Forage grass growth under future climate change scenarios affects fermentation and ruminant efficiency.

With an increasing human population access to ruminant products is an important factor in global food supply. While ruminants contribute to climate change, climate change could also affect ruminant production. Here we investigated how the plant response to climate change affects forage quality and subsequent rumen fermentation. Models of near future climate change (2050) predict increases in temperature, CO2, precipitation and altered weather systems which will produce stress responses in field crops. We hypothesised that pre-exposure to altered climate conditions causes compositional changes and also primes plant cells such that their post-ingestion metabolic response to the rumen is altered. This "stress memory" effect was investigated by screening ten forage grass varieties in five differing climate scenarios, including current climate (2020), future climate (2050), or future climate plus flooding, drought or heat shock. While varietal differences in fermentation were detected in terms of gas production, there was little effect of elevated temperature or CO2 compared with controls (2020). All varieties consistently showed decreased digestibility linked to decreased methane production as a result of drought or an acute flood treatment. These results indicate that efforts to breed future forage varieties should target tolerance of acute stress rather than long term climate.

Detection of Galba truncatula, Fasciola hepatica and Calicophoron daubneyi environmental DNA within water sources on pasture land, a future tool for fluke control?

BACKGROUND: Increasing trematode prevalence and disease occurrence in livestock is a major concern. With the global spread of anthelmintic resistant trematodes, future control strategies must incorporate approaches focusing on avoidance of infection. The reliance of trematodes on intermediate snail hosts to successfully complete their life-cycle means livestock infections are linked to the availability of respective snail populations. By identifying intermediate snail host habitats, infection risk models may be strengthened whilst farmers may confidently apply pasture management strategies to disrupt the trematode life-cycle. However, accurately identifying and mapping these risk areas is challenging. METHODS: In this study, environmental DNA (eDNA) assays were designed to reveal Galba truncatula, Fasciola hepatica and Calicophoron daubneyi presence within water sources on pasture land. eDNA was captured using a filter-based protocol, with DNA extracted using the DNeasy® PowerSoil® kit and amplified via PCR. In total, 19 potential G. truncatula habitats were analysed on four farms grazed by livestock infected with both F. hepatica and C. daubneyi. RESULTS: Galba truncatula eDNA was identified in 10/10 habitats where the snail was detected by eye. Galba truncatula eDNA was also identified in four further habitats where the snail was not physically detected. Fasciola hepatica and C. daubneyi eDNA was also identified in 5/19 and 8/19 habitats, respectively. CONCLUSIONS: This study demonstrated that eDNA assays have the capabilities of detecting G. truncatula, F. hepatica and C. daubneyi DNA in the environment. Further assay development will be required for a field test capable of identifying and quantifying F. hepatica and C. daubneyi infection risk areas, to support future control strategies. An eDNA test would also be a powerful new tool for epidemiological investigations of parasite infections on farms.

Comparative metabolite fingerprinting of the rumen system during colonisation of three forage grass (Lolium perenne L.) varieties.

The rumen microbiota enable ruminants to degrade complex ligno-cellulosic compounds to produce high quality protein for human consumption. However, enteric fermentation by domestic ruminants generates negative by-products: greenhouse gases (methane) and environmental nitrogen pollution. The current lack of cultured isolates representative of the totality of rumen microbial species creates an information gap about the in vivo function of the rumen microbiota and limits our ability to apply predictive biology for improvement of feed for ruminants. In this work we took a whole ecosystem approach to understanding how the metabolism of the microbial population responds to introduction of its substrate. Fourier Transform Infra Red (FTIR) spectroscopy-based metabolite fingerprinting was used to discriminate differences in the plant-microbial interactome of the rumen when using three forage grass varieties (Lolium perenne L. cv AberDart, AberMagic and Premium) as substrates for microbial colonisation and fermentation. Specific examination of spectral regions associated with fatty acids, amides, sugars and alkanes indicated that although the three forages were apparently similar by traditional nutritional analysis, patterns of metabolite flux within the plant-microbial interactome were distinct and plant genotype dependent. Thus, the utilisation pattern of forage nutrients by the rumen microbiota can be influenced by subtleties determined by forage genotypes. These data suggest that our interactomic approach represents an important means to improve forages and ultimately the livestock environment.

Evidence of a role for foliar salicylic acid in regulating the rate of post-ingestive protein breakdown in ruminants and contributing to landscape pollution.

Ruminant farming is important to global food security, but excessive proteolysis in the rumen causes inefficient use of nitrogenous plant constituents and environmental pollution. While both plant and microbial proteases contribute to ruminal proteolysis, little is known about post-ingestion regulation of plant proteases except that activity in the first few hours after ingestion of fresh forage can result in significant degradation of foliar protein. As the signal salicylic acid (SA) influences cell death during both biotic and abiotic stresses, Arabidopsis wild-type and mutants were used to test the effect of SA on proteolysis induced by rumen conditions (39 °C and anaerobic in a neutral pH). In leaves of Col-0, SA accumulation was induced by exposure to a rumen microbial inoculum. Use of Arabidopsis mutants with altered endogenous SA concentrations revealed a clear correlation with the rate of stress-induced proteolysis; rapid proteolysis occurred in leaves of SA-accumulating mutants cpr5-1 and dnd1-1 whereas there was little or no proteolysis in sid2-1 which is unable to synthesize SA. Reduced proteolysis in npr1-1 (Non-expressor of Pathogenesis Related genes) demonstrated a dependence on SA signalling. Slowed proteolysis in sid2-1 and npr1-1 was associated with the absence of a 34.6 kDa cysteine protease. These data suggest that proteolysis in leaves ingested by ruminants is modulated by SA. It is therefore suggested that influencing SA effects in planta could enable the development of forage crops with lower environmental impact and increased production potential.

From plants to animals; the role of plant cell death in ruminant herbivores.

Plant cell death occurring as a result of adverse environmental conditions is known to limit crop production. It is less well recognized that plant cell death processes can also contribute to the poor environmental footprint of ruminant livestock production. Although the forage cells ingested by grazing ruminant herbivores will ultimately die, the lack of oxygen, elevated temperature, and challenge by microflora experienced in the rumen induce regulated plant stress responses resulting in DNA fragmentation and autolytic protein breakdown during the cell death process. Excessive ruminal proteolysis contributes to the inefficient conversion of plant to microbial and animal protein which results in up to 70% of the ingested nitrogen being returned to the land as the nitrogenous pollutants ammonia and urea. This constitutes a significant challenge for sustainable livestock production. As it is estimated that 25% of cultivated land worldwide is assigned to livestock production, it is clear that understanding the fundamental biology underlying cell death in ingested forage will have a highly significant role in minimizing the impact of human activities. This review examines our current understanding of plant metabolism in the rumen and explores opportunities for exploitation of plant genetics to advance sustainable land use.