Abstract:
Animal Production in Australia THE NUTRITIVE VALUE OF CASSAVA FOR CATTLE G.D. TUDOR* and B.W. NORTON** Cassava (Manihot esculenta Crantz.)is a tropical shrubby for its starch rich tuberous roots. Although the roots are low 3-5% in DM) the energy concentration is similar to cereal grain 1974) and with yields ranging from l0-25t/ha(dry weight) (Hicks potential as animal feed is large. plant cultivated in crude protein (Muller et al. et - al.1981) the The nutritive value of a cassava diet, dried chipped tubers (3.9% CP in DM) and tops (4.4% CP), was compared with a cereal grain diet, rolled sorghum (11.4%CP) and cotton seed hulls (CSH 4.4% CP) both fed as 80/20 diets, in a 4 x 4 replicated latin square digestibility experiment with periods of 21 days, 14 days adaptation and 7 days collection. Four diets, two cassava and two sorghum, were prepared with either 4 or 8% peanut meal (PM) (C4, C8, S4 and S8) plus minerals and urea. The latter was used to balance the diets with different levels of PM. Animals were fed once daily just above maintenance, with feeding levels based on liveweight recorded at the start of each period. Measurements included apparent digestibility of organic matter (OM), starch and N,N retention and VFA concentrations. The data were analysed by least squares analyses of variance. A diet predominantly of cassava tubers and tops with 4-8% PM supplement was more highly digested than a diet of sorghum grain and similar proportions of PM. The higher digestibility of the cassava due to the higher digestibility of the starch and N fractions which due to a higher digestibility of the cassava tops compared with CSH. as a protein CSH with diet would be may partly be Animals fed cassava utilized absorbed dietary N with a 34% lower efficiency than did steers given the sorghum diet. This lower efficiency may be attributed to the higher levels of urea in the cassava diets (57 and 35%oftotal N for C4 and C8 respectively) compared with the sorghum diets (12 and 0% of total N for S4 and s8 respectively) . The iso-nitrogenous substitition of urea with PM in both diets did not increase N retention or efficiency of N use and suggests the PM is little better than urea as a protein source for these steers. Analysis of the rumen liquor showed there was less propionic and more butyric relative to acetic acid on the cassava diet compared with the grain diet. HICKS, L.N., HAMMER, G.L., FUKAI, S., and HOBMAN, F.R. (1981). 5lst ANZAAS Congress, Brisbane. MULLER, L., CHOU, K.C., and NAH, K.C. (1974). P-P - 19. World Anim. Rev. 12: *Department of Primary Industries, Animal Research Institute, Yeerongpilly, Qld 4105. ** Department of Agriculture, University of Queensland, St. Lucia, Qld 4067. 599