Future forages: Implications of forage response to climate change for ruminant production

Lead Research Organisation: Cardiff University
Department Name: School of Biosciences

Abstract

Are our current forage-grass varieties fit for the future?

Ruminant farming enables production from marginal land that cannot be used to grow human food, thus contributing to global food security. Grazing land makes up ~60 % of the world's agricultural land supporting 360 million cattle and > 600 million sheep and goats. Continual improvement of the forage grasses used as animal feed has underpinned increases in ruminant production in an industry sector worth over £6 billion a year to the UK. Continued development of forage varieties for livestock production is essential to keep up with future demands of the growing human population.

Forage grass varieties currently under development are grown and assessed under current field conditions, Our preliminary research indicates that a change in growing conditions can affect how grass is digested and impact on animal production. Climate models predict near future (2050) increases in atmospheric CO2, increases in average temperatures, increased average precipitation, and increased frequency of extreme events. These trends are particularly pertinent to western England and Wales that are the primary sites of UK ruminant production. As it takes at least 10 years of selective breeding to go from concept to marketable product we need to know now if we are targeting the correct traits for forages of the future.

Previous work at Aberystwyth has shown that following ingestion by the animal, fresh forage feeds are degraded by enzymes of both microbial and plant origin. Grazed ryegrass entering the rumen of the animal is colonised by a subset of the microbial species present. These microbial communities are associated with the production of hydrolases, enzymes that break down plant cell walls. Efficient break down of plant cell walls in the forage is the key to energy provision for microbial growth in the rumen. If energy is limiting and plant protein breakdown is rapid, amino acids are used as an energy source generating levels of ammonia that cannot be assimilated by the animal and are excreted. This results in a loss of up to 70% of feed protein. Grazed grasses contribute to these protein losses because of stress responses to the rumen conditions. Modification of forage quality by exposure of the grass to stress during growth (eg drought) affects the process of early digestion in the rumen through stress memory; the effect of pre-exposure to a stress on the response to a subsequent stress. Hence, growth of current ryegrass varieties in a changed climate will alter the plant's response to stresses in the rumen. This will change the microbial colonisation in the rumen, which in turn will affect animal production and the environment through increased waste.

We will test the hypothesis that the response of grass leaves to climate change affects post-ingestion metabolism in plant and microbial cells, thus altering rumen system efficiency. In vitro fermentation of 10 ryegrass varieties will be assessed under current (2020) and 4 future (2050) conditions of elevated CO2 and temperature. These include scenarios that involve exposure to acute stress (drought, flooding or heat). Two varieties showing maximum and minimum differential response to at least one 2050 condition will be studied in detail to assess changes in the chemistry, protein content and composition of the forage, changes in the response of their genes to the rumen environment and how this affects the development and function of the rumen microbial communities. Predictions formed by in vitro experimentation will be confirmed with small ruminant trials to verify the whole animal effect focusing on decreasing methane and nitrogen release. The key output of our work will be to inform plant breeders on optimal targets to ensure forage grasses are fit for the future.

Technical Summary

We will test the hypothesis that growth of forage grass under conditions typical of 2050 UK climate will invoke a stress memory response, negating predicted gains in forage grass quality from targeted breeding. Our central hypothesis is that this will be caused by a combination of plant and microbial factors in the rumen. We hypothesise that the transcriptional and post-transcriptional plant stress responses will alter microbial colonisation profiles, which will result in limited fibre degradation and decreased rumen efficiency. This is based on preliminary data demonstrating effects of forage genotype on rumen efficiency and effects pre-harvest stress on the forage transcriptome and rumen metabolome.
1) We will screen current commercial and pre-commercial ryegrass (Lolium perenne) varieties/ lines in vitro. Feed quality (dry mass, nitrogen, carbohydrates etc), fermentation efficiency (CO2, methane and volatile fatty acids), metabolic profile (including volatile organic compounds, VOCs) will be compared under 5 environmental conditions: 1) current, 2) predicted climate for 2050 (CO2 of 500 ppm and a temperature increase of 5oC) and predicted climate plus, 3) 1 week drought, 4) 1 week flood and 5) 2 d heat (40oC).
2) Two contrasting variety/ lines and 2 environment combinations (including control) will be selected for metabolomics and proteomics, transcriptomics, VOC profiles and metagenomics in a system wide network analysis of the perturbations.
3) Continuous flow fermentation will be used to test whether effects of stress memory in the forage can be overcome by adaptation by the rumen microbiota.
4) An animal trial will be used to verify predictions from the in vitro work. To minimise feed requirements small/miniature sheep will be used comparing intake, nitrogen partitioning and methane production when fed ryegrass grown under current or future scenario.
We will deliver markers for breeders to optimise forage for future climate conditions.

