Bloat in cattle

The presence of protein precipitants in non‐bloating legume pastures is correlated with the presence of flavanols in leaves of these plants. This result is consistent with the precipitants being flavolans (polymeric flavanols). Methods for their detection in pasture plants, a rapid screening test (using vanillin/HCl) to detect flavanols and gel electrophoresis to confirm the presence of flavolans in those plants which contain flavanols, are described. These methods have been applied to the examination of white clover (5000 plants, 70 populations) and red clover (4000 plants, 100 populations). Flavolans were not found in the leaf blades of any of the white or red clover plants, but were found in medium amounts in white and red clover petals and in trace amounts in the stems and extremities of the petioles of some plants. Forty‐two other Trifolium species were also examined for flavolans. T. arvense L. and T. affine L. were the only species that contained flavolans in leaf tissue. The implications of these results are discussed in terms of possibilities for producing bloat‐free plants.