Canola oil is a very high-quality lipid source that
is widely used within the poultry industry. It is a palatable,
uniform product that has the added advantage of remaining liquid
throughout the cold Canadian winters. Crude canola oil is the
most common form added to diets; however, degummed oils and acidulated
fatty acid byproducts are also reportedly sold as feed ingredients.
1. Nutritional Aspects of Canola Oil for Poultry
Canola oil is well-suited for use in the diets of young birds because it has a high content of unsaturated fatty acids. High levels of saturation have been shown to have a negative impact on the AMEn of fat sources, especially in younger birds (1.5 weeks) ( Wiseman and Salvador, 1991 [endnote]). Compared to tallow, diets containing canola or other vegetable oils (50 g kg-1) had improved fat retention (P<0.01) and improved dietary energy value for young turkeys (0-6 weeks) (Leeson and Atteh, 1995 {335}). Older broilers (36d) also exhibited a trend toward improved performance and fat digestibility with canola, soybean or animal-vegetable blend oils versus a processed, long chain saturated fat (Zollitsch et al. 1997{299}). An elevated free fatty acid content in fat sources has also been associated with reduced performance in broilers (Wiseman and Salvador, 1991(endnote), but reported levels in crude and degummed canola oil are quite low (4 - 12 g kg-1 fat; Mag (1990) and Ying (1989) in {2061}).
Omega-3 fatty acids have potential health benefits for both poultry (Fritsche et al. 1991 {427}) and humans. Poultry may be able to synthesize these omega-3 fatty acids from dietary lipids and store them in the form of carcass or eggs. Evidence suggests that chickens contain relatively high levels of the desaturase activity required to convert alpha-linolenic acid (C18:3n-3) to the omega-3 fatty acids, eicosapentaenoic acid (C20:5n-3) and docosahexaenoic acid (C22:6n-3) (Fritsche et al. 1991 {427}). Supplementation of diets with linseed or canola oil (70 g kg-1) was shown to increase the amount of linolenic acid in poultry diets (37.8, 5.5 g kg-1, respectively). Canola oil contained less linolenic acid than linseed oil, but it stimulated similar (P<0.05) serum, bursa, splenocyte and thymus docosahexaenoic acid levels in young broilers (Fritshce et al. 1991 {427}); however, immune response as measured by splenocyte proliferation and antibody production was better enhanced by linseed oil supplementation (Fritsche et al. 1991 {426}).
Interest exists in manipulating the fatty acid profile of poultry carcasses because it would be a simple, cost-effective method of providing an improved dietary fatty acid balance for humans. Broilers consuming diets supplemented with different fat sources were reported to have corresponding changes in the levels of some fatty acids in the muscle (Scaife et al. 1994{338}). In contrast, Hrdinka et al. (1996 {308}) found only the abdominal and subcutaneous fatty acid profile of broilers corresponded to that of the diet, so that poultry portions would have to be consumed with skin intact for humans to benefit from dietary fatty acid manipulation. Without genetic manipulation to increase linolenic acid levels in canola oil, linseed oil is likely to stimulate greater total omega-3 fatty acid production in poultry; however, storage and organoleptic properties of poultry products containing these easily oxidizable fats may encourage a moderate, canola-based, approach to supplementing LNA, if and when a large-scale market for these poultry products develops.
The polyunsaturated fats in canola oil are highly
sensitive to oxidation. Broiler chicks (10d) consuming a diet
supplemented with an artificially oxidized (16 meq O2 kg-1
oil) canola/soybean oil blend (90 and 20 g kg-1 diet,
respectively) had reduced retention of fat (P=0.07), energy (P=0.09)
and a-tocopherol
(P<0.01; Engberg et al.1996{309}). Fortunately, the
high level (Ferrari et al. 1996 {310}) and superior antioxidant
qualities of the tocopherols naturally present in canola oil may
help reduce its oxidation during storage (Lampi et al.
1997 {298}).