Karls Caleb W, Shinners Kevin J, Schaefer Daniel M
Department of Animal and Dairy Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA.
Department of Biological Systems Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA.
Transl Anim Sci. 2022 May 4;6(2):txac055. doi: 10.1093/tas/txac055. eCollection 2022 Apr.
Single-pass corn stover harvest is a method whereby combine harvester tailings consisting of cob, stalk, leaf, husk, and tassel fractions are collected and baled without coming into contact with soil. The objective was to feed beef steers diets that included a roughage component consisting of harvested corn residue in chopped form from conventional corn stover bales () or single-pass bales () to assess intake selectivity of corn stover fractions and estimate net energy values of these corn stovers. Whole plant corn silage served as the control roughage in the control diet (). Steers ( = 90, 5 pens per treatment) were fed during Grow (84 d) and Finish (66 d) trials. Steers sorted through corn stover during both trials and consumed 52.5% of corn stover offered and 40% of cob offered. Intake of SPB cob was 2.6-fold and 3.3-fold greater than CST cob intake ( < 0.01) in Grow and Finish trials, respectively, indicating that when more cob was available, cattle consumed more. During the Grow trial, stover intake tended ( = 0.07) to be lower for SPB and diet dry matter intake () was less ( ≤ 0.05) for SPB, which may be due to the elevated cob intake by SPB steers. Across treatments, stover DMI was similar in the Grow (1.10 kg per steer per d) and Finish (1.11 kg per steer per d) trials. The proportion (65%) of Fines (<8 mm) consumed from the Grow diet (40% neutral detergent fiber, ) was greater than the Finish diet (25% aNDF; 18% to 31%) and gleaning of concentrate feeds from orts seemed to be more extensive in the Grow diet. Steers consuming Finish diets containing SPB and CST had DMI that were 17% and 18%, respectively, greater ( ≤ 0.05) than CSIL, an indication of compensatory intake. The physical effectiveness factors for stovers fed in the Grow and Finish diets were 0.85 and 0.95, respectively. Estimates for net energy maintenance and net energy gain (), respectively, using National Research Council methods from 2001 were as follows for consumed stovers: SPB (1.09 and 0.54 Mcal/kg) and CST (0.98 and 0.44 Mcal/kg) in the Grow trial, and SPB (0.96 and 0.42 Mcal/kg) and CST (0.95 and 0.40 Mcal/kg) in the Finish trial. Although SPB and CST differ in botanical fraction composition and net intakes of botanical fractions, their energetic contributions to steer performance were very similar. Steers fed the Finish diet (1.25 Mcal performance-adjusted NEg per kg) selected stover botanical components to achieve a diet composition of 25% aNDF.
单程玉米秸秆收获法是一种将联合收割机产生的由玉米芯、秸秆、叶片、苞叶和雄穗部分组成的尾料进行收集并打捆，且不与土壤接触的方法。目的是给育肥牛饲喂包含粗饲料成分的日粮，该粗饲料成分由来自传统玉米秸秆捆（）或单程收获打捆（）的切碎形式的收获玉米残渣组成，以评估玉米秸秆各部分的采食选择性，并估算这些玉米秸秆的净能值。全株玉米青贮料用作对照日粮（）中的对照粗饲料。在生长（84天）和育肥（66天）试验期间给肉牛（ = 90头，每个处理5栏）喂食。在两个试验中，肉牛都对玉米秸秆进行挑选，消耗了提供的52.5%的玉米秸秆和40%的玉米芯。在生长和育肥试验中，单程收获打捆玉米芯的摄入量分别比传统玉米秸秆捆玉米芯的摄入量高2.6倍和3.3倍（<0.01），这表明当有更多玉米芯时，牛会消耗更多。在生长试验期间，单程收获打捆的秸秆摄入量有降低的趋势（ = 0.07），且单程收获打捆的日粮干物质摄入量（）较少（≤0.05），这可能是由于单程收获打捆组的肉牛对玉米芯摄入量增加所致。在所有处理中，生长试验（每头肉牛每天1.10千克）和育肥试验（每头肉牛每天1.11千克）中的秸秆干物质摄入量相似。生长日粮（中性洗涤纤维含量40%，）中消耗的细料（<8毫米）比例（65%）高于育肥日粮（酸性洗涤纤维含量25%；18%至31%），并且在生长日粮中从剩余饲料中挑选精饲料的情况似乎更普遍。采食含单程收获打捆和传统玉米秸秆捆育肥日粮的肉牛的干物质摄入量分别比全株玉米青贮料组高17%和18%（≤0.05），这表明存在代偿性采食。生长和育肥日粮中饲喂的秸秆的物理有效性因子分别为0.85和0.95。使用2001年美国国家研究委员会的方法，对采食的秸秆的净能维持值和净能增重值（）的估计如下：生长试验中，单程收获打捆为（1.09和0.54兆卡/千克），传统玉米秸秆捆为（0.98和0.44兆卡/千克）；育肥试验中，单程收获打捆为（0.96和0.42兆卡/千克），传统玉米秸秆捆为（0.95和0.40兆卡/千克）。尽管单程收获打捆和传统玉米秸秆捆在植物部分组成和植物部分的净摄入量方面存在差异，但它们对肉牛生产性能的能量贡献非常相似。采食育肥日粮（每千克性能调整后的净能增重为1.25兆卡）的肉牛选择秸秆植物成分，以使日粮组成达到酸性洗涤纤维含量25%。
