This study was conducted to observe changes in chemical composition according to plant height at harvest of a sorghum × sudangrass hybrid and silage quality during fermentation. The sorghum × sudangrass hybrid (Sorghum bicolor(L.) Moench) cultivar‘Turbo Gold’was sown on May 27, 2024, in the Pyeongchang area. The cultivated samples were harvested and analyzed when plant height reached 50 cm (July 3), 100 cm (July 10), 150 cm (July 22), and 200 cm (July 30). In addition, samples harvested on August 22 were prepared as silage and opened after 0, 1, 2, 3, 5, 10, 15, 30, 45, and 60 days to evaluate changes in silage quality. The crude protein(CP) content was 7.35% in the 200 cm harvest group, and it was higher in the leaves (9.53%) than in the stems (4.81%). The acid detergent fiber(ADF) and neutral detergent fiber(NDF) contents increased as plant height increased. Digestibility did not differ significantly among plant parts, but it differed markedly according to plant height at harvest. The total digestible nutrients(TDN) tended to decrease with increasing plant height, and the relative feed value(RFV) averaged around 90. The water soluble carbohydrate(WSC) content also increased significantly with increasing plant height. Nitrate nitrogen content generally tended to decrease in the leaves as plant height increased, whereas it increased in the stems. CP content showed the highest value on day 5 of fermentation and then gradually decreased. The pH gradually decreased over time and, in particular, dropped rapidly to below 4.0 within the first 5 days. Ammonia nitrogen content gradually increased as fermentation progressed, with most of the increase occurring within the first 5 days of fermentation. Regarding the correlations among quality-related parameters, CP content showed a weak correlation with digestibility, while ADF content showed strong negative correlations with pH, WSC. These results indicate that, when the crop is harvested at a generally appropriate stage, nitrate-nitrogen in the sorghum × sudangrass hybrid does not reach a level harmful to livestock. In addition, nitrate-nitrogen did not reach a harmful level during the silage fermentation process.

ABSTRACT
Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Cultivation of Sorghum × Sudangrass Hybrid
    2. Harvesting of Sorghum × Sudangrass Hybrid
    3. Analysis of Feed Value
    4. Silage Analysis
Ⅲ. Results and Discussion
    1. Changes in Feed Value According to Cutting Heightand Plant Part
    2. Changes in Feed Value According to FermentationPeriod
    3. Changes in Silage Quality According to FermentationPeriod
    4. Correlations Among Silage Quality Parameters
Ⅳ. CONCLUSIONS
Ⅴ. ACKNOWLEDGEMENT
Ⅵ. REFERENCES

• Xaysana Panyavong(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea)
• Yan Fen Li(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea)
• Ikram Muhammad(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea)
• Jong Geun Kim(Graduate School of International Agricultural Technology, SNU, Pyeongchang 25354, Republic of Korea, Research Institute of Eco-friendly Livestock Science, GBST, SNU, Pyeongchang 25354, Republic of Korea) Corresponding author
• Li Zhuang Wu(Research Institute of Eco-friendly Livestock Science, GBST, SNU, Pyeongchang 25354, Republic of Korea)