Comparative nutritive value of hay made normally and by desiccation with paraquat

Abstract

In a series of five experiments, hay made by conventional methods was compared with hay made by spraying with paraquat prior to mowing. In all the experiments, chemical composition of the hays was measured and in three of them the hays were fed to sheep. In the first experiment the digestible organic matter intake (DOMI) and digestibility of oaten hay made by the two methods was similar. In the second experiment rapid desiccation was achieved using paraquat on a pasture of Wimmera ryegrass (Lolium rigidum) and subterranean clover (Trifolium subterraneum), but leaf losses during baling were higher than for turning and baling mown herbage. In the third experiment, on a densestand of Wimmera ryegrass, the stem bases were not reached by the paraquat spray and desiccation took 14 days longer than with mowing and turning. In both experiment 2 and 3 sheep consumed similar amounts of DOMIand had similar liveweight changes when fed the two types of hay, although digestibilities were lower for the hays made using paraquat. Also, in these two experiments there were higher concentrations of cell wall constituents, and in experiment 3 lower concentrations of water soluble carbohydrates (WSC), in hay made by using paraquat. In experiments 4 and 5 it was shown that large losses of WSC occurred consistently when herbage on ryegrass pastures was desiccated with paraquat. The effect was shown to occur within 24 hours of application. A further effect, that needs more research, was that the digestibility of cell wall material was lower in hay made with paraquat than in normal hay. It is concluded that the use of paraquat to provide rapid desiccation of herbage is unlikely to result in hay of higher quality than that made conventionally.