Pasture samples were collected and analysed for total nitrogen (N), soluble N, and soluble protein N as part of a survey of bloat on North Island dairy farms. Soluble protein N was 35 higher on farms with severe bloat than on farms with no bloat. When a range of animal, soil and plant factors were correlated with bloat, the best multiple correlation (R2= 35,P 0.01) was with cow numbers, soil potassium, clover content of the sward, and soluble protein N. In a subsequent field trial, factors affecting the soluble protein N level in pasture were examined. There was relatively little effect of pasture maturity (5#x2013;32 days regrowth after mowing) on soluble protein N, except for some decline by 32 days regrowth. Clover composition of a sward was important because concentrations of soluble protein N in clover were about 6 times those in grass. N fertiliser application reduced the soluble protein N concentration in clover, and therefore in the mixed sward. The clover content in pasture was also reduced by N application and it is suggested that N fertiliser use may reduce the incidence of bloat.
展开▼
