Abstract: In order to evaluate the potential of Broussonetia papyrifera for use in ruminant production as an unconventional feed, three beef cattle aged 24 months, each with a permanent rumen fistula, were used to investigate the degradability characteristics and nutritive value of different plant parts of B. papyrifera. Leaves, leafless branches, and whole plants of B. papyrifera were evaluated with a nylon bag technique, to calculate ruminal energy and nitrogen balance using digestibility and degradation parameters. Tests were carried out for smaller (height 125-135 cm) and larger (height 145-155 cm) plants. It was found that: 1) Crude protein (CP) content of the leaves was 23.18%, which was significantly higher than branches or whole plants of B. papyrifera (P<0.05), while the CP contents of the whole plants were significantly higher than that of the leafless branches (P<0.05). As expected, the pattern of results for acid detergent fiber (ADF) was opposite to that for CP. The ADF content of 125-135 cm whole plants was lower than that of 145-155 cm whole plants (P>0.05). 2) For leaves, values for effective degradability (ED) of dry matter (DM), organic matter (OM), CP and ADF were significantly higher than for whole plants of either height range (P<0.05). Furthermore, leaves and whole plants of B. papyrifera had higher ED of DM, OM, CP and ADF than leafless branches (P<0.05). The ED of DM of all tested B. papyrifera materials was above 40%, and the ED of leaves was up to 66%. 3) The ratio of rumen degradable protein (RDP) to rumen undegradable protein (RUP) of leaves was significantly higher than that of branches or whole plants (P<0.05), indicating that RDP proportion was in leaves. For branches and whole plants, the RDP content was lower than RUP content. 4) Rumen energy nitrogen balance value (RENB) of leaves was negative (-22.27 g·kg^-1) while the RENB values of leafless branches (28.79 g·kg^-1), 125-135 cm whole plants (30.87 g·kg^-1) and 145-155 cm whole plants (27.74 g·kg^-1) were positive. In conclusion, the ranking for nutritive value of the tested B. papyrifera materials was: leaves>125-135 cm whole plants>145-155 cm whole plants>leafless branches. All of the tested materials have the potential for use in high-quality feeds. Leaves can be used as a dietary protein source, while branches or whole plants can be used as roughage. However, energy and nitrogen balance are practical details also needing to be considered.

Key words: Broussonetia papyrifera, whole plant, rumen degradability, cutting height, beef cattle