Tannins
All parts of the plant contain high levels of tannins that may hamper protein digestibility and animal performance (Carter, 1994). Incidences of lethal poisoning, probably due to tannins, when goats consumed excess Acacia nilotica pods, were reported in South Africa. Symptoms included abortions, dyspnoea, tachycardia, methemoglobinemia, rumen atony and hyperglycemia. Caution is recommended when feeding Acacia nilotica pods to goats on a daily basis (Terblanche et al., 1967 cited by Mlambo et al., 2008). It should be noted that the measurement and nutritional interpretation of phenolics and tannins content in Acacia species are particularly difficult (Mlambo et al., 2008).
Other secondary metabolites
Acacia nilotica foliage and pods contain alkaloids and saponins that may have antinutritional effects (Cheema et al., 2011; Cook et al., 2005).