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Toasted rapeseed meal
Description
Rapeseed meal, called canola meal in North America, Australia and some other countries, is the by-product of the extraction of oil from rapeseed. It is a protein-rich ingredient that is widely used to feed all classes of livestock. Worldwide production of rapeseed meal is second only to soybean meal. Rapeseed oil used to have a poor reputation due to the presence of erucic acid, which has a bitter taste and was later found to cause health problems. The use of rapeseed meal as an animal feed was also limited by the presence of glucosinolates, which are antinutritional factors detrimental to animal performance. In the 1960-1970s, low-erucic varieties ("0") and low-erucic, low-glucosinolate varieties ("00", double-zero, double low, canola) were developed, allowing rapeseed oil to become a major food oil, and rapeseed meal and rapeseeds to grow in importance as fed to livestock. The first 00 varieties were introduced commercially in Canada in the mid-1970s. In some countries, such as France, 00 varieties became commercially available in the late 1980s. Low-erucic, low-glucosinolate varieties are now the main types grown worldwide for edible oil, biofuel, industrial oil and lubricants. There are also high-erucic varieties grown for specific industrial purposes. While solvent-extracted rapeseed meal remains the main type of rapeseed meal commercially available, oil-rich rapeseed meals obtained by mechanical pressure have gained popularity since the turn of the century with the development of organic farming and on-farm oil production.
Note: the name "canola" was originally a trademark licensed by the Canadian Canola Council and referred to low erucic/low glucosinolate varieties developed in Canada. It is now used as a generic term for 00 varieties in North America, Australia and other countries. In this datasheet the term "rapeseed" is used to describe 00 varieties and canola varieties, except when otherwise specified, because 00 varieties have become the standard in animal feeding.
Rapeseed meal, called canola meal in North America, Australia and some other countries, is the by-product of the extraction of oil from rapeseed. It is a protein-rich ingredient that is widely used to feed all classes of livestock. Worldwide production of rapeseed meal is second only to soybean meal. Rapeseed oil used to have a poor reputation due to the presence of erucic acid, which has a bitter taste and was later found to cause health problems. The use of rapeseed meal as an animal feed was also limited by the presence of glucosinolates, which are antinutritional factors detrimental to animal performance. In the 1960-1970s, low-erucic varieties ("0") and low-erucic, low-glucosinolate varieties ("00", double-zero, double low, canola) were developed, allowing rapeseed oil to become a major food oil, and rapeseed meal and rapeseeds to grow in importance as fed to livestock. The first 00 varieties were introduced commercially in Canada in the mid-1970s. In some countries, such as France, 00 varieties became commercially available in the late 1980s. Low-erucic, low-glucosinolate varieties are now the main types grown worldwide for edible oil, biofuel, industrial oil and lubricants. There are also high-erucic varieties grown for specific industrial purposes. While solvent-extracted rapeseed meal remains the main type of rapeseed meal commercially available, oil-rich rapeseed meals obtained by mechanical pressure have gained popularity since the turn of the century with the development of organic farming and on-farm oil production.
Note: the name "canola" was originally a trademark licensed by the Canadian Canola Council and referred to low erucic/low glucosinolate varieties developed in Canada. It is now used as a generic term for 00 varieties in North America, Australia and other countries. In this datasheet the term "rapeseed" is used to describe 00 varieties and canola varieties, except when otherwise specified, because 00 varieties have become the standard in animal feeding.
Global rapeseed meal production was 38.8 million t in 2018 which is slightly lower than in 2015-2016 (39.1 million t). In 2018, the main producer of rapeseed meal was the European Union (12.8 million t), followed by China (9.6 million t), Canada (5.3 million t) and India (4.0 million t). The main users of rapeseed meal were the EU, China, North America (USA and Canada), and India.
Solvent-extracted rapeseed meal Rapeseeds contain 40-45% oil and yield about 55-60% oil meal when fully extracted by crushing followed by solvent extraction. The main steps of this process are seed cleaning, seed pre-conditioning, rolling and flaking, seed cooking and pressing to mechanically remove a portion of the oil, solvent extraction (hexane) of the press-cake to remove the remainder of the oil, desolventizing and toasting. Temperature is one of the main factors affecting the quality of rapeseed meal. Solvent-extracted rapeseed meal should not contain more than 2-3% oil.
Expeller or cold-extracted rapeseed meal
Heat treatments
Heating deactivates myrosinase, the enzyme that breaks glucosinolates into toxic aglycones, and results in their 30-70% degradation. High temperatures affect protein quality, which is deleterious to monogastrics as it reduces amino acid digestibility, but beneficial to ruminants as it reduces rumen protein degradability. However, excessive heat processing of rapeseed meal suppressed phytate degradation in the rumen and led to lower availability of dietary phosphorus. Steam treatment also reduced protein digestibility in poultry. Overheating may occur during desolventizing and temperatures should not be higher than 100°C. Cold-pressed rapeseed meal may contain higher amounts of glucosinolates than solvent-extracted meal as glucosinolates need heat for their degradation and subsequent deactivation of myrosinase.
Dehulling
Rapeseed meal is relatively rich in fibre and removing the hull fraction results in a meal containing more protein and less fibre, thus improving its digestibility and nutritional value, particularly for monogastric animals. The production of high-protein, low-fibre rapeseed meal has been extensively studied since the late 1970s and many technologies have been tested. Some consist in removing the hulls before oil extraction (cracking and air-classification, crushing seeds directly on a hard surface or in the gap between two rotating rolls) while other separate the hulls after extraction (air-classification, liquid cyclone fractionation). Dehulling of rapeseed prior to oil pressing allows to maintain the screw press temperature below 40°C, while oil extraction from dehulled rapeseeds enables recovery of most of the oil from kernel. Oil produced from dehulled seeds has better sensory characteristics (milder taste and flavour, bright yellowish colour, and lower content of waxes).
However, dehulling has some important drawbacks, particularly a lower profitability (additional cost of the process, loss of oil in the hull fraction, limited market interest in the dehulled meal or in the hulls). For those reasons, rapeseed dehulling is still not widely used in large-scale oil mills. For instance, a dehulling process was implemented industrially in France in the 1980s, but abandoned after a few years for technical and economic reasons.
Since the 2000s, the search for plant-based protein sources other than soybean has sparked renewed interest in rapeseed dehulling and new technologies are being investigated. A process developed in EU Feed-a-Gene project consists in applying tail-end fractionation to the meal obtained after crushing. Using a plansifter, the meal is separated into a high-protein fraction and a low-protein fraction.
Enzyme treatments
There have been several attempts at improving nutrient availability by reducing the encapsulating effect of the cell wall through the use of enzymes. Tests with phytases have been positive in poultry, as the use of microbial phytase increased significantly P utilization in broilers and laying hens. Many experiences have been inconclusive for NSP-degrading enzymes, perhaps due to the fact that the tested enzymes had been developed for in cereal grains rather than for rapeseed products, but some have been more positive.
Addition of processing by-products
By-products of rapeseed processing are sometimes added back into the meal, notably in Canada. Adding gums, which mostly consist of phospholipids, and soapstocks, which are oil-rich components, increases the energy content of the meal and reduces dustiness. Screenings and foreign materials decrease meal quality.
