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Nutrient composition
Canadian canola meal is made from a blend of Brassica napus and Brassica campestris/rapa seed by prepress solvent extraction. Its nutrient composition may be influenced by environmental conditions during the growing of the crop, by harvest conditions, and to a minor extent by cultivar and processing of the seed and meal. The basic nutrient composition of canola meal is shown in Table 1.
TABLE 1 Typical chemical composition of canola meal (10% moisture basis)
Component
|
Average |
| Moisture (%) |
10.0
|
| Crude protein (N x 6.25;%) |
35.0
|
| Rumen bypass protein (%) |
35.0
|
| Oil (%) |
3.5
|
| Linoleic acid (%) |
0.6
|
| Ash |
6.1
|
| Crude fibre (%) |
12.0
|
| Tannins (%) |
1.5
|
| Sinapine (%) |
1.0
|
| Phytic acid (%) |
4.0
|
| Glucosinolates (µmoles/g) |
16
|
Protein and Amino Acids
The minimum crude protein guarantee for Canadian canola meal is 34.0% (as fed basis), although the actual protein content usually is between 35% and 36%. The minimum allows for yearly variation in canola seed composition due to growing conditions. As well, the canola crusher has some influence on the protein composition of canola meal by adjusting the level of oil and carbohydrate. The influence of weather and soil conditions on the protein content of the canola seed as indicated by the period from 1990 to 2000 is shown in Figure 1. This publication uses a default value of 35% crude protein on a 90% dry matter basis in the nutrient composition tables.
Canola meal has a good amino acid profile for animal feeding (Table 2). Like many vegetable protein sources canola meal is limiting in lysine but it is noted for having high levels of methionine and cystine. Amino acid content varies with protein content. This relationship has been studied and there are useful equations to predict amino acids from crude protein (Table 3). Note that the prediction equations in Table 3 do not yield exactly the same levels of lysine, methionine, cystine and threonine that are listed in Table 2 for the same level of crude protein. This is because the amino acid prediction equations were developed from data derived from one source (Degussa) whereas the values in Table 2 were developed from multiple sources. When using the prediction equations, users may wish to add a correction factor to bring the values in line with those in Table 2.
TABLE 2 Amino acid composition of canola meal* (35% crude protein basis)
Amino Acid
|
Average |
Alanine
|
1.53
|
Arginine
|
2.12
|
Aspartate
|
2.55
|
| Cystine |
0.94
|
| Glutamate |
6.43
|
| Glycine |
1.75
|
| Histidine |
1.13
|
| Isoleucine |
1.41
|
| Leucine |
2.39
|
| Lysine |
2.02
|
| Methionine |
0.77
|
| Methionine + cystine |
1.71
|
Phenylalanine
|
1.54
|
Proline
|
2.23
|
Serine
|
1.64
|
Threonine
|
1.50
|
Tryptophan
|
0.46
|
| Tyrosine |
1.05
|
| Valine |
1.71
|
*Based on: Anderson-Hafermann et al., 1993; Bell and Keith, 1991; Bell et al., 1998; Bell et al., 2000; Boila et al., 1992; Heartland Lysine, 1998; Kendall et al., 1991; Lee et al., 1995 and Slominski et al., 1999.
TABLE 3 Regression equations for predicting amino acid levels in canola meal from crude protein levels* (n=97)
| Amino acid |
Equation |
R value |
| Arginine |
% CP X .0758 - .535 |
0.73
|
| Lysine |
% CP X .0402 + .546 |
0.57
|
| Methionine |
% CP X .0156 + .181 |
0.66
|
| Methionine + cystine |
% CP X .0468 - .033 |
0.64
|
| Threonine |
% CP X .0262 + .641 |
0.62
|
| Tryptophan |
% CP X .0215 - .294 |
0.79
|
*Beste et al., 1992.
