Department of Animal Science, University of California, Davis, CA, USA.
Nutr Res Rev. 2011 Dec;24(2):183-90. doi: 10.1017/S0954422411000096. Epub 2011 Nov 21.
The primary reason for processing maize is to enhance feeding value. Total tract starch digestion is similar for coarsely processed (dry rolled, cracked) dry maize. Enhancements in starch digestion due to dry rolling maize v. feeding maize whole may be greater in light-weight calves than in yearlings, and when DM intake is restricted ( < 1·5 % of body weight). The net energy (NE) maintain (NEm) and NE gain (NEg) values for whole maize are 8·83 and 6·02 MJ (2·11 and 1·44 Mcal)/kg, respectively. Compared with conventional dry processing (i.e. coarse rolled, cracked), finely processing maize may increase the initial rate of digestion, but does not improve total tract starch digestion. Tempering before rolling (without the addition of steam) may enhance the growth performance response and the NE value of maize. Average total tract starch digestion is similar for high-moisture and steam-flaked maize. However, the proportion of starch digested ruminally is greater (about 8 %) for high-moisture maize. The growth performance response of feedlot cattle to the feeding of high-moisture maize is highly variable. Although the NEm and NEg value of whole high-moisture maize was slightly less than that of dry processed maize (averaging 9·04 and 6·44 MJ (2·16 and 1·54 Mcal)/kg, respectively), grinding or rolling high-moisture maize before ensiling increased (6 %) its NE value. Substituting steam-flaked maize for dry processed maize increases average daily gain (6·3 %) and decreases DM intake (5 %). The comparative NEm and NEg values for steam-flaked maize at optimal processing (density = 0·34 kg/l) are 10·04 and 7·07 MJ (2·40 and 1·69 Mcal)/kg, respectively. These NE values are greater (3 %) than current tabular values (National Research Council, 2000), being more consistent with earlier standards (National Research Council, 1984). When maize is the primary or sole source of starch in the diet, concentration of starch in faeces (faecal starch, % of DM) of feedlot steers can serve as an indicator of total tract starch digestion, and, hence, the feeding value of maize.
加工玉米的主要原因是提高饲料的营养价值。对于粗加工（干压、破碎）的干玉米，全肠道淀粉消化率相似。与整粒玉米相比，在轻量级小牛中，干压玉米 v. 整粒玉米可能会增加淀粉消化的增强效果，而当干物质摄入量受到限制（<1.5%体重）时。整粒玉米的净能维持（NEm）和净能增益（NEg）值分别为 8.83 和 6.02 MJ（2.11 和 1.44 Mcal）/kg。与传统的干法加工（即粗压、破碎）相比，细加工玉米可能会增加初始消化速度，但不会提高全肠道淀粉消化率。压片前调质（不添加蒸汽）可能会提高玉米的生长性能反应和净能值。高水分和蒸汽压片玉米的全肠道淀粉消化率相似。然而，高水分玉米瘤胃中消化的淀粉比例较大（约 8%）。肥育牛对高水分玉米的喂养的生长性能反应差异很大。虽然整粒高水分玉米的 NEm 和 NEg 值略低于干法加工玉米（平均分别为 9.04 和 6.44 MJ（2.16 和 1.54 Mcal）/kg），但在青贮前将高水分玉米研磨或压片会增加其净能值（6%）。用蒸汽压片玉米替代干法加工玉米可提高平均日增重（6.3%），减少干物质摄入量（5%）。优化加工（密度=0.34 kg/l）时，蒸汽压片玉米的比较 NEm 和 NEg 值分别为 10.04 和 7.07 MJ（2.40 和 1.69 Mcal）/kg，分别。这些净能值比当前表值（国家研究委员会，2000 年）高（3%），与早期标准（国家研究委员会，1984 年）更一致。当玉米是日粮中淀粉的主要或唯一来源时，肥育牛粪便中淀粉的浓度（粪便淀粉，占 DM 的百分比）可作为全肠道淀粉消化率的指标，从而反映玉米的饲料价值。
