Grain legumes as alternative protein sources for imported protein-rich feed

The low self-sufficiency rate for protein-rich feed and their partly problematic provenance has put the search for alternative protein sources on the political agenda. The main protein source for Swiss livestock is domestic roughage, which accounts for 67 % of the required amount. 25 % of the protein supply is imported. Among the protein-rich, imported feeds, soy covers 63 % of the protein supply. Substituting the roughly 200 000 t of protein originating from imported high-protein feed would take up close to 75 % of the Swiss arable surface. There still is potential to increase domestic grain legume production. As N-fixing plants, legumes have beneficial environmental effects. Growing pulses on up to 10 % of the arable area would generate approx. 20 000 t of protein. The suitability for soy farming is however limited. Peas, field beans and lupines are better adapted to the Swiss climate. The nutrient profiles of pulses differ from each other. Only yellow lupines attain a protein content comparable to that of soybeans. Peas and field beans are equal and even superior to soy protein with respect to g lysine/100 g CP. All grain legumes, on the other hand, are deficient in S-containing amino acids (met, cys) and partly threonine and tryptophan when fed to demanding monogastric animals. The antinutritive factors (ANF) present in legumes require thermal treatment for their inactivation. Overall, grain legumes make a valuable contribution to increasing feed autonomy but soy imports will be substituted only to a limited extend.

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