Primary supervisor: Prof Liam Sinclair, Harper Adams University

Non-academic partner: Dr Jules Taylor-Pickard, Alltech

Project description

Grass silage is the predominant forage fed to dairy cows in the UK. The aim when ensiling grass is to create an anaerobic environment to restrict proliferation of undesirable microbes thereby maintaining the nutritive value over the winter-feeding period and prevent spoilage (McDonald et al., 2021; Snelling et al., 2023). Factors such as dry matter and sugar content of the grass, along with plant maturity and ensiling conditions can all affect the forage epiphytic microbiome (Gonda et al., 2023). Under adverse forage growing and ensiling conditions, or aerobic spoilage of clamps or bales at feed-out, fungal spoilage can be widespread (Manni et al., 2023; Webster et al., 2023a). Under these conditions fungi can produce secondary compounds, including mycotoxins (Fink-Gremmels, 2008), which have been reported to occur in over 90% of the forage fed to cattle in temperate regions such as the UK, Ireland and Northern Europe (Manni et al., 2023; O’Brien et al., 2005). When present in the diet of cattle, mycotoxins and biologically active breakdown products can negatively affect health, fertility and production, and, in extreme cases, lead to death (Gallo et al., 2015). Moreover, there is a risk that mycotoxins can be passed into the human food chain via the milk or meat (Bennett and Klich, 2005).

Cattle can be more resistant to certain mycotoxins such as deoxynivalenol, due to the activity of the rumen microbial community (Fink-Gremmels, 2008). However, most work has been undertaken on maize silage and few studies have been conducted on the mycotoxins commonly found in grass silage such as fusaric acid, penicillic acid, mycophenolic acid, or deoxynivalenol (Manni et al., 2023), or the subsequent effect of these compounds on the rumen microbiome (Webster et al., 2023). The ability of the rumen microbiome to efficiently digest forages is also dependent on a delicate balance of microbial species that can break down fibre and protein in the diet. An imbalance or shift in microbial population as a result of mycotoxin ingestion may reduce digestive efficiency and indirectly reduce health, milk performance and fertility (Becker-Algeri et al., 2016).

Harper Adams University is one of the few centres in the UK that has the capability to carry out high impact research investigating forage mycotoxin production in grass silage and subsequent effects on the rumen microbiome, rumen fermentation and immune response in dairy cows. These facilities allow us to ensile grass silage at multiple scales and under varying conditions to produce different levels of mycotoxins (Snelling et al., 2023) and examine the capability of the microbiome to detoxify mycotoxins and the uptake of biologically active compounds into milk (Webster et al., 2023). Lactating dairy cows fitted with a rumen cannula are available on site, which allow direct access to the rumen for digesta sampling either for microbiome analysis or for inoculation of in vitro systems. The rumen microbial community will be analysed using the current metagenomic and metabarcoding methodologies. Blood samples will be collected to examine the immune response to feeding forages with different mycotoxin loads, and strategies will be examined to mitigate and deactivate the effects of mycotoxins, such as the use of in-feed binder supplements. Mycotoxin analysis will be conducted by LC/MS/MS at a dedicated Alltech laboratory using a validated technique that can quantify 54 mycotoxins in a single sample (Jackson et al., 2012).

Candidates are encouraged to contact Prof Liam Sinclair to discuss the project before applying if they wish to.