Canola meal (CM) is a high-quality protein supplement well-suited for use in poultry diets. Canola meal has benefited from an intensive breeding program designed to reduce glucosinolate (GL) and erucic acid levels in canola seed. Canada continues to heighten these standards, as indicated by recently proposed changes to the canola definition (Daun & Adolphe 1997 {296}).
Certain nutritional aspects are unique to using CM
as a protein supplement in poultry diets. High fibre levels and
GL effects remain the top issues of concern. Product knowledge
and feed formulation approaches will help the feed industry take
maximum advantage of the opportunities afforded by this locally-produced
feedstuff.
1. Nutrient Specifications of Canola Meal for Poultry
It is important for users of CM to perform regular nutrient analysis on the product received from each supplier. Regional variations exist for crude protein (CP), fibre fractions, mineral and amino acid contents. Bell and Keith (1991 {421}) performed an extensive nutrient survey of CM collected for four consecutive weeks from seven western Canadian plants. The results are shown in Tables 1 and 2, along with data from other analyses of Canadian CM.
The apparent metabolizable energy (AMEn) of CM for
young chicks has been investigated in two recent studies. The
AMEn of conventional (cv. Tower, 1837 kcal kg-1) and
of very low-glucosinolate (VLGL) CM (2130 kcal kg-1)
was determined using 3-week-old chicks (450 g kgppm)bdietary
inclusion, 1988 crop). Total GL levels were 15.63 and 0.54 mMol
g-1 (oil-free basis), respectively. Subsequent feeding
trials supported the accuracy of these AMEn values (Classen et
al. 1991{440}). The nutritive characteristics of Brassica
napus and B. rapa (campestris) were compared
to four low-GL samples of B. juncea (Newkirk et al.
1997 {303}). Ileal protein digestibility (75.34, 76.72, and
78.5%, respectively) and AMEn (1832, 1557 and 2217 kcal kg-1
DM basis, respectively) were determined using 28-day-old commercial
broiler cockerels and 40% meal in the test diets. The low AMEn
value for B. rapa may have been related to an inadequate
sample processing temperature or a cultivar effect (H. Classen,
personal communication). Total dietary fibre (TDF) was negatively
related to AMEn (kcal kg-1 = -183 TDF + 7179.9; P<0.02;
R2=0.78) and ileal protein digestibility (% = -1.567 TDF + 121.6;
P<0.03; R2=0.73) (Newkirk et al. 1997{303}). Dietary
fibre in canola was also negatively correlated with CP level (Y=
59.294-0.687X; r= -0.71; P=0.0001), indicating a reduction in
AMEn value may be appropriate for samples with lower CP values
( Simbaya et al. 1995{328}).
| Table 1. Proximate composition of Canadian canola meal. | |||||||
| Dry matter, % | 91.5 ± 0.20 | 88.3 | 92 | 90.05 | Calcium, % | 0.64 ± 0.07 | 0.73 |
| Cr. protein, % | 38.29 ± 2.33 | 33.59 | 37 | 34.83 | Magnesium, % | 0.52 ± 0.04 | 0.46 |
| Cr. fibre, % | 12.01 ± 0.68 | 6.90 | Potassium, % | 1.24 ± 0.12 | 3.25 | ||
| Ether extract, % | 3.59 ± 0.69 | 3.22 | 3.7 | Phosphorus, % | 1.03 ± 0.06 | 1.06 | |
| Ash, % | 6.90 | Copper, ppm | 5.80 ± 0.22 | 10 | |||
| Gross Energy, kcal/kg | 4453 ± 48 | 4389 | 4420 | Manganese, ppm | 50.1 ± 5.46 | 40 | |
| TMEn Poultry, kcal/kg | 1964 | 2090 | Iron, ppm | 144 ± 26 | 160 | ||
| AMEn Poultry, kcal/kg | 1980 | Zinc, ppm | 69.4 ± 4.8 | 80 | |||
| Selenium, ppm | 1.12 ± 0.40 | ||||||
| Reference # | {421}a | {439}b | {452}c | {326}d | {421}a | [439}b | |
a Mean ± standard
deviation of 4 weekly samples from 7 canola crushing plants in
Western Canada, 91.5% dry matter (DM) basis.
b Values from S.
Korean analysis of Canadian CM; assumed expressed on DM basis
indicated.
c Sample obtained
from Alberta grain elevator; assumed expressed on DM basis indicated.
d Canola meal obtained
from Alberta crushing industry; assumed expressed on DM basis
indicated; assay used SCWL cockerels.
