a 61.92b <0.01
 Pro 101.18a 80.32ab 91.56a 55.39b 97.21a 83.05ab 22.47c <0.01
 Ser 91.97a 89.16a 91.25a 90.41a 91.82a 81.41b 74.83c <0.01
 Tyr 92.43a 89.52a 90.85a 90.39a 90.61a 81.15b 76.67c <0.01
Mean 90.04a 83.82ab 85.59ab 81.31b 88.91ab 83.69ab 67.41c <0.01
Total AA, % 90.64a 86.11abc 87.34abc 84.05bc 89.60ab 83.56c 71.10d <0.01
a-e Means within a row lacking a common superscript letter differ (P<0.05)

Key Points

Digestibility of crude protein and most amino acids was the same in the four processed soy products as in SBM-CV. However, reduced lysine digestibility and lysine:crude protein ratio in ESBM-2 indicated possible heat damage.

Crude protein and amino acid digestibility in SPC was less than in ESBM-1, indicating that this particular source of SPC was not of as high quality as other processed soybean products.

The digestibility of crude protein and amino acids in rapeseed products was generally less than in soy products.

Fermentation did not improve amino acid digestibility in rapeseed expellers; FCM had the least digestible amino acids of all of the ingredients tested. This may be due to damage in the drying process, or to inclusion of low-quality ingredients in FCM.

This report is based on unpublished research by D.M.D.L. Navarro, Y. Liu, T.B. Christensen and H.H. Stein.

March 2014

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