Expeller or cold-extracted rapeseed meal
- Expeller rapeseed meal results from the mechanical extraction of seeds previously conditioned by a heat treatment. It is also called rapeseed press-cake, canola press-cake or double-pressed canola.
- Cold-extracted press-cake: with the growing interest of consumers for cold-pressed rapeseed oil, another process consisting in pressing the seeds at low temperature (60°C) yields cold-pressed rapeseed press-cake.
Heat treatments
Heating deactivates myrosinase, the enzyme that breaks glucosinolates into toxic aglycones, and results in their 30-70% degradation. High temperatures affect protein quality, which is deleterious to monogastrics as it reduces amino acid digestibility, but beneficial to ruminants as it reduces rumen protein degradability. However, excessive heat processing of rapeseed meal suppressed phytate degradation in the rumen and led to lower availability of dietary phosphorus. Steam treatment also reduced protein digestibility in poultry. Overheating may occur during desolventizing and temperatures should not be higher than 100°C. Cold-pressed rapeseed meal may contain higher amounts of glucosinolates than solvent-extracted meal as glucosinolates need heat for their degradation and subsequent deactivation of myrosinase.
Dehulling
Rapeseed meal is relatively rich in fibre and removing the hull fraction results in a meal containing more protein and less fibre, thus improving its digestibility and nutritional value, particularly for monogastric animals. The production of high-protein, low-fibre rapeseed meal has been extensively studied since the late 1970s and many technologies have been tested. Some consist in removing the hulls before oil extraction (cracking and air-classification, crushing seeds directly on a hard surface or in the gap between two rotating rolls) while other separate the hulls after extraction (air-classification, liquid cyclone fractionation). Dehulling of rapeseed prior to oil pressing allows to maintain the screw press temperature below 40°C, while oil extraction from dehulled rapeseeds enables recovery of most of the oil from kernel. Oil produced from dehulled seeds has better sensory characteristics (milder taste and flavour, bright yellowish colour, and lower content of waxes).
However, dehulling has some important drawbacks, particularly a lower profitability (additional cost of the process, loss of oil in the hull fraction, limited market interest in the dehulled meal or in the hulls). For those reasons, rapeseed dehulling is still not widely used in large-scale oil mills. For instance, a dehulling process was implemented industrially in France in the 1980s, but abandoned after a few years for technical and economic reasons.
Since the 2000s, the search for plant-based protein sources other than soybean has sparked renewed interest in rapeseed dehulling and new technologies are being investigated. A process developed in EU Feed-a-Gene project consists in applying tail-end fractionation to the meal obtained after crushing. Using a plansifter, the meal is separated into a high-protein fraction and a low-protein fraction.
Enzyme treatments
There have been several attempts at improving nutrient availability by reducing the encapsulating effect of the cell wall through the use of enzymes. Tests with phytases have been positive in poultry, as the use of microbial phytase increased significantly P utilization in broilers and laying hens. Many experiences have been inconclusive for NSP-degrading enzymes, perhaps due to the fact that the tested enzymes had been developed for in cereal grains rather than for rapeseed products, but some have been more positive.
Addition of processing by-products
By-products of rapeseed processing are sometimes added back into the meal, notably in Canada. Adding gums, which mostly consist of phospholipids, and soapstocks, which are oil-rich components, increases the energy content of the meal and reduces dustiness. Screenings and foreign materials decrease meal quality.
Rapeseed meal from genetically-modified (GM) seeds
GM rapeseed cultivars have been developed and are widely used in Canada (95% of the crops) and in the USA (82%). In the European Union, the cultivation of GM rapeseed crops is banned but the seeds, oil and oil meal resulting from the cultivation of certain cultivars can be imported and used as feed and food. The harmonisation of GM rapeseed labelling has been recommended so that livestock farmers can make an informed choice, but no compulsory labelling is required for animal products from livestock fed GM oilseed rape products.
GM rapeseed cultivars have been developed and are widely used in Canada (95% of the crops) and in the USA (82%). In the European Union, the cultivation of GM rapeseed crops is banned but the seeds, oil and oil meal resulting from the cultivation of certain cultivars can be imported and used as feed and food. The harmonisation of GM rapeseed labelling has been recommended so that livestock farmers can make an informed choice, but no compulsory labelling is required for animal products from livestock fed GM oilseed rape products.
Rapeseed meal is often included in the diets of several species of livestock because of its high protein content (35-44% of DM). It is often fed as a substitute for soybean meal. Rapeseed protein is poorer in lysine than soybean (5.5% vs. 6.3% of the crude protein) but is richer in sulphur-containing amino acids (sum of methionine + cysteine: 4.3% vs. 3% of the crude protein). Rapeseeds are small and contain about 18-21% hulls, and the oil meal contains about 30% hulls. Thus rapeseed meal has a relatively high fibre content, crude fibre being between 10-18% of DM, which is higher than the crude fibre content of all types of soybean meals, but lower than that of other oil meals such as sunflower meal. Its lignin content is also high (about 10% of DM), whereas the lignin content of soybean meal is usually lower than 1%. The low lysine and high fibre content tends to limit the use of rapeseed meal in monogastric and fish species. Feeding pigs and poultry with rapeseed meal as their only source of supplementary protein often results in lower animal performance. Solvent-extracted rapeseed meal contains small amounts of residual oil (about 3% DM). Canadian solvent-extracted canola meal may have a higher oil content due to the reintroduction of gums and soapstocks into the meal during processing.
Rapeseed oil is rich in polyunsaturated fatty acids (60% C18:1 oleic acid, 21% C18:2 linoleic acid and 10% C18:3 linolenic acid), which makes it valuable for human and animal diets. In Australia, a comparison of the fatty acid profile of the residual oil expeller and solvent-extracted meals showed significant differences between them: solvent-extracted meal tended to have a lower proportion of oleic acid than expeller meal (54 vs. 59%) and a higher proportion of linoleic acid (25 vs. 22%).
Expeller and cold-pressed rapeseed meals
Rapeseed meal obtained by mechanical pressure only has extremely variable quantities of oil, usually between 7-15% but sometimes as high as 20% of DM, resulting in a higher energy value than solvent-extracted meal. Cold-pressed rapeseed meal usually has a higher oil content than expeller rapeseed meal. Lysine availability was found to be higher in cold-pressed rapeseed meal than in expeller meal, indicating less heat damage. Glucosinolates tended to be higher in expeller and cold-pressed rapeseed meal as myrosinase was not, or less, deactivated than in solvent-extracted meal. However, another study found cold-pressed meal to have a much lower glucosinolate content, below the maximum level tolerated for optimal pig growth.
Dehulling
Dehulling has been shown to improve the nutritional value of rapeseed meal. Dehulling reduced fibre content and increased amino acid and nutrient digestibility in pigs, but did not affect the rumen disappearance of amino acids in ruminants.
Rapeseed oil is rich in polyunsaturated fatty acids (60% C18:1 oleic acid, 21% C18:2 linoleic acid and 10% C18:3 linolenic acid), which makes it valuable for human and animal diets. In Australia, a comparison of the fatty acid profile of the residual oil expeller and solvent-extracted meals showed significant differences between them: solvent-extracted meal tended to have a lower proportion of oleic acid than expeller meal (54 vs. 59%) and a higher proportion of linoleic acid (25 vs. 22%).