TABLE 4 Digestibility coefficients of essential amino acids for pigs* and poultry**
| Amino acid |
Swine true ileal
digestibility (%) |
Poultry true
digestibility (%) |
| Arginine |
85
|
88
|
| Cystine |
83
|
73
|
| Histidine |
85
|
86
|
| Isoleucine |
78
|
83
|
| Leucine |
81
|
86
|
| Lysine |
78
|
79
|
| Methionine |
86
|
90
|
| Methionine + cystine |
85
|
81
|
| Phenylalanine |
82
|
86
|
| Threonine |
76
|
72
|
| Tryptophan |
75
|
82
|
| Valine |
77
|
81
|
* NRC, 1998.
** Heartland Lysine, 1998.
The rumen bypass protein of canola meal is 35% (Table 1). This rumen bypass protein value of canola meal is discussed in more detail in the section "Canola meal in cattle diets."
As indicated in the section "Canola meal processing," research by Newkirk et al., (1999) and Newkirk and Classen (2000) has shown that processing temperatures are the main reason for the lower amino acid bio-availability. Although processing temperatures are relatively constant at Canadian canola crushing companies, it is prudent for canola meal users to monitor amino acid bio-availability as part of their quality control programs. Two rapid in-vitro tests, which correlate to amino acid digestibility, are the KOH nitrogen solubility test and the Neutral Detergent Insoluble Nitrogen (NDIN) test. Anderson-Haferman et al., (1993) made the first attempts at rapid estimation of amino acid availability in canola meal by adapting the KOH nitrogen solubility test which has been widely used on soybean meal. Daun and Kisilowsky (1999) made further methodology improvements to the KOH test. Recently, however, Newkirk et al., (2000) evaluated NDIN as a measure of canola meal protein and amino acid digestibility. They found that NDIN values below 10% indicate a canola meal with greater than 85% lysine availability. The NDIN method appears to offer greater prediction accuracy than does the KOH solubility index (R2 = 0.77 vs. 0.59). They also reported that a near-infrared reflectance spectroscopy equation is being developed using the same data, and is showing promise as a rapid, precise tool for predicting lysine availability in canola meal (R2=0.92).
Oil
The oil content of Canadian canola meal tends to be relatively high at 3.5% (Table 1) compared to 1 to 2% oil in canola meals produced in most other countries. This is because in Canada, canola gums are added back to canola meal at 1 - 2%. The gums are obtained during the refining of canola oil and consist of glycolipids, phospholipids and variable amounts of triglycerides, sterols, fatty acids, etc. Addition of gums to canola meal increases the energy value of canola meal. The addition of up to 6% gums to canola meal has been shown to have no detrimental effects on the feeding value of the canola meal for broilers or layers (Summers et al., 1978). In studies involving beef cattle (Mathison, 1978), dairy cattle (Grieve, 1978) and swine (McCuaig and Bell, 1981), addition of gums to canola meal at levels higher than that added by Canadian canola seed processors had no adverse effects on the feeding value of the meal for these classes of animals. Likewise canola processors in Canada also add back 1 to 2% of the acidulated soapstocks derived from canola oil refining.
Carbohydrates and Fibre
The carbohydrate matrix of canola meal is quite complex. The levels of starch, free sugars and soluble non-starch polysaccharides in canola meal total about 15% (Table 5). This should result in a significant contribution to digestible energy. However, it appears that these carbohydrates are protected by cell walls and that their actual contribution to digestible energy is modest (Bell, 1993; Slominski and Campbell, 1990). The 12% crude fibre is higher than found in soybean meal because, unlike soybean meal, the canola hull stays with the meal and the hull is a relatively high proportion of the canola seed. Canola meal contains a moderate amount of acid detergent fibre (ADF) but a relatively low level of neutral detergent fibre (NDF).
This relatively low NDF:ADF ratio may actually benefit the feeding of canola meal to ruminants.
