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

Bioavailability study of OTA, ZEN, and AFB1 along with bioactive compounds from tiger nut beverage and its by-products

Mycotoxins pose significant health risks due to their prevalence in food products and severe health implications, including carcinogenicity. This study investigates the bioavailability of mycotoxins aflatoxin B1 (AFB1), ochratoxin A (OTA), and zearalenone (ZEN) individually and combined, in the presence of identified polyphenols from tiger nut beverage (TNB) and tiger nut by-product (TNBP) using the in vitro model Caco-2 cells, which simulates the human intestinal barrier. The objective is to understand how bioactive compounds from TNBP can mitigate the effects of AFB1, OTA and ZEN (and their combination) by bioavailability interference, contributing to safer food products and innovative food safety strategies. In vitro gastrointestinal digestion was simulated using the INFOGEST protocol, followed by a bioavailability assessment through transepithelial transport assays in differentiated Caco-2 cells. OTA bioavailability significantly increased in the presence of TNB and TNBP, suggesting interactions that enhance its intestinal absorption. AFB1 maintained high bioavailability across all conditions (up to 83%), while ZEN showed a general decrease (up to 24%), thus indicating a potential protective effect of TNB and TNBP against ZEN toxicity. Regarding the effect of mycotoxins on the bioavailability of polyphenols from TNB and TNBP, a general enhancement was observed for TNB consistently showing higher bioavailability than for TNBP. Notably, OTA and ZEN significantly increased polyphenols bioavailability, reaching up to 79.2% in TNB. Individual polyphenol generally showed a notable reduction in trans-ferulic acid and an increase in trans-cinnamic acid in the presence of mycotoxins. For TNBP, individual mycotoxins generally enhanced polyphenol bioavailability, with AFB1 showing the most significant increase. In conclusion, tiger nut products show promise as sources of bioactive compounds for mitigating mycotoxin toxicity in food products. However, further studies are necessary to clarify these interactions and optimize the conditions of use for their safe and effective application in the food industry.

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

The contamination of feed and food by heavy metals represents a significant concern for the health of both animals and humans. This study investigates the impact of geographical location on heavy metal distribution in dairy cattle feeds sourced from Free State and Limpopo, South Africa (SA). A total of 70 feed samples (40 from Free State and 30 from Limpopo) were collected from 2018 to 2019 and analyzed for heavy metals, including cadmium (Cd), arsenic (As), copper (Cu), zinc (Zn), lead (Pb), and chromium (Cr), using inductively coupled plasma mass spectrometry (ICP-MS). Our findings revealed the presence of Cr, Cu, and Zn in the feeds, but at levels below the FAO/WHO permissible limits. Additionally, As, Cd, and Pb concentrations in the feeds were below the Limit of Detections (LODs). Generally, Cr concentrations (0.032-0.454 mg/kg) identified in the Free State samples were lower than those found in Limpopo (0.038-1.459 mg/kg), while the levels of Cu (0.092-4.898 mg/kg) and Zn (0.39-13.871 mg/kg) recorded in the Free State samples were higher than those from Limpopo [(0.126-3.467 mg/kg) and (0.244-13.767 mg/kg), respectively]. According to independent sample t-tests, Cu and Zn levels were substantially higher (p ≤ .05) in Free State feeds compared to Limpopo, while Limpopo feeds exhibited significantly higher (p ≤ .05) Cr concentrations than Free State feeds. Despite the low recorded heavy metal levels, regular monitoring of these elements in cow diets across all SA provinces is essential for ensuring the well-being of animals and humans.

Mycotoxins evaluation of total mixed ration (TMR) in bovine dairy farms: An update

The total mixed ration (TMR) is currently a widespread method to feed dairy cows. It is a mixture of raw fodder and concentrate feed that can be contaminated by several mycotoxins. The main aim of this paper was to provide a critical review on TMR mycotoxin occurrence and its usefulness to monitor and control them on-farm. Aflatoxins, zearalenone, deoxynivalenol, T-2 toxin and fumonisins (regulated mycotoxins) are the most prevalent mycotoxins evaluated in TMR. Nonetheless, several emerging mycotoxins represent a health risk at the animal level regarding their prevalence and level in TMR. Even when measured at low levels, the co-occurrence of mycotoxins is frequent and synergistic effects on animal health are still underevaluated. Similar to the animal feed industry, on-farm plans monitoring mycotoxin feed contamination can be developed as a herd health management program. The estimated daily intake of mycotoxins should be implemented, but thresholds for each mycotoxin are not currently defined in dairy farms.

Molecular characterization of gliotoxin-producing Aspergillus fumigatus in dairy cattle feed

Background and Aim

Several strains of Aspergillus fumigatus produce mycotoxins that affect the health and productivity of dairy cattle, and their presence in dairy cattle feed is a serious concern. This study aimed to determine the densities of A. fumigatus and gliotoxin in commercial dairy feed.

Materials and Methods

More than 60 dairy feed samples were examined for fungal contamination, specifically for A. fumigatus, using phenotypic approaches and DNA sequencing of the internal transcribed spacer (ITS) and β-tubulin regions. Thin-layer chromatography and high-performance liquid chromatography (HPLC) were used to assess gliotoxin production in A. fumigatus. Real-time polymerase chain reaction (RT-PCR) was used to investigate the expression of gliZ, which was responsible for gliotoxin production. High-performance liquid chromatography was used to detect gliotoxin in feed samples.

Results

Aspergillus was the most commonly identified genus (68.3%). Aspergillus fumigatus was isolated from 18.3% of dairy feed samples. Only four of the 11 A. fumigatus isolates yielded detectable gliotoxins by HPLC. In total, 7/11 (43.7%) feed samples tested had gliotoxin contamination above the threshold known to induce immunosuppressive and apoptotic effects in vitro. The HPLC-based classification of isolates as high, moderate, or non-producers of gliotoxin was confirmed by RT-PCR, and the evaluation of gliZ expression levels corroborated this classification.

Conclusion

The identification of A. fumigatus from animal feed greatly depended on ITS and β-tubulin sequencing. Significant concentrations of gliotoxin were found in dairy cattle feed, and its presence may affect dairy cow productivity and health. Furthermore, workers face contamination risks when handling and storing animal feed.

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.