THE INCIDENCE OF BLOAT ON PASTURES DIFFERING IN K:Na RATIO

Abstract

The effect on bloat of increasmg the concentration of Na in herbage was investigated in two experiments at Ruakura. NaCl fertiliser applied at 190-200 kg/ha to pastures containing ryegrass and white clover increased the concentration of Na by two to three times. This resulted in K:Na ratios of 7 to 15 in fertilised herbage compared with 18 to 40 in unfertilised herbage in subsequent spring and autumn periods. Bloat was assessed using cows of high susceptibility to bloat. Under conditions when only moderate bloat was observed, the incidence and severity of bloat on NaCl fertlized areas was similar to or higher than that on unfertilised areas in all seasons. These data do not support suggestions that lowering the K:Na ratlo through use of NaCl fertiliser will control or eliminate bloat. Keywords: NaCl, survey, dairy cows, ryegrass, white clover.