Abstract:
THE UTILIZATION OF THE DIETARY ENERGY OF TWO TROPICAL GRASSES BY YOUNG GROWING BEEF CATTLE G.D. TUDOR* and D.J. MINSON Although the apparent, digestibility of setaria (S. sphacelata 'var. sericea cv. Nandi) is generally equal or better than pangola (Digitaria decumbens) at' the same stage of growth (Wnson 1972), the productivity of the former is generally lower than the latter (Stobbs and Sandland 1972). ' The efficiency of utilization of the metabolizable energy (ME=O.H5DE) and the net energy (NE) concentration of the two grasses were determined using a comparative slaughter technique in which 12 steers were individually fed each grass for 152 days at three levels of intake. Twelve similar steers were slaughtered initially for analysis. Energy retention between final and initia.1 animals'was used to calculate, by' regression methods, the efficiency of utilization of metabolizable energy for fattening (kf), and the. NEf values of 'the two grasses. A concurrent experiment determined the digestible energy (DE). of the two grasses. TAB&E 1: The efficiency of utilization of the calculated metabolizable energy and the NE concentration of pangola and setaria, both with similar energy and nitrogen values. Although intakeswere similar, the NEf and kf values for pangola w.ere higher (PcO.01) than for setaria and appear to be a factor causing differences in productivity between the two grasses. The kf value for these tropical grasses are lower than values reported for temperate grass species and may account I'or the lower level of production of cattle which graze tropical'grasses. It is concluded that kf values as we11 as intake and digestibility must be taken into account when evaluating grasses in animal production systems. MINSON, D.J. (1972). Aust. J. exp. Agric. Anim. Husb. 12 : 21. STOBBS, T.H., and SANDLAND, R.L. (1972). Aust. J., exp. Agric. Anim. Husb. 12 : 463. k Department of Primary Industries,.Animal Research Institute, Yeerongpilly, Queensland, 4105. + CSIRO, Division of Tropical Crops and Pastures; Cunningham Laboratory, St. Lucia, Queensland, 4067.
