Palmonari A, Fustini M, Canestrari G, Grilli E, Formigoni A
Department Of Veterinary Medicine, Università di Bologna, 40084 Bologna, Italy.
Department Of Veterinary Medicine, Università di Bologna, 40084 Bologna, Italy.
J Dairy Sci. 2014 Dec;97(12):7729-34. doi: 10.3168/jds.2014-8123. Epub 2014 Sep 26.
This study focused on changes in fibrous and protein fractions, changes in fiber digestibility and amount of indigestible neutral detergent fiber (NDF) as a consequence of increased maturity in alfalfa. A total area of 720 m(2) was divided in 18 blocks randomly assigned to 3 treatments, differing in cutting intervals. Treatment 1 was harvested with a 21-d cutting schedule, at a prebloom stage; treatment 2 with a 28-d schedule, at about first-bloom stage; whereas a full bloom was observed in treatment 3, harvested with a 35-d cutting schedule. Treatments were replicated 4 times through the spring-summer period for 2 subsequent years, 2011 and 2012. Statistical differences were observed for crude protein [treatment 1: 20.8%, treatment 2: 17.3%, and treatment 3: 17.0%; standard error of the mean (SEM)=0.83], soluble protein, and nonprotein nitrogen among treatments on a dry matter basis. Similar results were observed for acid detergent lignin (6.3, 6.9, and 7.3%, respectively; SEM=0.39), lower in treatment 1 compared with others, and in vitro NDF digestibility at 24 or 240 h. Indigestible NDF at 240 h resulted in lower values for treatment 1 compared with treatments 2 and 3 (15.5, 17.2, and 18.3%, respectively; SEM=1.54). Moreover, the indigestible NDF:acid detergent lignin ratio varied numerically but not statistically among treatments, being as much as 9% greater than the 2.4 fixed value applied for rate of digestion calculation and Cornell Net Carbohydrate Protein System (Cornell University, Ithaca, NY)-based model equations. Assuming the diet composition remained unchanged, treatment 3 (35-d cutting interval) would be expected to yield 1.4 kg less milk per day based on energy supply, and 2.8 kg less milk daily based on protein supply than treatment 1.
本研究聚焦于苜蓿成熟度增加导致的纤维和蛋白质组分变化、纤维消化率变化以及不可消化中性洗涤纤维（NDF）含量变化。720平方米的总面积被随机分为18个区组，分配给3种处理方式，其刈割间隔不同。处理1在初花期按21天的刈割计划进行收获；处理2在大约始花期按28天的计划进行收获；而处理3在盛花期按35天的刈割计划进行收获。在2011年和2012年这随后的两年里，春夏期间各处理重复4次。在干物质基础上，各处理间粗蛋白[处理1：20.8%，处理2：17.3%，处理3：17.0%；平均标准误（SEM）=0.83]、可溶性蛋白和非蛋白氮存在统计学差异。酸性洗涤木质素也有类似结果（分别为6.3%、6.9%和7.3%；SEM=0.39），处理1低于其他处理，以及24或240小时的体外NDF消化率。与处理2和3相比，处理1在240小时时不可消化NDF值更低（分别为15.5%、17.2%和18.3%；SEM=1.54）。此外，各处理间不可消化NDF与酸性洗涤木质素的比值在数值上有所不同，但无统计学差异，比用于消化率计算和基于康奈尔净碳水化合物蛋白质系统（纽约州伊萨卡市康奈尔大学）的模型方程所采用的2.4固定值高出多达9%。假设日粮组成不变，基于能量供应，预计处理3（35天刈割间隔）每天产奶量比处理1少1.4千克，基于蛋白质供应则每天少2.8千克。
