Grassland management systems are evolving continually, leading to many countries placing greater emphasis on grazed grass rather than grass/maize silage or concentrates in animal production. Where grazing is included in the production system, effcient grazing is pivotal. The competitive advantage of grass-based livestock production systems is based on the effcient production and utilisation of grazed grass. Irish pasture has, for example, the potential to grow up to 10–14 t DM/ha/annum (DM, dry matter; O’Donovan et al., 2020). In the context of a changing climate, warmer and wetter winters are expected in northern Europe and increasingly warmer and drier summers in southern Europe (Ergon et al., 2018). Although grazing systems have specifc challenges such as unstable feed supply and reduced individual animal intake and performance, the principal beneft of improved grazing management has been to optimise the quantity and nutritive value of the forage consumed by grazing animals. Key livestock production decisions like calving date (dairy, beef) and lambing date are targeted to maximise the use of grazed grass. Such parameters will have to be continually evaluated if grass growth curves are changing based on climatic conditions.