Mechanisms utilised within the IBERS diploid Lolium perenne L. forage grass breeding programmes to improve rumen nitrogen use efficiency

Researchers at Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, have completed 3 years of a 5 year LINK project, sponsored by Defra through the Sustainable Livestock Production LINK programme (www.greener-grasslands.ibers.aber.ac.uk) which aims to breed new forages that will reduce the environmental footprint of livestock production. One of the key objectives is to improve nitrogen use efficiency (NUE) in the rumen through the breeding of new forage grasses to improve protein utilisation. Previously it has been shown that feeding ryegrasses with higher water soluble carbohydrate content leads to improved rumen efficiency and evidence suggests that this results in increased meat and milk production and reduced nitrogen losses with lower ammonia and nitrous oxide emissions through improved protein utilisation. IBERS diploid perennial ryegrass breeding programmes involve a combination of spaced plant assessment and half-sibling plot performance as a basis for recurrent selection over many generations, the current focus of which is to combine increased NUE along with other desirable agronomic traits including improved yields, increased persistency and higher dry matter digestibility.