Soya protein in pig feed

By feed application manager Lars Sangill Andersen, Hamlet Protein

Soya protein is the protein source mostly used in pig feed. This is e.g. due to the fact that the composition of amino acids in soya protein is very close to the amino acid demand to pigs and that soya protein is manufactured in a quantity which secures the supply in the long term, more than 200,000,000 tons soya beans per year

Soya proteins are available in many different varieties depending on the preceding processes.

Soya proteins are available in many different varieties depending on the preceding processes. From the raw beans to purified protein isolate with 90% protein, CP.

Together with the soya protein comes the remaining part of the soya bean or soya bean meal, and this part con­sists of different types of sugar and fibres. Some of these will damage the intestinal micro flora of pigs, others can be beneficial.

Some of the proteins may cause an allergic reaction in the small intestine of piglets — «antigenic proteins». These proteins are partly heat consistent and cannot be destroyed by a simple heat treatment.

Other soya proteins lower the digestibility of feed protein by blocking the intestinal enzymes which should digest the feed protein — «Trypsin inhibitors, TIA». TIA can be destroyed by heat treatment, but usually quite high tempera­tures are necessary and the quality of the remaining protein is often damaged, especially the utilization of Lysine can be heavily reduced in this way.

It seems paradoxically that the most used protein source causes so many negative side effects in the intestine of pigs being fed soya. There are definitely also instances where it would be an advantage to consider if the soya level should be as high as it is.

Good idea for piglets

Hogs and sows with a developed intestine can overcome the worst of these side effects, because their digestive system is fully developed. But also because the content of protein in the feed for sows and hogs is lower than for piglets. Therefore, soya will only make up a limited part of the total protein in the feed.

In this way I have also mentioned the reason why it is a good idea to use specially processed soya proteins for piglets.

Piglets from before weaning till some weeks after weaning do not have a very robust intestinal micro flora. Therefore, the sugars in soya bean meal and soya beans can easily affect the balance and this will often result in a growth in the harmful bacteria, e.g. E. Coli. By removing these sugars the growth medium for the harmful bac­teria will also be removed. E. Coli and similar bacteria must compete with lactic acid for the remaining dietary fibres. E. Coli will lose this fight because of lacking efficiency.

Habituation to proteins

If the antigenic proteins can be removed or reduced heavily the allergic reaction in the intestine and the often subsequent diarrhoea is prevented. But does this reaction then just appear later on? Apparently fragments of the proteins causing this reaction are sufficient to teach the piglet’s immune system to get used to the proteins, and therefore a slow change to ordinary soya bean meal from 12-30 kg does not cause any problems.

The enzyme blocking effect, TIA, is especially characteristic for weaning piglets. Since they are just about to change their digestion from milk proteins to vegetable proteins, the production of the enzymes, which will break down the proteins, is not up to full speed yet. The piglets cannot replace all the enzymes which are blocked and, therefore, the digestion of protein is reduced. The undigested protein is lost together with the enzymes.

The loss of feed protein is bad enough in itself, but when the large intestine is supplied with undigested protein the number of pathogenic bacteria and thus the risk of diarrhoea is increased.

However, the loss of enzymes is worse than the loss of feed protein as these enzymes contain a lot of Threonine, Cysteine and Tryptophane, all amino acids that will influence the feed efficiency because they belong to the limiting amino acids.

Therefore, there are good reasons to choose specially manufactured soya proteins for piglet feed, both to supply the piglets with the amino acids needed to grow and also avoid the damaging substances which cause problems to the piglets from before weaning until 25-30 kg.

DK-8700 Horsens, Denmark.
Phone +45 75631020.
E-mail: info@hamletprotein.dk