NUTRITIONAL EVALUATON OF RAPESEED MEAL FROM DEHULLED RAPESEED FED FOR PIGLETS AND GROWING-FINISHING PIGS

W. Kracht* , H. Jeroch*, S. Daenicke*, W. Matzke, U. Hennig**, W. Schumann***

Institute of Animal Nutrition and Planned Crop Storage, Agricultural Faculty of Martin-Luther-University Halle-Wittenberg, Emil-Abderhalden-Str.26, D-06108 Halle/Saale, Germany

** Research Institute for Biology of Farm Animals, Dummerstorf, Section Physiology of Nutrition „ Oskar Kellner“, Justus-von-Liebig-Weg 2, D-18509 Rostock, Germany

*** Research Insitute of Agriculture and Fishery of Mecklenburg-Vorpommern, Dorfplatz 1, D18276 Gülzow, Germany

ABSTRACT

Rapeseed, variety EXPRESS, was dehulled before oil extraction. The oil was removed by a prepress-solvent procedure. The rapeseed meal (Rm) of not dehulled (nd) and dehulled (d) rapeseed was examined analytical. The nutrient composition of Rm was as follows ( g/kg dry matter): crude protein: nd 396, d 424; sugar: nd 105, d 120; crude fibre: nd 117, d 72; ADF: nd 209, d 139. In digestibility- and energy balance experiments with piglets (15-20 kg live weight) and pigs (80-85 kg live weight) the digestibilities of organic matter (dOM) and crude nutrients (%) and the digestible and metabolizable energy (ME) contents  were determined. The dOM (%) and the ME contents (MJ/kg dry matter) of Rm, determined with piglets, were: dOM % nd 68, d 78; ME MJ nd 10.96, d 12,36; with pigs were found: dOM % nd 69, d 79; ME MJ nd 11.37, d 12.97. With minipigs (50 kg), which were fitted with ileorectal anastomoses, the precaecal digestibility (pcd) of amino acids were determined. The pcd of lysine was: nd 81 %, d 84 % and of methionine+cystine: nd 84 %, d 87%.

KEYWORDS: Digestibility, metabolizable energy, precaecal digestibility, amino acids

INTRODUCTION

The by-products of the production of rapeseed oil are in Germany, in the order of the consumption of feedstuffs with high protein content, after the soybean products on the second place. The prevailing share of nearly 90 % of the rape by-products are rapeseed meals (Rm), which results from applying the prepress solvent procedure. After reducing the glucosinolate content of rapeseed by plant breeding, the fibre substances became an important factor, which diminishes the feed value of rape products. Because of the fibres are mainly located in the hulls of the seed, in some countries investigations were performed to develop a procedure for dehulling the rapeseed and to study the effect of dehulling on feed value (Burghart and Evrard NN; Jörgensen et al.1985, Bell 1993). A spreading of application did not take place because of economical reasons. The following studies were conducted to examine the influence of dehulling rapeseed on the ingredients of Rm on its feed-value for piglets and pigs.

MATERIAL AND METHODS

A black-seeded rapeseed, variety Express, was dehulled before the withdrawal of oil applying a procedure, which was developed by CIMBRIA-SKET GmbH, Magdeburg (Germany) in cooperation with the University Essen (Germany). The procedure will be described by Rasehorn (1999) on the occasion of this Congress. The oil was removed by the prepress-solvent procedure. The rapeseed and the rapeseed meals (Rm) from not (nd) and dehulled (d) seed were subjected to chemical analyses using standard analytical techniques, which were described by Kracht et al. (1998). The digestibility of crude nutrients and the metabolizable energy contents (ME) of the Rm. from nd and d seed were examined in balance experiments with piglets (15-20 kg live weight) and pigs (80-85 kg live weight). Two successive collection periods were performed in both trials, each of which comprised 5 days with piglets and 7 days with pigs, Per feeding variant were assigned five piglets respectively four pigs. The Rm from nd or d seed were substituted in basal diets at a proportion of 40 %. As basal diets were used a commercial starter diet for piglets and barley (supplemented with 0.3 % L-lysine and 0.2 % mineral-vitamin premix) in the trial with pigs. The contents of digestible energy (DE) based on the measurements of energy input with feed and the energy output in feces by means of a bomb calorimeter. The ME contents of the total diets were calculated from the measured digestible nutrients by using an equation which was published in the German feed-value table (DLG-Futterwerttabelle-Schweine, 1991).The DE and ME contents of the Rm was calculated according to the difference method by substracting the ME content of the basal diet, determined with group 1, from the ME contents of the total ration, considering the Rm proportion of the diet.

