Molasses as an energy supplement for zebu steers grazing nitrogen-fertilized and unfertilized colonial guineagrass pasture

Abstract

Molasses supplement increased the gain per animal 36 kg in a 308-day trial (Table 1) and 29.7 kg during a 364-day period in a second trial [Figure 7(a)]. If only the increase in liveweight gain per animal is considered, 24.8 kg of molasses was required for each additional kilogram of liveweight gain. When the molasses was credited for decreasing the consumption of forage and as a consequence increasing the carrying capacity of the pastures, from 9.5 to 14.0 kg of molasses was required to produce an additional kilogram of liveweight gain. Feeding molasses at the rate of 2 kg per steer per day reduced the intake of forage (Figure 8) and as a consequence increased the carrying capacity of the pastures 20 percent [Figure 9 (a)]. Feeding 2 kg of molasses per steer per day increased the liveweight gain per hectare from 246 to 364 kg. [Figure 11(a)], an increase of 118 kilograms. Nitrogen fertilizer at the rate of 100 kg N per ha. increased the protein content of the pasture forage by 2.5 to 3.0 percent (Figure 10). Steers consuming nitrogen-fertilized grass gained an additional 20.5 kg. [Figure 7(b)] over the control animals during the winter-dry seasons, but much of this advantage was lost during the subsequent summer seasons so that the advantage for nitrogen by the end of the summer was only 6.9 kg per steer. The nitrogen fertilizer increased the amount of forage produced per hectare, the amount of T.D.N. per hectare, the carrying capacity of the pastures as measured by steer days per hectare, and the liveweight gain per hectare. A kilogram of nitrogen gave a return of 1.9 kg. of liveweight as an average for the three-year period (Table 10). The combined effects of nitrogens fertilizer and molasses supplement were additive for steers per hectare and liveweight gain per hectare, and there was no interaction between the two factors. A rationale for the put-and-take method is given. Its application to grazing experiments in which factors are being studied that influence the number of animals which the pastures will support and the output of animal product per hectare are carefully examined and discussed.