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

Abstract

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