Ordakowski A L, Kronfeld D S, Holland J L, Hargreaves B J, Gay L S, Harris P A, Dove H, Sklan D
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061, USA.
J Anim Sci. 2001 Jun;79(6):1516-22. doi: 10.2527/2001.7961516x.
Dry matter intake (DMI), dry matter digestibility (DMD), and fecal output (FO) are difficult to measure directly in the field, and indirect methods using external and internal markers have thus been developed. An experiment was conducted consisting of two digestion trials with two periods in each trial to examine the use of five odd-chain alkanes (C25 to C33) of plant cuticular wax as internal markers to estimate DMD of hay or hay plus concentrate diets in horses. Eight mature Thoroughbred geldings were housed in 4- x 4-m stalls and randomly assigned to one of two mixed grass/legume hays (Diets 1 and 2) in Trial 1 and to mixed grass/legume hay plus one of two concentrates (Diets 3 and 4) in Trial 2. After the first 12-d period was conducted, dietary assignments for each group were switched for the second period in each trial. Each period consisted of a dietary accommodation from d 1 to 7 and total fecal collection from d 8 to 11. Results indicated that fecal recoveries of odd-chain alkanes were 88 to 90% for Diet 1, 75 to 92% for Diet 2, 71 to 81% for Diet 3, and 71 to 82% for Diet 4. Alkane recoveries were not related to alkane chain lengths. Digestibilities calculated from alkane concentration data adjusted using the mean fecal recovery of individual odd-chain alkanes (DA1) were not significantly different from the digestibilities estimated from total collection (DTC) for Diets 1 and 2 in Trial 1 and Diets 3 and 4 in Trial 2. When adjustment was based on the mean recovery of all alkanes (DA2; estimated by linear regression), all DA2 estimates for horses offered all diets were similar to DTC. Results indicate that accurate mean estimates of DMD can be obtained by using plant wax alkane markers and adjusting for the mean recovery of five odd-chain alkanes in a diet.
干物质采食量（DMI）、干物质消化率（DMD）和粪便排出量（FO）很难在野外直接测量，因此已开发出使用外部和内部标记物的间接方法。进行了一项实验，包括两个消化试验，每个试验有两个阶段，以研究使用植物表皮蜡的五种奇数碳链烷烃（C25至C33）作为内部标记物来估计马干草或干草加精料日粮的DMD。八匹成年纯种阉马被安置在4×4米的马厩中，在试验1中随机分配到两种混合禾本科/豆科干草（日粮1和日粮2）之一，在试验2中随机分配到混合禾本科/豆科干草加两种精料之一（日粮3和日粮4）。在第一个12天阶段结束后，每个试验中每个组的日粮分配在第二个阶段进行了切换。每个阶段包括从第1天到第7天的日粮适应期和从第8天到第11天的粪便全收集期。结果表明，日粮1的奇数碳链烷烃粪便回收率为88%至90%，日粮2为75%至92%，日粮3为71%至81%，日粮4为71%至82%。烷烃回收率与烷烃链长度无关。根据使用单个奇数碳链烷烃平均粪便回收率（DA1）调整后的烷烃浓度数据计算的消化率，与试验1中日粮1和日粮2以及试验2中日粮3和日粮4通过全收集估计的消化率没有显著差异。当基于所有烷烃的平均回收率（DA2；通过线性回归估计）进行调整时，所有日粮组马匹的所有DA2估计值均与全收集法（DTC）相似。结果表明，通过使用植物蜡烷烃标记物并根据日粮中五种奇数碳链烷烃的平均回收率进行调整，可以获得准确的DMD平均估计值。
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