Study On The Yield And Nutritive Value Of Different Sweet Sorghum

Sorghum is the fifth-largest crop after wheat, corn, rice and barley in the world. Sweet sorghum as an ordinary sorghum's variety has a chance to become a preferred forage crop. Promoting full use of sweet sorghum can provide sufficient feed for herbivorous livestocks and poultry, and it is an effective measure to promote the development of milk cow industry. However, with the increasing of national demand for milk products and the decreasing of forage planting area, sweet sorghum is a good choice to develop animal husbandry due to its high yield and good silage quality, especially in the south China. This paper compared five varieties of forage sorghums: Dalishi, Lvjuren, Desheng, Sorghum�Sudan grass, and B6. These sorghum varieties were cultivated on the Zengcheng Experimental Field of South China Agricultural University in Guangzhou, and their agronomic traits and nutritive value were studied, so as to select the suitable sorghum varieties. By adding different lactic acid bacteria to research the silage fermentation quality at different times, and research the removal efficiency of ensiling on hydrogen cyanide and tannin. The main findings were as follows:(1) Based upon biomass production, nutrition composition, feeding value and silage ease, B6 was the best variety for growing in Guangzhou. The DM yield of five sorghum varieties ranged from 4.28 to 20.35 t/hm2. Among them, Dalishi and B6 were the highest(reached 20.35 t/hm2 and 19.15 t/hm2, respectively), significantly higher than the other varieties(P<0.05). Crude protein contents were ranged from 0.24 to 1.14 t/hm2. Among them, B6 was the highest, significantly higher than the other varieties(P<0.05). The relative feeding value of Dalishi and B6 were 83.60 and 80.64, respectively, significantly higher than the other varieties. Sweet sorghum B6 had good growth potential(average height 337.3 cm, diameter 19.99 cm), its dry matter yield was the largest, the crude protein content and forage value were also higher than other sorghum varieties. In addition, it Had high content of water-soluble carbohydrate. Therefore, B6 was the best variety of five forage sorghum varieties.(2) Three kinds of additives(lactic acid bacteria YM3, YM8 and complex bacteria BPS) were added to B6 sorghum at ensiling. Under this experimental conditions, lactic acid bacteria population in YM3 added silage was significantly higher than the other additives(P<0.05). The p H of silage reduced at first days and rose after ensiled for 7 days. The number of lactic acid bacteria was in the order YM8 silage < BPS silage < control silage(P <0.05). In the whole process, adding YM3 produced more lactic acid, less butyric acid and ammonia nitrogen. Thus, the fermentation quality of YM3 added silage was the best.(3) The removal rates of hydrogen cyanide and tannin by ensiling were 40.56 to 40.88% and 64.39% to 71.21%, respectively. The removal effects to hydrocyanic acid were not significant(P>0.05) among additives. While for the removal efficiency of tannin by ensiling, YM3 added silage had the lowest content of tannin(0.38% DM), the removal rate was 71.21%. Thus, its removal effect was the best, and significantly(P < 0.05) higher than BPS and the control. After ensiling for 60 days, the tannin of YM8 added silage was the most(0.47% DM), its removal rate was only 64.39%.