Influence of replacing rice straw with wormwood (Artemisia montana) silage on feed intake, digestibility and ruminal fermentation characteristics of sheep

An experiment was conducted to examine feed intake, apparent digestibility, N balance and ruminal fermentation characteristics of sheep fed diets containing increasing levels of wormwood (Artemisia montana) silage (WS). The experimental design was a 4 × 4 Latin square with four sheep in four 20 day periods. Sheep were fed a diet consisting of 700 g/kg DM rice straw, wormwood silage mix and 300 g/kg DM concentrates, and allotted to one of four treatments in which wormwood silage replaced 0 g/kg DM (Control), 50 g/kg DM (LWS), 100 g/kg DM (MWS) and 150 g/kg DM (HWS) of the rice straw. Intakes of dry matter (DM), organic matter (OM), crude protein (CP), ether extract (EE), neutral detergent fibre (aNDF) and acid detergent fibre (ADF) increased quadratically (P<0.01) as the dietary WS level increased. The digestibility coefficients of DM (P<0.01), OM (P<0.05), CP (P<0.01), EE (P<0.001) and ADF (P<0.01) linearly increased with increasing dietary WS level. Nitrogen intake, microbial N yield, and efficiency of microbial N synthesis linearly increased (P<0.001) as the dietary WS level increased. Furthermore, rumen pH was linearly decreased (P<0.05), while rumen NH3-N (P<0.01) and total VFA (P<0.05) concentrations were linearly increased as the dietary WS level increased. Acetic acid concentration was not affected by increasing the level of WS substitution, but propionic (P<0.001) and butyric acid (P<0.05) concentrations increased quadratically, while the ratio of acetic acid to propionic acid decreased quadratically (P<0.001). Substituting rice straw with up to 150 g/kg DM of wormwood silage improved feed intake, digestibility, N retention and microbial N yield in finishing sheep.