Intestinal and Total Tract Digestibility of Canola Oil
Apparent intestinal digestibility of
oil fatty acids was calculated to be 68% (Chilliard et al. 1990
{1017}). When 1.0 to 1.5 kg/d of rapeseed oil were infused into
the duodenum of lactating dairy cows, 63 to 74% of the fatty acid
apparently was digested. This digestibility was not decreased
when oil infusion was increased from 1.0 to 1.5 kg/d. However
a large increment in fecal non-FA lipids was observed, resulting
in a sharp decrease in the energy value of the infused oil supplement
compared with the value from FA digestibility alone (Chilliard
et al. 1991 {975}; Ferlay et al. 1993 {926}).
Early lactation cows cannot consume enough dietary energy to meet their nutrient requirements for high milk production, and thus they rely extensively on body lipid mobilization to furnish energy and long-chain fatty acids for milk synthesis (Gagliostro and Chilliard 1991 {976}). Supplemental rapeseed oil can be used to increase the energy density of diets and substitute, in part, for mobilized adipose fatty acids (Gagliostro and Chilliard 1991 {976}). As well direct transfer of long chain fatty acids from diet to milk is more efficient than de novo synthesis from short-chain precursors, and maximum efficiency of energy utilization can be achieved theoretically when the diet provides 12 to 16% of metabolizable energy as long chain fatty acids (Gagliostro and Chilliard 1991 {967}; Ferlay et al. 1993 {926}). However, polyunsaturated fatty acids have a negative effect on the metabolism of rumen cellulolytic bacteria and reduce the numbers of protozoa (Ben Salem et al. 1993 {894}). This has prompted research in protected lipid supplements to protect dietary FA against ruminal microorganisms or to protect ruminal fermentation against effects of dietary lipids (Ben Salem et al. 1993 {894}; Chilliard 1993). Methods of protecting canola or rapeseeds or oil include hydrogenation or saponification of FA, crystallization of fats, encapsulation of lipids in a FA-treated protein coat, and FA treatment of whole seeds (Chilliard 1993). Intestinal absorption of polyunsaturated fatty acids is higher in comparison to saturated fatty acids (Ferlay et al. 1993 {926}). Milk with higher levels of polyunsaturated fatty acids would increase the nutritional quality of milk fat and its acceptability by consumer's (Atwal et al. 1991 {983}; Wood and Enser 1997 {785}; Jenkins and Jenny 1992 {955}).
The effectiveness of these processes seem partial and results variable. The process of saponification of fatty acids did not protect polyunsaturated fatty acids against microbial biohydrogenation (Ferlay et al. 1993 {926}). Calcium salts were dissociated to the same extent as rapeseed oil (Ferlay et al. 1993 {926}). In this trial, Ca salts of FA were as biohydrogenated as triglyceride FA (Ferlay et al. 1993 {926}). Studies from four farms, two using Protec® and two not, were used to determine if feeding Protec® at approximately 5% of the grain portion had any detrimental effect on milk composition, butter quality and on performance of the animals. The results indicated that Protec® did not have any significant effect on milk composition (fat, protein, lactose, ash, and total solids) (Cadden et al. 1984 {1222}). Protec®, feeding high levels of formalin-treated canola oil (850 g/d) or 4% dietary DM to cattle in midlactation tended to reduce milk yield (24.0 to 20.0 kg/d) and milk fat (3.9 to 3.6%) (Atwal et al. 1991 {983}). Feeding canola oil as Protec® at 4% dietary DM significantly increased the proportion of stearic (C18:0), oleic (18:1 n-9), linoleic (18:2 n-6) and linolenic (18:3 n-3) fatty acids with a concomitant decrease in C6 to C16 fatty acids (Atwal et al. 1991 {983}). In this study Protec® provided about 140 g of C18:2 (n-6)/d per cow, which significantly increased linoleic fatty acid from 2.7 to 3.8% in milk fat (Atwal et al. 1991 {983}).
