Birdsfoot trefoil is a valuable forage for ruminants. Legume-based swards including birdsfoot trefoil providing moderate concentrations of condensed tannins can be used to increase the efficiency of protein digestion and to improve animal health under grazing, producing more sustainable grazing systems.
Comparison with other legumes
When compared to other plants rich in condensed tannins, such as chicory (Cichorium intybus) and sainfoin (Onobrychis viciifolia), harvested at the same stage, birdsfoot trefoil contained less fibre (NDF and ADF) and more protein, but its protein was more degradable (Cassida et al., 2000; Arrigo, 2012). The OM digestibility of Lotus corniculatus in cattle was comparable to that of alfalfa and sainfoin (Kraiem et al., 1990). The intake of Lotus corniculatus silage in sheep (71 to 81 g DM/kg LW0.75) was comparable to that of late-cut sainfoin and red clover (Trifolium pratense) silages, but higher than that of early-cut alfalfa and red clover (Fraser et al., 2000).
The condensed tannins (2-3% DM) of birdsfoot trefoil did not affect OM digestibility in sheep (Waghorn et al., 1987; Wang et al., 1996c). With mixed diets, the nutritive value of fresh forages for sheep was not affected when the condensed tannins from birdsfoot trefoil (2.6% DM) did not exceed 1% of total dietary DM (Waghorn et al., 1997). However, high concentrations of condensed tannins (more than 5.5% DM) in birdsfoot trefoil reduced voluntary feed intake and digestibility, and depressed weight gain and wool growth in grazing sheep (Min et al., 2003).
The content of condensed tannins in birdsfoot trefoil is related to other forage quality parameters. Plants with a high concentration of condensed tannins (6.9% DM) had lower, but less degradable, protein and lower in vitro digestible DM than low-tannins plants (2.1 g/kg DM). Lignin concentration was positively correlated with condensed tannins concentration (Miller et al., 1996; Hedqvist et al., 2000). In plants without condensed tannins, N degradability was high (78 and 89% for hay and silage, respectively), but N degradability declined with increasing condensed tannins concentrations (Miller et al., 1994; Hedqvist et al., 2000). Each unit of condensed tannins protected 0.61 units of protein (Coblentz et al., 2013), thereby increasing the duodenal flow of amino acids (Wang et al., 1996b), but the undegradable protein remained less than 24% of the total protein intake (Cassida et al., 2000). The effect of condensed tannins on degradability may be related to a specific effect on some proteolytic bacteria in the rumen (Min et al., 2002).
The condensed tannins of birdsfoot trefoil have anthelminthic properties and have been reported to decrease nematodes in wild and domestic ruminants (Min et al., 2003; Novobilsky et al., 2011; Waghorn, 2008; Molan et al., 2001). Birdsfoot trefoil was reported to decrease dagginess and fly-strike in grazing lambs in New-Zealand (Leathwick et al., 1995).
In dairy cows, birdsfoot trefoil with condensed tannins accounting for 1.6% DM increased yields of milk, protein, and solids-not-fat compared to birdsfoot trefoil containing 0.8% DM of condensed tannins. Overall, diets containing birdsfoot trefoil silage support greater production than diets containing alfalfa or red clover silage, indicating that feeding birdsfoot trefoil or other legume silages containing condensed tannins can enhance performance and N utilization in lactating dairy cows (Hymes-Fecht et al., 2013). Interaction between the condensed tannins of birdsfoot trefoil and preservation also occurs: with a high condensed tannins concentration (70 to 120 g of tannins per kg protein), hay provided sufficient rumen-undegradable protein (35% of total protein) to support 35 kg/d milk yield, whereas ensiling was required to increase rumen-undegradable protein with birdsfoot trefoil containing less tannins (Grabber, 2008; Grabber et al., 2009). However, in a comparison of ryegrass-legume silages, birdsfoot trefoil containing low levels of condensed tannins resulted in a higher milk protein yield than white clover (Trifolium repens), and had a protein-sparing effect in dairy rations (Eriksson et al., 2012).
In ewes rearing twin lambs and grazing birdsfoot trefoil, the condensed tannins increased milk yield and the secretion rates of protein and lactose without affecting voluntary forage intake, thereby increasing the efficiency of milk production (Wang et al., 1996a).
Meat sheep and lambs
In grazing meat sheep, birdsfoot trefoil provided lower indole and skatole concentrations in body fat than a pasture of perennial ryegrass plus white clover (Schreurs et al., 2008). More generally, grazing finishing lambs on forage legumes rather on ryegrass makes it possible to increase growth rate and reduce time to finishing without compromising carcass quality (Speijers et al., 2004).
In sheep fed birdsfoot trefoil, efficiency of both reproduction and wool production was improved (Min et al., 1999; Luque et al., 2000). The wool was of reduced yellowness (Min et al., 1998; Min et al., 2001).
Red deers (Cervus elaphus) and elk-deer hybrids
In grazing red deers and elk-deer hybrids, with the same DM allowance as from perennial ryegrass-white clover pasture, birdsfoot trefoil provided superior performance in terms of voluntary feed intake, daily weight gain (91 vs. 20 g/day), weaning weight (52.6 vs. 48.1 kg) and calf daily weight gain (485 vs. 399 g/day) (Adu et al., 1998).