Spray-topping annual grass pasture with glyphosate to delay loss of feeding value during summer. IV. Diet composition, herbage intake, and performance in grazing sheep

Abstract

We report the effects of spray-topping annual grass pasture with glyphosate (180 g a.i./ha as Roundup CT, at the seed head emergence stage) on the nutritive value of herbage and on subsequent performance of grazing sheep. Eight 1-ha plots, consisting of 4 sprayed and 4 unsprayed (control) plots, were set-stocked with Merino wethers (18 months old, 12 sheep/ha) from 8 days after anthesis in the control plots (late spring) until 165 days after anthesis (mid-autumn). In 4 periods (15-20, 36-41, 71-76, and 99-104 days after anthesis; Periods 1-4, respectively) sheep were dosed with synthetic alkanes and herbage and faecal samples were taken, in order to estimate diet composition (in terms of pla..