Abstract:

The aim of this study was to determine the effects of cellulase treatment on the fiber structure and nutrient composition of buckwheat straw， the quantity of microbes in fermented buckwheat straw， and the mutton quality of Tan sheep fed with the treated straw. This experiment was divided into two parts； the first part consisted of enzyme treatments， and the second part was a feeding test. The enzyme treatment experiment had three groups： the control group （unprocessed buckwheat straw）， trial group Ⅰ （cellulase Ⅰ treatment of buckwheat straw）， and trial group Ⅱ （cellulase Ⅱ treatment of buckwheat straw）. Each group had three replicates. Buckwheat straw with enzymes was sealed and stored in a fermenting tank for 30 days and then sampled. The fiber structure， nutrient composition， and microorganism abundance in buckwheat straw before and after the enzyme treatments were analyzed. In the feeding experiment， 24 healthy 3-month-old Ningxia Tan sheep with similar body weight were randomly assigned to three groups （eight sheep/group）.The ratio of basal diet to forage was 30∶70. The control group was fed basal diet+unprocessed buckwheat straw， trial group Ⅰ was fed basal diet+buckwheat straw treated with cellulose Ⅰ， and trial group Ⅱ was fed basal diet+buckwheat straw treated with cellulose Ⅱ. The preparation period was 15 d， and the formal experimental period was 60 d. At the end of the formal experimental period， five Tan sheep with approximately equal body weight were selected from each group and slaughtered after fasting for 24 hours. Then， the physicochemical indexes and nutrient contents of the mutton were determined. The main results were as follows： 1） The cell wall fibrous structure of untreated buckwheat straw remained intact， while that of buckwheat straw treated with cellulase was disrupted to different degrees； 2） The acid detergent fiber content of buckwheat straw in trial group Ⅰ and trial group Ⅱ was reduced by 18.71% and 13.78%， respectively， compared with that in the control group （P<0.05）， and the neutral detergent fiber content of buckwheat straw in trial group Ⅰ and trial group Ⅱ was reduced by 19.75% and 17.81%， respectively， compared with that in the control group （P<0.05）； 3） The contents of lactic acid bacteria were higher in the cellulase-treated groups than in the control （P<0.05）， and the contents of molds were lower in the cellulase-treated groups than in the control （P<0.05）； 4） Compared with mutton from sheep in the control group， mutton from sheep in trial group Ⅱ showed a significantly improved muscle cooked meat rate （P<0.05）， and that from sheep in trial groups Ⅰ and Ⅱ showed a reduction in shear force by 9.31% and 11.84%， respectively （P<0.05）； 5） The crude protein content of mutton from sheep in trial group Ⅰ and trial group Ⅱ was increased by 14.22% and 14.23%， respectively， compared with mutton from sheep in the control group （P<0.05）. In summary， these results show that cellulase treatment can effectively degrade the fiber structure and improve the nutrient status of buckwheat straw， thereby enhancing its feed quality. Ultimately， this leads to better meat quality. Under these experimental conditions， treatment with cellulase Ⅰ provided the best improvement in the feed quality of buckwheat straw.

Key words: cellulase, buckwheat straw, fiber structure, feed quality, Tan sheep, meat quality