Biomass production and nutritive value of Kenaf (Hibiscus cannabinus) at various stages of growth

This study has investigated the chemical composition and in vitro digestibility of leaves and stems of Kenaf (Hibiscus cannabinus L.) harvested throughout the growing season. Kenaf (‘Everglades 41’) was planted in June 2011 and harvested at 25, 50 and 75 days after planting (DAP). Crude protein (CP) in leaves was more (P < 0.01) than double than in stems harvested at the same growth stage. Protein concentration in leaves decreased (P < 0.01) as harvesting date was delayed from 50 to 75 DAP, whereas no significant changes in CP were detected in mature stems (75 DAP) as compared to those collected at an earlier stage (50 DAP). Regardless of the maturity stage, cell wall content (NDF and ADF) was higher (P < 0.05) in stems than in leaves. Cell walls were more lignified (P < 0.05) in stems harvested at 50 and 75 DAP and mature leaves (75 DAP) than in young leaves harvested at 25 and 50 DAP. True in vitro dry matter digestibility was lowest (P < 0.05) in mature stems (62%) and highest in leaves harvested at 50 DAP (93%). Conclusively, Kenaf can be grown during the summer season and harvested as a relatively high-quality forage (with high protein content and in vitro digestibility) as early as 50 DAP.