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Rapeseed hulls

IMPORTANT INFORMATION: This datasheet is pending revision and updating; its contents are currently derived from FAO's Animal Feed Resources Information System (1991-2002) and from Bo Göhl's Tropical Feeds (1976-1982).

Datasheet

Description
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Common names 

Rapeseed hulls, canola hulls [English]; coques de colza, pellicules de colza, coques de canola, pellicules de canola [French]; cascara de colza, cascara de canola [Spanish]

Related feed(s) 
Description 

Rapeseed hulls are fibrous byproducts resulting from rapeseed oik extraction. They are fibrous materials with valuable oil and protein content and they can be used to feed ruminants and rabbits.

Description

Rapeseed hulls are the fibrous byproducts of rapeseed oil and rapeseed oilmeal production. Rapeseed hulls account for 12−20% of rapeseed weight. As there is never perfect separation between kernel and hulls, the hull fraction contains parts of kernel and thus have an unusual composition: high fibre (with high proportion of lignin), high protein and high oil content (up to 12%). Complete dehulling of the rapeseed prior to oil extraction yield a high (43%) protein meal with enhanced added value (Carré et al., 2015).

Uses

Because of their high fibre (lignin), oil and protein content rapeseed hulls are mainly used in ruminant and rabbits feeding (Carré et al., 2015; Kazmi, 2011). With their high fat content they can be either used as biofuel for the heater where the seeds are dried either fermented to produce biogas. The hulls can also be further extracted but they yield a low grade oil (with high acidity, poor storage and dark colour)(Kazmi, 2011). Rapeseeds hulls are also used as substrate for mushroom production (Usubharatana et al., 2016). Rapeseeds hulls could be source of high value added biopolymers (Asad et al., 2017).

Distribution 

Rapeseed hulls can be virtually produced in every country where rapeseed oil and rapeseed oil meals are produced. However dehulling process is not widely used. In Europe, in 2011, it was reported that only one plant in Germany and one in France did dehulling at industrial scale (Kazmi, 2011).

Considering that the amount of worldwide rapeseed processed was 60 million tons it can be inferred that dehulling could virtually yield 6-12 million tonnes (in case of complete extraction = 12-20% hulls) (FAO, 2019; Carré et al., 2015). It was suggested that most probable amount would be about 0.6 to 1.2 million tonnes as 10% dehulling was the most profitable level (Kazmi, 2011).

Processes 

Rapeseed dehulling process

This dehulling technology was tested on rapeseed at an industrial scale in France and in Germany in the 1980s. However, the process did not extend a lot. The rapeseeds are cleaned, dried to 8-10 % moisture and crushed in order to remove the hulls. Then the hulls undergo screening to remove pieces of kernels while the kernels are extracted for oil (Kazmi, 2011; Huang Fenghong et al., 2007).

Rapeseed meal dehulling process (tail-end process)

This is a relatively new process, investigated in the Feed-a-Gene programme (Bach Knudsen, 2018). Dehulling does not start from the seed but from the rapeseed meal obtained after the extraction of the non-dehulled rapeseeds. The rapeseed meal undergoes mixing, crushing and fractionation through a fractionation plantsifter which separates the protein fraction (High Protein meal) from the fibrous fraction (pieces of hulls) (see picture above)(Bach Knudsen, 2018).

Environmental impact 

Methane emissions

The use of crushed rapeseeds in the diet of dairy cows has yielded substantial reductions in methane emissions (Beauchemin et al., 2009).With their high oil and fibre content, rapeseed hulls could also lower the amount of methane emitted by ruminants (Carré et al., 2015).

Nutritional aspects
Ruminants 

Rapeseed hulls composition is somewhat similar to that of alfalfa in terms of crude protein content and fibre content. It has additionnally  high fat content and is thus a good energy source for dairy ruminants. Moreover, this fat content could help reducing enteric methane emissions and thus makes rapeseed hulls a promising forage for ruminants in the climate change context (Carré et al., 2015; Beauchemin et al., 2009).

Degradability, digestibility

Compared to other fibrous materials (soybean hulls or beet pulp), rapeseed hulls were reported to have relatively poor OM (59.6%), CP (55.0%) and CF (47%) digestibilities in sheep (Grenet et al., 1990). This could be explained by the high lignin content of the cell layer. Rapessed hulls have poor rumen degradation: after 72h in nylon bag in cannulated sheep only 61% DM of rapeseed hulls had disappeared (Grenet et al., 1990).