Table 5 Carbohydrate components of canola meal*
(10% moisture basis)
Component
|
Average |
| Sugars (%) |
8.0
|
| Starch (%) |
5.2
|
| Cellulose (%) |
4.6
|
| Oligosaccharides (%) |
2.3
|
| Non-starch polysaccharides (%) |
16.1
|
| Soluble NSP's (%) |
1.4
|
| Insoluble NSP's (%) |
14.7
|
| Crude fibre (%) |
12.0
|
| Acid detergent fibre (%) |
17.2
|
| Neutral detergent fibre (%) |
21.2
|
| Total dietary fibre (%) |
33.0
|
* Bell, 1993; Slominski and Campbell, 1990
Minerals
Most references on the mineral content of canola meal use the values derived by Bell and Keith (1991). These values were reconfirmed in a recent survey by Bell et al., 1999. The data show that canola meal is a relatively good source of essential minerals (Table 6) compared to other vegetable-origin oilseed meals. Canola meal is an especially good source of selenium and phosphorus. Similar to other vegetable sources of phosphorus where it is present as phytate, the bioavailability is estimated to be between 30 and 50% of the total phosphorus level. The sodium content of canola may vary somewhat depending on whether soapstocks from refining (usually sodium salt of fatty acids) are added to the meal.
TABLE 6 Mineral content of canola meal* (10% moisture basis)
Mineral
|
Average |
Calcium (%)
|
0.63
|
Phosphorus (%)
|
1.08
|
Available P (%)
|
0.3-0.5**
|
Sodium (%)
|
0.10
|
Chlorine (%)
|
0.10
|
Potassium (%)
|
1.22
|
Sulphur (%)
|
0.85
|
Magnesium (%)
|
0.54
|
Copper (mg/kg)
|
5.8
|
Iron (mg/kg)
|
166
|
| Manganese (mg/kg) |
52
|
| Molybdenum (mg/kg) |
1.4
|
Zinc (mg/kg)
|
58
|
| Selenium (mg/kg) |
1.1
|
* Bell and Keith, 1991; Bell et al., 1999.
** The higher value may be preferred for mature birds.
Vitamins
Information on the vitamin content of canola meal is very limited. Canola meal appears to be rich in choline, biotin, folic acid, niacin, riboflavin and thiamin (Table 7). As is the case with most natural sources of vitamins in animal feeds, it is recommended that users not place too much reliance on these values and use supplemental vitamin premixes instead.
TABLE 7 Vitamin content of canola meal* (10% moisture basis)
Vitamin
|
Amount |
Biotin (mg/kg)
|
0.98
|
| Choline (mg/kg) |
6700
|
| Folic acid (mg/kg) |
0.8
|
| Niacin (mg/kg) |
160
|
| Pantothenic acid (mg/kg) |
9.5
|
| Pyridoxine (mg/kg) |
7.2
|
| Riboflavin (mg/kg) |
5.8
|
| Thiamin (mg/kg) |
5.2
|
| Vitamin E (mg/kg) |
13
|
* Values as reported by NRC, 1998.
Energy
The energy values of canola meal for various types of animals are given in Table 8. It is recognized that energy levels will vary as nutrient composition varies-especially protein, oil and fibre. The energy values in Table 8 reflect the composition of canola meal produced in Canada.
For poultry, the appropriate AMEn and TME values for canola meal are 2000 and 2070 kcal/kg (NRC, 1994), respectively. The values agree well with European results with low glucosinolate rapeseed meal.
For pigs, there is some variability in energy levels as reported in different databases. Canadian and European studies indicate that the energy fraction of meal is 69 to 72% digestible (Bell et al., 1991; Bell and Keith, 1989; Bourdon and Aumaître, 1990). About 95% of canola meal samples fall within the range of 3000 to 3270 kcal DE/kg (Table 8) with an average value of 3100. The values for net energy for pigs were taken from Noblet's prediction equations (Ajinomoto, 1996).
For cattle, TDN, DE, ME and NE values were adopted from the recent 7th edition of the Nutrient Requirements of Dairy Cattle, (NRC 2001). These values agree with previous editions of this guide and with those cited by Hill (1991). Lower values than shown may apply to calves with immature rumen development.