Expeller and cold-pressed rapeseed meals
Rapeseed meal obtained by mechanical pressure only has extremely variable quantities of oil, usually between 7-15% but sometimes as high as 20% of DM, resulting in a higher energy value than solvent-extracted meal. Cold-pressed rapeseed meal usually has a higher oil content than expeller rapeseed meal. Lysine availability was found to be higher in cold-pressed rapeseed meal than in expeller meal, indicating less heat damage. Glucosinolates tended to be higher in expeller and cold-pressed rapeseed meal as myrosinase was not, or less, deactivated than in solvent-extracted meal. However, another study found cold-pressed meal to have a much lower glucosinolate content, below the maximum level tolerated for optimal pig growth.
Dehulling
Dehulling has been shown to improve the nutritional value of rapeseed meal. Dehulling reduced fibre content and increased amino acid and nutrient digestibility in pigs, but did not affect the rumen disappearance of amino acids in ruminants.
Oil rapeseeds used to have a high content of erucic acid and glucosinolates that are of concern for animal and human health, but those problems have been eliminated or largely reduced through traditional genetic selection since the 1970s.
Erucic acid
Erucic acid (cis 13-docosenoic acid, 22:1n-9) used to be a major component of rapeseed oil (up to 50% in earlier cultivars). Erucic acid causes a bitter taste and has adverse effects on heart health and animal performance that were demonstrated in early studies with rats, ducklings, poultry, and pigs. This concern led to the development of low-erucic cultivars ("0") in the 1970s, and by 2005 most rapeseed oil produced worldwide contained less than 2% of erucic acid. The content in erucic acid of foods is now regulated: in Canada, canola oil must contain less than 2% erucic acid; in the EU the fat content of foodstuffs must contain less than 5% erucic acid (less than 1% for infant formulae).
However, the scientific consensus on erucic acid has softened since the 1970s. An extensive literature review found that while a high intake of erucic acid does result in myocardial lipidosis in pigs and rats, this lipidosis regresses after animals return to a low-fat diet without erucic acid. For pigs, a NOAEL (no observed adverse effect level) of 700 mg/kg BW per day was identified. For dairy cows, a reduction in feed intake and milk yield by dairy cows was reported at an intake of 0.4 g erucic acid/kg BW per day from rapeseed meal. In fish, rabbits and horses, no conclusion could be drawn due to the limited studies available. The most severe effects were observed in poultry: high-erucic diets resulted in growth retardation, cardiac lipidosis, and other adverse effects on health and production. A LOAEL (lowest observed adverse effect level) of 0.02 g/kg BW per day was defined, and a health risk exists in poultry when maximum inclusion rates are applied. It is important to note that, in all livestock species, it is difficult to distinguish the adverse effects of erucic acid from those of other dietary factors such as glucosinolates. Still, erucic acid remains a concern, as dietary erucic acid is transferred to products of animal origin and a dose-related increase in erucic acid in food of animal origin has been shown. As of 2019, the question of the toxicity of erucic acid for livestock remains elusive.
Since the late 1990s, high-erucic acid rapeseed (HEAR) cultivars are grown for niche industrial purposes to produce erucamide (an additive in polyethylene and polypropylene manufacture and a surfactant) and behenic acid.
Glucosinolates
Glucosinolates are a family of sulphur-rich glucosides that are characteristic of Brassicaceae plants. The hydrolyzed products of glucosinolates (isothiocyanates and other sulphur-containing compounds) give a pungent and bitter taste to the oil that is often enjoyed by humans (mustard) but tends to reduce the palatability of brassica products for livestock, affecting feed intake. Glucosinolates also interfere with iodine metabolism. In monogastrics, they cause physiological disorders in the liver, kidneys, and thyroid glands, and, as a consequence, reduce growth and performance. Mortality can increase, especially in laying hens, due to hemorrhagic liver syndrome.
Since the 1970s, glucosinolates have been mostly bred out of rapeseed cultivars, though not eliminated. Modern 00 rapeseed/canola cultivars have very low levels of glucosinolates. In Canada, canola oil must contain less than 30 µmoles of glucosinolates per gram of air-dried oil-free meal . The glucosinolate content of rapeseeds has been declining steadily, and is now often below 10 µmol/g vs. 120 µmol/g for former non-00 cultivars. Surveys conducted since 2010 reported averages of 3.9 µmol/g (Canadian canola meal), and 10 µmol/g (French rapeseed meal). The use of rapeseed meal in pigs and poultry diets can now be increased without affecting feed intake or the physiological functions of livestock. In poultry the limitation is not due to glucosinolates but to the high fibre content.
Tannins
Tannins are phenolic compounds that bind with various compounds, including proteins, making them less available to the animal. In rapeseeds, most tannins are contained in the seed coat. With pigs it was found that dark hulled seeds were nearly indigestible whereas yellow hulled seeds were reasonably well digested. This was attributed to a lower tannin and lignin content in the brighter seeds. Lighter varieties of rapeseeds were reported to contain less tannins ("000" varieties). Some breeding programmes aim at reducing the thickness of the seed coat, and thus the level of tannins. Dehulled rapeseed meal and rapeseed meal from light-coloured varieties may thus have a lower tannin content.
Phytic acid
The phosphorus of rapeseed meal is mostly in the form of phytic acid, with a phytic P:total P ratio comprised in the range of 67-95%. Phytic acid binds to cations such as Zn, Ca, and Fe, thus reducing their bioavailability.
Sinapine and choline
Rapeseed meal contains about 1% sinapine, an alkaloidal amine found in the seeds of Brassica species including rape. Sinapine is a choline ester converted into trimethylamine by the micro-organisms in the gastrointestinal tract of birds. Trimethylamine is then converted by an enzyme into an odourless form later excreted through urine. Hens with brown-shelled eggs lack that enzyme and, in these breeds, trimethylamine accumulates in the egg, causing them to have a fishy taste. The amount of rapeseeds should thus be limited for this category of layers (Pickard, 2005). All sources of choline (choline chloride and sinapine from canola meal) can be transformed in trimethylamine, but the tainting effect of rapeseed meal seemed to override the one with choline chloride. Sinapine also reduces palatability and has a depressing effect on feed consumption.
Erucic acid
Erucic acid (cis 13-docosenoic acid, 22:1n-9) used to be a major component of rapeseed oil (up to 50% in earlier cultivars). Erucic acid causes a bitter taste and has adverse effects on heart health and animal performance that were demonstrated in early studies with rats, ducklings, poultry, and pigs. This concern led to the development of low-erucic cultivars ("0") in the 1970s, and by 2005 most rapeseed oil produced worldwide contained less than 2% of erucic acid. The content in erucic acid of foods is now regulated: in Canada, canola oil must contain less than 2% erucic acid; in the EU the fat content of foodstuffs must contain less than 5% erucic acid (less than 1% for infant formulae).
