Incidence of fungi and mycotoxins in dairy cattle feeds from some selected smallholder farms in South Africa

Abstract: Dairy feed is an indispensable part of the dairy industry, essential for high-quality and nutritious milk. These feeds are vulnerable to contamination by a diverse range of mycoflora, that produce several mycotoxins, causing severe feed quality loss and posing a significant challenge to animal and human health. The aim of this present study was to determine the safety levels of 70 dairy cattle feeds and feed ingredients sourced from some selected smallholder dairy farms in the Free State and Limpopo provinces of South Africa during two seasons (summer and winter) from2018 to 2019 regarding fungal contamination and to evaluate the effects of seasonal and geographical variation on the mycotoxigenicity of the isolated fungal species. The feeds were screened for fungal contamination following both macro- and microscopic methods, and their identities were confirmed by molecular means. Additionally, mycotoxins produced by the isolated mycotoxigenic fungal species were analysed using liquid chromatography with tandem mass spectrometry (LC- MS/MS). In this study, a total of 237 fungal isolates from 14 genera were isolated from the dairy feeds and feed ingredients. Also, mean fungal loads recorded in the feeds ranged from 9.3 x 103 to 3.6 x 105 CFU/g in the Free State and Limpopo provinces, respectively. Multivariate analysis of variance (MANOVA) showed that none of the single factors (season or province) had a significant effect on the mycotoxins production capacity of the isolated fungal species. However, levels of AFB1 (0.22 to 10445.8 μg/kg) produced during summer was higher than in winter (0.69 to 190.22 μg/kg). The same trend was observed for AFB2 in the summer (0.11 to 3.44 μg/kg) and winter (0.21 to 2.82 μg/kg). Furthermore, maximum and minimum zearalenone (ZEN) concentrations (97.18 and 5.20 μg/kg) were observed in the Limpopo summer and Free State winter samples, respectively. Lastly, the mycotoxogenic fungal species failed to produce other mycotoxins tested for. Therefore, since milk is majorly consumed in different forms, the high prevalence of mycotoxigenic fungi and mycotoxins recorded in this present work is a matter of concern to the health of the dairy cattle and consumers of dairy milk and milk by-products in South Africa. Keywords: Dairy feed, milk, fungal loads, mycotoxins, LC-MS/MS.M.Sc. (Biotechnology

Seasonal Diversity and Occurrence of Filamentous Fungi in Smallholder Dairy Cattle Feeds and Feedstuffs in South Africa

This study investigated 65 (35 in summer and 30 in winter) smallholder dairy cattle feeds from Free State and Limpopo provinces in South Africa from 2018 to 2019 for fungal contamination and assessed the impacts of seasonal variation on fungal contamination levels, isolation frequency, and diversity. Samples were examined for fungal contamination using macro- and microscopic approaches, and their identities were confirmed by molecular means. A total of 217 fungal isolates from 14 genera, including Aspergillus, Fusarium, and Penicillium, were recovered from feeds from both seasons. The most prevalent fungal species recovered were A. fumigatus and P. crustosum. Mycological analyses showed that 97% of samples were contaminated with one or more fungal isolates, with the summer fungal mean level (6.1 × 103 to 3.0 × 106 CFU/g) higher than that of feeds sampled during winter (mean level: 1.1 × 103 to 4.1 × 105 CFU/g). Independent sample t-test revealed that the isolation frequencies of the genera Aspergillus and Fusarium were significantly (p ≤ 0.05) higher in summer than winter, while Penicillium prevalence in both seasons was not statistically (p > 0.05) different. Furthermore, the Shannon–Weiner diversity index (H′) revealed a higher fungal diversity in summer (H′ = 2.8) than in winter (H′ = 2.1). This study on fungal contamination could be used for future fungal control and mycotoxin risk management in South Africa

Seasonal and Geographical Impact on the Mycotoxigenicity of Aspergillus and Fusarium Species Isolated from Smallholder Dairy Cattle Feeds and Feedstuffs in Free State and Limpopo Provinces of South Africa

This study evaluated the impact of seasonal and geographical variations on the toxigenicity of Aspergillus and Fusarium strains previously isolated from smallholder dairy cattle feeds and feedstuffs sampled during summer and winter in the Free State and Limpopo provinces of South Africa (SA). In total, 112 potential toxigenic fungal species were obtained and determined for their capability to produce mycotoxins on solid Czapek Yeast Extract Agar (CYA); followed by liquid chromatography-mass spectrometry (LC-MS/MS) analysis. Our result revealed that 41.96% of the fungal species produced their respective mycotoxins, including aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), and zearalenone (ZEN), with higher levels of AFB1 (0.22 to 1045.80 µg/kg) and AFB2 (0.11 to 3.44 µg/kg) produced by fungal species isolated from summer samples than those in winter [(0.69 to 14.44 µg/kg) and (0.21 to 2.26 µg/kg), respectively]. The same pattern was also observed for AFB1 and AFB2 in Limpopo (0.43 to 1045.80 µg/kg and 0.13 to 3.44 µg/kg) and Free State (0.22 to 576.14 µg/kg and 0.11 to 2.82 µg/kg), respectively. More so, ZEN concentrations in summer (7.75 to 97.18 µg/kg) were higher than in winter (5.20 to 15.90 µg/kg). A similar observation was also noted for ZEN in Limpopo (7.80 to 97.18 µg/kg) and Free State (5.20 to 15.90 µg/kg). These findings were confirmed via Welch and Brown-Forsythe tests with significantly (p ≤ 0.05) higher mycotoxin levels produced by fungal strains obtained in samples during summer than those in winter. In contrast, the concentrations of mycotoxins produced by the fungal species from both provinces were not significantly (p > 0.05) different