摘要
ABSTRACT The objectives of the current studies were to evaluate the effects of silage (S) and cereal grain (G) source and their interaction (S × G) on growth performance, digestibility, and carcass characteristics (Study 1) and dry matter intake, ruminal fermentation, total-tract digestibility, and nitrogen balance (Study 2) for finishing beef cattle. For Study 1, 288 steers weighing 465 ± 28 kg were randomly assigned to 1 of 24 pens (12 steers/pen) in an 89-d finishing study. Study 2 used five ruminally cannulated heifers in an incomplete 6 × 6 Latin square design. Periods were 25-d in duration with 5 d of diet transition, 13 d of dietary adaptation, and 7 d of sample collection. Dietary treatments for both studies included corn silage (CS) or barley silage (BS) at 8% of DM. Within each silage source, diets contained dry-rolled barley grain (BG; 86% of DM), dry-rolled corn grain (CG; 85% of DM), or an equal blend of barley and corn grain (BCG; 85% of DM). In Study 1, there were no interactions between silage and cereal grain source (P ≥ 0.10). Feeding CG increased (G, P < 0.01) DMI by 0.8 and 0.6 kg/d relative to BG and BCG, respectively. Gain-to-feed was greater (G, P = 0.04) for BG (0.17 kg/kg) than CG (0.16 kg/kg), but not different from BCG (0.17 kg/kg). Furthermore, average daily gain (2.07 kg/d) and final body weight were not different among treatments (P > 0.05). Hot carcass weight was 6.2 kg greater (372.2 vs. 366.0 kg; S, P < 0.01) and dressing percent was 0.57% greater (59.53 vs. 58.96 %; S, P = 0.04) for steers fed CS than BS, respectively. In Study 2, DM intake and mean pH were not affected by diet. Total SCFA concentrations were greater for BCG than BG or CG (G, P < 0.01) and for CS (S, P < 0.01) relative to BS. Molar proportion of acetate was increased for BS-BG and BS-CG (S × G, P < 0.01), while molar proportion of propionate was greatest for CS-BG (S × G, P < 0.01). Rumen ammonia-nitrogen concentrations were greatest for CG (G, P < 0.001), and higher for CS than BS (S, P = 0.02). Apparent total-tract digestibility of DM, OM, aNDFom, starch and gross energy were greatest for BG (G, P ≤ 0.04). Dietary digestible energy content (Mcal/kg) was greatest for BG treatments (G, P = 0.03). Total nitrogen retention (g/d and % of intake) was greatest for CS-BG (S × G, P ≤ 0.03). The potentially degradable fraction of DM, CP, and starch were greater for CG (P ≤ 0.03) than BG. For silage sources, CS had greater 24, 48 and 72-h starch digestibility (P ≤ 0.03) relative to BS. These results indicate that feeding dry-rolled BG may improve performance and digestibility when compared to CG and BCG and CS may provide benefits over BS. Improvements related to feeding BG and CS may be due to greater propionate production, improved nutrient digestibility, and greater N retention.
摘要译文
摘要目前研究的目的是评估青贮饲料和谷粒（G）源的影响及其相互作用对生长性能，消化率和胴体特征（研究1）和干物质摄入量的影响，用于整理肉牛的瘤胃发酵，总介质消化率和氮气平衡（研究2）。对于研究1，在89-D整理研究中，将重量为465±28千克的288个终端被随机分配给24张（12个Steers / Pen）的1个中的1个。研究2使用了五个不完整的6×6拉丁方形设计中的五个仪式插管的小母牛。期间为25-D，持续5 d饮食转型，13d膳食适应，7 d样品收集。两项研究的膳食治疗包括玉米青贮（CS）或大麦的青贮饲料（BS），在8％的DM。在每个青贮源内，饮食含有干轧大麦谷物（BG; 86％的DM），干轧玉米粒（CG; 85％的DM），或大麦和玉米谷物的相同混合物（BCG; 85％的DM）。在研究1中，青贮和谷物源之间没有相互作用（P≥0.10）。进料CG相对于BG和BCG分别增加0.8％和0.6kg / d的DMI。 BG（0.17kg / kg）的增益进料比Cg（0.16kg / kg）（0.16kg / kg），但与Bcg（0.17kg / kg）不同。此外，在治疗中平均每日增益（2.07kg / d）和最终体重在（p> 0.05）中没有不同。热胴体重量为6.2千克（372.2与366.0千克; S，P <0.01）和敷料百分比为0.57％（59.53 vs.58.96％; S，P = 0.04）对于CS的阉牛体积多于BS。在研究2中，DM摄入和平均pH不受饮食的影响。 BCG的总SCFA浓度比BG或CG（G，P <0.01）和相对于BS（S，P <0.01）更大。对于BS-BG和BS-CG（S×G，P <0.01）而增加乙酸盐的摩尔比例，而CS-BG（S×G，P <0.01）最大的丙酸盐比例最大。 Cg（g，p <0.001）最大的瘤胃氨 - 氮浓度最大，Cs比bs（s，p = 0.02）更高。对于BG（G，P≤0.04）来说，DM，OM，Andfom，淀粉和总能量的表观总沟热性最大。 BG处理最大的饮食消化能量含量（MCAL / kg）（g，p = 0.03）。对于CS-BG（S×g，P≤0.03），总氮保留（G / D和摄入量）最大。 CG（P≤0.03）的DM，CP和淀粉的潜在可降解的级别大于BG。对于青贮源，CS相对于BS具有更大的24,48和72-H淀粉消化率（p≤0.3）。这些结果表明，与CG和BCG和CS相比，进料干辊BG可以改善性能和消化率，并且BCG和CS可以提供对BS的益处。与饲料BG和CS相关的改进可能是由于丙种丙酸酯的产生，改善营养消化率和更高的保留。