However, the scientific consensus on erucic acid has softened since the 1970s. An extensive literature review found that while a high intake of erucic acid does result in myocardial lipidosis in pigs and rats, this lipidosis regresses after animals return to a low-fat diet without erucic acid. For pigs, a NOAEL (no observed adverse effect level) of 700 mg/kg BW per day was identified. For dairy cows, a reduction in feed intake and milk yield by dairy cows was reported at an intake of 0.4 g erucic acid/kg BW per day from rapeseed meal. In fish, rabbits and horses, no conclusion could be drawn due to the limited studies available. The most severe effects were observed in poultry: high-erucic diets resulted in growth retardation, cardiac lipidosis, and other adverse effects on health and production. A LOAEL (lowest observed adverse effect level) of 0.02 g/kg BW per day was defined, and a health risk exists in poultry when maximum inclusion rates are applied. It is important to note that, in all livestock species, it is difficult to distinguish the adverse effects of erucic acid from those of other dietary factors such as glucosinolates. Still, erucic acid remains a concern, as dietary erucic acid is transferred to products of animal origin and a dose-related increase in erucic acid in food of animal origin has been shown. As of 2019, the question of the toxicity of erucic acid for livestock remains elusive.
Since the late 1990s, high-erucic acid rapeseed (HEAR) cultivars are grown for niche industrial purposes to produce erucamide (an additive in polyethylene and polypropylene manufacture and a surfactant) and behenic acid.
Glucosinolates
Glucosinolates are a family of sulphur-rich glucosides that are characteristic of Brassicaceae plants. The hydrolyzed products of glucosinolates (isothiocyanates and other sulphur-containing compounds) give a pungent and bitter taste to the oil that is often enjoyed by humans (mustard) but tends to reduce the palatability of brassica products for livestock, affecting feed intake. Glucosinolates also interfere with iodine metabolism. In monogastrics, they cause physiological disorders in the liver, kidneys, and thyroid glands, and, as a consequence, reduce growth and performance. Mortality can increase, especially in laying hens, due to hemorrhagic liver syndrome.
Since the 1970s, glucosinolates have been mostly bred out of rapeseed cultivars, though not eliminated. Modern 00 rapeseed/canola cultivars have very low levels of glucosinolates. In Canada, canola oil must contain less than 30 µmoles of glucosinolates per gram of air-dried oil-free meal . The glucosinolate content of rapeseeds has been declining steadily, and is now often below 10 µmol/g vs. 120 µmol/g for former non-00 cultivars. Surveys conducted since 2010 reported averages of 3.9 µmol/g (Canadian canola meal), and 10 µmol/g (French rapeseed meal). The use of rapeseed meal in pigs and poultry diets can now be increased without affecting feed intake or the physiological functions of livestock. In poultry the limitation is not due to glucosinolates but to the high fibre content.
Tannins
Tannins are phenolic compounds that bind with various compounds, including proteins, making them less available to the animal. In rapeseeds, most tannins are contained in the seed coat. With pigs it was found that dark hulled seeds were nearly indigestible whereas yellow hulled seeds were reasonably well digested. This was attributed to a lower tannin and lignin content in the brighter seeds. Lighter varieties of rapeseeds were reported to contain less tannins ("000" varieties). Some breeding programmes aim at reducing the thickness of the seed coat, and thus the level of tannins. Dehulled rapeseed meal and rapeseed meal from light-coloured varieties may thus have a lower tannin content.
Phytic acid
The phosphorus of rapeseed meal is mostly in the form of phytic acid, with a phytic P:total P ratio comprised in the range of 67-95%. Phytic acid binds to cations such as Zn, Ca, and Fe, thus reducing their bioavailability.
Sinapine and choline
Rapeseed meal contains about 1% sinapine, an alkaloidal amine found in the seeds of Brassica species including rape. Sinapine is a choline ester converted into trimethylamine by the micro-organisms in the gastrointestinal tract of birds. Trimethylamine is then converted by an enzyme into an odourless form later excreted through urine. Hens with brown-shelled eggs lack that enzyme and, in these breeds, trimethylamine accumulates in the egg, causing them to have a fishy taste. The amount of rapeseeds should thus be limited for this category of layers (Pickard, 2005). All sources of choline (choline chloride and sinapine from canola meal) can be transformed in trimethylamine, but the tainting effect of rapeseed meal seemed to override the one with choline chloride. Sinapine also reduces palatability and has a depressing effect on feed consumption.
Rapeseed meal is a common feed ingredient for all classes of ruminant livestock, as a source of protein and energy. Due to its lower protein content, higher fibre and higher protein degradability, rapeseed meal is often considered of significantly lower value than soybean meal. However, several meta-analysis of dairy cattle studies concluded that both the energy and the protein value of rapeseed meal were higher than previously thought.
Palatability
Rapeseed meal is a highly palatable source of protein for ruminant animals. In dairy cows, replacing soybean meal with rapeseed meal maintained intake (with 20% rapeseed meal), or increased intake (with 9% rapeseed meal). Substituting 20% rapeseed meal for high-protein maize distillers grains maintained intake. In beef cattle, diets with 10% rapeseed meal resulted in a higher intake than diets based on maize distillers grains or wheat distillers grains. In finishing cattle, diets containing 30% expeller or solvent-extracted rapeseed meal did not cause intake issues. In calves, feed intake was similar for diets containing 00 rapeseed meal and those containing soybean meal. However, intake was reduced for calves fed a diet with a high-glucosinolate rapeseed meal (more than 100 µmol/g). In dairy calves, using flavouring agents was found unnecessary when feeding a diet containing rapeseed meal. Preweaning calves offered low-protein starter pellets and either rapeseed meal or soybean meal consumed more soybean pellets than rapeseed pellets.
Palatability
Rapeseed meal is a highly palatable source of protein for ruminant animals. In dairy cows, replacing soybean meal with rapeseed meal maintained intake (with 20% rapeseed meal), or increased intake (with 9% rapeseed meal). Substituting 20% rapeseed meal for high-protein maize distillers grains maintained intake. In beef cattle, diets with 10% rapeseed meal resulted in a higher intake than diets based on maize distillers grains or wheat distillers grains. In finishing cattle, diets containing 30% expeller or solvent-extracted rapeseed meal did not cause intake issues. In calves, feed intake was similar for diets containing 00 rapeseed meal and those containing soybean meal. However, intake was reduced for calves fed a diet with a high-glucosinolate rapeseed meal (more than 100 µmol/g). In dairy calves, using flavouring agents was found unnecessary when feeding a diet containing rapeseed meal. Preweaning calves offered low-protein starter pellets and either rapeseed meal or soybean meal consumed more soybean pellets than rapeseed pellets.
Digestibility and energy value
Rapeseed meal is a good source of energy for ruminants. For solvent-extracted rapeseed meal, the net energy values for range from 6.8 to 7.45 MJ/kg DM. These correspond roughly to 80% of the net energy value for soybean meal. OM digestibility is about 74-77%. However, it has been suggested that the fibre digestibility of rapeseed meal may be undervalued. Some experiments have shown than rapeseed meal can result in dairy performance similar to that obtained with soybean meal. Further research is needed to determine the correct energy value of rapeseed meal. Expeller and cold-pressed rapeseed meals have a higher energy value than solvent-extracted meal because of the higher amount of residual oil.
Protein value
Rapeseed meal is a common source of protein for ruminants. Its protein has long been considered as more degradable than that of soybean, but estimates of rumen-undegraded protein (RUP), made using newer methods taking into account the contribution of the soluble-protein fraction to the RUP available to the animal, suggest that the RUP (expressed as a % of protein) of rapeseed meal is in the 40-56% range, compared to 27-45% for soybean meal.
