Effects of production energy savings on pig performance

Meal versus pellets

Practice shows that almost 75% of a production plant’s energy consumption is required to produce pellets. So should you should switch to using meal instead?

Meal has advantages compared to pellets:

• Meal production consumes less energy resulting in lower costs.
• There's no reduction in coarse particles caused by the pressing process.
• No steam is used so there's a reduced risk of mould formation.

But meal also has disadvantages compared to pellets:

• Increased feed conversion required due to lower digestibility.
• There's a risk of separation and blocked feed systems and feed troughs.
• The lack of heat treatment increases the risk of pathogens.
• Transport costs are higher due to increased volume, meaning fewer tonnes per truckload.

Digestibility of pellets versus meal

Various studies have shown that pelletised feed is easier to digest. The difference varies from 1.3% to 6% (Johnston et al., 1999a/b; O’Doherty et al., 2000; Ball et al., 2015). Studies limited to pellets processed by expander alone show that the digestibility of pellets compared to meal is 3% to 6% higher. For fattening pigs fed in accordance with their energy needs, there's a 3% to 6% impact on feed conversion with an average of 5% across the studies conducted.

Separation is higher in meal

Homogeneous feed produces better results whereas there's increased separation with meal. Depending on your plant's facilities, there are a few points to consider when formulating meal feeds:

• The addition of liquid products is limited and difficult compared to pellets. Whey products and liquid enzymes are examples.
• The maximum level of oil in meal is lower compared to pellets, making it more difficult to produce high-energy meal feeds.
• The combination of high-fibre and very fine or sticky raw materials can result in clotting.
• Coarse and light particles may separate during transport.

Higher transport costs with meal

Actual practice shows that a bulk tanker designed for 32 tonnes of pelletised feed can hold up to 4 tonnes less meal feed. This is a reduction of 12.5%, which has a major impact on transport costs.

In addition, meal feed varies more in terms of volume. Raw materials, like wheat grits, have a greater impact on volume in meal feeds than pellet feeds. 5% wheat grits can produce a difference in volume of 13% to 17%.

Options for reducing energy consumption in pellet production

By adding moisture, oil and auxiliary pressing agents and adjusting other technical parameters, such as roller settings, mould thickness, steam and temperature, it's possible to reduce resistance in the pellet press.

Each option has its own specific effects that you need to consider. For example, adding 2% water results in a 0.75 kWh/tonne reduction in energy consumption (Figure 1). Naturally, it's important not to exceed critical moisture content and water activity values.

Reducing energy consumption of a hammer mill

Grinding at different speeds affects a hammer mill's energy consumption, but will also affect its capacity. Vigneault et al. (1992) demonstrated that grinding at progressively higher tip speeds of 54, 71 and 86 m/s clearly increases energy consumption (Table 2).

However, a lower tip speed also means lower capacity (Wang et al., 2020, Figure 2). If the hammer mill is not the limiting factor in your plant, you may be able to reduce RPMs and therefore energy consumption.

A lower RPM also affects particle size however. Reducing the hammer mill’s tip speed produces larger particles with the same sieve (Saensukjaroenphon et al., 2017), which certainly has a direct impact on digestion if you use protein-rich raw materials.

Pelletised feed continues to be an interesting option

After considering all the relevant factors, we conclude that despite higher production costs, pelletised feed continues to be an interesting option due to lower transportation costs and better feed conversion. Calculations for a full cycle of fattening pigs, assuming 5% better feed conversion for pelletised feed, 8.5% higher volume for meal and additional production costs for pelletised feed, show that meal feeds produce a 1% lower financial result*.

* Calculated using the Koudijs energy calculator. Differences based on completed studies and referenced literature.