Bui Van Chinh et al., 1993. Livest. Res. Rural Dev., 5 (1): 6-10

In North Vietnam a farming system of two rice crops and one winter crop system is common but only in the land where the summer rice crop is harvested early. The chance for a winter crop to mature is minor in the land where the summer crop is harvested late. Trials were therefore made to evaluate the use of the land for a forage crop, specifically soybean which was harvested at the flowering stage (60-70 days). The yield was 8,100 kg of green foliage from one ha, which contained 360 kg of crude protein equal to the amount of crude protein normally produced from one ha of soybean harvested as grain. The harvested soybean foliage was chopped and supplemented with rice bran (5 kg rice bran: 100 kg of chopped material) prior to ensiling in a pit. The silage was fed after 60 - 70 days. Crossbred pigs ( Local x Large White) were used as experimental animals. The silage was used to substitute 25-37% of the crude protein in the ration for growing pigs and 20-30% in that for fattening pigs. The silage was palatable. The control diet consisted of (%): rice bran 30.5; maize 50; fish meal 7.5; groundnut cake 7.5; soybean meal 3; mineral premix 1; vitamin premix 0.5. This was partially substituted in the two treatment groups by soybean silage which provided 25.3% or 37.5% of the total protein. Weight gains from 20 to 50 kg were (g/d): 435±33.3, 406±29.0 and 395±27.6. Results during the fattening phase (0, 19, 31% substitution of the protein with soybean foliage) were weight gain (g/d): 610±12, 600±46.7 and 601±12.6. Feed cost for 1 kg of liveweight gain decreased by 24% in the group substituted with 30% protein from ensiled soybean foliage