PERFORMANCE AND VITAMIN A STATUS OF SHEEP GRAZING HIGH-NITRATE PASTURES

Nitrogen levels of 0,184 and 368 Ib (0,83.47 and 166.94 kg) were applied, as calcium ammonium nitrate, in six dressings throughout the grazing season to a perennial ryegrass/white clover sward. Herbage samples taken, periodically from each treatment and analysed nitrate for, indicated that the latter increased with increasing levels of applied nitrogen. Herbage nitrate levels were higher towards the end of the grazing season than at any other time. There was no consistent relationship between applied nitrogen and total plant nitrogen, although the latter tended to run parallel with applied nitrogen levels during the early part of the year. Sheep performance was significantly increased with the first increment of 184lb (83.47 kg) of nitrogen; a second increment of 1841b resulted in a further, but non‐significant, increase. High‐nitrate pastures did not significantly reduce liver vitamin A storage in sheep. It is suggested that approximately 350 Ib (158.79 kg) of nitrogen, applied uniformly throughout the grazing season, results in pasture nitrate levels which have no adverse affect on sheep performance.