Nutritional value of grain legumes

Systems to evaluate protein feeds for ruminants use solubility measurements as proxies for protein degradation in the rumen. Soluble protein (nitrogen, N) is assumed to be rapidly degraded in the rumen and so likely to be used inefficiently. This practice note demonstrates that this assumption is not appropriate for pea, faba bean and lupin and has led to an under-valuing of protein from these feeds. There are large discrepancies between solubility methods, as well as the lack of relationship to measured protein degradability. This insight helps farmers and the feed industry better evaluate the protein value of these alternative grain legumes. Current feed evaluation systems, based on soluble nitrogen measurements, tend to undervalue pea, faba bean and lupin in comparison with other protein sources for ruminants. New work on protein feed evaluation systems is needed since the current systems constrain the use of these grain legumes in ruminant feeding. This information provides a foundation to industry placing a higher financial value on protein in pea, faba bean and lupin.