Utah State University Extension
Like alfalfa, birdsfoot trefoil is a deep-rooted legume that fixes its own nitrogen. However, it contains a small amount of tannin which means that cattle and sheep will not bloat, even when grazing birdsfoot trefoil in pure stands. In this bulletin, we report on the dry matter production of a number of cultivars of birdsfoot trefoil and find that it yielded about two-thirds as much as alfalfa in pure stands.
MacAdam, Jennifer W. and Griggs, Thomas C., "Irrigated Birdsfoot Trefoil Variety Trial: Forage Yield" (2013). All Current Publications. Paper 1337.