Feeding of Protec® improved low temperature spreadability (Atwal et al. 1991 {983}) and softness of butter (Cadden et al. 1984 {1222}). With Protec® supplement an increase in C18:1 content of the milk fat was increased (35.2 vs. 23.4%) and was reported to increase the proportion of milk fat liquid at 50 C from 18 to 35% and to decrease the exclusion thrust of butter at 50C from 4700 to 1220 g (Atwal et al. 1991 {983}). When feeding calcium salts of rapeseed oil, compared with rapeseed oil itself, the proportion of trans-monoenic acids increased and decreased oleic and linoleic fatty acids in milk (Ferlay et al. 1993 {926}). Holstein cows in midlactation were given 850 g/d of formalin-treated canola oil as Protec® (20% CP and 30% ether extract) and the effect on fatty acid composition of milk fat was typical of feeding a high untreated oil. Therefore it was concluded that the unsaturated fatty acids of canola oil in Protec® were not well protected from hydrogenation in the rumen (Atwal et al. 1991 {983}).
Milk yield has been found to increase
linearly when Ca salts of canola oil FA are fed at the rate of
4% (percentage of DM) to cows that were at 84 d of lactation (Chouinard
1996 as cited in reference Chouinard et al. 1997 {789}). With
supplementation of Ca salts of canola oil the addition of buffers
may be needed to maintain ruminal pH and to minimize the dissociation
of salts (Chouinard et al. 1997 {789}). Feeding 850 g of Protec®
canola oil/d to cows in midlactation significantly decreased DM
intake from 24.0 kg DM/d to 20.9 kg/d and tended to reduce BWG
(723 g/d vs. 490 g/d) (Atwal et al. 1991 {983}). Early lactating
cows continuously infused with 1.0 to 1.1 kg rapeseed oil/d did
not differ from the controls in losses of empty body weight and
condition score (Gagliostro and Chilliard 1991 {967}; Chilliard
et al. 1990 {1017}). As well in early lactation with supplementation
of 0, 2. 4% calcium salts of canola oil. However, in midlactation
there were significant differences (2 kg gain vs. -14 kg loss)
in empty body weight and body condition score in cows infused
with oil (a drop of 0.7 in body score compared to no decrease)
(Gagliostro and Chilliard 1991 {976}). Midlactating cows infused
(640 g/d of rapeseed oil) into the duodenum had reduced BW and
empty BW and it declined (-17 vs. -7 kg loss) over a three week
period and body score was reduced by (P < 0.05) oil infusion
(Ottou et al. 1995 {812}).
| Table 12. Fatty acid composition of rapeseed oil compared with canola oil and gross energy values | ||||||
|---|---|---|---|---|---|---|
| Fatty acid | Target rapeseed % | Regent Canola % | Canola oil | Soybean oil | Tallow | |
| C16:0 | Palmitic | 2.7 | 3.7 | 4 | 8 | 26 |
| C16:1 | Palitoleic | 0.2 | 0.4 | |||
| C18:0 | Stearic | 1.0 | 1.5 | 2 | 3 | 19 |
| C18:1 | Oleic | 20.6 | 58.0 | 52 | 24 | 40 |
| C18:2 | Linoleic | 13.8 | 22.9 | 25 | 58 | 5 |
| C18:3 | Linolenic | 6.2 | 9.3 | 13 | 8 | 1 |
| C20:0 | Arachidic | 1.0 | 1.1 | |||
| C20:1 | Gadoleic | 13.2 | 1.7 | |||
| C22:0 | Behenic | 0.4 | 0.3 | |||
| C22:1 | Erucic | 39.8 | 0.1 | |||
| C24:0 | Lignoceric | 0.1 | 0.1 | |||
| C24:1 | Nervonic | 0.9 | 0.3 | |||
| Gross Energy | kcal/kg | 9.76 | 9.60 | |||
| Saturated | 6 | 10 | 48 | |||
| Unsaturated | 94 | 90 | 52 | |||
| Reference: | 1091 | 1091 | 1253 | 866 | Rode 1992 as cited by 808 | |
Canola Oil and Canola Soapstocks in Calf Milk Replacers
There are reports of high levels of dietary free fatty acids and unsaturated vegetable oils causing calf scours, reduced calf gains and feed utilization (Jenkins et al. 1986 {1151}). However, (Jenkins et al. 1986 {1151}) reported comparable weight gain (0.61 vs. 0.59 kg/d) and feed utilization (1.41 vs. 1.42) with canola oil instead of tallow (20% DM). The higher 18:3 n-3 and lower 18:2 n-6 may have been the important factor. Canola soapstocks plus tallow (1:1) reduced gains by 25% in comparison to tallow alone (Jenkins et al. 1986 {1151}).