不同含水量和糖蜜添加量对青贮杂交构树发酵品质、营养成分和瘤胃降解特性的影响

Effects of Different Moisture Contents and Molasses Adding Levels on Fermentation Quality,Nutrient Composition and Rumen Degradation Characteristics of Hybrid Broussonetia papyrifera Silage

本试验旨在研究不同含水量和糖蜜添加量对青贮杂交构树发酵品质、营养成分和瘤胃降解特性的影响。采用2×4两因素试验设计,其中含水量分别为73%(新鲜构树)和60%(萎蔫构树),糖蜜添加量分别为0(对照)、2.5%、5.0%和7.5%。将全株杂交构树切短至1~2 cm,按照试验设计混匀后装入透明聚乙烯袋中,密封后于室温避光发酵90 d。选用3头装有永久性瘤胃瘘管的健康泌乳荷斯坦奶牛(体重约650 kg)测定青贮样品的瘤胃降解率,并采用体外法测定瘤胃未降解残渣养分的小肠消化率。结果表明:1)所有糖蜜添加组的青贮杂交构树感官评价均达到德国农业协会评价等级1级(优良)标准。2)随着含水量的降低和糖蜜添加量的升高,乳酸含量显著升高(P<0.05),pH和氨态氮(NH3⁃N)含量显著降低(P<0.05),且上述指标随着糖蜜添加量的升高呈二次变化(P<0.05);除2个对照组和73%含水量+2.5%糖蜜组外,其余组均为未检出丙酸和丁酸。3)随着含水量的降低和糖蜜添加量的升高,粗蛋白质(CP)、非纤维性碳水化合物(NFC)和可溶性碳水化合物(WSC)含量显著升高(P<0.05),中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、酸性洗涤木质素(ADL)、纤维素、半纤维素、中性洗涤不溶性粗蛋白质(NDICP)和酸性洗涤不溶性粗蛋白质(ADICP)含量显著降低(P<0.05),且上述指标随糖蜜添加量的升高呈二次变化(P<0.05)。4)降低含水量和添加糖蜜可显著提高青贮杂交构树养分瘤胃降解率和过瘤胃CP小肠消化率(P<0.05)。综上可知,降低含水量和添加糖蜜有利于提高杂交构树青贮品质,改善青贮杂交构树营养价值,在60%含水量条件下添加2.5%~5.0%糖蜜即可获得优质的杂交构树青贮饲料。

This experiment was conducted to study the effects of different moisture contents and molasses adding levels on fermentation quality,nutrient composition and rumen degradation characteristics of hybrid Broussonetia papyrifera silage.A 2×4 twofactor experimental design was adopted,in which the moisture content was 73%(fresh)and 60%(wilted),and the molasses adding levels were 0(control),2.5%,5.0%and 7.5%,respectively.The whole hybrid Broussonetia papyrifera was cut to 1 to 2 cm,mixed according to the experimental design,put into transparent polyethylene bag,and sealed and fermented at room temperature for 90 days away from light.Three healthy lactating Holstein cows with permanent rumen fistulas(body weight about 650 kg)were used to determine the rumen degradation rate of silage samples,and the small intestinal digestibility of undegraded rumen residual nutrients was determined by in vitro method.The results showed as follows:1)the sensory evaluation of the hybrid Broussonetia papyrifera silage in all molasses adding groups reached the evaluation grade 1(excellent)standard of German Agricultural Society.2)With the decrease of moisture content and the increase of molasses adding level,the lactic acid content was significantly increased(P<0.05),pH and ammonia nitrogen(NH3N)content were significantly decreased(P<0.05),and the above indices showed a quadratic change with the increase of molasses adding level(P<0.05);no propionic acid and butyric acid were detected in all the other groups except 2 control groups and 73%moisture content+2.5%molasses group.3)With the decrease of moisture content and the increase of molasses adding level,the contents of crude protein(CP),nonfiber carbohydrate(NFC)and watersoluble carbohydrate(WSC)were significantly increased(P<0.05),while the contents of neutral detergent fiber(NDF),acid detergent fiber(ADF),acid detergent lignin(ADL),cellulose,hemicellulose,neutral detergent insoluble crude protein(NDICP)and acid detergent insoluble crude protein(ADICP)were significantly decreased(P<0.05),and the above indices showed a quadratic change with the increase of molasses adding level(P<0.05).4)Reducing moisture content and adding molasses significantly increased the rumen degradation rates of nutrients and rumen CP digestibility in small intestine(P<0.05).In conclusion,reducing moisture content and adding molasses are beneficial to improve the quality and nutritive value of hybrid Broussonetia papyrifera silage,and highquality hybrid Broussonetia papyrifera silage silage can be obtained by adding 2.5%to 5.0%molasses under 60%moisture content.