peer-reviewedLegume forages have an important position in ruminant production in Western Europe
and with further development can play an even larger role. Red clover for silage and white
clover in grazed swards lead to enhanced growth rate and milk yield in comparison with
pure grasses. Much of the production benefit of these legumes relates to enhanced intake
since digestibilities are not markedly different to grasses. The higher intake of legume
silages reflects differences in the cell structure of legume plants which combined with
high fermentation rates means that they break down into small particles in the rumen,
and leave the rumen more rapidly than perennial ryegrass. Ease of ingestion leads to
high rates of intake, which explains higher intakes for grazed legumes. A further benefit
of legumes is the reduced rate of decline in digestibility with advancing maturity. Whilst
legumes have limited effects on gross milk composition or carcass characteristics, there
are marked increases in levels of beneficial n−3 PUFA. Legumes have often led to a reduction
in methane production from the rumen and again, this relates to both physical and
chemical differences between forage species. The high rates of release of soluble protein
and of breakdown to small particles from clovers and lucerne is associated with susceptibility
to bloat, which is a limitation to further exploitation in grazing systems. The high
concentration of rapidly degraded protein in legumes also leads to inefficient utilisation
of dietary N and increased urinary N output. Research with tanniniferous forages, such
as birdsfoot trefoil and sulla, demonstrates the potential for future legumes with reduced
environmental and health effects, though these particular forage legumes are not well
adapted to temperate regions of Western Europe that are the focus of this review