The impact of storage facilities on animal feed quality with reference to mycotoxin contamination around Ngaka Modiri Molema District, North West Province

Abstract

The improper storage system of feed is a major factor influencing the presence of fungi and mycotoxin contamination. Hence the aim of the study was mainly to compare the impact of storage facilities on fungal and mycotoxin contaminants in animal feed collected from emerging farmers' and commercial supplier's storages in the Ngaka Modiri Molema District, North West Province of South Africa. To achieve this, a survey and an interview were carried out during the collection of samples to obtain the views and level of knowledge of farmers and suppliers in connection with the manner in which they stored animal feed. It was noted that major challenges faced by emerging farmers versus feed commercial suppliers were that they were not knowledgeable about proper feed storage, effects of mycotoxin contamination on feed and, not educationally trained. It was also found in this study that participated farmers mainly used two types of storage systems, about 41.7% used open storage system and 58.3% used closed storage systems and their animal feeds were preserved in bags or dustbin, whilst feed commercial suppliers mainly used closed storage. Data collected also revealed that majority of farmers did not produce their own feed, fed to their animals but purchased from different feed suppliers around their individual areas. Feed contaminant, in this case, could have been from different sources such as the field obtained from the processing, the supplier's storage or recipient farmer's storage. Contaminants could persists in harvested and stored grain and grow in storage when moisture content becomes favourable. This may explain their presence in these analysed samples from both storages of emerging farmers and feed suppliers storage by late harvesting and proper storage. There were a 100 samples of which 40 were collected from closed and open storages from emerging farmers and 60 samples from commercial supplier's closed storages. The moisture content was determined using the oven drying method, and fungal isolation and identification were performed using serial dilution and cultured on malt extract agar (MEA), potato dextrose agar (PDA), and Sabouraud dextrose agar (SDA) media. Isolated fungi were confirmed using the molecular techniques and Polymerase Chain Reaction (PCR). The mycotoxins extraction, determination, and quantification were done using the ELISA and HPLC and TLC methods. The results obtained revealed that emerging farmers, in general, did not have knowledge of fungi and mycotoxins as well as the impact of storage on the quality of animal feed. Whilst suppliers were knowledgeable about fungi and mycotoxins but did not implement necessary measures to keep the feed in a proper environment. Data obtained from the sample analysis showed significant differences (P>0.05) in moisture contents among the feed types. Silage samples had the highest moisture content as compared to other types of feed. Results for fungal isolation showed that the fungal loads (Cfu/g) in cultures from the feed samples collected from feed suppliers' closed storage were significantly higher than the ones from the open as well as the closed storages from the emerging farmers. In addition, the fungal analysis revealed that 78% of the screened samples were contaminated with fungi, of these fungi, the most important mycotoxin-producing strains were Aspergillus spp (42%), Penicillium spp (26%) and Fusarium spp (10%). Among isolated fungal strains, A. flavus, A. oryzae, A. terreus, A. fumigatus, A. clavatus, A. niger, A. parasisticus, A. nomius, P. verrucosum, P. chrysogenum, P. polonicum, P. rubens, P. brevicompactum and F. oxysporum were the main contaminants. The study also found that there was a statistically significant difference across storage systems (P>0.05), with samples obtained from the supplier's closed storages being more contaminated than the closed and open storages of emerging farmers. Whilst samples from among the farmer's storage samples collected from the closed tanks were more contaminated than those of open storage (P>0.05). The results obtained revealed that Aflatoxin (B1, B2, G1, and G2), were the predominant mycotoxins amongst all the the contaminants with about 97.7% occurring in emerging farm storage (open & closed) and commercial feed suppliers storage 100% with a mean concentration of 326.3 ppb and 422.4 ppb respectively. Emerging farms and commercial feed supplier's samples respectively were contaminated with Ochratoxin A with a mean concentration of 387 ppb and 575 ppb respectively. Zearalenone mean concentrations were 31.3 ppb on emerging farm storages and 7.32 ppb from commercial feed supplier's storage with respective contamination of 8.3% and 23.3% while fumonisin (B1, B2) in emerging farms and commercial supplier's samples had a mean value of 525.5 ppb and 193.67 ppb, respectively. The study clearly showed that both closed and open storages had fungal and mycotoxin contamination. Although the closed storages showed high contamination with fungi and mycotoxins, the study noted that this was due to improper control of the environment in the storage. The open storage has a major challenge that there are no means of controlling the environment during storage. Feed quality regarding fungi and mycotoxin remain primarily a training issue for farmers so they can be able to control the storage and reduce the risk of contamination. Therefore environmental control is the key to fungal and mycotoxin control. Storage duration, type of feed and type of storage have a significant influence on fungal growth and mycotoxin production.