Abstract

The effects on bloat of herbage mass and of removing Poa from pasture was investigated. Twelve paddocks were paired on pasture composition in autumn and Poa seedlings were removed from one paddock in each pair. Each paddock was halved and two levels of herbage mass were established. The resulting treatments, high herbage mass with Poa (H+P), high mass without Poa (H-P), low mass with Poa (L+P), and low mass without Poa (L-P), were grazed by four groups of six cows of high susceptibility to bloat over four 12-day periods in spring. Herbage mass was 814 kg DM higher (P<0.001) before grazing and 518 kg DM/ha higher (P<0.001) after grazing on H versus L.Poa content (% DM) was higher and white clover in +P compared to -P (Poa 11 and 2%, P<0.001; clover 16 and 26%, P<0.001). The average bloat score was highest on L-P and least on H+P and was 2.4 times greater on L than H and 5.5 times greater on -P than +P. Results indicated that bloat could be manipulated by altering herbage mass, but any effect on bloat of Poa was confounded with changes in white clover content.

JL, Dick, and RMW Sumner

Proceedings of the New Zealand Society of Animal Production, Volume 55, , 31-34, 1995