Abstract

Developed initially for use in fuel ethanol production, Enogen Feed Corn (EFC; Syngenta Crop Protection) is genetically modified to express high concentrations of α-amylase in the corn kernel. Experiments were conducted to evaluate processing characteristics of EFC, in vitro digestion, and effects on feedlot performance, carcass characteristics, and liver abscess incidence. Experiment 1 used a randomized complete block design (3 × 3 × 5 factorial) to evaluate starch availability, in situ dry matter disappearance (ISDMD), in vitro gas production (IVGP), and volatile fatty acid (VFA) profiles of in vitro cultures. Grains (EFC or mill-run control [CON]) were flaked to a density of 360 g/L, and mixtures with 0%, 25%, 50%, 75%, or 100% EFC were prepared. Grains were tempered with added moisture (0%, 3%, or 6%) prior to steam conditioning for 15, 30, or 45 min. No two- or three-way interactions were observed. Adding moisture improved starch availability (linear; P < 0.01), and tended to improve ISDMD (linear, P = 0.06). Steam conditioning for 30 min improved starch availability, IVGP, and production of acetate, propionate, butyrate, valerate, and total VFA (P < 0.01) compared with conditioning for 15 or 45 min. Starch availability, ISDMD, IVGP, acetate, propionate, valerate, and total VFA production increased with an increasing proportion of EFC (linear, P < 0.01). Experiment 2 used 700 beef heifers (394 ± 8.5 kg initial body weight [BW]) fed finishing diets with steam-flaked corn as CON or EFC for 136 d. Targeting similar starch availabilities, grains were processed to 360 g/L (CON) and 390 g/L for CON and EFC, respectively. Heifers were blocked by BW, stratified, and then randomly assigned to 28 dirt-surfaced pens (25 animals per pen). Dry matter intakes were similar between treatments (P = 0.78), but cattle fed EFC had greater average daily gain (P < 0.01), improving feed efficiency by 5% (P < 0.01). Hot carcass weight was 6 kg greater for EFC cattle (P <0.01) than CON. No differences were observed for longissimus muscle area (P = 0.89), 12th-rib fat thickness (P = 0.21), or USDA yield grade (P = 0.13). Cattle fed CON had greater marbling scores than EFC (P = 0.04), but this did not affect the USDA quality grade (P > 0.33). Cattle fed EFC had 23% fewer abscessed livers than CON (P = 0.03). High-amylase corn may be used to improve microbial digestion, mill-throughput, and cattle performance, and it may mitigate liver abscesses.

中文翻译：

---

高淀粉酶玉米对育肥小母牛性能和胴体品质的影响。

摘要

Enogen 饲料玉米（EFC；先正达作物保护）最初开发用于燃料乙醇生产，经过基因改造，可在玉米粒中表达高浓度的 α-淀粉酶。进行了实验以评估 EFC 的加工特性、体外消化以及对饲养场性能、胴体特性和肝脓肿发生率的影响。实验 1 使用随机完整区组设计（3 × 3 × 5 析因）来评估淀粉可用性、原位干物质消失 ( ISDMD )、体外产气量 ( IVGP ) 和体外培养物的挥发性脂肪酸 ( VFA ) 曲线. 谷物（EFC 或轧机运行控制 [ CON]) 压成 360 g/L 的密度，并制备含有 0%、25%、50%、75% 或 100% EFC 的混合物。在蒸汽调质 15、30 或 45 分钟之前，谷物用添加的水分（0%、3% 或 6%）调温。没有观察到两种或三种方式的相互作用。添加水分可提高淀粉可用性（线性；P < 0.01），并倾向于改善 ISDMD（线性，P = 0.06）。与调节 15 或 45 分钟相比，蒸汽调节 30 分钟提高了淀粉可用性、IVGP 以及乙酸盐、丙酸盐、丁酸盐、戊酸盐和总 VFA 的产量（P < 0.01）。淀粉可用性、ISDMD、IVGP、醋酸盐、丙酸盐、戊酸盐和 VFA 总产量随着 EFC 比例的增加而增加（线性，P< 0.01)。实验 2 使用 700 头小母牛（394 ± 8.5 kg 初始体重 [ BW ]）饲喂以蒸汽压片玉米作为 CON 或 EFC 的育肥日粮 136 天。针对相似的淀粉可用性，将谷物加工成 360 g/L (CON) 和 390 g/L 的 CON 和 EFC。小母牛被 BW 阻挡，分层，然​​后随机分配到 28 个土面围栏（每围栏 25 只动物）。处理之间的干物质摄入量相似（P = 0.78），但饲喂 EFC 的牛具有更高的平均日增重（P < 0.01），饲料效率提高了 5% （P < 0.01）。EFC 牛的热胴体重比 CON 高6 公斤（P <0.01）。最长肌面积没有观察到差异（P= 0.89)、第 12 肋脂肪厚度 ( P = 0.21) 或美国农业部产量等级 ( P = 0.13)。饲喂 CON 的牛具有比 EFC 更高的大理石花纹分数（P = 0.04），但这并不影响美国农业部的质量等级（P > 0.33）。饲喂 EFC 的牛的肝脏脓肿比 CON 少 23%（P = 0.03）。高淀粉酶玉米可用于改善微生物消化、磨粉机产量和牛性能，并可减轻肝脓肿。