TABLE 8 Available energy values for canola meal (10% moisture basis)
| Animal |
|
Average value |
| Chickens* |
AMEn (kcal/kg) |
2000
|
| |
TMEn (kcal/kg) |
2070
|
| Pigs** |
DE (kcal/kg) |
3100
|
|
ME (kcal/kg) |
2900
|
| |
NE (kcal/kg) |
1750
|
|
Cattle***
|
TDN (%) |
63.0
|
| |
DE (kcal/kg) |
3100
|
| |
ME (kcal/kg) |
2480
|
| |
NEM (kcal/kg) |
1690
|
| |
NEG (kcal/kg) |
1130
|
| |
NEL (kcal/kg) |
1580
|
* NRC, 1994
** Bell et al., 1991; Bell and Keith, 1989; Bourdon and Aumaitre, 1990; Ajinomoto, 1996
*** NRC, 2001
Glucosinolates
The low glucosinolate content of canola, compared to previous cultivars of rapeseed, constitutes the major improvement in meal quality achieved by plant breeders. Canola glucosinolates are composed of two main types, aliphatic and indolyl. Aliphatic glucosinolates remain the predominant form - approximately 12 µmol/g of meal. Canola meal contains approximately 4 µmol/g of indolyl glucosinolates. The total glucosinolate content of Canadian canola meal is approximately 16 µmol/g (Table 1). By comparison, traditional rapeseed meal contains between 120 and 150 µmol/g of total glucosinolates.
The problem with glucosinolates is that they break down into toxic aglucones, which have a variety of negative effects on animals. There are many different types of glucosinolates with different breakdown products - thiocyanate, isothiocyanate, oxazolidinethione (goitrin) and nitriles. Each of these products will have unique effects on the animal - most will inhibit thyroid hormone production but others will effect the liver. The reason that glucosinolates are expressed on a molecular (µmol/g) basis rather than on a weight (mg/kg) basis is that glucosinolates have significantly different molecular weights depending on the size of their aliphatic side chain. Since the negative effect in the animal is at the molecular level, the most accurate estimate of the negative effect on the animal can be gauged by expressing glucosinolate concentration on a molecular basis. In addition to the toxic effect of glucosinolates, their bitter taste results in reduced feed intake for many animals.
The level of glucosinolates in Canadian canola has continued to decrease in recent years due to selection pressure by canola plant breeders. Both the trend and levels of glucosinolates can be seen in Figure 2.
Figure 2 Glucosinolate content of canola seed, 1990 - 2000 (µmol/g, 8.5% moisture), CGC, 2000
Other Minor Components
There are a few minor components in canola meal which may have anti-nutrient effects (Bell, 1993). Tannins are present in canola meal in a range of 1.5% to 3.0%, with brown seeded varieties having higher levels than yellow seeded varieties. The tannins in canola meal do not appear to have the same negative effects on palatability and protein digestibility that they do in other plants. Canola meal contains from 0.6% to 1.8% sinapine, which can result in a fishy flavour in chicken eggs from some strains of layers. Canola meal also contains from 3% to 6% phytic acid. Similar to phytic acid in other plants, less than half of this phosphorus is digestible by monogastics.
Nutrient Comparison of Canola Meal from Different Sources
Most feed ingredient databases around the world have listings of nutrient values for canola and/or rapeseed meal. Not surprisingly, there are some differences in nutrient values between different references, as is illustrated in Table 9. Some of these differences are caused by variations in seed nutrient composition in different countries while other differences are due to processing. Canola meal produced in Canada generally has a higher level of oil and lower level of protein than European or Asian canola/rapeseed meal. This is because canola crushing companies in Canada usually add some of the gums from crushing and some of the soapstocks from oil refining back into the meal. This extra 1.5 to 2.0% higher oil content in Canadian canola meal increases its metabolizable energy value for swine and poultry by about 100 kcal/kg. Also, there are differences between the references in reported levels of NDF, where the Canadian values are generally lower. It is unclear why there is a discrepancy here although the Canadian values are consistent between different laboratories and samples. Also, the lysine level in Chinese canola meal is lower than other references despite its having a high level of crude protein. It is likely that the high temperatures used in processing canola in China results in the lower lysine values.
