Preference of grazing sheep for pasture of high phosphate content

Abstract

Nine levels of phosphorus were applied in the autumn of two seasons to 180 plots laid out in a clover pasture.

Under common grazing of the dry residues during the summer period, Merino sheep preferentially grazed the higher phosphate treatments. Selection continued to a higher level of phosphorus application than was needed to give maximum pasture growth. A less marked preference was shown for high phosphate during the growing season.

Chemical analysis of the dry residues within each year showed little difference due to phosphate treatment except an increase in phosphorus concentration. This ranged from 0.08 to 0.26% phosphorus at the end of the growing season, and from 0.06 to 0.17% in the dry summer residues. Above 0.10–0.15% no marked preference for higher phosphate feed was shown. A small (20–28%) but consistent and significant decrease in the free phenol content of the pasture occurred at higher phosphate levels. and could possibly have accounted for the observed preferences.