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.

Results

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
	Ingredient
Item	ESBM-1	FSBM-2	SBM-EX	SPC	SBM-CV	RSE	FCM
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
	Ingredient							P-value
Item	ESBM-1	FSBM-2	SBM-EX	SPC	SBM-CV	RSE	FCM
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