Dairy cows

Rapeseed hulls have valuable oil content for dairy cow or goats. The introduction of lipids from rapeseeds in the rations can result in higher milk production with more proteins and in reduced saturated fatty acids (Brunschwig et al., 2006).

Growing cattle

It was shown that growing cattle could consume rapeseed hulls at 1% of their body weight  (BW) when they were 100 kg and 1.67% when their BW was 300 kg (Ahlström, 1973). A further experiment with growing heifers during 13 weeks showed that rapeseed hulls could represent 50% of the concentrate of the ration without impairing feed intake. Heifers growth rate was similar with rapeseed hulls and control during the first 11 weeks. In the last 3 weeks, a change in composition of hulls decreased animal performance (Ahlström et al., 1978).

In another experiment, 9 month-old steers were fed during 6 months on 25% rapeseed hulls (DM dietary level) in order to replace maize silage and thus to provide energy and protein. Apart from a lower feed intake, nor growth rate, nor carcass weight or carcass composition were affected by the inclusion of 25% rapeseed hulls in steers ration (Baudet et al., 1978).

Sheep

Lambs were fed on 25%, 50% and 75% processed (ammonia treated, solvent extracted or a combination of both processes) or not rapeseed hulls as a partial replacer of alfalfa hay. It was reported that increasing rapeseed hulls decreased feed intake as well as DM, CP, ADF and NDF and energy digestibilities whatever the process (McKinnon et al., 1995). 

Pigs 

It was suspected that the level of fibre of rapeseed hulls could impair feed nutritive value of a pig diet. However, it was reported that the fibre brought by rapeseed hulls in pig diet did not alter N retention or the utilization of ileal digestible N for retention (Grala et al., 1998). The apparent ileal digestibility for CP and for the sum of AA in the rapeseed hulls were 26 and 41%, respectively. This could be explained to the linkage between protein and fibre in the hulls (Grala et al., 1999).

In weanling pigs, including rapeseed hulls during 4 weeks in the diet had contrasted effects. One type (cv R500) of rapeseed hulls significantly reduced average daily weight gain (273 g/day) and feed intake (481g/day) while the other type resulted in performance and intake similar to those obtained with soybean hulls or a purified fibre source (respectively 400-466 g/day and 755-882 g/day)(Mitaru et al., 1985). The difference couls be due to the presence of glucosinolates byproducts (Mitaru et al., 1985).

Poultry 

Rapeseed hulls have very poor nutritional value in poultry. Metabolizable energy and protein digestibility of diet decreased linearly with the inclusion of rapeseed hulls, being alsmost null for pure rapeseed hulls in cockerel diets (Lessire et al., 1991).

Rapeseed hulls could be included at 10% dietary level in broiler chicken diet without impairing bird growth, feed efficiency or protein digestibility and matabolizable energy. The tannins contained in the rapeseed hulls were not reported to be detrimental to the birds (Mitaru et al., 1983).

Rabbits 

When available, rapeseed hulls can be included in the list of raw ingredients usable to feed rabbits (Lebas et al., 1983; Kowalska et al., 2016). The incorporation level of rapeseed hulls was tested with success in balanced diets for growing rabbits as partial or almost complete replacement of alfalfa, up to 39-40% of the diet, without significant modification of growth rate (Lebas et al., 1981; Gidenne 1987 ).

As a consequence of the higher lipid content of rapeseed hulls (12-15%) in comparison with dehydrated alfalfa (2.5-3%), the feed efficiency was improved (reduction of 16% of feed conversion ratio) but without significant modification of the diets digestibility for proteins or energy, and without modification of slaughter yield (Lebas et al., 1981). With the same diets, increasing dietary rapeseed hulls induced a significant decrease in saturated fatty acids (especially palmitic acid) in kidney fat and a significant increase in mono-unsaturated fatty acids, especially oleic acid, and in polyunsaturated fatty acids. The kidney fat of rabbits fed the largest amount of rapeseed hulls (40%) was more flabby and translucent than that of the controls (Ouhayoun et al., 1981).
Despite these modifications in the lipids composition, the acceptability of rabbits meat was not altered during a tasting test, even after prolonged storage in frozen form (Ouhayoun et al., 1982). This absence of effect on meat taste is most probably related with very moderate influence of rapeseed hulls on lipids of the longissimus dorsi, in comparison with those of kidney fat (Ouhayoun et al., 1982).
Use of a diet with 20% rapeseed hulls 2 weeks before first mating of young rabbit does and during first gestation reduced mating acceptation and gestation rate in comparison with diets containing soybean meal (16%) raw or dehulled rapeseed meal (20%). The reduction of performance at first mating was associated with a lower growth rate of the young does although they received the same limited quantity of diet : 150 g/d (Lebas et al., 1982).
However for pregnant does, individual growth rate during gestation, number and weight of embryos alive at 28 days of gestation was not affected by the mother dietary treatment (Lebas et al., 1982).

