摘要
The amount of rumen undegradable protein (RUP) in corn silage and the extent to which it is digested in the small intestine are uncertain. Three studies were conducted to determine RUP content of corn silage, and the effects of supplementing increasing concentrations of RUP on the growing performance of calves fed a corn silage diet. Experiments 1 and 2 used in situ methods to evaluate the RUP content of corn silage. In experiment 1, corn silages harvested at 37% or 42% dry matter (DM) were compared. In experiment 2, dry-rolled corn (89.4% DM) was reconstituted to 75%, 70%, 65%, and 50% DM and ensiled in mini-silos (2,265 cm3) for 30, 90, 180, or 270 d to simulate the corn grain within corn silage, dry-rolled corn is more mature than corn grain harvested in corn silage. Experiment 3 used 60 steers (275 kg initial body weight, SD = 18) in an 83-d growing study to evaluate the effects of supplementing 0.4%, 1.7%, 3.0%, 4.2%, or 5.5% RUP (% of diet DM) on performance. In experiment 1, RUP as a % of DM was not different between the two corn silages (P ≥ 0.12), averaging 0.59% for samples refluxed in a neutral detergent solution (NDS) and 1.8% for samples not refluxed in NDS. Dry matter digestibility (DMD) also did not differ (P ≥ 0.19), averaging 67.4%. In experiment 2, as moisture content of the corn grain increased, DMD increased linearly (P < 0.01) and RUP content decreased linearly (P < 0.01). The DMD increased quadratically (P = 0.02), whereas RUP content decreased linearly (P < 0.01) as days of ensiling increased. In experiment 3, there were no differences in DM intake (DMI; P ≥ 0.33) among treatments for period 1 (d 1 to 37). However, average daily gain (ADG) and gain-to-feed ratio (G:F) both linearly increased (P < 0.01) as RUP supplement inclusion increased. There were no differences in DMI (P ≥ 0.16), ADG (P ≥ 0.11), or G:F (P ≥ 0.64) in period 2 (d 38 to 83). For the overall growing period (d 1 to 83), a linear increase was observed for ending body weight (P = 0.01), ADG (P < 0.01), and G:F (P < 0.01) as RUP supplement inclusion increased from 0.4% to 5.5% of diet DM. The RUP content of corn silage is lower than previously reported. Data collected suggest the crude protein within corn silage is 13% RUP, and approximately 1/2 is digestible. The moisture content of corn silage at the time of harvest and the amount of time corn silage is stored continually impact protein availability. Supplementing growing calves fed corn silage with RUP will improve performance.
摘要译文
玉米青贮饲料中瘤胃不可降解蛋白质（RUP）的量及其在小肠中消化的程度尚不确定。进行了三项研究以确定玉米青贮饲料的RUP含量，以及补充增加浓度的RUP对饲喂玉米青贮饲料的小牛的生长性能的影响。实验1和2使用原位方法评估玉米青贮饲料的RUP含量。在实验1中，比较了在37％或42％干物质（DM）下收获的玉米青贮饲料。在实验2中，将干轧玉米（89.4％DM）重构成75％，70％，65％和50％DM，并在小筒仓（2,265cm 3 ）中青贮30天，用于模拟玉米青贮饲料中玉米粒的90,180或270d，干玉米比玉米青贮饲料中收获的玉米粒更成熟。实验3在83天的生长研究中使用了60个阉牛（275 kg初始体重，SD = 18）来评估补充0.4％，1.7％，3.0％，4.2％或5.5％RUP（饮食DM的百分比）的效果）关于表现。在实验1中，RUP作为DM的％在两种玉米青贮之间没有差异（P≥0.12），在中性洗涤剂溶液（NDS）中回流的样品平均为0.59％，对于未在NDS中回流的样品为1.8％。干物质消化率（DMD）也没有差异（P≥0.19），平均为67.4％。在实验2中，随着玉米粒含水量的增加，DMD呈线性增加（P <0.01），RUP含量线性下降（P <0.01）。 DMD呈二次方增加（P = 0.02），而随着青少年天数的增加，RUP含量呈线性下降（P <0.01）。在实验3中，DM摄入量没有差异（DMI;在第1期（d 1至37）的治疗中，P≥0.33）。然而，随着RUP补充剂包含的增加，平均日增重（ADG）和增重 - 饲料比（G：F）均线性增加（P <0.01）。在第2期（d 38至83），DMI（P≥0.16），ADG（P≥0.11）或G：F（P≥0.64）没有差异。对于整个生长期（d 1至83），随着RUP补充包含物从0.4增加，观察到最终体重（P = 0.01），ADG（P <0.01）和G：F（P <0.01）的线性增加。饮食DM的％至5.5％。玉米青贮饲料的RUP含量低于先前的报道。收集的数据表明玉米青贮饲料中的粗蛋白质为13％RUP，约1/2是可消化的。收获时玉米青贮饲料的水分含量和玉米青贮饲料储存的时间不断影响蛋白质的可用性。补充生长的小牛饲喂玉米青贮饲料和RUP将提高性能。
Colton R Oney[1];Jana K Gramkow[1];F Henry Hilscher[1];Galen E Erickson[1];Jim C MacDonald[1];Terry J Klopfenstein[1];Andrea K Watson[1]. Corn silage rumen undegradable protein content and response of growing calves to rumen undegradable protein supplement[J]. Translational Animal Science, 2019,3(1): 51-59