The Effect of Increasing Pasture Species on Herbage Production, Chemical Composition and Utilization under Intensive Sheep Grazing

A complete randomized design was used to investigate the effect of increasing pasture species on herbage production, chemical composition and utilization under intensive sheep grazing. Four experimental farmlets were established, namely perennial ryegrass (Lolium perenne) only, receiving 163 kg N ha(-1) year(-1) (PRG); a perennial ryegrass and white clover (Trifolium repens) sward (PRGWC); a six species sward containing two grasses, two legumes and two herbs (6S); and a nine species sward containing three grasses, three legumes and three herbs (9S), each receiving 90 kg N ha(-1) year(-1). Ewes (12.5 ewes ha(-1)) and lambs rotationally grazed each farmlet from turnout post-lambing until housing. Target pre-grazing herbage mass (above 4 cm) was 1,200 kg dry-matter (DM) ha(-1), Target post-grazing sward height was 4 cm for all rotations. Herbage samples were collected for DM yield, botanical and chemical composition determination at each grazing. Annual DM production of the 6S, 9S and PRG swards was similar (10.3, 9.9 and 9.9 +/- 0.5 t DM ha(-1), respectively) despite differences in N application. The 6S sward, however, had greater annual DM production compared to the PRGWC sward (9.1 t DM ha(-1), p < 0.05). Herb proportions decreased in the 6S and 9S swards from 2015 to 2016 (p < 0.05) resulting in increased proportions of grass in these swards (p < 0.05). In conclusion, the PRGWC, 6S and 9S swards produced similar annual herbage DM from lower N inputs to PRG swards; however, maintaining the proportions of herbs is a challenge under intensive sheep grazing.