The measurement of the precaecal digestibilities of nutrients and amino acid were conducted with 8 Minipigs (52-54 kg), which were fitted with an end to end ileorectal anastomosis, with a preserved ileo-caeco-colic valve according to Hennig et al. (1990). Animals were fed each diet 7 days in total, 3 days for adaption and 4 days for quantitative digesta collection. Further details were reported by Kracht et al (1998).

RESULTS AND DISCUSSION

Analytical results

The crude fibre content of the Rm decreased by dehulling the rapeseed per kg dry matter(dm) by around 40 % and the ADF level by approximately 35 %. The protein- and sugar contents rose by 7 and 14 % (Table1). The ether extract level remained unchanged.

Table 1. Contents  of crude nutrients, fibres, lignin and sugar of rapeseed and                                        rapeseed meals (Rm) from not dehulled and dehulled rapeseed (g/kg dry matter)

	Crude ash	Crude protein	Ether extract	Crude fibre	NDF	ADF	Lignin (ADL)	Sugar
rapeseed	39	198	495	64	164	144	60	49
Rm not dehulled	77	396	21	117	286	209	88	105
Rm dehulled	82	424	21	72	193	135	44	120
Rm not dehulled=100	106	107	100	61	72	65	50	114

The contents of the sums of the total of 18 amino acids (AA) and of the 10 essential AA per kg Rm dm were increased by dehulling about 11 % (Table 2), while the lysine content rose around 15 % and the contents of methionine and cystine about 26 %.   

The increases of GSL level in the seed after dehulling and in Rm as consequence of oil withdrawal were overcome by hydrothermal treatment during the extraction- and toast- procedures. In Rm from dehulled seed took place a more intensive decomposition of GSL than in Rm from not dehulled seed. Apparently the hulls, which remain in the Rm of not dehulled seed, reduce the intensity of steam penetration into the meal and by it diminish the destroying of GSL (Table 3)

Table 2. Contents of some essential amino acids in rapeseed and rapeseed meals (Rm)                        from not dehulled and dehulled rapeseed (g/kg dry matter)

	Dry matter g/kg	Crude protein	Lysine	Methionine +Cystine	Threonine	Tryptophane	å 10 essent. amino acids	å18 amino acids
rapeseed	939	198	10.3	9.4	8.2	2.6	74.7	170.7
Rm  not dehulled	896	396	19.2	21.9	18.7	5.5	159.8	370.0
Rm  dehulled	896	424	22.0	27.7	19.6	5.8	178.8	410.9

The sinapine- and phytate contents, which are corresponding with the GSL located in the rape-kernels, were increased by dehulling. The level of phytate P and its proportion  of total P content were diminished by steam treatment.

Table 3. Antinutritional substances in rapeseed and rapeseed meals (Rm) from not de-                         hulled and dehulled rapeseed in dry matter

	total Glucosinolates(µmol/g)	Sinapine SCN    (g/kg)	Phytic acid                (g/kg)	Phytate- P (g/kg)	Phytate-P from total P (%)
rapeseed	11.90	7.14	22.68	8.40	97
Rm  not dehulled	9.01	11.29	40.21	11.34	86
Rm dehulled	7.86	14.93	36.53	10.30	72

Results of balance experiments with piglets and pigs

Digestibility experiments

The piglets of all groups consumed daily 400 g of one of the diets and the pigs 2600 g.

Table 4. Digestibility of crude nutrients and fibres of rapeseed meals (Rm) from not                  dehulled and dehulled rapeseed, determined with piglets and pigs (%)

	Dry- matter	Organicmatter	Crude protein	Ether extract	N-free extract	Crude fibre	NDF	ADF
Rm not dehulled
piglets 15-20 kg	65±2.8	68±2.6	73±3.7	40±14	72±5.0	46±4.4	50±3.1	42±2.9
pigs     80-85 kg	68±2.8	69±1.3	75±1.0	51±3.3	73±2.2	41±1.0	38±2.7	23±3.3
Rm dehulled
piglets  15-20 kg	74±1.7	78±2.4	79±3.7	41±13	84±5.1	61±4.7	63±2.9	54±2.9
pigs     80-85 kg	75±1.7	79±2.4	83±3.7	45±4.8	81±2.0	58±3.3	63±3.9	64±1.7