Amino acid value
Rapeseed meal has a good amino acid profile for ruminants, and contributes a significant amount of methionine, which is often the first limiting amino acid in production. In addition, the amino acid profile of the RUP fraction more closely matches requirements for maintenance and milk than other vegetable proteins.
Rapeseed meal is a good source of energy for ruminants. For solvent-extracted rapeseed meal, the net energy values for range from 6.8 to 7.45 MJ/kg DM. These correspond roughly to 80% of the net energy value for soybean meal. OM digestibility is about 74-77%. However, it has been suggested that the fibre digestibility of rapeseed meal may be undervalued. Some experiments have shown than rapeseed meal can result in dairy performance similar to that obtained with soybean meal. Further research is needed to determine the correct energy value of rapeseed meal. Expeller and cold-pressed rapeseed meals have a higher energy value than solvent-extracted meal because of the higher amount of residual oil.
Protein value
Rapeseed meal is a common source of protein for ruminants. Its protein has long been considered as more degradable than that of soybean, but estimates of rumen-undegraded protein (RUP), made using newer methods taking into account the contribution of the soluble-protein fraction to the RUP available to the animal, suggest that the RUP (expressed as a % of protein) of rapeseed meal is in the 40-56% range, compared to 27-45% for soybean meal.
Amino acid value
Rapeseed meal has a good amino acid profile for ruminants, and contributes a significant amount of methionine, which is often the first limiting amino acid in production. In addition, the amino acid profile of the RUP fraction more closely matches requirements for maintenance and milk than other vegetable proteins.
Solvent-extracted rapeseed meal
Rapeseed meal is an excellent protein supplement for lactating dairy cows and can be included in relatively large amounts to their diet. Inclusion rates as high as 20% have been reported with no negative effect on intake and production. A meta-analysis of 122 studies comparing rapeseed meal to soybean meal found that for each additional kg of protein supplied in the diet, milk production increased by 3.4 kg with rapeseed meal, and 2.4 kg with soybean meal, showing a 1 kg advantage to the rapeseed meal. Another meta-analysis of 49 studies comparing rapeseed meal with other protein sources found that at the average level of inclusion, rapeseed meal increased milk yield by 1.4 kg when all the other ingredients were considered, but only by 0.7 kg when rapeseed meal was substituted for soybean meal. A follow-up of the latter study focused on plasma amino acids suggested that feeding rapeseed meal increased the absorption of essential amino acids, resulting in higher milk protein secretion and, thus, higher protein efficiency. Rapeseed meal was effectively used in combination with maize distillers grains to restore amino acid balance and maximise animal performance. Blends of rapeseed meal and wheat distillers grains have also been shown to support high levels of milk production. A comparison between rapeseed meal and wheat distillers grain resulted in similar dairy performances.
Rapeseed meal is an excellent protein supplement for lactating dairy cows and can be included in relatively large amounts to their diet. Inclusion rates as high as 20% have been reported with no negative effect on intake and production. A meta-analysis of 122 studies comparing rapeseed meal to soybean meal found that for each additional kg of protein supplied in the diet, milk production increased by 3.4 kg with rapeseed meal, and 2.4 kg with soybean meal, showing a 1 kg advantage to the rapeseed meal. Another meta-analysis of 49 studies comparing rapeseed meal with other protein sources found that at the average level of inclusion, rapeseed meal increased milk yield by 1.4 kg when all the other ingredients were considered, but only by 0.7 kg when rapeseed meal was substituted for soybean meal. A follow-up of the latter study focused on plasma amino acids suggested that feeding rapeseed meal increased the absorption of essential amino acids, resulting in higher milk protein secretion and, thus, higher protein efficiency. Rapeseed meal was effectively used in combination with maize distillers grains to restore amino acid balance and maximise animal performance. Blends of rapeseed meal and wheat distillers grains have also been shown to support high levels of milk production. A comparison between rapeseed meal and wheat distillers grain resulted in similar dairy performances.
Rapeseed meal is a suitable protein source for growing and finishing cattle. In post-weaning beef calves, a comparison of rapeseed meal and legume seeds (field peas, chickpeas and lentils) showed that the rapeseed meal diet resulted in a lower daily gain and in a higher feed:gain ratio. In dairy calves, rapeseed meal and soybean meal resulted in similar DM intakes and daily gains. In heifers, a comparison of rapeseed meal and several types of wheat or maize distillers grains showed that all ingredients improved performance and increased DM intake, while total tract digestibility of OM and NDF was highest with rapeseed meal. In dairy heifers fed diets containing either soybean meal or rapeseed meal, pregnancy rates were higher for the heifers given rapeseed meal during prepubertal development, than for those receiving soybean meal. In steers, a similar study found that rapeseed meal improved intake and daily weight gain compared to those fed distillers grain. Supplementing grass silage with rapeseed meal increased weight gains in growing beef steers. With finishing steers, it increased daily gains and reduced the number of days of feeding required. In finishing cattle, 15 or 30% expeller or solvent-extracted rapeseed meal gave similar average daily gains but the 30% rapeseed diet reduced feed efficiency.
In grazing beef cows, protein supplementation with either rapeseed meal, sunflower meal or cull beans resulted in similar calf birth weights, calf weaning weights and cow body condition change, whereas weight loss during gestation was lowest with rapeseed meal. Grazing beef cows produced more milk when rapeseed meal was partially substituted for wheat.
Rapeseed meal has been shown to support growth in sheep. In growing lambs, rapeseed meal was found superior to lupins for weight gain and feed efficiency. In lambs fed high-roughage diets, supplementation of hay or silage diets with rapeseed meal or fish meal improved daily gains and feed efficiency, with the rapeseed meal appearing to be as effective as fish meal. In lambs fed diets containing up to 30% rapeseed meal, there were no effects on weight gain or feed intake, despite the fact that thyroid hormone production was lower at the higher inclusion levels.
Because of its methionine content, rapeseed meal is an ideal supplement for the production of wool and mohair.
Because of its methionine content, rapeseed meal is an ideal supplement for the production of wool and mohair.
Rapeseed meal is a high-quality, high-protein feed ingredient for pigs. However, compared to soybean meal, the lower lysine content, the lower amino acid availability and the higher fibre content and lower energy value (about 80% that of soybean meal) of rapeseed meal make it less valuable for pigs. Rapeseed meal is a better source of calcium, selenium and zinc than soybean meal, but a poorer source of potassium and copper. Its high phytic acid and fibre contents reduce the availability of many mineral elements. Rapeseed meal is a good source of vitamins (choline, niacin, riboflavin and biotin). In the past glucosinolates limited the use of rapeseed meal in pig diets. An estimate of the tolerable level of glucosinolates in the total diet of pigs is 2.4-2.5 µmol/g. Palatability of rapeseed meal is a limiting factor for pigs.
Solvent-extracted rapeseed meal
The response of pigs of all ages to rapeseed meal inclusion in the diet is generally favourable. It must be noted that recommendations established in the 1980-1990s were often conservative (e.g. 5% in starter diets, 10% for sows and finishers, and 15% for growing pigs), as they were based on early studies with meals containing significant amounts of glucosinolates. Recent studies show that rapeseed meal, from modern 00 cultivars, is much better tolerated by pigs.