Studies performed in France indicated that the true
digestibility of CM amino acids, determined using caecectomized
adult ISA Brown males, was similar to that stated in Table 2,
regardless of whether seeds were dry-heated at 80°C
for 20 minutes, or at 100°C
for 30 minutes (Green and Kiener 1989 {484}). Growth assay of
male broilers, 11 to 20 d of age, indicated the lysine availability
of SBM, hulled CM and dehulled CM differed significantly (P<0.05;
85.5, 72.8 and 78.3%, respectively). The corresponding true lysine
digestibilities of these ingredients also differed significantly
(P<0.05; 87.5, 76.9 and 81.4%), as determined using adult ISA
Brown cockerels (Larbier et al. 1991 {431}). The age and
sex of birds also had a significant effect (P<0.05) on the
true digestibility of amino acids. At three weeks of age, the
approximate digestibilities of lysine, methionine and threonine
in male and female broilers were 76, 83 and 78%, respectively.
In birds six weeks of age, true digestibility of these amino
acids for males (approx. 65, 73 and 63%) was greater than those
for females (59, 73 and 53%), respectively. The authors noted
that improved efficiency of digestion in younger birds had been
observed in studies by other workers (Zuprizal et al. 1992{394}).
| Table 2. Amino acid analysis of canola meal. | ||||||||||
Amino Acid Content (% of meal) | Amino Acid Digestibility (%) | |||||||||
| True | Apparent | |||||||||
| Aspartic acid | 2.02 | 2.7 | 1.91 | 91 | 78 | 69.9 | ||||
| Glutamic acid | 6.04 | 7.2 | 5.57 | 96 | 92 | 86.8 | ||||
| Serine | 1.32 | 1.5 | 1.25 | 92 | 81 | 72.1 | ||||
| Histidine | 1.41 ± 0.04 | 0.92 | 1.2 | 1.04 | 0.84 | 89 | 93 | 86 | 87.4 | |
| Glycine | 1.44 | 2.3 | 1.92 | 1.59 | ||||||
| Threonine | 1.90 ± 0.12 | 1.45 | 1.8 | 1.68 | 1.35 | 79 | 78 | 82.2 | 71.1 | |
| Arginine | 2.38 ± 0.18 | 1.67 | 2.4 | 2.26 | 1.74 | 98 | 88 | 89 | 91.8 | 78.0 |
| Valine | 2.29 ± 0.13 | 1.66 | 2.0 | 1.64 | 1.54 | 90 | 81 | 81 | 81.2 | 74.7 |
| Phenylalanine | 1.56 ± 0.09 | 1.10 | 1.6 | 1.45 | 1.31 | 93 | 86 | 86 | 80.8 | |
| Isoleucine | 1.79 ± 0.14 | 1.29 | 1.7 | 1.28 | 1.26 | 91 | 82 | 83 | 82.8 | 76.4 |
| Leucine | 2.78 ± 0.16 | 2.12 | 2.8 | 2.57 | 2.22 | 93 | 86 | 86 | 85.8 | 81.0 |
| Lysine | 2.28 ± 0.09 | 1.64 | 2.6 | 2.21 | 1.9 | 92 | 83 | 78 | 84.4 | 74.8 |
| Cystine | 1.10 ± 0.14 | 0.63 | 0.6 | 0.4 | 79 | 73 | 81.5 | |||
| Methionine | 0.79 ± .07 | 0.62 | 0.6 | 0.68 | 0.6 | 88 | 83 | 88 | 90.4 | 79.6 |
| Alanine | 1.36 | 1.42 | 83 | 76 | ||||||
| Tryptophan | 0.44 | 82 | ||||||||
| Tyrosine | 1.16 ± 0.06 | 0.77 | 0.85 | 82 | 74.4 | |||||
| Ref # | {421} a | {439} b | {452}c | {540} d | {326} e | {452} c | {326}e | {2054}f | {404}g | {326}e |
a Mean ± standard
deviation of 4 weekly samples from 7 canola crushing plants in
Western Canada, 91.5% DM basis.
b Values from S.
Korean analysis of Canadian CM; assumed expressed on 88.3% DM
basis.
c Assay of product
from Alberta grain elevator used adult SCWL males (n=3); values
assumed expressed on 92% DM basis.
d University of Alberta
data; based on a CP value of 37.15%.
e Canola meal from
Alberta crushing industry, 90.05 DM basis; amino acid availability
assays used adult SCWL males (n=6).
f Canola Council
of Canada {2054} values based on Heartland Lysine analysis.
g True amino acid
availabilities measured using an undisclosed number of 7-week-old
hen turkeys.
