M.Tech. (Biomedical Technology) / Aflatoxins (AFs) are naturally occurring secondary metabolites produced principally by Aspergillus flavus and Aspergillus parasiticus in food and feed commodities worldwide. Contaminations of compound feeds by AFs do not only affect animal health, but the economy as well. It is for this purpose that a study was carried out to establish the quality of South African feeds with respect to AF-producing fungi, establish a correlation between levels of AFs and determinant gene (nor-1) responsible for producing these toxins. To this end, compound feeds (n=92) from various feed manufacturers in South Africa were sampled and analysed for aflatoxigenic fungi (Aspergillus flavus and Aspergillus parasiticus) and nor~1 genes using the conventional identification and real time- polymerize reaction (RT-PCR) methods, respectively. Data obtained revealed that 66.5 and 53.1% of samples were positive for A. flavus and A. parasiticus, respectively. Aflatoxins levels in similar samples were estimated by high performance liquid chromatography (HPLC) following an immune-affinity clean-up and multi mycotoxin extraction procedures. Accordingly, levels established ranged from 0.06 – 77.97 ppb (mean: 16.8 ppb) with feeds for poultry being the main contaminating substrate and no correlation (overall R2=0.093) was established between the concentrations of AFs and those of nor~1. The cytotoxic effect of some selected AF extracts from these feeds on human lymphocyte cells was performed in comparison to that of AFB1 standard. Data obtained from the cytotoxic assay revealed that cell viability was affected significantly (P<0.001) by both the dose and duration of exposure, which was much more noticeable when cells were exposed to AFB1 standard than for individual extracts. In conclusion, even though none of the feeds analysed contained levels of AFs above regulatory limits established in South Africa, such feeds when consumed on a continuous basis may pose some serious health problems especially when AFs is found in co-contamination with such significant mycotoxins as ochratoxins (OTs) and fumonisins (FBs). Thus, the continuous need to limit AFs levels in feed commodities from South Africa is imperative.

M.Tech. (Biomedical Technology) / A study was conducted with the aim to determine the incidence and contamination levels of fumonisin (FB) and FB producers in South African compound feeds. A total of 90 compound feed samples were screened for FB producing Fusarium species conventionally based on the morphological macroscopic and microscopic features. Data revealed that Fusarium spp. were most prevalent in feeds for chicken with an incidence rate of 34% recorded followed by cattle (6%) and pig feed (1%), meanwhile no Fusarium spp. was recovered from any of the horse feed analyzed. Similar samples were also analyzed for FB and in general, data indicate that 68% of samples were positive for FB1 which was the most frequent, ranging from 24 to 5515 μg/kg (mean concentration: 796.5 μg/kg). Quantification of fum 1 gene in 30 animal feed samples was performed by quantitative real time-polymerase chain reaction (qRT-PCR). Detection as well as quantification of fum 1 gene in animal feed was made possible but a positive correlation between fum 1 gene and FB levels was not established, however, an association between fungal contamination, FB and the determined fum 1 gene concentrations was evident in this study. The cytotoxic effect of FB extract from feeds was evaluated in vitro on human lymphocyte cells. Data obtained revealed that cell viability of lymphocytes was strongly influenced by both the concentration of toxin and duration of exposure. This study demonstrates that in South Africa, animals are constantly exposed to FB via consumption of feeds contaminated with the toxin even though the levels obtained are within the acceptable levels. Their presence thus highlights the need for proper quality control measures to be put in place at every step in the animal feed production chain.