Abstract: Creosote bush and tar bush are 2 xerophilic shrubs considered as potential animal feed after their fungal fermentation to reduce the tannins content. Kinetics of biodegradation of tannins during the fermentation of both plants by 2 strains of Aspergillus niger (GH1 and PSH) were evaluated under solid state culture conditions. The in vitro digestibility and the presence of mycotoxins were also analyzed in the fermented plants. The growth of fungal strain was directly associated to biodegradation of tannins (hydrolysable and condensed tannins) in both plants. A. niger GH1 degraded more than 94% of total tannins of creosote bush while, A. niger PSH degraded already of 77% of total tannins of tar bush. Results of digestibility of fermented materials were 9.72% for creosote bush and 13.98% for tar bush, respectively. Aflatoxins present in creosote bush were B1 (692 ppt), B2 (< 160 ppt) and G1 (< 160 ppt) and for tar bush B1 (182 ppt), B2 (< 160 ppt) and G1 (< 160 ppt). These results showed that animal health risk by the consumption of these kinds of fermented products is very low because are according with the official norms.