The effects of increasing the sodium content of grass or concentrates on the nutrition of sheep

Abstract

AbstractSupplementary salt is often added to the diet of sheep by including it in concentrate food, but an alternative is to soak their forage in a weak salt solution, which could prevent the sudden influx of large doses of sodium(Na) to the rumen. An experiment was conducted to compare low and moderate levels of salt in forage with moderate and high levels added to the concentrate. Twenty sheep were housed in individual chambers equipped for faeces and urine collection and offered fresh grass and concentrate, with the salt being added to the grass by soaking in salt water and to the concentrate by direct mixing. The grass for sheep offered the supplementary Na in concentrates and for a control treatment was soaked in water without salt. Grass was offered in two daily meals and was availablead libitum, and concentrates were offered at a restricted level just before the first feeding of grass. Adding salt at the low and moderate levels to the water in which the grass was soaked increased the Na intake from 1·1 g/day (the control treatment) to 2·1 and 3·8 g/day, respectively, and reduced the Mg and Ca contents in the grass, compared with grass soaked in unsalted water. Adding salt to the concentrate at moderate and high levels increased Na intake to 3·7 and 5·9 g/day, respectively. Grass dry matter (DM) intakes were increased by adding Na to the concentrates, but not to the grass, and DM digestibility was increased in all salt supplement treatments except the high level added to the concentrate. The apparent absorption of Na was increased in proportion to the amount of Na added to the diet and that of K was increased at the moderate and high levels. The apparent absorption and retention of Mg and Ca were decreased at the low level of Na supplementation in herbage. It is concluded that the potential benefits of adding salt to the diet, namely increased food intake and digestibility and increased mineral absorption, are dependent on the level of addition and the method of adding it.