This study used 18 calves (295 ± 29 kg) and 18 yearlings (521 ± 29 kg) fed whole, cracked, or steam-flaked corn (SFC) to evaluate nutrient digestion and energy balance across different types of processed corn and sizes of cattle. Cattle were fed a diet comprised of 75% corn (dry matter [DM]-basis) from whole, cracked, or SFC to 2.5-times maintenance energy requirements. Subsequently, cattle were placed in individual stanchions, and urine and feces were collected together with measures of gas production via indirect calorimetry. Data were analyzed using the MIXED procedure of SAS. There was no interaction between corn processing and cattle size (P ≥ 0.40). Time spent ruminating (min/d) and rumination rate (min/kg DM intake [DMI]) were not affected by corn processing or cattle size. The eating rate (min/kg DMI) was faster (P < 0.01) for yearlings compared with calves. Total tract starch digestion was greatest (P = 0.01) for cattle fed SFC (97.5%), intermediate in cattle fed cracked (92.4%), and least in cattle fed whole corn (89.5%). Dietary digestible energy and metabolizable energy (Mcal/kg DMI) were greater (P ≤ 0.05) for cattle fed SFC compared with cracked or whole. A greater proportion of digestible energy was lost to heat production (P = 0.01) in cattle fed whole corn compared with cracked and tended to be greater (P = 0.08) in cattle fed SFC than cracked. Conversion of digestible energy to metabolizable energy in this study was more closely related to a dynamic model used to estimate metabolizable energy of feeds to dairy cows than to a linear model used to predict metabolizable energy of feeds to beef cattle. If library estimates of net energy for maintenance are correct, then retained energy (Mcal/d) should have been similar between each type of processed corn; however, retained energy was greater (P < 0.01) for cattle fed cracked compared with whole corn and tended to be greater (P = 0.06) compared with SFC. Yet, observed amounts of net energy based on measures of retained energy were not different (P ≥ 0.60) between cracked and SFC. Nitrogen balance was not affected (P ≥ 0.30) by corn processing or cattle size, although cattle fed cracked had numerically greater (P ≤ 035) N retention. These data indicate that physical processing of corn provides greater net energy to cattle in comparison to whole corn.

中文翻译：

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玉米加工和牛体型对全消化道消化和能量与氮平衡的影响

本研究使用 18 头小牛 (295 ± 29 kg) 和 18 头一岁马 (521 ± 29 kg) 喂食整粒玉米、碎玉米或蒸汽压片玉米 (SFC)，以评估不同类型的加工玉米和不同大小的牛的营养消化和能量平衡. 牛被喂食由 75% 玉米（干物质 [DM] 基础）组成的饮食，来自完整的、破碎的或 SFC 到 2.5 倍的维持能量需求。随后，将牛放在单独的支柱中，收集尿液和粪便，并通过间接量热法测量产气量。使用SAS的混合程序分析数据。玉米加工与牛体型之间没有交互作用 (P ≥ 0.40)。反刍时间 (min/d) 和反刍率 (min/kg DM 摄入量 [DMI]) 不受玉米加工或牛体型的影响。进食率 (min/kg DMI) 更快 (P < 0. 01) 与小牛相比，一岁鸽。饲喂 SFC 的牛 (97.5%) 的总消化道淀粉消化最大 (P = 0.01)，饲喂碎玉米的牛居中 (92.4%)，而饲喂整粒玉米的牛最少 (89.5%)。饲喂 SFC 的牛的日粮可消化能和代谢能 (Mcal/kg DMI) 高于裂解或全脂牛 (P ≤ 0.05)。与裂解玉米相比，饲喂全玉米的牛在产热中损失的可消化能比例更大 (P = 0.01)，而饲喂 SFC 的牛比裂解玉米的消化能损失更大 (P = 0.08)。在本研究中，消化能向代谢能的转化与用于估计奶牛饲料代谢能的动态模型比与用于预测肉牛饲料代谢能的线性模型更密切相关。如果图书馆对维持净能的估计是正确的，那么每种加工玉米的保留能 (Mcal/d) 应该是相似的；然而，与整粒玉米相比，饲喂碎玉米的牛的保留能量更高 (P < 0.01)，并且与 SFC 相比往往更高 (P = 0.06)。然而，根据保留能量的测量观察到的净能量在裂化和 SFC 之间没有差异 (P ≥ 0.60)。氮平衡不受玉米加工或牛体型的影响 (P ≥ 0.30)，尽管饲喂开裂的牛在数值上具有更大 (P ≤ 035) 的氮保留。这些数据表明，与整粒玉米相比，玉米的物理加工为牛提供了更多的净能量。与整粒玉米相比，饲喂碎玉米的牛的保留能量更高 (P < 0.01)，与 SFC 相比往往更高 (P = 0.06)。然而，根据保留能量的测量观察到的净能量在裂化和 SFC 之间没有差异 (P ≥ 0.60)。氮平衡不受玉米加工或牛体型的影响 (P ≥ 0.30)，尽管饲喂开裂的牛在数值上具有更大 (P ≤ 035) 的氮保留。这些数据表明，与整粒玉米相比，玉米的物理加工为牛提供了更多的净能量。与整粒玉米相比，饲喂碎玉米的牛的保留能量更高 (P < 0.01)，与 SFC 相比往往更高 (P = 0.06)。然而，根据保留能量的测量观察到的净能量在裂化和 SFC 之间没有差异 (P ≥ 0.60)。氮平衡不受玉米加工或牛体型的影响 (P ≥ 0.30)，尽管饲喂开裂的牛在数值上具有更大 (P ≤ 035) 的氮保留。这些数据表明，与整粒玉米相比，玉米的物理加工为牛提供了更多的净能量。30) 由玉米加工或牛的大小决定，尽管饲喂开裂的牛在数值上具有更大的 (P ≤ 035) N 保留。这些数据表明，与整粒玉米相比，玉米的物理加工为牛提供了更多的净能量。30) 由玉米加工或牛的大小决定，尽管饲喂开裂的牛在数值上具有更大的 (P ≤ 035) N 保留。这些数据表明，与整粒玉米相比，玉米的物理加工为牛提供了更多的净能量。