2. Feeding Canola Meal to Broilers and Turkeys
The high fibre level is one of the greatest restrictions to CM use in broiler diets. Non-starch polysaccharide (NSP) digestibility determined using adult SCWL cockerels (11.6% {210}) and hens (<3%) (Slominski and Campbell 1990{460}) indicated this fraction of CM was poorly digested by chickens, and effectively reduced available CP and AMEn values (Newkirk et al. 1997{303}). Traditional broiler rations have high AMEn and CP requirements, however, the considerable appetite of the commercial broiler allows birds to maintain good growth rates on reduced-density diets. These diets increase the use of higher-fibre, local ingredients like CM or barley, and can reduce the cost of poultry production. Density reduction of diets is also suitable for use in turkey production.
Alternatively, CM can be pelleted with off-grades of ground canola seed (1:3 ratio) to provide a high-energy (3261 kcal kg-1), moderate protein (23.9% CP) feed ingredient. When the blend was included (338 g kg-1) in diets for broiler chicks the nitrogen retention, AMEn and protein and fat digestibilities were similar to that of a SBM control (DM basis, Fasina et al. 1997 {304}). Feed efficiency and body weight gain were significantly reduced at or above 50 g kg-1 inclusion, respectively, of the pelleted whole canola-CM blend despite diets containing comparable calculated levels of available lysine, methionine and ME (Fasina and Campbell 1997 {305}).
It has been suggested that CM may be better suited to use in the later stages of broiler and turkey phase-feeding programs, however, studies have not conclusively supported this theory. The AMEn of CM is higher for adult birds than for young chickens (2000 vs. 1900 kcal kg-1)(Clandinin and Robblee 1983 in Canola Council of Canada 1997 {2054}), indicating that mature birds may be better able to utilize or cope with the fibre component. Conversely, workers in France (Zuprizal et al. 1992 {394}) showed a significant difference in the true digestibility of CP in VLCM for 21 and 42 day-old Hubbard chicks (73.9 vs 70.5%; P<0.001), and a corresponding reduction in amino acid digestibilities. A similar reduction in digestibility was noted for the SBM control, and was attributed to superior protein utilization in the younger birds. In a feeding study involving market turkeys, there was no benefit to delaying the age at which canola products were included in diets (Salmon and Stevens 1988{517}).
Canola meal has lower amino acid digestibility than
its major marketplace competitor, SBM. In a study using young
broilers (3 - 6 week), true digestibility was an average of 15,
8 and 12% lower for lysine, methionine and threonine in VLCM (40.1%
CP) than in SBM (52.7% CP) (Zuprizal et al. 1992 {394}),
respectively. Similar differences can be calculated from information
published by Heartland Lysine (12, 3.5 and 11%, respectively;
Heartland Lysine, 1995). Lysine is the amino acid most likely
to be limiting in CM-based diets, and studies show that its supplementation
improves broiler performance to levels seen with SBM-based diets.
The weight gain and feed/gain ratios (1984g and 1.83, respectively)of
broilers consuming CM-based diets (150 g kg-1) were
equivalent to a SBM control (P>0.05; 2093g and 1.83, respectively)
but improved numerically by supplementing lysine to total 3.75
mg kcal-1 ME of diet (2021g and 1.79, respectively)(Campbell
1988 {507}). Another study involving graded levels of CM (0,
75 and 150 g kg-1) in starter and finisher diets for
broilers used elevated total lysine (13, 11g kg-1)
and methionine (5, 4 g kg-1) levels to ensure these
amino acids did not limit performance. Weight gain (2.66, 2.68
and 2.68 kg) was equivalent for these rations, but feed conversion
was significantly improved for the diet containing 75 g CM kg-1
(1.86, 1.83 and 1.86g g-1 gain P<0.05) (Guenter
1990, unpublished data). Nearly all other CM feeding studies
published to date have failed to modify diets to compensate for
the lower available lysine levels in CM. Performance erosion
is frequently seen with elevated dietary levels of CM (Table 4
), and it cannot be distinguished whether this effect should be
attributed to GL or inadequate dietary formulation.