By removing the hulls the following changes of the digestibility units were determined with piglets (1) respectively pigs (2) (Table 4): dry matter, (1) +9, (2) +7; organic matter, (1+2) +10; crude protein, (1) +6, (2) +8; N-free extract, (1) +12, (2) +8; crude fibre, (1) +15, (2) +17; NDF, (1) +7, (2) +25; ADF,(1) +12, (2) +41.

The largest improvements after dehulling were observed at fibre digestibilities, whereas the crude protein digestibility increase was rather low. Notwithstanding the digestibility of organic matter of Rm from dehulled rapeseed was lower than the corresponding values of soybean oil meal, which has levels of 87% for meal from not dehulled seed and of 92 % for meal from dehulled seed (DLG-Futterwerttabellen-Schweine 1991).

Energy- balance experiments

The energy contents of the Rm, which were calculated according to the difference method, showed in consequence of dehulling significant improvements (Table 5).The following increases of the digestible energy content of Rm were determined for piglets (1) and pigs (2): (1), 1.76 MJ (=14 %), (2), 1.83 MJ (=14 %). The digestibility of the gross energy was improved about 8 units. The ME contents rose significantly (1) about 1.40 MJ (=14 %) and (2), 1.60 MJ (=14 %). The metabolizability of the digestible energy was not changed. That shows that the whole improvement by dehulling is based on increases of digestibility. Despite the improvement of the ME content of Rm d, the by-product of the dehulled rapeseed remains on a lower level than the ME- values of soybean oil meal, which amounted to 14.82 MJ from not dehulled and 16.21 MJ from dehulled soybeans (DLG-Futterwerttabelle-Schweine 1991)

Table 5. Energy content of rapeseed meals (Rm) from not dehulled and dehulled rape                           seed, determined with piglets and pigs (per kg dry matter)

	Gross energy (GE)   MJ	Digestible energy (DE) MJ	Digestibili-ty of  (GE)              (%)	Metabolizable  energy (ME) MJ	Metaboliza bility  of DE (%)
Rm not dehulled
piglets	19.40	13.01 a	56	10.96 a	84
pigs	19.40	13.36 a	59	11.37 a	85
Rm dehulled
piglets	19.43	14.77 b	64	12.36  b	84
pigs	19.43	15.19 b	67	12. 97 b	85

P< 0.05 values in one column with unequal superscripts are significantly different

Precaecal digestibility

The precaecal digestibility (pcd) of the organic matter of Rm from dehulled seed was increased about 8 units (Table 6).

 Table 6.  Precaecal digestibility  of organic matter, and of some nutrients and ami-                      no acids (AA) (%) 

	Organic matter	Crude protein	N- free extract	Lysine	Met. +Cys.	Threonine	Tryptophan	å ess. AA
Rm not dehulled	52a	75	41	81.0	84.2	79.0	83.6	83.1
Rm dehulled	60 b	78	52	83.9	87.0	82.5	83.7	86.2

This rise was caused predominantly by the improved absorption of the nitrogen free extract, while the pcd of crude protein rose only about 3 units, because of increased outflow of endogenous proteins. The fibre outflow into the hindgut remained unchanged, independent of the amount of fibre intake. The pcd of amino acids were increased only around 2-3 units. It is meaningful that the pcd of lysine ( 84 %) agrees with the pcd of lysine from soybean oil meal( Veevoedertabel 1995)

CONCLUSIONS

The feed value of rapeseed meal will be improved to a significant extent by removing the hulls of the seed. In studies with piglets and pigs was shown, that the digestibility of nutrients, the content of metabolizable energy and the precaecal digestibilities of amino acids of rapeseed meal are increased by dehulling the rapeseed. It seems advisable to split the market for rapeseed meal and to sell one meal from not dehulled seed for feeding ruminants and a second meal from dehulled seed for feeding monogastric animals.                  

ACKNOWLEDGEMENTS

The authors are grateful to the UNION ZUR FÖRDERUNG VON OEL-UND PROTEINPFLANZEN, BONN, for the financial support of these researches.

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