Strategies in grass silage production to mitigate enteric CH4 emissions from ruminants

Food production results in emissions of greenhouse gases. Today, greenhouse gas emissions from the agricultural sector account for 8.6 per cent of the total emissions from Norway. Through the Paris agreement, Norway is committed to reducing greenhouse gas emissions. This means that emissions in the non-ETS sector, which agriculture is a part of, will be reduced by 40% by 2030. Enteric methane (CH4) is a significant contributor to greenhouse gas emissions, as it accounts for almost half of the total emissions from Norwegian agriculture. . Grass is grown on as much as two thirds of the cultivated area in Norway and silage is the dominant roughage for the ruminants. International research shows that replacing roughage with more concentrate can be a strategy for reducing enteric methane emissions. However, this is not the current strategy in Norway, because national feed resources such as silage are the basis of Norwegian ruminant production, which was also emphasized in the latest Norwegian agricultural report. Silage is produced in many different ways, resulting in a wide variety of botanical composition, chemical composition, digestibility and fermentation results. These are properties of the silage that can affect enteric methane emissions. It is therefore of crucial importance to map out what properties this applies to. In work package 1 we have published one scientific article in Journal Animal Feed Science and Technology (Weiby et al., 2022). Here, 78 round bales were collected from all over Norway, which were analyzed for chemical content, in vitro methane gas production and a digestion test was carried out on sheep. The results showed that NDF, iNDF and water-soluble carbohydrates (sugar compounds) were the most important parameters influencing in vitro methane production. Models were also developed that can predict methane production from silage based on the content of nutrients in the sample material. In work package two (field trials at NIBIO Fureneset) we have published one scientific paper in the journal Scientific Reports (Weiby et al., 2023). We found that in vitro CH4 production was on average 2.8 mL/g OM lower in a two-cut harvestregime compared to a three-cut harvest regime, and 1.9 mL/g OM lower in silage with timothy compared to perennial ryegrass. Wilting (increased dry matter content) had no effect on in vitro CH4 production. However, silage added formic acid obtained 1.2 mL/g OM greater in vitro CH4 production compared to silage without formic acid. We concluded that less frequent harvesting and extensive silage fermentation reduced in vitro CH4 production, while perennial ryegrass increased in vitro CH4 production compared to timothy. In work package three (In vivo CH4 measurement using Greenfeed equipment at Senter for Husdyrforsøk, NMBU) all research activity, data handling and writing of scientific paper is concluded. The scientific paper are submitted to Journal of Dairy Science. In this WP we found that timothy obtained 5.2% lower in vivo CH4 intensity compared to perennial ryegrass. Further, we found that increasing the proportion of red clover from 0 to 100% resulted in a linear increase in CH4 intensity of 9.8%. Lastly, we found that a three-cut harvesting regime reduced in vivo CH4 intensity 6.8% compared to a two-cut harvesting regime. The aim of the PhD project was to develop strategies in silage production to reduce enteric methane gas emissions. A realistic goal is to achieve a reduction of enteric CH4 emissions from ruminants in the order of 20 % by 2030, ie approx. 430,000 tonnes of CO2 equivalents. This project will thus contribute to achieving Norway's climate goals for 2030. References: 1. Weiby, K. V., S. J. Krizsan, M. Eknæs, A. Schwarm, A. C. Whist, I. Schei, H. Steinshamn, P. Lund, K. A. Beauchemin and I. Dønnem. 2022. Associations among nutrient concentration, silage fermentation products, in vivo organic matter digestibility, rumen fermentation and in vitro methane yield in 78 grass silages. Anim. Feed. Sci. Technol. 285. 115249. https://doi.org/10.1016/j.anifeedsci.2022.115249 2. Weiby, K. V., S. J. Krizsan, I. Dønnem, L. Østrem, M. Eknæs and H. Steinshamn. 2023. Effect of grassland cutting frequency, species mixture, wilting and fermentation pattern of grass silages on in vitro methane yield. Sci. Rep. 13:4806. https://doi.org/10.1038/s41598 802 023 31964 3

