Occurrence of Aspergillus species in mixed feeds and component raw materials and their ability to produce ochratoxin A

The mycobiota of 147 samples of mixed feeds and 153 samples of raw materials (cereals and legumes) was studied in order to ascertain the occurrence of Aspergillus spp. and their ability to produce ochratoxin A (OTA). Total fungal counts ranged from <102 to 5.3×106 cfu/g. Aspergillus spp. (including teleomorphs) were isolated from 77.7% of the samples and ranged from non-detectable to 5.3×106 cfu/g with a mean value of 2.2×104 cfu/g. On average, Aspergillus spp. comprised 15.6% of the total fungal population. Aspergillus spp. were present in 94.4% of legume samples and 89.8% of mixed feeds, whereas in cereal samples Aspergillus spp. had a much lower occurrence (57.3%). Fourteen Aspergillus spp. (including teleomorphs) were identified. The predominant species were A. flavus, Eurotium chevalieri, E. amstelodami, and E. rubrum. Among the OTA-producing aspergilli only A. niger var. niger and A. ochraceus were isolated in this survey. Aspergillus niger var. niger was detected in 23% of the samples, whereas A. ochraceus was present in 7.3%. Three out of 52 of the A. niger var. niger isolates (5.8%) and one out of 20 A. ochraceus strains (5%), were able to produce OTA.