Puffed cereals for piglet feed

By Gerard van der Hoek and Bram Gunter, Meneba, the Netherlands

For piglets, weaning involves an abrupt switch from milk to solid feed. The supply of nutrients changes radically. Carbohydrates replace fat as the main energy source, and there is a shift from animal to vegetable protein. Piglets often have difficulty coping with this sudden switch because it takes time for the enzyme production in their digestive system to adapt to the new situation. In its native form, the starch is difficult to digest in the small intestine. A large amount of undigested starch passes into the large intestine where the intestinal bacteria cause explosive fermentation.

For better starch utilisation, the starch needs to be mechanically or thermally gelatinised. The thermal treatment also affects the viscosity of the mass in the stomach and the intestine and therefore nutrient intake. For thermal gelatinisation of starch in cereals, Meneba has developed the Presco process (Figure 1). This process has positive benefits over other techniques such as steam flaking, micronising, expanding and extruding. In-vitro tests, performed at Schothorst Feed Research, clearly showed these positive benefits.

The Presco process

The Presco process produces unprecedented starch gelatinisation. Cereals are treated under high pressure (20-25 bar) with overheated steam for 15 to 30 seconds. By suddenly reducing the pressure, the grains expand rapidly and destroy the crystalline structure of the starch entirely. Microscopic images of untreated wheat and wheat treated with Presco reveal the effect of the treatment as can be seen in the microscope photos.

The untreated wheat contains whole, undamaged starch granules. After treatment with Presco, the starch granules are fully gelatinised and no retrograde effect occurs. The puffing process has an impact on the functionality in terms of degree of gelatinisation, ileal digestibility, faecal digestibility and viscosity which gives Presco unique characteristics to be used in piglet feed.

Degree of gelatinisation

The intensive heat treatment during the process gelatinises the starch. In untreated maize the degree of gelatinisation is about 25%, whereas the Presco treatment achieves at least 75%. In wheat, starch gelatinisation increased from about 35% in untreated wheat to at least 80% with the Presco treatment.

Compared with other gelatinisation techniques, the puffing process generates a higher degree of gelatinisation (see Figure 2) which has a positive effect on the starch utilisation by the piglets.

Even more important than the degree of gelatinisation is digestibility. In-vitro tests have been performed at Schothorst Feed Research to determine the ileal digestibility of untreated and puffed maize and wheat. These in-vitro tests were performed with a validated pig model, which provides a reliable forecast of in-vivo digestibility. The Presco process was shown to have a positive effect on this parameter. For comparison purposes, the digestibility of other starch gelatinisation techniques was also determined. Presco produced the highest ileal digestibility in both starch and organic matter.

In addition to ileal digestibility, the faecal digestibility of the organic matter and the starch was measured, with increased figures for the gelatinised product. The differences are much smaller at faecal level. This is due to microbial fermentation in the large intestine: anything that remains undigested in the small intestine ferments in the large intestine. Too much fermentation in the large intestine is harmful. That is why high ileal digestion is beneficial to piglets.

Viscosity

Because of their high degree of gelatinisation, Presco maize and wheat generate the highest viscosity in the piglets’ stomach compared with other techniques. The piglet feed remains in the stomach for longer, enabling the piglet’s protein-splitting enzymes to digest the protein in the feed more effectively. This results in higher ileal amino acid digestion. One positive consequence of this is that there is less undigested protein, which can act as a substrate for pathogenic micro-organisms in the piglet’s gut.

After the longer retention time in the stomach the feed passes regularly into the small intestine. The high degree of gelatinisation means that the starch is quickly broken down by the enzymes present in the digestive juices. Besides the high ileal digestibility of the organic matter and starch, this results in a rapid reduction in the viscosity of the mass in the small intestine, which simplifies the transport of nutrients to the intestinal wall. Also, optimum nutrient uptake is ensured. It is clear that this combination of positive effects leads to faster growth and a better health status for the piglets.

[Source: AllAboutFeed magazine, 2010]