The effect of grazing versus cutting on dry matter production of multispecies and perennial ryegrass-only swards

Dry matter (DM) production of multispecies swards compared to perennial ryegrass (Lolium perenne; PRG) swards under intensive grazing warrants investigation as it is relatively unknown. A 5 x 2 factorial experiment, with five sward types and two defoliation methods, was used to investigate the effect of grazing versus cutting on dry matter (DM) production of multispecies and PRG-only swards. Five sward types were established namely: a PRG-only sward, receiving 250 kg N ha(-1) year(-1) (PRG250), and a PRG-only sward (PRG90), a two-species sward with PRG and white clover (Trifolium repens; PRGWC), a six-species sward (6S) and a nine-species sward (9S), each receiving 90 kg N ha(-1) year(-1). Cutting plots measured 1.95 x 10 m and grazing plots measured 10 x 10 m. All plots were harvested concurrently every 21-30 days from April-November for two years (2015 and 2016). A strip from the grazing plots was cut for DM yield determination prior to turning in cattle for grazing. There was an interaction between sward type and defoliation method (p < .01), whereby there was no effect of defoliation method on the PRG-only swards, however, the annual DM production of PRGWC, 6S and 9S swards reduced under grazing compared to cutting (p < .001; on average 1,929 kg DM/ha lower). Multispecies swards had lower DM production under grazing compared to cutting, while the DM yield of PRG-only swards was unaffected by defoliation method.