1.0 Nutritional Specifications of Canola Oil
Canola oil provides a convenient, palatable, concentrated energy source for swine diets. The digestible energy value of canola oil for growing pigs (20-30 kg) is 8.0-8.5 mcal/kg (Baidoo et al. 1996 {1613}) with a digestibility of 92.7% and an efficiency of ME for energy retention of 0.638 and for NE 0.894 (Jorgenson et al. 1996 {1615}). Although digested primarily in the duodenum Shi and Noblet (1994 {1654}) found that 10% of rapeseed oil energy escaped for degradation in the hind gut. This was not utilized by young pigs (<45kg) but was almost fully utilized by older pigs. For castrated males given a diet containing 80g kg-1 RS oil, energy digestibility improved from 89-97% with body weight (45-100kg) with no difference being noted between 100 and 150kg (Noblet and Shi 1994 {1658}). Ileal and fecal digestibility of DM and fat were the same for beef tallow and rapeseed oil (Ozimek et al. 1984{1912}).
Rapeseed oil is rich in natural tocopherols (370mg/kg) which consist of alpha, gamma and delta tocopherol and alpha tocotrienol (272, 686, 14 and 116mg kg-1 respectively) (Jorgenson et al. 1996 {1615}). Unfortunately placental transfer of these antioxidants does not occur as the addition of 50g kg-1 canola oil to the diet of first parity gilts had no significant effects on the -tocopherol concentration of the milk nor the plasma -tocopherol concentration of the piglets (Hidiroglou et al. 1995{1632}).
Despite the presence of natural antioxidants, canola oil, like any other fat source, is susceptible to oxidation if improperly stored. Hydroperoxides are the primary products from the oxidation of unsaturated fatty acids during storage and processing. They are involved in the development of rancidity, odours and flavours and the formation of toxic and physiologically active compounds. Malonaldehyde is closely related to odour and rancidity in lipids and is derived from the oxidation of mono or polyenoic fatty acids. As expected, the substitution of 150g kg-1 canola oil for 150g kg-1 starch in a grower pig diet resulted in a significant increase in the pancreatic secretion of lipase and a decrease in secretion of -amylase. Oxidized canola oil further stimulates the biosynthesis of pancreatic lipase (P<0.05) (Ozimek et al. 1995 {1626}). Attention should be paid to oil condition as rancidity has a severe negative effect on palatability and may adversely affect animal physiology.
A recent application for canola oil in pig barns
is to reduce dust. Whether applied to the feed, sprayed as an
aerosol or sprayed directly on the pigs, canola oil is an effective
dust suppressant (Takai et al.1995 {1624}). Although Welford
et al. (1992 {1768}) reported reductions of inhalable (71%)
and respirable (76%) dust concentrations by sprinkling canola
oil, Zhang et al. (1996 {1606}) found only a reduction
in nuisance dust levels by the addition of 20g kg-1
canola oil and no advantage in reducing the respirable dust levels.
Pigs were not affected by the small intake of oil from spraying
or sprinkling (Takai et al. 1995{1624}).
2.0 Benefits of Canola Oil on Animal Performance
Generally, canola oil is included in swine diets to increase energy or control dust. Myer et al.(1992 {1767}) found the addition of 50 and 100g kg-1 canola oil to grower-finisher diets resulted in improved performance (ADG and FC) when the ME:lysine ratio was kept constant. In another trial, ADG and FC were similar whether added fat was from rapeseed oil or bovine milk (Mourat et al. 1995 {1631}). Few effects were noted in pancreatic secretions when rapeseed oil, fish oil and coconut oil were compared in pig diets at a level of 150g kg-1. Volume, pH, protein and bicarbonate secretions along with specific and total enzyme activities remained unchanged in the pancreatic fluid. Digestibilities of energy, fat, DM and protein did not differ between diets (Gabert et al. 1996 {1609}).
An advantage of including canola oil in the diet
is the improvement of apparent ileal digestibilities of indispensable
amino acids and CP despite no change in rate of passage. Comparing
canola oil inclusion at 20, 60 or 100g kg-1 , there
was a small (2-3%) curvilinear response for CM and a quadratic
response for SBM based diets in 45 kg pigs (Imbeah and Sauer 1991
{1804}). For younger pigs (11-12kg) the response of canola oil
addition to a SBM based diet was linear (P<0.05) (Li and Sauer
1994 {1685}). Digestibilities were highest at the highest oil
inclusion. This apparent protein sparing effect indicates that
oil addition can possibly reduce the nitrogen requirement of the
diet. Increasing the rapeseed oil content from 0-160g kg-1
resulted in improved dietary protein digestibility and protein
utilization (protein retained/protein digested). This may have
resulted from an improved essential to non essential amino acid
ratio as crystalline amino acids were used at higher levels of
oil addition. Alternatively, dietary fat may have a depressing
effect on the intestinal microflora (indicated by lower methane
production). Lower microbial synthesis resulted in lower microbial
protein synthesis and improved faecal protein digestibility (Jorgenson
et al. 1996)(1615).