Sulphur as a nutrient for Merino sheep

Abstract

1. Faecal and urinary sulphur excretions of Merino sheep given fifty-one forage diets were measured in 205 balance experiments to derive estimates of the dietary requirements of Merino sheep for S.2. Faecal S excretion varied with the S, organic matter and digestible organic matter intakes. Non-dietary faecal S excretion was estimated by regression analysis and was approximately 0·7 g S/kg organic-matter intake. Apparent S digestibility declined linearly with the reciprocal of dietary S content, and was predicted to be zero when the dietary S content was 0·81 g S/kg organic matter.3. Both urinary S excretion and S retention varied with the digestible S and digestible organic-matter intakes. Endogenous urinary S excretion was taken to be the urinary S excretion when digestible S intake was zero, and the sheep was at zero energy balance. It was estimated by regression analysis to be 38 mg S/d.4. The S and digestible S intakes necessary to maintain the fleece-free tissues in S equilibrium can be calculated from the equations derived in this study. An example is presented.