Sheep select combinations of high and low sodium chloride, energy and crude protein feed that improve their diet

Abstract

A major limitation of saltland pasture systems is the high sodium chloride content of the forage and the physiological implications of this for the grazing animal. Incorporating low salt alternatives has been found to improve livestock performance from high salt feeds. The aim of this study was to investigate how sheep offered high salt diets (such as saltbush pastures) select low salt alternatives to improve their diet. Five groups of six Merino weaner wethers were individually penned and offered a choice of two feeds. Sheep were offered a high salt feed containing 18.5% added NaCl and one of five alternative feeds. The alternatives were high–high, high–low, low–high, low–low energy and crude protein feed that contained no added salt or the high salt feed. Diet selection, liveweight gain and wool growth were determined in the sheep over 4 weeks. Additionally, water intake, pattern of feed intake and digestibility were measured. This study shows that sheep actively select combinations of high salt and alternative feeds that improve the overall feeding value of their diet. Sheep offered a low energy alternative feed had a higher intake of the high salt feed compared with those offered high energy alternatives (788 g/day versus 183 g/day). However, intake of the high salt feed did not differ significantly in sheep offered a low crude protein alternative compared with sheep offered a high crude protein alternative feed (422 g/day versus 550 g/day). Sheep selected an initial combination of high and low salt feeds that did not change as they became familiar with the feeds. The total organic matter intake of the sheep offered any of the four low salt alternatives was about 50% higher and their liveweight gain was at least double that of sheep offered only the high salt feed.