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

Abstract

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.

Morphed aflaxotin concentration produced by Aspergillus flavus strain VKMN22 on maize grains inoculated on agar culture

“…In this study, higher levels of AFB 1 formation were detected over 7 weeks compared to AFB 2 , confirming the report of ( Xie et al, 2018 ), that the branch biosynthesis pathway responsible for AFB 1 production is more active and dominant than that of AFB 2 branch biosynthesis pathway. The optimal temperature range for maximum AF formation is reported to be between 25 and 35 °C ( Adelusi et al, 2023 , Hassane et al, 2017 ). The same pattern was observed in AFB 1 .…”

Influence of geographical location on the distribution of heavy metals in dairy cattle feeds sourced from two South African provinces

“…LODs were determined by multiplying the ratio of residual standard deviation to the slope by 3.3 (according to Equation 1 ), and LOQs were calculated by multiplying the same ratio by 10 (as per Equation 2 ), following the method described by Adelusi et al. ( 2023 ). Also, the recovery was calculated according to equation (3).…”

“…The validation of the study's methodology included an assessment of parameters like linearity, limits of detection (LOD), limits of quantification (LOQ), and recovery. LODs were determined by multiplying the ratio of residual standard deviation to the slope by 3.3 (according to Equation 1), and LOQs were calculated by multiplying the same ratio by 10 (as per Equation 2), following the method described by Adelusi et al (2023). Also, the recovery was calculated according to equation (3).…”

The Biosynthesis, Structure Diversity and Bioactivity of Sterigmatocystins and Aflatoxins: A Review

“…Mycotoxins are toxic secondary metabolites synthesised by specific fungi belonging to Aspergillus, Alternaria, Fusarium and Penicillium species. These mycotoxins have the potential to contaminate produce at various points in the food supply chain [2][3][4]. Aspergillus mycotoxins, including sterigmatocystin (STC) and aflatoxin (AF), are the most important mycotoxins [5,6].…”