EFFECT OF TREATING OR SUPPLEMENTING MAIZE STOVER WITH UREA ON ITS UTILIZATION AS FEED FOR SHEEP AND CATTLE

The effects of treatment or supplementation of maize stover with urea were compared in three experiments. Treatment was by the addition of 50 g urea in 200 g of water per kg of stover dry matter (DM) and incubation under plastic sheeting for 5 weeks, to enable hydrolysis of urea to ammonia. In Experiment 1, steers fitted with rumen cannulae and lambs were given stover either untreated (Control), treated with urea (UT) or supplemented with 10 g (W.10) or 30 g (W.30) urea per kg DM applied in solution. Voluntary intake and rumen degradation characteristics of the diets were determined. In steers, daily intake (g per kg weight0.75) was 45.4, 48.4, 51.8 and 78.9 for the Control, W.10, W.30 and UT respectively (P < 0.05). Rate and extent of rumen degradation of stover were improved (P < 0.05) to the greatest extent following treatment with urea. Corresponding values for rumen ammonia levels measured 3 h after the morning feed were 8.1, 12.0, 26.8 and 26.3 mg per 100 ml (P < 0.05). In lambs, intakes (g per kg body weight0.75 per day) were lower, but the general effects of urea treatment or supplementation were similar to those observed with steers. A supplement of cotton seed meal increased intake by an average of 20% across treatments, but did not alter the ranking of the diets. In Experiment 2, the diets were fed to lambs with a supplement of maize meal and no significant differences were observed between diets based on urea supplemented or urea treated maize stover. However, consumption of urea treated and urea supplemented diets was greater than the control. In Experiment 3, urea was either incorporated in maize meal supplement or dissolved in molasses and sprayed onto the stover. In this experiment, urea supplementation increased intake of maize stover, especially when added at 30 g per kg DM (P < 0.05). In both Experiments 2 and 3, nitrogen retention was positively correlated with nitrogen intake (R2 = 0.806; P > 0.05). Data from this study showed no consistent advantage to treating stover with urea compared with supplementing stover with urea. It is suggested that urea-molasses supplements may be a cost-effective alternative.