Recently, researchers at Agroscope Changins-Wädenswil ACW in Switzerland have, through conventional breeding methods, developed new soybean varieties with a lower trypsin inhibitor level.
This approach is cheaper and more environmentally friendly than the industrial processes in which the inhibitor is destroyed by heating.
Soy is an important source of vegetable protein in animal feed. The soy bean contains between 40% and 50% protein and about 20% oil. Main proteins are glycinin and conglycinin. These include a well-balanced content of essential amino acids.
The exception is sulphur-containing amino acids such as methionine and cysteine, which are present only in very low concentrations in the soy bean.
Raw soybeans contain a temperature-sensitive inhibitor that restricts the ability of animals to take full advantage of the proteins of the bean.
Except for ruminants the inclusion of raw soybeans in animal diets leads to disturbances in protein digestion. This occurs because certain soy constituents (so-called anti-proteases) inhibit two protein-cleaving enzymes of the pancreas (trypsin and chymotrypsin).
Two ways of trypsine removal
Without the inhibitors from soybeans, the digestive enzymes trypsin and chymotrypsin, which are rich in methionine and cysteine, are decomposed in the digestive tract into amino acids that are useful to the animal. Therefore it makes sense to take away the inhibitors from the animal feed ban.
By various industrial processes based on a heating of the (crushed) soybeans, it is possible to reduce the levels of inhibitors. However, from an economic and environmental point of view is better to avoid these treatments, because they are expensive and require much energy. They also prevent the farmer to directly feed soy to his animals.
In order to find a more natural way of minimising trypsin inhibitors in soybeans the soybean breeding group of Agroscope ACW started some ten years ago with conventional breeding methods to breed soybean varieties without trypsin inhibitor.
In 2009, in the first series, early-and late-maturing soybean varieties emerged that possess this characteristic.
Should the 2010 results confirm the excellent results, then a new Swiss early soybean variety with high nutritional value for the test in 2011 will be proposed. This will expand the possibilities of using this valuable culture in the near future.