Planned Impact

Ruminants provide high quality protein from land that can grow grass but cannot grow grain. Farmed grasslands in the UK represent >40 % of all land-area and provide a cost-effective platform to supply protein feed for ruminants. Maintaining productivity as the climate changes is vital to ensuring food supply and choice. Core to this is understanding the causes of inefficiency of ruminant conversion of plant into animal protein and mitigation of consequent environment damage. Improvements in rumen efficiency require improvements in the forage grasses they are fed on. We will deliver information needed to develop the next generation of grasses to optimise ruminant performance for the future climate conditions.
Understanding now how grasses perform as feeds in the near future (2050) is important because of the long timescale of breeding. This work will therefore directly benefit the UK livestock industry worth £6bn pa as well as researchers in plant, microbial and ruminant science.
1) Farmers will benefit from this research by having appropriate choice of climate ready crops to maximise pasture and animal performance under an altered climate and evidence on which to make decisions. This will indirectly contribute to social inclusion and leisure tourism by increasing the profitability and sustainability of pasture based rural life. We will engage with industry practitioners and representatives by attending industry-facing shows and co-operating with the efforts of the Farming Connect Knowledge Exchange Hub (KE Hub, a Welsh Government funded conduit for information from primary research to the farming community in Wales) and Grassland Development Centre (GDC, an extension service working with focus farms to demonstrate best practice), both based at IBERS.
2) This project will benefit forage plant breeders by providing them with information on the traits needed in future climate-appropriate forage varieties, which they can incorporate immediately into current breeding programmes. The molecular data on the response of forage grass incorporating stress memory in the rumen will inform long-term breeding strategies and provide information on biochemical pathways and target genes for breeders to use as markers in their longer-term high-throughput breeding programmes. We will ensure translation of research to product via our links with Germinal Holdings, an international grass seed company.
3) The scientific community will benefit from increased knowledge of the impact of climate change on non-model, perennial crops which are often poorly studied in comparison with annual species. We plan to produce 6 open access papers from this project spanning the continuum from frontier research into transcriptomics to verification in animals.
4) Policy makers on the reduction of greenhouse gas emissions will benefit from the outputs of this project through improved understanding of effects of climate change on forage digestion and hence on the knock on effects for meeting emission targets set for livestock.
5) There will be a strong training aspect in this project. The PDRAs will benefit from experience of a multifaceted project. They will be expected to present the work at conferences and contribute to writing of publications, so developing their career skills.
6) Consumers will benefit from increased sustainability of ruminant farming delivering cost-effective animal protein. The public will also gain from the environmental benefits in addressing ruminant efficiency thus reducing waste production, which contributes to greenhouse gas emissions and run off from fields. Finally, the gains made in animal productivity by correct tailoring of the forage grass varieties in 2050 will potentially reducing land dedicated to grazing that could be used for growing food crops, and hence both directly and indirectly support food security.
 
Description This work is based on the hypothesis that exposure of plants to stress in the field will affect digestibility of the forage feed in the rumen of grazing cattle and sheep. We have completed in vitro experiments based on batch and continuous culture fermentations of grasses with a rumen fluid inoculum. The experimental work to date has shown that differences in digestibility can be observed in a number of pasture grass species when they have been exposed to heat, drought or elevated CO2 as compared with current ambient (control) conditions. Analysis of ten different grass varieties revealed that in vitro digestion (with a rumen microbial inoculum) of the grasses was affected by the plant's growth environment, with responses to specific stresses being determined by grass variety. A paper has been submitted to Nature Scientific Reports, based on these results. We have conducted more detailed evaluation on three grass varieties to confirm initial results which indicated that future climate conditions could decrease methane production from animals grazing currently marketed high quality grasses. This means that growth conditions do affect subsequent utilisation in the rumen (our main hypothesis). It is now important to understand what is driving this in terms of fundamental biology so that a targeted plant breeding approach can be applied to produce future varieties that mitigate negative effects. Despite limited access to laboratories due to Covid we have continued with data analysis of collected samples where possible. Transcriptomic (Cardiff University) and metagenomic fingerprint (Aberystwyth University) analysis of representative samples from plant and rumen fluid respectively, has been completed to understand the relationship between plant metabolism and microbial colonisation. Data analysis is progressing with the aim of identifying candidate genes/ microbial profiles associated with altered feed degradation. In parallel, gaseous (headspace) samples have been analysed for volatile compounds (VOCs) by project partners at Cardiff University. These results also indicate that a pre-fermentation stress exposure alters the way that commercial forage varieties are digested. We were to undertake an animal feeding experiment in late 2020/early 2021 to confirm that results of in vitro experimentation would translate to practical implementation, ie when considering the whole animal, but this has been delayed due to Covid. The animals required (miniature Southdown sheep) were purchased in February 2020 to allow time for them to get accustomed to their new environment before the experiment. Based on results from in vitro studies we have identified the contrasting environmental stresses to be tested and these plants are being grown in preparation.
Exploitation Route This work is of direct relevance to UK's objectives of achieving net zero carbon. It is recognised that ruminant agriculture has significant challenges in reducing carbon output but identification of a plant based methodology to contribute to decreased environmental impact, that would be easily adopted by the farmers would be of significant social and economic benefit. We anticipate that our findings will be of direct relevance to forage grass breeders by identifying resilience and quality traits that will be important in a future unstable climate. Identification of candidate genes or microbial profile associated with beneficial rumen fermentation profile could be applied as part of plant breeding selection protocols. To facilitate this, we will communicate our findings internally and externally via the Head of Plant Breeding at IBERS and via our links with the forage breeding company Germinal Holdings. We will use our industry practitioner networks to inform of best practice when selecting varieties for re-sowing of grasslands. We will also incorporate our findings into teaching materials (lectures at Undergraduate and Masters level as appropriate) and include in distance learning schemes operated by Aberystwyth University specifically targeted towards upskilling industry practitioners.
Sectors Agriculture, Food and Drink,Environment

