Bui Van Chinh et al., 1992. Livest. Res. Rural Dev., 4 (3): 6-9

An important economic issue, which has not been adequately evaluated, is the relative effectiveness of ammoniation using urea as compared with supplementing untreated rice straw with a molasses-urea block. The present trial was designed to compare these two systems. Growing crossbred heifers (Sindhi X Local Yellow cattle) were fed either (ARS) ammoniated rice straw (ensiled with 2.5 kg urea, 0.5 kg of lime [Ca(OH)2] and 0.5 kg of salt/100 kg air dry straw) or untreated straw and a molasses-urea block (MUB) (final molasses 50, urea 10, salt 5, lime 8, sugar cane bagasse 27%). Growth rates were consistently higher on the ammoniated straw compared with the MUB supplemented untreated straw. Improvement was 25% (P=.001) mainly because of an almost 50% increase (P=.001) in intake of straw when it was ensiled with urea. Total DM intake also tended to be higher with the ammoniated straw treatment (P=.13) but the slight differences in feed conversion were not significant (P=.42). On both treatments the straw was offered at levels only slightly exceeding measured intake (about 20% above) thus there was little opportunity for selection. It is possible that if, in the present experiment, the untreated straw had been offered at a much higher level (100% above intake) then growth performance would have been the same on both treatments but with cost advantages for the MUB treatment. This hypothesis will be tested in the next series of trials on this topic.