Abstract 257

Eggington,-AR

Dep. Primary Production, Darwin, NT 5794, Australia.

Technical-Bulletin,Department-of-Primary-Production,-Northe n-Territory. 1986, No.91, v + 37 pp.; 65 ref.

Chemical composition of whole leaves of Sorghum plumosum, Themeda triandra and Chrysopogon latifolius were assessed monthly from Oct. 1979 to Sept. 1981. N, P and DDM of these 3 species and Chrysopogon fallax, Heteropogon triticeus, H. contortus, Coelorhachis rottboellioides, Bothriochloa bladhii, Eragrostis spp., Alloteropsis semialata, Sorghum intrans, Eriachne obtusa, E. burkittii and Erythrophleum chlorostachys were assessed at 4- to 6-week intervals from Sept. 1981 to Jan. 1983. All plant samples were collected from an area 5-10 km S. of Adelaide River township. For S. plumosum, T. triandra and C. latifolius, N, P, S and Na contents were deficient throughout the year, Ca was seasonally marginal and K was adequate in terms of published animal requirements. Cu was marginal and Zn, Fe and Mn were above requirements. Similar overall trends were shown by the 11 other species for N and P contents though there was some seasonal variation between species. Mean in vitro digestibility (% DM) for 14 species was 50, 43, 44, 43, 36 and 39% for early wet, mid-wet, late wet, transition, early dry and late dry seasons, resp., leading to a reduction in DM intake from mid-wet to the end of the dry season. Burning during the early dry season increased the nutrient content of the regrowth to a level similar to that at the beginning of the wet season. Faecal N and P levels from Brahman cross breeders followed a similar trend to that for pasture levels.