Sulla is reported to be safe to livestock. In particular, it does not cause bloat in ruminants (FAO, 2013).
Tannins
The leaves, stems and flowers of sulla are rich in condensed tannins and levels of 0.8-5% (Italy, Amato et al., 2005) and 3-12% DM (Australia, Foster, 2010) have been reported. Tannin levels depend on the environment, growth stage and genotype (Amato et al., 2005). In New Zealand, a sulla pasture contained more condensed tannins in spring than in autumn (8.4 vs. 5.1% DM) (Hoskins et al., 1999).
Condensed tannins have detrimental effects in monogastrics and their effects in ruminants are debated. On the one hand, it has been suggested that levels lower than 6% DM, such as those found in sulla, have a positive effect in ruminants as they bind protein and improve protein utilization and thus performance (Bonanno et al., 2011). Sulla tannins may help to lower methane emissions in ruminants (Woodward et al., 2002). They also have beneficial effects on animal health by reducing parasite numbers (Waghorn, 2008). On the other hand, in warm and hot climates, the condensed tannins of sainfoin, sulla and Lotus species tend to be detrimental to ruminant performance, as they reduce protein availability in forage diets that are already deficient in protein (Waghorn, 2008). When sulla was grazed at flowering by dairy sheep, the condensed tannins had negative effects on DM and protein digestibility, though this was partially counterbalanced by a better metabolic utilisation of the nutrients (Molle et al., 2009).