Studies on salt tolerance of sheep. II. The tolerance of sheep for mixtures of sodium chloride and magnesium chloride in the drinking water

Abstract

Seven groups, each of six sheep, were fed in pens for 16 months on a ration of chaffed lucerne and wheaten hays. One group was offered rain-water to drink, another group was offered 1.30 per cent. sodium chloride, whereas the others were offered one of the following mixtures of sodium and magnesium chlorides : 1.27 + 0.02, 1.24 + 0.05, 1.18 + 0.10, 1.05 + 0.20, and 0.69 + 0.50 per cent. Many of the animals refused to eat or drink satisfactorily when the saline waters were first offered. If, however, the concentrations were increased gradually over a period of 3 weeks to the desired levels, satisfactory performance by most animals was obtained. The intake of water containing 1.30 per cent. sodium chloride was higher than that of rain-water, and the intake increased with increasing concentrations of magnesium chloride up to 0.10 per cent.; the mean daily intakes for the entire experiment by the seven groups were 2.3, 3.9, 4.2, 4.8, 5.0, 4.3, and 3.5 1. respectively. The intake also increased in all groups with temperature, being 60-100 per cent. higher in the hottest months than in the coldest months. A concentration of 1.3 per cent. sodium chloride, and concentrations of up to 0.10 per cent,. magnesium chloride with 1.2 to 1.3 per cent. sodium chloride, had no adverse effect on the sheep, but 0.20 or 0.50 per cent. magnesium chloride (with 1.05 and 0.69 per cent. sodium chloride respectively) was detrimental to some of the sheep. The principal effect was a reduction in food consumption. The only other obvious sign in these last two groups was an occasional diarrhoea; this was more frequent on the higher concentration of magnesium chloride. The saline drinking waters had no effect on the concentrations of sodium, potassium, calcium, or chloride in the blood plasma. Magnesium, however, was significantly higher, throughout most of the experiment, in the plasma of the sheep which received 0.50 per cent. magnesium chloride.