Piglets
Rapeseed meal was included in piglet diets at up to 15-20% (DM basis) without compromising growth performance, organ weights, bone ash or blood parameters.
Growing pigs
It used to be recommended to include rapeseed meal in grower diets to supply up to 50% of the protein requirements, but recent studies have shown that it is possible to use 100% rapeseed meal as the protein source in these diets. Using rapeseed meal as the sole protein source had no effect on feed intake and growth performance of growing pigs. When pig diets (growing or finishing pigs) were formulated in order to get the same amount of digestible lysine from rapeseed meal or soybean meal, growth performance and carcass quality were similar.
Fattening pigs
In fattening pigs, rapeseed meal completely replaced soybean meal without significant changes in growth performance, visceral mass, carcass characteristics, fresh meat quality, or carcass cutability, provided that the diets were formulated to contain similar quantities of standardized ileal digestible amino acids. In France, fattening pigs were fed up to 18% rapeseed meal and 40% peas as protein sources in order to totally replace soybean meal.
Sows
In sows, it is important to limit the level of glucosinolates in order to prevent reproductive problems. Sow diets containing up to 10% rapeseed meal during lactation and gestation had no deleterious effect on sow health, reproductive performance (including hyperprolific sows) and piglet growth. Rapeseed meal had a positive effect on feed intake during lactation. Heat treatment (103°C) of rapeseed meal improved palatability and increased feed intake compared to untreated rapeseed meal.
Solvent-extracted rapeseed meal
The response of pigs of all ages to rapeseed meal inclusion in the diet is generally favourable. It must be noted that recommendations established in the 1980-1990s were often conservative (e.g. 5% in starter diets, 10% for sows and finishers, and 15% for growing pigs), as they were based on early studies with meals containing significant amounts of glucosinolates. Recent studies show that rapeseed meal, from modern 00 cultivars, is much better tolerated by pigs.
Piglets
Rapeseed meal was included in piglet diets at up to 15-20% (DM basis) without compromising growth performance, organ weights, bone ash or blood parameters.
Growing pigs
It used to be recommended to include rapeseed meal in grower diets to supply up to 50% of the protein requirements, but recent studies have shown that it is possible to use 100% rapeseed meal as the protein source in these diets. Using rapeseed meal as the sole protein source had no effect on feed intake and growth performance of growing pigs. When pig diets (growing or finishing pigs) were formulated in order to get the same amount of digestible lysine from rapeseed meal or soybean meal, growth performance and carcass quality were similar.
Fattening pigs
In fattening pigs, rapeseed meal completely replaced soybean meal without significant changes in growth performance, visceral mass, carcass characteristics, fresh meat quality, or carcass cutability, provided that the diets were formulated to contain similar quantities of standardized ileal digestible amino acids. In France, fattening pigs were fed up to 18% rapeseed meal and 40% peas as protein sources in order to totally replace soybean meal.
Sows
In sows, it is important to limit the level of glucosinolates in order to prevent reproductive problems. Sow diets containing up to 10% rapeseed meal during lactation and gestation had no deleterious effect on sow health, reproductive performance (including hyperprolific sows) and piglet growth. Rapeseed meal had a positive effect on feed intake during lactation. Heat treatment (103°C) of rapeseed meal improved palatability and increased feed intake compared to untreated rapeseed meal.
Rapeseed meal is used as a protein source in poultry diets as an alternative to soybean meal. However, its nutritional quality for poultry is usually lower than soybean meal, due to lower protein and amino acid contents, lower amino acid digestibilities (particularly when the meal is overheated and undergoes a Maillard reaction) and a higher fibre content, which is inversely related to the metabolizable energy value of rapeseed meal, which is 10 to 15% lower than that of soybean meal. Products resulting from a Maillard reaction during processing are responsible for these low values. Tannins might also reduce amino acid digestibility. Rapeseed meal compares favourably with soybean meal for sulphur-containing amino acids and these two meals tend to complement each other. The use of dietary enzymes in poultry feeds containing rapeseed meal may improve digestion, but results are not completely conclusive
Glucosinolates
Dietary inclusion of rapeseed meal from modern 00 and canola varieties in poultry diets should not exceed 20% in broilers and 15% in layers, so that the total glucosinolate content is lower than 2-4 μmol/g. Higher levels of glucosinlates have been linked to performance decrease.
Sinapine
Rapeseed meal fed to sensitive layers was reported to cause a fishy taint when the inclusion rate was higher than 12% of the diet, which is above the levels recommended for layers. No off-flavours have been detected in the carcass.
Dietary inclusion of rapeseed meal from modern 00 and canola varieties in poultry diets should not exceed 20% in broilers and 15% in layers, so that the total glucosinolate content is lower than 2-4 μmol/g. Higher levels of glucosinlates have been linked to performance decrease.
Sinapine
Rapeseed meal fed to sensitive layers was reported to cause a fishy taint when the inclusion rate was higher than 12% of the diet, which is above the levels recommended for layers. No off-flavours have been detected in the carcass.
Generally, recommended levels of rapeseed meal do not go beyond 20%. However, in Australia, rapeseed meal from very low glucosinolate varieties could be included in starting chicks diets at levels ranging from 20 to 30%, and up to 30% for finishing chicks. The recommended inclusion rate of rapeseed meal in the diet also reduced bird abdominal fat percentage and intestinal viscosity, without affecting liver and pancreas weight. In Pakistan, up to 25% rapeseed meal was incorporated in broiler diets without any adverse effect on production parameters. In India, rapeseed meal was included at up to 30% in broiler diets without any adverse effects on health and performance.
The use of dehulled rapeseed meal, eiter by dehulling before crushing or by tail-end dehulling has led to inconclusive results. In a study in Pakistan where broilers were given diets containing rapeseed meal (25% of diet protein), dry heating or dehulling did not result in significant performance increase, though dehulling gave a better FCR. In China, broilers fed dehulled rapeseed meal (20 and 21.5% in growth and finishing phases respectively) diets had a higher growth rate, feed efficiency and lower feed intake than those fed hulled rapeseed meal (22.5 and 23.5% in growth and finishing phases respectively) diets during the overall phase. In Canada, tail-end dehulled canola meal included at 10 to 30% in broiler diets had no effect on gain and feed consumption, but improved the feed:gain ratio. Dehulling was found to improve amino acid digestibility and energy values.
The use of dehulled rapeseed meal, eiter by dehulling before crushing or by tail-end dehulling has led to inconclusive results. In a study in Pakistan where broilers were given diets containing rapeseed meal (25% of diet protein), dry heating or dehulling did not result in significant performance increase, though dehulling gave a better FCR. In China, broilers fed dehulled rapeseed meal (20 and 21.5% in growth and finishing phases respectively) diets had a higher growth rate, feed efficiency and lower feed intake than those fed hulled rapeseed meal (22.5 and 23.5% in growth and finishing phases respectively) diets during the overall phase. In Canada, tail-end dehulled canola meal included at 10 to 30% in broiler diets had no effect on gain and feed consumption, but improved the feed:gain ratio. Dehulling was found to improve amino acid digestibility and energy values.
