Bloat in cattle 46. Potential of dock (Rumex obtusifolius) as an antibloat agent for cattle

Abstract

The effect of condensed tannin (CT) in dock (Rumex obtusifolius) was investigated with regard to its ability to protect cows from bloat and in terms of its chemical composition. Two groups of four cows were stall-fed a lucerne/grass diet, with and without 10% dock in the herbage, in a cross-over design. Dock was eaten by all cows. Bloat did not occur when dock was included in the diet but did occur when dock was absent. Soluble protein concentration in rumen liquor was reduced when dock was present, and electrophoretic analysis showed 9% dock dry matter (DM) was able to precipitate 50% of the soluble protein in a 1:9 dock: lucerne mixture. Concentrations of CT in dock whole plants ranged from 1.13 to 2.29% DM, and in the experimental diets ranged between 0.13 and 0.23% ofDM eaten by the cows. The concentration of CT increased with increasing dock maturity. Concentrations were 2-3 times as high in leaf as in stem, and were highest in the inflorescence. Dock had similar nitrogen and fibre contents as lucerne, but the leaves had a high concentration of lignin, which is likely to result in a lower digestibility than lucerne or grass.