Canola Co-products for Feeding Pigs

Canola cold-pressed, expeller-pressed or solvent-extracted. What is the difference among these products, and why should it matter to pork producers?

After more than 30 years, pork producers have become familiar with feeding conventional canola meal. But in recent years, new terms have emerged that refer to novel canola co-products for animal feeding. Producers may wonder what these terms mean and what the differences are among co-products.

And for the bottom line, excellent buying opportunities exist when shopping for canola co-products to increase profit margins and reduce feed costs.

Cold- or Screw-pressed Canola Cake

When oilseed is pressed using a screw within a housing barrel, it is referred to as “screw-pressed” (see Figure 1). This term is preferred rather than “cold-pressed.” Screw pressing is “colder” relative to expeller pressing (see the following section), but it still generates some heat by friction.

Cold- or screw-pressed canola is the simplest type of oilseed processing. The process causes strands of churro-like “cake”(churro is a ring-shaped pastry) to shoot out, and oil drips down from the die. Producers with off-grade or immature green seed that crushers will not take can screw-press the seed and feed up to 15 per cent rolled cake to hogs.

The oil can also be fed to nursing sows or weanlings even if stained green. Feeding “green” oil will not hurt the animals, but as the oil is stained with chlorophyll, it would be costly to clear out for human oil consumption.


Figure 1. Simple oilseed screw press to produce cake and oil
for on-farm feed mixing.

Expeller-pressed Canola Cake

Expeller-pressed canola cake has a lower residual oil content (10 to 16 percent) than screw-pressed cake (16 to 22 per cent, see Table 1). A larger screw exerts greater pressure on the seed against a barrel cage lined with bars. The oil drips through the bars, and cake chunks come out at the end of the screw (see Figure 2).

To maximize oil yield, processing plants may “condition” the seed by warming it using a seed dryer before expelling the oil. Or alternatively, they may flake it using steam-heated rollers or “puree” it using an extruder before expelling. Two presses may also be installed in tandem to squeeze oil out of the seed first and then from the cake in sequence.

Producers may feed up to 20 per cent expeller-pressed canola cake in late nursery and grower pig rations. Nursing sows may also benefit from the remaining oil in expeller-pressed cake by including up to 15 per cent expeller cake in the nursing diet, provided that sows have become accustomed to the taste of canola during gestation.

Expeller plants source some heated, off-grade canola seed, so the risk of both contaminants (for example, mycotoxins) and nutrient variability increases. Commodity traders buy the oil from expeller plants and re-sell it either for bio-diesel production or to animal producers as feed-grade oil. Therefore, producers should develop a relationship with cake suppliers, so they can learn to trust the safety and nutrient consistency of the products.


Figure 2. In an expeller press, greater pressure is exerted by a
large screw expelling more oil out of the seed pressed against
a barrel cage lined with bars.

Solvent-extracted (Conventional) Canola Meal

Large crushers that produce oil for human consumption also expel press the canola seed as described before, but the cake is subsequently washed in tanks with a solvent to remove the remaining oil. The solvent is evaporated, and the cake is lightly toasted and ground to make canola meal. Some gums (phospholipids) recovered during oil refinement are added back to the canola meal increasing its fat content somewhat (<3 per cent).

Conventional canola meal is what producers have become familiar with as a supplementary protein source (36 to 38 per cent protein). Canola meal is also the most consistent in terms of nutrient content versus cakes. Meal is also the safest to feed as crushers source mostly #1 or #2 clean canola seed to press for human food oil consumption.

However, canola meal is relatively low in dietary energy value (see Table 1) given that it has no residual oil content. Nonetheless, producers may feed up to 30 per cent canola meal to hogs and gestating sows, and up 20 per cent to nursing sows or weaned pigs in substitution for imported soybean meal.

Residual Oil is a Good Deal

Assuming that a producer is satisfied with the safety and nutrient content of canola cake produced on-farm or sourced from an expeller press plant, Table 1 highlights the economic benefit of the greater residual oil content. Most importantly, residual oil content increases the dietary energy value of canola cake compared with solvent-extracted canola meal.

Cakes do have lower protein due to the greater oil content diluting them. But cakes provide more concentrated calories per bite that increase weight gain and reduce days to market. Late nursery-age pigs and grower pigs benefit the most from feeding canola cake instead of meal. Nursing sows also benefit from the extra calories in canola cake versus meal as the cake helps them reduce body tissue loss, a loss triggered by the need to support milk production for ever larger litters.

Table 1. Comparison of nutrient content and cost per unit of dietary energy (screw-pressed cake= 20% residual oil, expeller-pressed cake = 10% residual oil and solvent-extracted (conventional) canola meal = 3% fat)
	Screw- pressed cake1	Expeller- pressed cake1	Solvent- extracted canola meal2
Moisture, %	12.7	9.6	10.5
Protein, %	25.8	31.4	38.1
Available lysine, %	1.4	1.6	2.0
SID lysine, g/kg	12.0	13.2	15.0
Fat, %	20.2	10.5	2.7
Crude fibre, %	5.8	8.3	7.4
NDF, %	15.3	18.8	27.4
ADF, %	11.5	15.0	19.8
Ash, %	4.5	5.7	7.6
P, %	0.9	1.0	1.1
Ca, %	0.5	0.4	0.6
GE, MJ/kg	22.3	20.9	18.1
DE, MJ/kg	16.5	14.3	14.0
NE, MJ/kg	11.5	9.0	7.7
$/1000 kg	300	300	300
¢/MJ NE	2.6	3.3	3.9
¢/g SID lys	2.5	2.3	2.0