Recommended levels of inclusion in laying hens used to be restricted in the range of 4-10% of the diet. However, recent results reported that higher inclusion levels are possible without hampering health and performance. In Canada, both solvent-extracted and expeller canola meal were well tolerated by laying hens at high (20%) dietary inclusions. In Romania, commercial layers were fed up to 15% canola meal without problems. In Iran, with local breeds of laying hens, it was reported that including rapeseed meal at up to 15-20% had no adverse effects on egg weight, yolk weight and yolk weight ratio. Diets containing 24% rapeseed meal were fed to a commercial line of brown-shell laying hens (Hy-Line), hatched after 2009, without impairing egg quality (no fishy taint). These findings suggest that brown-shell laying hens could be fed at conventional rates applied to white-shell laying hens, i.e. 8-10% of the diet.
Rapeseed meal from early canola varieties included at up to 45% as partial replacement of soybean meal and fish meal in turkey diets resulted in similar weights at 42 days as soybean meal, but reduced feed efficiency as the level of canola meal increased. In a recent trial, 5 or 10% inclusion of rapeseed meal in fattening turkey diets did not cause any adverse impact on weight gain. An increase of the amount of omega-3 fatty acids in the meat was positively related to the increase of rapeseed meal in the diet, and there was a positive trend of a decrease of the ratio of omega-6:omega-3 polyunsaturated fatty acids. Diets including rapeseed meal were cheaper than diets based on soybean meal. It was thus recommended to use rapeseed meal for the fattening of hybrid turkeys at up to 10% of the diet. No off-flavours in the meat were observed when canola meal was fed to turkeys.
Ducklings (2 week-old) fed on diets containing rapeseed meal at increasing levels (0, 7%, 14%, and 21%) had decreasing body weights. Feeding rapeseed meal at any level depressed body weight gain and, at 28 day-old, ducklings fed on 21% rapeseed meal had significantly lower body weight than ducklings fed on control or on diet with only 7% rapeseed meal. Ducklings fed on rapeseed meal (14 and 21%) and slaughtered at 28 days had lighter tights and higher abdominal fat. At the same age, state of feathering was poorer in ducks fed on 14 and 21% rapeseed meal.
On the long term (12 weeks), all ducks had similar final weights whatever the rapeseed meal level in the ducks diet. Rapeseed meal had no negative effect on feed intake nor on carcass quality. These results were slightly different from those obtained earlier by the same team on a smaller number of ducks. It was then observed that, on fattening ducks, the higher inclusion of rapeseed meal (21%) in the diet resulted in higher abdominal fat and in heavier thyroid gland suggesting alterations in the metabolism of ducks fed on rapeseed meal.
On the long term (12 weeks), all ducks had similar final weights whatever the rapeseed meal level in the ducks diet. Rapeseed meal had no negative effect on feed intake nor on carcass quality. These results were slightly different from those obtained earlier by the same team on a smaller number of ducks. It was then observed that, on fattening ducks, the higher inclusion of rapeseed meal (21%) in the diet resulted in higher abdominal fat and in heavier thyroid gland suggesting alterations in the metabolism of ducks fed on rapeseed meal.
Rapeseed meal has been used in rabbit feeding for a long time, and is still used in experimental and commercial diets.
Early varieties and low-erucic varieties
Until the 1970s, it was recommended to use rapeseed meal in moderate levels in rabbit diets due to the presence of erucic acid and glucosinolates. After the development of low-erucic varieties ("0"), several studies concluded that low-erucic rapeseed meal could be introduced in diets for growing rabbits as partial or complete replacement for sunflower meal or soybean meal, at inclusion rates up to 12-15% without affecting growth rate, slaughter yield, thyroid and liver development, or changing the flavour of the meat. The same maximum inclusion rate of 12-15% was recommended for breeding rabbits. In some studies, reproductive problems have been reported with levels of 20% and above.
Low-erucic, low glucosinolate varieties
After 00 rapeseed varieties were introduced, comparisons between 0 and 00 rapeseed meals failed to demonstrate the superiority of the 00 varieties for rabbits. This is due to the high tolerance of rabbits for glucosinolates. They can tolerate successfully levels of glucosinolates 50% higher than poultry, 2-3 times higher than ruminants and 10 times higher than pigs. Experiments conducted with 00 varieties confirmed that 00 rapeseed meal could completely replace soybean meal. Inclusion levels of 10-12% rapeseed meal in the diet can be recommended for growing rabbits or breeding does.
Early varieties and low-erucic varieties
Until the 1970s, it was recommended to use rapeseed meal in moderate levels in rabbit diets due to the presence of erucic acid and glucosinolates. After the development of low-erucic varieties ("0"), several studies concluded that low-erucic rapeseed meal could be introduced in diets for growing rabbits as partial or complete replacement for sunflower meal or soybean meal, at inclusion rates up to 12-15% without affecting growth rate, slaughter yield, thyroid and liver development, or changing the flavour of the meat. The same maximum inclusion rate of 12-15% was recommended for breeding rabbits. In some studies, reproductive problems have been reported with levels of 20% and above.
Low-erucic, low glucosinolate varieties
After 00 rapeseed varieties were introduced, comparisons between 0 and 00 rapeseed meals failed to demonstrate the superiority of the 00 varieties for rabbits. This is due to the high tolerance of rabbits for glucosinolates. They can tolerate successfully levels of glucosinolates 50% higher than poultry, 2-3 times higher than ruminants and 10 times higher than pigs. Experiments conducted with 00 varieties confirmed that 00 rapeseed meal could completely replace soybean meal. Inclusion levels of 10-12% rapeseed meal in the diet can be recommended for growing rabbits or breeding does.
Rapeseed meal is used as a source of protein for many fish species. The main issue of rapeseed meal for fish feeding is its high fibre content, which limits its nutritional value for carnivorous fish species. However, as rapeseed meal is included at rates much lower than 50%, the fibre content is unlikely to exceed 8% of the diet and to impair growth performance. Glucosinolates appear to be better tolerated by fish species, such as carp, than by swine and poultry. In trout, the most conservative limit is set at 1.4 µmol/g of the diet. Rapeseed meals containing very low amounts of glucosinolates could, therefore, be included at 20-30% of the diet. The combination of rapeseed meal and soybean meal is often a good solution to replace fish meal. The use of plant protein to replace fish meal in fish diets reduces the price of the diet and does not introduce dioxins and PCBs, which is reassuring for consumers.
For these reasons, it has been suggested that rapeseed meal can be included at levels between 10 and 20% in fish diets, but rapeseed meal high in erucic acid should not be over 5%
Salmonids
Rapeseed meal has a digestible energy lower than that of soybean meal in salmonids (9.6-11.5 vs. 13.0 MJ/kg as fed). The amino acid profile of rapeseed protein is the best of the plant protein sources currently available and the amino acids are highly digestible (83-99%) in Atlantic salmon (Salmo salar). Rapeseed meal has been routinely fed for over 20 years to salmonids.
Rainbow trout (Oncorhynchus mykiss) Rapeseed meal has been extensively assessed in rainbow trout and was generally found to be deleterious to performance. Rapeseed meal included in juvenile rainbow trout diets at 10, 20 and 30% for 9 weeks had deleterious effects at all levels, on hepatosomatic index, growth performance, feed conversion ratio and immunological status of the fish (Hernandez et al., 2012). A few studies differed from this trend. Inclusion of rapeseed meal containing 26 µmol/g glucosinolates in diets for juvenile rainbow trout at up to 30% had no effect on growth, voluntary feed intake, or feed efficiency after 58 days of experimental feeding. It was possible to include rapeseed meal at 17,5% (diet DM) in combination with soybean meal (14.5% diet DM) to replace 40% of the protein provided by fish meal.