Table 9 Comparison of canola meal nutrient composition between different literature databases and origins of canola/rapeseed meal
|
Nutrient, 10%
moisture basis (%)
|
Canada
|
Europe
FeedBase
2001*
|
China
FeedBase
2001*
|
Feeds
Directory
1997**
|
NRC 1982
|
NRC
Poultry
1994
|
NRC
Swine
1998
|
NRC
Dairy
2001
|
Crude protein
|
35.0
|
34.5
|
37.2
|
33.9
|
36.5
|
36.9
|
35.6
|
33.9
|
| Oil |
3.5
|
2.6
|
2.4
|
3.1
|
1.6
|
3.7
|
3.5
|
3.1
|
| Crude fibre |
12.0
|
12.1
|
12.1
|
9.7
|
11.9
|
11.6
|
-
|
9.7
|
| Ash |
6.1
|
7.1
|
8.8
|
6.2
|
6.8
|
-
|
-
|
6.2
|
| ADF |
17.2
|
18.9
|
21.9
|
16.8
|
-
|
-
|
17.2
|
16.8
|
| NDF |
21.2
|
28.0
|
34.9
|
32.1
|
-
|
-
|
21.2
|
32.1
|
| Calcium |
0.63
|
0.78
|
0.71
|
0.79
|
0.60
|
0.66
|
0.63
|
0.79
|
| Phosphorus |
1.08
|
1.15
|
1.05
|
1.06
|
0.94
|
1.13
|
1.01
|
1.06
|
| Lysine |
2.02
|
1.87
|
1.67
|
1.85
|
1.96
|
1.71
|
2.08
|
1.85
|
| Met + cys |
1.71
|
1.52
|
1.67
|
0.99
|
-
|
1.39
|
1.65
|
1.56
|
| Threonine |
1.50
|
1.52
|
1.40
|
1.41
|
1.55
|
1.35
|
1.59
|
1.41
|
| Tryptophan |
0.46
|
0.41
|
-
|
0.35
|
0.42
|
0.39
|
0.45
|
0.35
|
*FeedBase, 2001.
**Ewing, 1997.
Table 10 Nutrient composition of canola oil and seed (as fed basis)
| Nutrient, as is basis |
Canola oil
|
Canola seed |
Dry matter
|
100
|
|
| Crude protein |
0
|
|
| Oil |
100
|
|
|
Crude fibre
|
0
|
|
| Poultry ME* |
9200
|
|
|
Swine DE**
|
8760
|
|
| Swine ME** |
8410
|
|
| Swine NE** |
5365
|
|
| Ruminant TDN*** |
184
|
|
| Ruminant NEmaint*** |
5650
|
|
| Ruminant NEgain*** |
3890
|
|
| Ruminant NElact*** |
5650
|
|
| Linoleic acid (C18:2) |
21.0
|
|
| Linolenic acid (C18:3) |
12.0
|
|
* NRC, 1994.
** NRC, 1998.
*** NRC, 2001.
Nutrient Composition of Canola Oil and Seed
The key nutrient values for canola oil and seed are shown in Table 10. Most nutrient values for canola seed can be calculated from the nutrient values in canola meal and oil, by knowing that approximately 57% of the seed is meal and 43% is oil. The exception is energy content, where the energy value of canola seed cannot be reliably estimated from the addition of the energy values for canola oil and meal. For swine and poultry, the seed has less energy than the sum of its oil and meal components. This is likely because whole canola seed is not processed to the same degree as canola oil and meal and it is, therefore, not as well digested. Heat treatment and particle size reduction of canola seed by micronization, extrusion or expansion is often used to increase its energy digestibility.
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Effects of processing on the nutritional quality of canola meal. Poult. Sci. 72:326-333.
Bell, J.M. 1993.
Factors affecting the nutritional value of canola meal: a review. Can. J. Anim. Sci. 73:679-697.
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Factors affecting the digestibility by pigs of energy and protein in wheat, barley and sorghum diets supplemented with canola meal. Anim. Feed Sci. Technol. 24:253-265.
Bell, J.M. and M.O. Keith. 1991.