| Table 4. Results from broiler feeding trials involving different levels of canola meal. | ||
| Reference | Treatment | Value or Effect |
| Classen et al.1991
{440} | Cereal grain-SBM control replaced by CM(15.6 mMol/ga) or VLCM (0.5 mMol/ga) at 100, 200 and 300 g kg-1 of diet to 42d. | Body weight declined with increasing CM level (P<0.05); VLCM performance equal to SBM control. |
| Nassar 1986 {537} | CM replaces 0, 25, 50, 75 or 100% of SBM in corn-soy starter and finisher diets to 7 weeks. | Trend toward reduced body weight up to 50% SBM replacement; body weight, feed consumption reduced (P<0.05) at higher CM levels. |
a total glucosinolates
A recent feeding trial using broiler chicks (0 - 21d) compared Brassica napus, B. rapa and B. juncea at 20% dietary levels versus a SBM control. Performance did not differ significantly between diets, except for inexplicably poor results from the B. rapa diet. It was concluded that meal from B. juncea was at least equal to the quality of conventional CM (Newkirk et al. 1997 {303}), which is important because low-GL mustard species will be included in the CM definition under the newly proposed changes (Daun and Adolphe 1997 {296}).
Several studies have been performed to determine the effect that the relatively high sulfur level in CM may have on chick performance (4.4 g kg-1) (Summers et al., 1990{461}; 1989{478}; 1990{462}; 1992{409}). It was concluded that the cation-anion balance of diets was altered by the sulfur content of CM, and that this could be ameliorated by supplementing diets with sodium, potassium or calcium (Summers and Bedford, 1994 {336}). The significance of these findings for industry is unclear because the diets used in these studies were formulated to impose nutritional stress on the broiler chicks and had dietary cation-anion imbalances that would not occur in diets formulated to commercial standards. In growth trial analysis where diets contained comparable levels of true digestible amino acids, diets containing 250 g kg-1 CM performed very well compared to SBM controls. The addition of sulfur (2 g kg-1 diet) affected the performance of chicks consuming either protein source similarly (Summers et al., 1992{409}). As indicated by the authors, this information may be of specific importance to producers with a high-sulphate water supply.
Canola meal is commonly used in turkey diets, especially during the grower and finisher phases. However, research indicates that CM can also be used at relatively high levels throughout the production cycle. The 18-week weights of Hybrid toms fed a corn-soy control, or diets supplemented throughout the start-grow-finisher phases with CM (150 g kg-1 of diet) or CM and meat-and-bone meal (150 and 100 g kg-1, respectively) were 13.58, 13.31 and 13.64 kg, respectively. It is significant that these diets were formulated to meet 100% of NRC protein and available methionine recommendations, and had similar determined available lysine values (Carlson et al. 1992{404}). Large White toms consuming diets supplemented with 200 g kg-1 CM up to 19 weeks of age performed equivalent to those fed an isocaloric corn-soy control. Reducing the CM content of the diets to approximately 50% of total supplemental protein did not improve performance (Waibel et al. 1992{390}). Supporting these findings was a study in which unsexed turkeys consuming CM-based rations (100 or 200 g kg-1 diet) to 12 weeks of age performed equivalently to those on a corn-soy control (Salmon et al. 1988{517}). Conversely, poults fed a ration containing CM, casein, blood meal and feather meal (210, 88, 37 and 37 g kg-1 diet, respectively) did not perform as well (P<0.05) to 13 days of age as those consuming a corn-soy diet or a complex diet containing fish meal (Angel et al. 1992{392}).
In summary, turkeys and broilers respond extremely
well to the use of CM-based diets, particularly when rations are
formulated on the basis of available amino acid/energy ratios
and incorporate a variety of digestible protein sources (Irish
and Belnave {381}). The quality of poultry products resulting
from feeding CM is at least equal to that from other protein sources
(Gardzielewska et al. 1992{413}; Waibel et al.
1992{390}).