Coumarin
If poorly harvested or ensiled, sour clover produces coumarin, a fragrant organic chemical compound in the benzopyrone chemical class that interacts with blood coagulation (Langer et al., 1991; Göhl, 1982). Deaths from internal bleeding have been reported (Göhl, 1982). Reported values for coumarin content in India and Australia are in the range of 1000-5000 mg/kg DM (Gupta et al., 1980a; Gupta et al., 1980b; Nair et al., 2010). Coumarin content may depend on cultivation stresses such as salinity (Nair et al., 2010), and increases with maturity (Gupta et al., 1980a). Cultivars with low coumarin content have been reported (Duke, 1981).
Risk of bloat
Sour clover should be cut when the pods are just being formed. If cut earlier, the risk of bloat is higher (Curasson, 1956).