Chinook salmon (Oncorhynchus tshawytscha)
In juvenile chinook salmon diets where rapeseed meal was used to replace 15 or 30% of herring meal, growth and feed intake were reduced. The use of low-temperature and high-temperature extruded rapeseed meals reduced these deleterious effects. These products also reduced thyroid problems in salmons.
Catfish
Channel catfish (Ictalurus punctatus) In channel catfish, apparent digestibilities of DM, energy and protein of rapeseed meal were 47-69%, 72% and 79%, respectively, and were lower than those of soybean meal. Rapeseed meal was included in juvenile channel catfish diets at up to 31% with no negative effects on performance.
Australian catfish (Tandanus tandanus)
Australian catfish fed 30 or 45% rapeseed meal in the diet to replace fish meal had reduced growth. Supplementation with inorganic P improved animal performance but resulted in water pollution because of higher P losses during digestion.
Carp
Rapeseed meal is commonly included in carp diets, which are normally based on plant protein. However, recent studies with juvenile grass carp (Ctenopharyngodon idellus) and juvenile crucian carp (Carassius auratus x Cyprinus carpio) found that high levels of rapeseed meal (45% or 50% of the diet) had deleterious effects on fish liver and subsequently impaired performance (growth, feed intake, feed conversion ratio) and health (blood parameters). It was suggested to either limit rapeseed meal inclusion in grass carp diet at 16% or to supplement it with glutathione (400 mg/kg), as glutathione has a protective effect on fish liver. In fry, it was suggested that rapeseed meal inclusion could be as high as 15% for grass carp (Ctenopharyngodon idellus) and 22% for common carp (Cyprinus carpio).
Tilapia (Oreochromis niloticus)
Apparent digestibilities of DM, energy and protein in Nile tilapia were higher than in catfish at 67%, 74% and 91%, respectively. In China, it was possible to use up to 19% rapeseed meal to replace 30% soybean meal in diets for juvenile hybrid tilapia without compromising growth, feed conversion and protein utilization. In Brazil, up to 24% rapeseed meal was fed to juvenile Nile tilapia with no health or performance issues. Earlier inclusion levels recommended have been in the 10-25% range. In China, genetically modified Nile tilapia were fed diets where 75% of the fish meal was replaced by rapeseed meal (thus representing 55% of the tilapia diet) without impairing growth performance.
Red seabream (Pagrus auratus)
Canola meal was included at up to 60% of red seabream diets without detrimental effects on performance.
For these reasons, it has been suggested that rapeseed meal can be included at levels between 10 and 20% in fish diets, but rapeseed meal high in erucic acid should not be over 5%
Salmonids
Rapeseed meal has a digestible energy lower than that of soybean meal in salmonids (9.6-11.5 vs. 13.0 MJ/kg as fed). The amino acid profile of rapeseed protein is the best of the plant protein sources currently available and the amino acids are highly digestible (83-99%) in Atlantic salmon (Salmo salar). Rapeseed meal has been routinely fed for over 20 years to salmonids.
Rainbow trout (Oncorhynchus mykiss) Rapeseed meal has been extensively assessed in rainbow trout and was generally found to be deleterious to performance. Rapeseed meal included in juvenile rainbow trout diets at 10, 20 and 30% for 9 weeks had deleterious effects at all levels, on hepatosomatic index, growth performance, feed conversion ratio and immunological status of the fish (Hernandez et al., 2012). A few studies differed from this trend. Inclusion of rapeseed meal containing 26 µmol/g glucosinolates in diets for juvenile rainbow trout at up to 30% had no effect on growth, voluntary feed intake, or feed efficiency after 58 days of experimental feeding. It was possible to include rapeseed meal at 17,5% (diet DM) in combination with soybean meal (14.5% diet DM) to replace 40% of the protein provided by fish meal.
Chinook salmon (Oncorhynchus tshawytscha)
In juvenile chinook salmon diets where rapeseed meal was used to replace 15 or 30% of herring meal, growth and feed intake were reduced. The use of low-temperature and high-temperature extruded rapeseed meals reduced these deleterious effects. These products also reduced thyroid problems in salmons.
Catfish
Channel catfish (Ictalurus punctatus) In channel catfish, apparent digestibilities of DM, energy and protein of rapeseed meal were 47-69%, 72% and 79%, respectively, and were lower than those of soybean meal. Rapeseed meal was included in juvenile channel catfish diets at up to 31% with no negative effects on performance.
Australian catfish (Tandanus tandanus)
Australian catfish fed 30 or 45% rapeseed meal in the diet to replace fish meal had reduced growth. Supplementation with inorganic P improved animal performance but resulted in water pollution because of higher P losses during digestion.
Carp
Rapeseed meal is commonly included in carp diets, which are normally based on plant protein. However, recent studies with juvenile grass carp (Ctenopharyngodon idellus) and juvenile crucian carp (Carassius auratus x Cyprinus carpio) found that high levels of rapeseed meal (45% or 50% of the diet) had deleterious effects on fish liver and subsequently impaired performance (growth, feed intake, feed conversion ratio) and health (blood parameters). It was suggested to either limit rapeseed meal inclusion in grass carp diet at 16% or to supplement it with glutathione (400 mg/kg), as glutathione has a protective effect on fish liver. In fry, it was suggested that rapeseed meal inclusion could be as high as 15% for grass carp (Ctenopharyngodon idellus) and 22% for common carp (Cyprinus carpio).
Tilapia (Oreochromis niloticus)
Apparent digestibilities of DM, energy and protein in Nile tilapia were higher than in catfish at 67%, 74% and 91%, respectively. In China, it was possible to use up to 19% rapeseed meal to replace 30% soybean meal in diets for juvenile hybrid tilapia without compromising growth, feed conversion and protein utilization. In Brazil, up to 24% rapeseed meal was fed to juvenile Nile tilapia with no health or performance issues. Earlier inclusion levels recommended have been in the 10-25% range. In China, genetically modified Nile tilapia were fed diets where 75% of the fish meal was replaced by rapeseed meal (thus representing 55% of the tilapia diet) without impairing growth performance.
Red seabream (Pagrus auratus)
Canola meal was included at up to 60% of red seabream diets without detrimental effects on performance.
Shrimps\
A series of experiments on kuruma shrimp (Marsupenaeus japonicus) showed that rapeseed meal could be included in the diets of shrimps in order to replace part of the fish meal. While it was not possible for rapeseed meal to replace more than 20% fish meal protein as a sole protein source, it could be used in a blend with soybean meal (ratio 4:6), supplemented with amino acids, phytase and fish solubles, when 85% of the fish meal protein could be replaced.
A series of experiments on kuruma shrimp (Marsupenaeus japonicus) showed that rapeseed meal could be included in the diets of shrimps in order to replace part of the fish meal. While it was not possible for rapeseed meal to replace more than 20% fish meal protein as a sole protein source, it could be used in a blend with soybean meal (ratio 4:6), supplemented with amino acids, phytase and fish solubles, when 85% of the fish meal protein could be replaced.