A survey of variation in the chemical composition of commercial canola meal produced in western Canadian crushing plants. Can. J. Anim. Sci. 71:469-480.
Bell, J.M., M.O. Keith and D.S. Hutcheson. 1991.
Nutritional evaluation of very low glucosinolate canola meal. Can. J. Anim. Sci. 71:497-506.
Bell, J.M., R.T. Tyler and G. Rakow. 1998.
Nutritional composition and digestibility by 80-kg to 100-kg pigs of prepress solvent-extracted meals from low glucosinolate Brassica juncea, B. napus and B. rapa seed and of solvent-extracted meal. Can. J. Anim. Sci. 78:199-203.
Bell, J.M., G. Rakow and R.K. Downey. 1999.
Mineral composition of oil-free seeds of Brassica napus, B. rapa and B. juncea as affected by location and year. Can. J. Anim. Sci. 79:405-408.
Bell, J.M., G. Rakow and R.K. Downey. 2000.
Comparison of amino acid and protein levels in oil-extracted seeds of Brassica and Sinapis species, with observations on environmental effects. Can. J. Anim. Sci. 80:169-174.
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Research evaluates amino acid composition of canola meal. Feedstuffs, May 4, p16-17.
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In situ digestion and escape of dry matter, nitrogen and amino acids in canola meal. Can. J. Anim. Sci. 72:891-901.
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Low glucosinolate rapeseeds and rapeseed meals: Effect of technological treatments on chemical composition, digestible energy content and feeding value for growing pigs. Anim. Feed Sci. Technol. 30:175-191.
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Quality of western Canadian canola. Canadian Grain Commission. Grain Research Laboratory. Winnipeg, Canada. www.cgc.ca
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Ewing, W.N. 1997.
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Rapeseed meal in the diets of ruminants. Nutr. Abs. Rev. Series B, 61:139-55.
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Variability in the rumen degradability and postruminal digestion of the dry matter, nitrogen and amino acids of canola meal. Can. J. Anim. Sci. 71:739-754.
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Metabolizable energy and amino acid availability of full-fat seeds, meals and oils of flax and canola. Poult. Sci. 74:1341-1348.
Mathison, G.W. 1978.
Rapeseed gum in finishing diets for steers.
Can. J. Anim. Sci. 58:139-42
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Effects of rapeseed gums on the feeding value of diets for growing-finishing pigs.
Can. J. Anim. Sci. 61:463-467.
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United States - Canadian Tables of Feed Composition. 3rd Revision. National Acad. Press, Washington, DC
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Nutrient requirements of poultry. 9th Rev. Ed., National Acad. Press, Washington, DC.
NRC. 1998.
Nutrient requirements of swine. 10th Rev. Ed., National Acad. Press, Washington, DC.
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Nutrient requirements of dairy cattle. 7th Rev. Ed., National Acad. Press, Washington, DC.
Newkirk, R.W., H.L. Classen,, T.A. Scott, and M.J. Edney. 1999.
Commercial desolventization-toasting conditions reduce the content and availability of amino acids in canola meal. Poult. Sci. 78 (Suppl. 1):16.
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The effects of standard oil extraction and processing on the nutritional value of canola meal for broiler chickens. Poult. Sci. 79 (Suppl. 1):10.
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Prediction of lysine availability in canola meal. XXI World's Poultry Congress. Abstracts and Proceedings. Montreal, Canada.
Slominski, B.A. and L.D. Campbell. 1990.
Non-starch polysaccharides of canola meal: Quantification, digestibility in poultry and potential benefit of dietary enzyme supplementation. J. Sci. Food Agric. 53:175-84.
Slominski, B.A., J. Simbaya, L.D. Campbell, G. Rakow and W. Guenter. 1999.
Nutritive value for broilers of meals derived from newly developed varieties of yellow-seeded canola. Anim. Feed Sci. Technol. 78:249-262.
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Performance of egg-strain birds during their commercial life cycle when continuously fed diets containing Tower rapeseed gums. Can. J. Anim. Sci. 58:183-89.
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