Studies on cattle with oesophageal fistulae: comparison of concentrations of mineral nutrients in feeds and associated boluses

Abstract

Eight forages were fed in small quantities to cattle with oesophageal fistulae. The feeds and boluses were analysed for Ca, Mg, S, Mn, Mo, Cu, Zn, and Ti. Bolus composition could be used to predict dietary levels of Ca, S, Cu, and Mg with reasonable precision (error <± 9 per cent), but feed concentrations of Mo and Mn could be predicted only with an error of ±15 per cent. Levels of Zn in boluses could not be used to predict dietary levels, since bolus Zn greatly exceeded that of the feed. The presence of Zn in bovine saliva was demonstrated. Concentrations of Ti in feeds and boluses were in close agreement; measurement of Ti in boluses appears to provide a potentially useful method for the identification of those contaminated with soil during grazing studies.