Effects of cellulase treatment of buckwheat straw on production performance of barn feeding Tan sheep and its economic benefit

The purpose of this experiment was to study the effects of cellulase treatment of buckwheat straw on growth performance, digestion and metabolism, and slaughter performance of Tan sheep in Yanchi County, Ningxia. Twenty-four healthy three-month-old Ningxia Tan sheep with similar body weights were randomly split into three groups of eight. The ratio of concentration to forage was 30∶70. The control group was fed a basal diet and unprocessed buckwheat straw. Trial group Ⅰ was fed a basal diet and buckwheat straw treated with cellulase Ⅰ (enzyme activity ≥ 10 000 U·g⁻¹). Trial group Ⅱ was fed a basal diet and buckwheat straw treated with cellulase Ⅱ (enzyme activity ≥ 5 000 U·g⁻¹). The preparation period was 15 d, and the formal experiment period was 60 d. Digestion and metabolism tests were carried out in the midway point and near the end of the feeding test feeding test. After the end of the formal experiment period, 5 Tan sheep with approximately equal body weight were selected from each group and slaughtered after fasting for 24 h to determine slaughter performance indexes. The results showed the following: 1) Cellulase treatment of buckwheat straw can improve the average daily weight gain and economic benefit of Tan sheep. Cellulase Ⅰ and cellulase Ⅱ treatment of buckwheat straw increased the average daily weight gain by 31.46% and 10.68%, respectively, compared to that of the control group (P > 0.05). The ratio of feed to gain of trial group Ⅰ was the lowest of the 3 groups at 7.28, which was significantly different from the control group (P < 0.05). 2) The apparent digestibility of dry matter (DM) and neutral detergent fiber (NDF) was significantly increased by 16.96% and 10.45% after treatment of buckwheat straw with cellulase Ⅰ (enzyme activity ≥ 10 000 U·g⁻¹) (P < 0.05). 3) Cellulase treatment of buckwheat straw may reduce fecal and urinary nitrogen (P > 0.05), and significantly improve nitrogen retention, along with the utilization efficiency of nitrogen (P < 0.05). The digested nitrogen and apparent biological value of nitrogen of trial group Ⅰ were significantly increased by 13.09% and 14.28% more than control group (P < 0.05). 4) Cellulase Ⅰ (enzyme activity ≥ 10 000 U·g⁻¹) treatment of buckwheat straw significantly improved the carcass weight, slaughter rate, and net meat weight of Tan sheep (P < 0.05), and the bone weight and loin eye area of trial group Ⅰ were significantly higher than those of the control group (P < 0.05). In summary, cellulase treatment of buckwheat straw can improve the average daily weight gain and carcass weight of sheep, reduce the ratio of feed to gain, increase the deposition of nitrogen, and reduce nitrogen emissions of house-fed Tan sheep to some extent. Under these experimental conditions, cellulase Ⅰ demonstrated the best effects.