Abstract:
Proc. Aust. Soc. Anim. Prod. 1996 Vol. 21 DECLINE IN NUTRITIVE VALUE OF DRY MATURE ANNUAL LEGUMES DURING SUMMER V.A. ROONEYA , M.E. LATTIMOREB, G. DUDDYB and R.C. KELLAWAYA * M.C. Franklin Laboratory, Dept of Animal Science, University of Sydney, Camden, N.S.W. 2570 * N.S.W. Agriculture, Yanco Agricultural Institute, Private Mail Bag, Yanco, N.S.W. 2703 The nutritive value of dry mature annual legumes declines significantly during the summer months. Much of the loss in nutritive value is due to environmental effects, in particular the leaching effect of rainfall (Rossiter et al. 1994). Most studies on the effect of environment on quality changes in annual legumes have focussed on subterranean clover (Trifolium subterraneum), with few other annual legumes being studied. With wide variability in digestibility values being reported for different genotypes of mature subterranean clover (Taylor et al. 1987), it would follow that different species of Trifolium may also vary widely in their resistance to environmental degradation. Such variation could have important effects on sheep performance. In this study we compared several commercial and experimental lines of annual legumes to identify differences in the rate of decline of digestibility during the summer months. Seven lines of Trzfilium sp. were sown at Yanco, N.S.W. in April 1994. Seed were inoculated with Rhizobia and were sown with 250 kg/ha MO super-phosphate in 3 replicate plots (0.25 ha) on a grey cracking soil. Following a dry December (8.0 mm of rain), samples were harvested during January and February, 1995 and rainfall data recorded. The experiment included Subterranean clover (T. subterraneum cv Junee), Balansa clover (T. michelianum cvs Paradana and 045855) and Persian clover (T. resupinatum cvs Kyambro, 132678, 132809 and 26202). The stem fractions were separated and milled through a 1 mm screen and their spectra read on a Near Infrared Spectrophotometer (NIRS). In vitro digestibility was determined using a pepsin-cellulase method (McLeod and Minson 1978) on a subset of the stem samples, which were then used to develop NIRS calibration equations to predict the digestibility of all stem samples in the experiment. Table 1. In vitro digestibility (%) of the stem fraction of seven annual Trifohm sp. during the summer . McLEOD, M.N. and MINSON, D.J. (1978) Anim. Feed Sci. TechnoZ. 3: 277-87. ROSSITER, R.C., TAYLOR, G.B. and KLEIN, L. (1994) Aust. J. Exp. Agr. 34: 25-32. TAYLOR, G.B., ROSSITER, R.C., KLEIN, L. and COLLINS, W.J. (1987) In 'Temperate Pastures: their production use and management,' (Eds J.L. Wheeler, C.J. Pearson and G.E. Robards.) pp. 432-4. (CSIRO: East Melbourne.) 410