Role of Pasture Composition and Grazing Management in Affecting the Incidence of Bloat on Farms

Farm operations, pasture composition and pre- and post-grazing association with herbage mass were monitored from May 1990 to November 1991 on 16 pairs of dairy farms. Each pair included one farm with a history of bloat despite routine use of chemical preventatives (bloat-prone) and one farm which did not routinely use chemicals to prevent bloat rarely observed bloat (bloat-free). The incidence of bloat during spring was low in both years. From August to November bloat-free farms had less ryegrass (Lolium) (58%, v. 66%) and more other grass species (25% v. 17%) in pasture, and higher pre- and post-grazing herbage masses than bloat-prone farms in both years. There were no differences between bloat-free and bloat-prone farms in white clover (Trlfolium repens) content of pasture, soil fertility, production or outbreaks within a season. The factors contributing to variations in stocking rate. The differences in pasture species and grazing levels indicate different management practices for the two groups, but an association with bloats could not be reliably assessed because of the mild bloating challenge during the trail period