Protein quality of legume seeds for non-ruminant animals: a literature review

Abstract

Peas and field beans have been increasingly grown in Europe during the last 15 years, to improve self-sufficiency in protein-rich feedstuffs. The protein profile of these crops is characterized by a high lysine content (7.3% crude protein in peas) and a relative deficiency in sulphur amino acids and tryptophan. Protein digestibility is slightly lower than in soyabean meal, especially for pigs (0.74 in peas vs. 0.80 in soyabean meal) and for young animals, and appears variable both between and within species. This lower digestibility can partly be explained by the presence in some species or cultivars of antinutritional factors (ANF; e.g. protease inhibitors, lectins or tannins) and/or fibrous material, leading to low accessibility of legume seed protein to digestive enzymes. More work is needed to separate the effects of these factors and their practical importance. Because of the high variability of ANF activity, it also appears necessary to develop reliable and quick assays which allow a check and selection of batches by plant breeders or feed manufacturers. Owing to the high variability within each species of these characteristics it seems possible to improve the nutritional value of legume seeds by selective breeding. In the short term, technological treatments can also lead to improved utilization, especially in poultry, but attention has to be paid to the cost of these treatments.