Influence of water salinity on sheep performance while grazing on natural grassland and saltbush pastures

Abstract

Merino sheep grazing a semi-arid natural grassland were given water containing 0.0, 1.2, 1.6 or 2.0 per cent (w/v) soluble salts and similar sheep grazing on saltbush (Atriplex vesicaria) were given water containing 0.0, 0.8, 1.2 or 1.6 per cent soluble salts. The saline water was made up from sodium chloride and magnesium sulphate to give an ionic concentration similar to that occurring in natural underground waters. On grassland, 1.2 per cent saline water was without effect on the sheep, 1.6 per cent water reduced weight and wool growth in the first year and 2.0 per cent water reduced both wool growth and body weight by a significant amount. The effects were confined to the summer period of November to March. On saltbush, the results for four years were essentially similar to those for sheep on the grassland, although the effects of 1.2 per cent and 1.6 per cent saline waters were more pronounced. However, in the fifth year when drought conditions prevailed, the effects of both these treatments were more severe Water intakes were up to 1 lday-1 higher on the saline water treatments than on the fresh water, except when water intakes of the sheep on saltbush were high (7-11 lday-1) and then water salinity reduced water intakes. It was concluded that water salinities up to 1.2 per cent on grassland and 0.8 per cent on saltbush will not affect sheep productivity. Higher concentration (up to 1.6 per cent on grassland and 1.2 per cent on saltbush) can be used for adult sheep when forage conditions are good.