体外发酵技术研究秸秆粗饲料营养价值及降解特性

Evaluation of the nutritive value and dynamic digestibility characteristics of roughage forage by in vitro fermentation

为了探究粗纤维饲料对反刍动物的营养特性,本试验研究了2种农作物秸秆（稻秸,麦秸）的发酵特性和动态降解率。试验分3组（稻秸组,麦秸组,混合组：50%稻秸＋50%麦秸）,采用瘤胃体外发酵技术,测定粗饲料的发酵参数变化。结果表明：三种粗饲料累计产气量和干物质（DM）降解率均随时间延长而增加,产气和DM降解主要集中在12~48 h。发酵12 h时,麦秸组和混合组累计产气量显著高于稻秸组（P〈0.05）,麦秸组和混合组差异不显著。发酵24 h时,麦秸组累计产气量显著高于稻秸组和混合组（P〈0.05）,稻秸组和混合组差异不显著。发酵36~72 h时,累计产气量均呈现麦秸组〉混合组〉稻秸组（P〈0.05）。发酵24 h时,稻秸组干物质降解率、中性洗涤纤维（NDF）降解率、发酵液中氨态氮（NH4-N）浓度均显著高于麦秸组和混合组（P〈0.05）,乙酸浓度显著高于麦秸组（P〈0.05）,而菌体蛋白（MCP）浓度呈现麦秸组〉混合组〉稻秸组（P〈0.05）。发酵48 h时,麦秸组乙酸浓度与酸性洗涤纤维（ADF）降解率均显著高于稻秸组和混合组（P〈0.05）。发酵72 h时,麦秸组ADF降解率显著高于混合组和稻秸组（P〈0.05）。结果提示,禾本科粗饲料在瘤胃内降解规律基本一致,主要发生在12~48 h,稻秸DM、NDF、ADF降解高峰期要早于麦秸及二者混合,稻秸的营养价值略高于麦秸。

This study was conducted to evaluate the nutritive value and dynamic digestibility characteristics of roughage forages. The rice straw and wheat straw were chosen to set three groups（ rice straw,wheat straw,and the mixture： 50% of rice straw ＋ 50% of wheat straw）.They were fermented for 72 h in vitro. Gas production was measured at 6,12,24,36,48,60,72 h. Samples were collected at 0,6,12,24,48 and 72 h for the analysis of dynamic digestibility and fermentation characteristics. Results showed that the gas production and dry matter（ DM） digestibility in three groups were both increased with incubation time. Gas production of wheat straw and the mixture was higher than that of rice straw（ P 〈0. 05）,and there was no significant difference between wheat straw and the mixture after 12 h of incubation. Gas production of wheat straw was significantly higher than that of rice straw and the mixture（ P 〈0. 05）,and there was no significant difference between rice straw and the mixture after 24 h of incubation. 36 ~ 72 h,Gas production ranked wheat straw the mixture rice straw（ P 〈0. 05）. After 24 h of fermentation,DM,neutral detergent fiber（ NDF） digestibility and ammonia nitrogen（ NH4-N） concentration of rice straw were significantly higher than wheat straw and the mixture（ P 〈0. 05）,and acetate concentration of rice straw was much more than that of wheat straw. MCP concentration were significantly lower（ P 〈0. 05）. After 48 h of fermentation,acetate of wheat straw was higher than that of rice straw（ P 〈0. 05）. After 48 and 72 h of fermentation,ADF digestibility of wheat straw was significantly higher than that of rice straw and the mixture（ P 〈0. 05）. In conclusion,the fermentation profiles of rice straw and wheat straw were similar and the straws were mainly degraded over 12-48 h.