An in vitro gas production experiment was conducted to determine the effect of yeast culture (YC) and cellulolytic enzyme (CE) included in urea-molasses-mineral (UMM) licking blocks on ruminal fermentation characteristics and fibre degradation of wheat straw. Five treatment blocks were: 1. control (CON, no UMM block added), 2. typical block (B), 3. yeast culture block (YCB), 4. cellulolytic enzyme block (CEB) and 5. yeast culture plus cellulolytic enzyme block (YCCEB). The results showed that gas production and both dry matter and cell wall degradabilities were significantly enhanced by supplemental UMM licking blocks (P<0.01), of which the greatest gas production and the fibre degradabilities were found with the treatment YCB, followed by YCCEB, CEB, and B. It is concluded that yeast culture, cellulolytic enzymes or their combination included in licking blocks has a potential to boost rumen fermentation and fibre degradation.