Abstract:
Animal Production in Australia THE POTENTIAL INTAKE AND GROWTH RATE OF YOUNG CATTLE FED A PREDOMINANTLY CASSAVA BASED DIET G.D. TUDOR* and K.R. McGUIGAN* The results of a trial investigating the nutritive value of a cassava diet (Tudor and Norton 1982) suggest that cattle fed a high energy diet should perform as well on cassava as on cereal grain. However, it is not known if digestive problems will occur in animals fed to appetite on a high soluble starch diet or what type of nitrogen (N) supplement is required to alleviate the low protein content of the tubers. The performance of eight-month old, individually stalled Droughtmaster steers, fed pelleted diets of either cassava or cereal grain, were compared over 89 days. The initial fasted liveweight (& SD) was 173 + 8.lkg. The cassava tubers (4.7 CP in DM) were supplemented with either NPN (urea, 4%) or true protein (TP, meat and bone meal, 15X), but the grain was only supplemented with NPN. The cassava (chipped, dried and rolled) and grain (finely rolled sorghum) were prepared as concentrate mixes with minerals (Gartner and O'Rourke 1977) and the necessary N supplement. The concentrate mix was pelleted with lucerne meal (23.4% CP) in the proportion of 9O:lO. The crude protein content of the grain, cassava + NPN, and cassava + TP diets were 18.2, 19.8 and 18.4%, respectively. Performance measurements included voluntary food consumption (DMI), growth rate (GR), feed conversion efficiency (FCE), apparent digestibility of organic matter (DOM) 9 and rumen VFA concentrations. The data were analysed by least square analysis of variance with growth rates calculated by regressing liveweight against time. Animals on the cassava diet with the TP supplement had lower growth rates kand intakes than those fed the sorghum grain diet, with the animals fed cassava plus NPN having the lowest growth rate and intake. The apparent digestibilities of organic matter of the cassava diets were better than the grain diet but the feed conversion efficiencies were slightly lower. Rumen fluid analyses showed there was a lower ratio of Ac:Pr in animals fed grain compared with cassava. Butyric acid concentrations in the rumen of cassava fed animals was nearly twice that for grain fed animals. At these levels of N in the diets the results show that cattle perform well on a cassava diet provided it is supplemented with a true protein. GARTNER, R.J.W., and O'ROURKE, P.K. (1977). Aust. J. Exp. Agric. Anim. Husb. 2: 214. TUDOR, G-D., and NORTON, B.W. (1982). Proc. Aust. Soc. Anim. Prod. 14: 599. * Department of Primary Industries, Animal Research Institute, Yeerongpilly, Qld 4105. 600
