Factors influencing mycotoxin production in grass silage, and their effects on rumen metabolism and the microbiome in dairy cows

Webster, J.M. (2025) Factors influencing mycotoxin production in grass silage, and their effects on rumen metabolism and the microbiome in dairy cows. Doctoral thesis, Harper Adams University.

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Abstract

Mycotoxins are secondary metabolites that can contaminate agricultural crops and forages (Eskola et al., 2020; Pusztahelyi et al., 2015) and are mainly synthesised by Fusarium, Aspergillus and Penicillium fungi, with harmful effects on humans and animals (Hussein and Brasel, 2001; Zain, 2011). Maize silage has been a focus of mycotoxin research as a matter of animal and public health, due to the acute toxicity of aflatoxin B1, and the potential carryover of this metabolite into milk (Min et al., 2021). In Great Britain, however, a considerable proportion of grass silage is produced for feeding dairy cows (Franco et al., 2021), where its mycotoxin profile has been understudied, and little is known of the effect on the rumen microbiome and metabolism. Previous studies identified mycotoxins of often Penicillium associated origin are dominant in grass silages, with non European Union (EU) regulated mycotoxins such as mycophenolic acid (MPA), present (O’Brien, 2010; Schneweis et al., 2000; Tangni et al., 2013). Most non-regulated grass silage mycotoxins identified to date, can elicit antibacterial and antifungal effects and even immunosuppressive effects (i.e. MPA (Heischmann et al., 2017)), that may lead to rumen dysbiosis and poorer dairy cow performance (Fink-Gremmels, 2008). Moreover, no correlation has been found between the presence of visible mould in silages and level of mycotoxin contamination (Manni et al., 2022), which could mean cows are exposed, unbeknownst to the farmer. This thesis details a range of studies with the following aims: 1) to identify grass silage mycotoxins in Great Britain, 2) to elucidate effects of silage fermentation and management on mycotoxin production, 3) to understand the effect of grass silage mycotoxins on rumen fermentation, and also, 4) on the rumen microbiome, and dairy cow performance. The findings of this thesis support that grass silage mycotoxin synthesis is influenced by fermentation parameters such as dry matter content, lactic acid and acetic acid concentration as well as management such as minimising oxygen proliferation through the clamp at opening. British grass silages often contain non EU regulated mycotoxins such as penicillic and fusaric acid that demonstrate the ability to alter rumen volatile fatty acid production, when in combination with other mycotoxins, at levels observed naturally synthesised on farm. Relative abundance of species of Succiniclasticum, Methanobrevibacter and Prevotella were impacted by the inclusion of MPA in the diet of dairy cows, with the potential to impact rumen function and animal performance, if fed for a prolonged duration. It highlights the necessity for regular mycotoxin testing on farm and for the EU Food and Safety Authority to consider synergistic mycotoxin combinations when deciding on guidance values in order to minimise impacts on the health and performance of cows in the British dairy industry.

Item Type:	Thesis (Doctoral)
Divisions:	Agriculture and Environment (from 1.08.20)
Depositing User:	Miss Anna Cope
Date Deposited:	03 Apr 2025 10:08
Last Modified:	03 Apr 2025 10:08
URI:	https://hau.repository.guildhe.ac.uk/id/eprint/18211

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