Målgruppen for dette PhD prosjektet er både forskningsinstitusjoner nasjonalt og internasjonalt, myndigheter (LMD, KMD, Landbruksdirektoratet, Miljødirektoratet), faglag (Bondelaget, Norges Bonde og Småbrukarlag), bønder og andre næringsaktører (TINE, Nortura, fôrfirma, Animalia, Tyr, NSG, Geno etc) i tillegg til almennheten. Resultatene fra doktorgradsprosjektet vil bidra med kunnskap om grovfôrrelaterte reduksjonsstrategier for metanutslipp hos nasjonale og internasjonale forskningsmiljøer. Resultatene vil også bidra til økning i kompetansen hos både næringsaktører (f eks klimarådgivere i TINE og NLR), og hos de som jobber med klimaarbeid i faglagene. Rådgiverne vil kunne tilpasse sin rådgivning slik at de er i tråd med disse resultatene, og det vil igjen kunne endre adferd og praksis ute hos bønder som har drøvtyggerproduksjoner slik at metangassutslippene på gården reduseres. Resultatene fra doktorgradsprosjektet vil også kunne bidra til endret politikk hos myndigheter og beslutningstakere, slik at politikk kan utformes på en slik måte at de stimulerer til en grovfôrproduksjon som reduserer metangassutslippene i tråd med disse resultatene. Helt konkret er potensielle virkninger og effekter disse: 1. Bruk av resultatene i annen forskning og implementering av resultatene i TINE og NLR sin klimarådgiving De publiserte resultatene fra dette PhD prosjektet kan brukes i andre internasjonale studier (internasjonale databaser, metastudier etc.) og blir nå også implementert i TINE og NLR sin klimarådgiving ut mot melkeprodusentene gjennom opplæring av rådgiverne. Bidrar til reduserte utslipp av CH4. 2. Sammenligning av beregnet utslipp i TINE Optifôr (Nielsen et al., 2013) og resultater fra WP3 i min doktorgrad. Rådgivere i TINE bruker TINE Optifôr når de er ute på gården og lager fôrrasjoner. I denne optimeringen kan man også beregne metangassutslippet ved hjelp av en modell (Nielsen et al., 2013). Jeg ønsket å undersøke om de beregnede CH4 utslippene i TINE Optifôr var forskjellige fra de jeg målte i WP 3. Vi fant kun små forskjeller. Det er mulig å implementere resultatene fra WP3 for å forbedre modellen for CH4 beregning i TINE Optifôr. 3. Implementering av resultatene i revidert utgave av landbrukets klimaplan 2024 I den reviderte utgaven av landbrukets klimaplan som kommer i 2024 under kapittelet om klimagassutslipp fra avl og fôring er resultatene fra denne doktorgraden og potensialet for utslippskutt gjennom forbedret grovfôrkvalitet beskrevet. Det er også linket til de publiserte artiklene fra doktorgradsprosjektet. 4. Formidling av resultater ut mot bønder Dette har skjedd og skjer kontinuerlig gjennom populærvitenskapelige artikler i Buskap (2 stk), artikler i meieriposten og i artikler i Bondebladet, Norsk Landbruk, Nationen, podcaster etc. 5. Formidling i massemedia Dette har skjedd gjennom artikler i lokalpresse og nasjonale medier som Nationen, NRK etc.

The practice for grass silage production is very diverse in Norway, manifested by different choices of botanical composition of the sward, different stages of maturity at harvesting, various numbers of cuts, extent of wilting, application of additives, etc. This is partly adoption to the particular local conditions, but there is still room for significant changes in practicing silage production. The variability in silage characteristics will probably be strengthened as an effect of the expected climate change, manifested in longer growing season, more frequent events of extreme precipitation, drought etc. (Svendgård-Stokke, 2015). It is apparent that the different characteristics of grass silage caused by the variety in grass silage production practices, may affect enteric CH4 emissions. In this project we will elucidate which characteristics in grass silage are of particular interest, and further study these characteristics systematically. The main research tasks necessary to acquire the adequate knowledge are discussed in the following section. The research work will be linked to the different objectives and organised in five WPs. The knowledge that will be acquired in this proposed project is of high relevance and importance for the Norwegian agricultural sector, advisory services and the authorities. The primary target group for this knowledge is the farmers who should implement the results in their strategy for grass silage production. However, to succeed in implementing the results into practice, not only the farmers, but also other target groups like the advisory services, media etc. need to be a part of the dissemination and communication strategy.