 
Description British Grassland Society 2021 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact A poster was presented at the British Grassland Society (BGS) conference held 2nd to 4th March 2021. This had been moved from a physical to online meeting due to Covid.
Future forages: Assessing forage of today for climate change conditions of the future
E.H. Hart1, S. Christofides2, C.T. Muller2, H. Rodgers2 and A. H. Kingston-Smith1
1IBERS, 2Cardiff University
Year(s) Of Engagement Activity 2021
 
Description British Science Week 2020 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Schools
Results and Impact Project members designed and ran a hands-on exhibit throughout a week at the Aberystwyth University Science Week (March 2020) "Our diverse planet". The event was designed to help school children (KS2 and secondary) understand the diversity of the rumen and why it, and the symbiotic bacteria and fungi it contains, are essential for transformation of plants that we can not eat into high quality (protein) milk and meat product for human consumption. Attendees were from local schools, plus from further afield in Wales and Shropshire.
Year(s) Of Engagement Activity 2020
 
Description EGF-EUCARPIA Joint Symposium 2019. 24-27th June, Zurich Switzerland. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact EGF-EUCARPIA Joint Symposium 2019. 24-27th June, Zurich Switzerland.
"Improving sown grasslands through breeding and management"
Poster: Implications of forage response to flooding for ruminant production
Year(s) Of Engagement Activity 2019
 
Description European Grassland Federation 2020 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Dr Hart gave a talk at the 28th meeting of the European Grassland Federation. This was due to be held in Helsinki, Finland but was rearranged to take place online (due to Covid) from19th to 21st October 2020.

Future forages: Differential effect of climate change scenarios on forage grasses for ruminant production.
Hart E.H.1, Christofides S.2, Rogers H.2, Creevey C.3, Müller C.2 and Kingston-Smith A.H.1
1IBERS, Aberystwyth University, UK
2School of Biosciences, Cardiff University, UK
3School of Biological Sciences, Queen's University Belfast, UK
Year(s) Of Engagement Activity 2020
URL https://www.europeangrassland.org/fileadmin/documents/Infos/Printed_Matter/Proceedings/EGF2020.pdf
 
Description Journey to the centre of the cow 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact School Science exhibit "Journey to the centre of the cow" to demoonstrate feed breakdown in the rumen and how plant genotype can affect this
Year(s) Of Engagement Activity 2019
 
Description Plants, People, Planet Symposium, Kew Gardens 4-5th Sept 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Plants, People, Planet Symposium, Kew Gardens 4-5th Sept 2019. The VOC Signature of Pasture Grass Subjected to Environmental and Rumen Stress. (poster)
Year(s) Of Engagement Activity 2019
 
Description Royal Welsh Agricultural Show 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Staff from the project participated in the IBERS exhibiiton at the Royal Welsh Agricultural Show. This involved discussing the potential for plant breeding in relation to climate change with attendees from the UK, Ireland and Europe. This was assisted by hte "touch the grass" exhibit designed to raise people's awareness of the phenotypic differences between different grasses, and forage quality.
Year(s) Of Engagement Activity 2019
 
Description Schools Science week, 2000 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact An exhibit to engage school children with exploring plant degradation in a rumen by rumen microorganisms, aiming to help them understand better the links in food production
Year(s) Of Engagement Activity 2019
 
Description visit by BBSRC CEO 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Supporters
Results and Impact A summary of the results from the project up to July 2019 were presented during a visit to IBERS by Prof Melanie Welham (CEO BBSRC).
Year(s) Of Engagement Activity 2019