Short term exposure to zearalenone and fumonisins shown to be harmful for cows' rumen ecosystem
“This is the first study to provide indications of acute adverse effects of ZEN and FUM on ruminal fermentation and microbiota composition as well as on systemic health and chewing activity in dry dairy cows fed a moderate-grain diet,” said the researchers.
The contamination of feedstuffs with mycotoxins is a major concern in livestock production worldwide.
Zearalenone and FUM are secondary metabolites of Fusarium molds and frequent contaminants in cattle diets (Kemboi et al., 2020; Seeling and Dänicke, 2005), with 60–80% of feedstuffs exceeding the detectable limits and 25% being situated above the EU and Codex limits (Eskola et al., 2020), noted the authors.
Previous research has shown that chronic exposure to both mycotoxins adversely affects animal health, with ZEN having estrogenic effects and causing fertility disturbances, such as vulva swelling and false estrus (Fink-Gremmels, 2008).
Fumonisins are mutagenic and genotoxic mycotoxins, which can cause severe organ pathologies like hepatic and renal damage, as well as lung edemas (Fink-Gremmels, 2008; Gallo et al., 2015).
But the authors of this paper, which was published in the journal, Food and Chemical Toxicology, says there is a need for better understanding of the impact of mycotoxins on the rumen microbiota, particularly during moderate- or high-grain feeding, which they said represents an additional challenge to the rumen microbes.
“Consequences of chronic mycotoxin exposure on animal health seem well studied, but acute effects need to be clarified to further increase the knowledge on mycotoxicosis-related symptoms in ruminants.”
Their study investigated the effects of a short-term exposure to either ZEN or FUM on ruminal fermentation pattern and microbial composition, as well as animal health parameters, including chewing behavior, in six rumen-cannulated dry Holstein cows fed a silage-based diet with 40% grain inclusion.
“We hypothesized that both ZEN and FUM would cause acute adverse shifts in the rumen fermentation pattern and microbial community composition and structure, along with implications on health characteristics due to the mycotoxin burden.”
The trial was conducted at the research dairy farm of the University of Veterinary Medicine Vienna in Pottenstein, Austria.
Six cows were fed a basal diet with 40% grain, on a DM basis, and exposed to either 5 mg of ZEN or 20 mg of FUM daily for two consecutive days each, separated by a 7-days washout period.
The exposure to ZEN or FUM led to a reduction of Lachnospiraceae and Prevotellaceae in the rumen. Similarly, ZEN lowered the ruminal pH and total short-chain fatty acid concentration, despite increased rumination activity of the cows.
Fumonisins increased the number of observed features and significantly impacted β-diversity structure and metagenome predicted function.
“At the systemic level, FUM exposure suggested an immediate hepatotoxic effect, as evidenced by increased liver enzyme concentrations, which were accompanied by altered heart and respiratory rates.”
They also saw that ZEN increased the body temperature up to a mild fever.
“Our study is the first to actually provide data on the modulating effect of FUM on composition and predicted function of the rumen microbiota,” commented the research team.