Energy utilization of rice straw supplemented with urea and molasses in swamp buffalo heifers

Eight swamp buffalo (Bubalus bubalis) heifers (age 10 months; weight 163 kg) were used to study the energy utilization of rice straw supplemented with urea and molasses. The buffalo were kept in individual pens within a barn and allowed rice straw ad libitum as a basal diet. Four of the heifers received rice straw supplemented with 40 g urea (equal to 1% of estimated DMI based on a DM requirement of 2.5% liveweight) and 150 g molasses (equal to 0.1% liveweight). The balance trials were measured by total collections obtained during a 4-day period following a 2-week feed adaptation period. Methane production was measured by the facemask method for 10minutes at 3-hour intervals for 2 days immediately after the 4-day period ended and was then converted to daily total production. The data were analyzed with the t-test. The results showed that supplementation of rice straw with urea-molasses increased dry matter intake (DMI, 3133 vs 2626 g/d; P<0.05), nitrogen intake (NI, 41.4 vs 20.1 g/d; P<0.001) and gross energy intake (GEI, 48.1 vs 41.5 MJ/d; P<0.05). Furthermore, the supplementation reduced methane production (4.7 vs 5.2 MJ/d, equal to 9.7 vs 12.7% of GEI; p<0.05)). However, the supplementation did not increase the intake of DE (14.2 vs 14.6 MJ/d) or of ME (8.9 vs 8.9 MJ/d).The reasons why the supplementation did not increase the heifers’ energy utilization of rice straw in this experiment are that the amount of supplementation and the ratio of urea to molasses were not optimal. We should clarify both the amount and the ratio of these supplements to improve the energy utilization of rice straw by swamp buffalo heifers.