Breeding new grass varieties for optimized digestible dry matter with least possible enteric methane emissions (Keynote Address)

Enteric fermentation of domestic ruminant livestock is the largest source of methane (CH4) emissions caused by the agricultural sector. The impact of CH4 on climate change is more than 25 times greater than that of CO2 and it is therefore important to reduce this emission through targeted breeding for grass varieties with a reduced methane footprint. Ruminants are dependent on a specialized microbial community in their rumen to degrade plant cell wall components and extract energy and the necessary building blocks for optimal animal production. In order to support optimal digestibility of feed without a loss of energy through methane emission the feed has to be readily fermentable and deliver a balanced substrate for the ruminal microbial community to thrive optimally. An increased feed digestibility will enhance animal efficiency (fewer cattle produce the same amount of milk or meat) and be one way of reducing enteric methane emissions. Another possibility is to feed cattle diets containing high levels of readily fermentable carbohydrates to minimise methane production by reducing the protozoal and archaeal population and lowering rumen pH, however this has to be a balanced strategy, otherwise it can be detrimental to the animal's health. DLF (Dansk Landbrugs Froforsyning) is in the process of tailoring new grass varieties with increased cell wall digestibility by modifying the cell wall structure (crosslinking of cell wall fibres) and lowering lignin content through a TILLING (Targeting Induced Local Lesions in Genomes) approach and advanced Genomic Selection (GS) strategies. With these initiatives, feed retention time in the rumen might be shortened, feed intake and animal production increased and concurrently enteric methane emissions might be ameliorated. The aim is to develop annual and perennial ryegrass species with increased dry matter digestibility and decreased enteric methane emissions. Preliminary results with mutations in either the cinnamoyl-CoA reductase (CCR) gene or the caffeic acid O-methyltransferase (COMT) gene with an up to 20% lower lignin content will be presented as well as an overview on our GS strategy with fibre composition and digestibility in combination with yield as main traits in our breeding strategy. In order to breed for these traits, monitoring fibre composition as well as digestibility had to be implemented in our breeding and testing scheme. Near infrared spectral analysis directly on our harvesters together with our own specialized grass feed quality calibration support our breeders to select the varieties with the most breeding advance for fibre composition, digestibility and yield.