As a conclusion, rapeseed hulls may be considered as safe raw material for growing rabbits feeding with an incorporation level of 20-30% . It is an atypical product with high levels of fibre (53% NDF and 23% ADL) and lipids (10-20% according to the separation process), and a moderate level of proteins (15-17% DM). The digestible energy content was estimated in vivo at 14.8 MJ/kg DM (Lebas et al., 1981). For breeding does, some new information seems useful before a recommendation of inclusion without restriction of rapeseed hulls in rabbit reproduction diets.

Nutritional tables
Tables of chemical composition and nutritional value 

Avg: average or predicted value; SD: standard deviation; Min: minimum value; Max: maximum value; Nb: number of values (samples) used

IMPORTANT INFORMATION: This datasheet is pending revision and updating; its contents are currently derived from FAO's Animal Feed Resources Information System (1991-2002) and from Bo Göhl's Tropical Feeds (1976-1982).

Main analysis Unit Avg SD Min Max Nb
Dry matter % as fed 87.2 1.2 85.2 89.0 17
Crude protein % DM 16.4 1.1 14.2 18.5 22
Crude fibre % DM 24.1 5.8 15.4 34.0 21
NDF % DM 53.3 9.7 38.7 74.2 14
ADF % DM 41.6 8.2 29.1 57.3 15
Lignin % DM 23.5 4.9 16.9 31.4 17
Ether extract % DM 14.1 3.6 8.6 21.8 18
Ash % DM 5.5 0.3 4.9 6.0 19
Starch (polarimetry) % DM 6.0 1
Total sugars % DM 2.8 1
Gross energy MJ/kg DM 21.3 1.1 20.4 22.8 4 *
 
Minerals Unit Avg SD Min Max Nb
Calcium g/kg DM 13.3 1.1 12.0 15.1 7
Phosphorus g/kg DM 2.5 0.8 1.8 4.2 7
Potassium g/kg DM 8.8 1
Sodium g/kg DM 0.1 0.1 0.2 2
Magnesium g/kg DM 1.4 1
Manganese mg/kg DM 40 1
Zinc mg/kg DM 20 1
Copper mg/kg DM 6 1
Iron mg/kg DM 165 1
 
Amino acids Unit Avg SD Min Max Nb
Cystine % protein 2.8 1
Lysine % protein 7.1 1
Methionine % protein 2.0 1
 
Ruminant nutritive values Unit Avg SD Min Max Nb
OM digestibility, Ruminant % 54.8 54.1 55.5 2
Energy digestibility, ruminants % 54.5 54.5 57.2 2 *
DE ruminants MJ/kg DM 11.6 *
ME ruminants MJ/kg DM 9.4 *
Nitrogen digestibility, ruminants % 58.1 56.6 59.6 2
Nitrogen degradability (effective, k=6%) % 50 39 62 2
 
Pig nutritive values Unit Avg SD Min Max Nb
Energy digestibility, growing pig % 52.3 *
DE growing pig MJ/kg DM 11.2 *
MEn growing pig MJ/kg DM 10.5 *
NE growing pig MJ/kg DM 7.2 *
Nitrogen digestibility, growing pig % 28.5 1

The asterisk * indicates that the average value was obtained by an equation.

References

AFZ, 2011; Ashes et al., 1978; Aufrère et al., 1988; Aufrère et al., 1991; Chapoutot et al., 1990; Michalet-Doreau et al., 1980; Noblet, 2001

Last updated on 24/10/2012 00:44:52

References
References 
Datasheet citation 

DATASHEET UNDER CONSTRUCTION. DO NOT QUOTE. https://www.feedipedia.org/node/15618 Last updated on July 8, 2019, 8:58