THE LATE C.J. GARDENER and A.J. ASH

Division of Tropical Crops and Pastures, CSIRO, Davies Laboratory, Townsville, Queensland, Australia

Abstract

Diet selection in 6 Stylosanthes-grass pastures was studied over 43 months at Lansdown, north-east Queensland. The Stylosanthes accessions were S. humilis cv. Paterson, S. hamata cv. Verano, S. scabra cv. Seca, S. scabra cv. Fitzroy, S. viscosa CPI 34904 and S. viscosa CPI 40264B. They were sown together with Cenchrus ciliaris into native pasture dominated by Heteropogon contortus, Themeda triandra and Bothriochloa spp.
All stylos except 40264B, which did not persist well, contributed significantly to the diet. The proportion of legume in the diet was greatest in the dry season and least in the wet season, when grass was preferred. High levels of dietary nitrogen were maintained for most of the year and cattle grazing the two annual stylos, S. humilis and S. hamata, recorded higher dietary nitrogen levels than those consuming perennial stylos.
Relative preference indices showed that, with the exception of S. humilis, grass was eaten in preference to legume over the duration of the experiment. In Seca and 34904 pastures, increasing legume dominance was associated with an increased selection for grass as the experiment progressed. The implications of such diet selection trends for long-term pasture stability are discussed.