Regression equations have been developed to predict
the amino acid levels of CM on the basis of its CP content. The
low r-value for these equations indicates that they should be
used with discretion (Beste et al. 1992{408}). Bell and
Keith (1991{421}) also performed a comprehensive study of Canadian
CM during the same time period (Table 1). They indicated that
amino acid variation among crushing plants was possibly due to
genetic (cultivar) and/or environmental factors, but that lysine
values were the most consistent.
| Table 3. Amino acid prediction equationsa and amino acid compositionb of Canadian canola meals (88% DM basis). | ||
| Amino acid | Regression equation | Mean (Range) |
| Lysine | = %CP * 0.0402 + 0.546; r=0.57 | 2.02 (1.83 to 2.16) |
| Methionine | = %CP * 0.0156 + 0.181; r=0.66 | 0.75 (0.67 to 079) |
| Methionine + Cystine | = %CP * 0.0468 + 0.033; r=0.64 | 1.65 (1.50 to 1.81) |
| Threonine | = %CP * 0.0262 + 0.641; r=0.62 | 1.59 (1.45 to 1.65) |
| Tryptophan | = %CP * 0.0215 + 0.294; r=0.79 | 0.50 (0.46 to 0.55) |
| Arginine | = %CP * 0.0758 + 0.535; r=0.73 | 2.25 (2.07 to 2.48) |
a (n=40 from 1990,
and 57 from 1988 Canadian crop)
b (n=40, 1990 Canadian crop, 88% DM)
Beste et al. 1992{408}
The xanthophyll level of commercial CM averaged 7.2 mg kg-1 (n=7), approximately one-third that of yellow corn. Values varied from 3.9 to 11.9 mg kg-1 as a result of varietal and environmental conditions (Blair and March 1989 {500}).
A recently developed bioassay technique determined that of the 6198 mg kg-1 choline measured in CM, 1464 to 1545 mg kg-1 (approximately 24%) was available to New Hampshire X Columbian chicks (10 - 22d). This value was stable even when the samples were overheated (121 °C, 105 kPa for 60 min) (Emmert and Baker 1997 {295}).
Canola meal was analyzed to contain 12.2g kg-1 total phosphorus, of which 5.3g kg-1 was phytate-bound, compared to 6.6 and 3.8g kg-1, respectively, for SBM (Bell 1993 {1714}).
As stated at the beginning of this section, it is
important for feed manufacturers to implement a quality control
program that monitors the nutritional value of CM and all other
feedstuffs used. A survey of CM from western Canadian crushing
plants showed significant differences in the proximate values
of CM; however, much of this variation was attributed to regional,
seasonal and cultivar effects on canola seed composition. Processing
conditions can also affect the available lysine content of CM,
and differences have been shown to exist between crushing plants
(Bell and Keith 1991 {421}). Fortunately, analyses have been
identified to assist in monitoring the effects of environment
and processing on the quality of CM (Dale 1996{316}).
The blending of seed lots during canola crushing reduces the regional, seasonal and cultivar effects on CM quality. The CP content of CM should be determined regularly to allow accurate diet formulation. Moisture content should also be monitored because this affects the nutrient concentration of CM. Ether extract, an important energy source in CM, may vary due to the type and level of oil refining byproducts added back into the meal and should be determined periodically. The fibre component of CM is poorly digested by poultry and is therefore a notable detractant from its nutritional value. Although formal equations relating neutral detergent fibre (NDF), crude fibre or ADF to metabolizable energy (ME) and protein digestibility are not available, relationships for total dietary fibre indicated AMEn and protein digestibility were reduced at elevated fibre levels (Newkirk et al. 1997{303}). The quality of CM protein is sensitive to overheating during processing. Autoclaving for 0 to 90 minutes reduced the indispensible amino acid availability, lysine availability and lysine content (P<0.05) of commercial canola meal. The growth of chicks (8-17d) fed this meal decreased linearly as autoclaving time increased (P<0.001)( Anderson-Hafermann et al. 1993{367}). Protein solubility is a practical measure of overheating in CM (Fernandez et al. 1993{361}), with values below 45% (0.5% KOH assay) or 35% (0.2% KOH assay), indicating that CM has probably been overprocessed (Anderson-Haffermann et al. 1993{367}).
Unfortunately, many of the assays mentioned are not
cost effective or easy to interpret in terms of adjusting nutrient
values for CM. Development and adoption of NIR technology holds
the greatest promise for allowing feed manufacturers to monitor
the quality of ingredients that they purchase.