Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409, USA.
J Anim Sci. 2010 Mar;88(3):1135-47. doi: 10.2527/jas.2009-2400. Epub 2009 Nov 20.
Effects of varying bulk densities of steam-flaked corn (SFC) and level of inclusion of roughage in feedlot diets were evaluated in 3 experiments. In Exp. 1, a total of 128 beef steers were used in a 2 x 2 factorial arrangement to evaluate the effects of bulk density of SFC (335 or 386 g/L) and roughage concentration (6 or 10% ground alfalfa hay, DM basis) on performance and carcass characteristics. No interactions were observed between bulk density and roughage concentration for performance data. From d 0 to the end, cattle fed the 335 g/L SFC had greater overall G:F (P = 0.04) than those fed the 386 g/L SFC, with tendencies (P < 0.10) for improved G:F with the lighter flake weight evident at all 35-d intervals throughout the feeding period. Dry matter intake was less for cattle fed 6 vs. 10% roughage from d 0 to 35 (P = 0.03) and d 0 to 70 (P = 0.05), but not for the overall feeding period. Feeding 6 vs. 10% ground alfalfa as the roughage source tended (P = 0.09) to improve overall G:F. Treatment effects on carcass measurements were generally not significant (P > 0.20). In Exp. 2, the effects of bulk density of SFC (283, 335, or 386 g/L) and 6 or 10% ground alfalfa hay on IVDMD and in vitro pH were evaluated at 6, 12, 18, and 24 h of incubation. With a reduced-strength buffer in vitro fermentation system, pH increased (P < 0.01) with increasing bulk density at 6 and 12 h, and IVDMD decreased (P < 0.03) as bulk density increased. In contrast, in a normal-strength buffer system, there were no treatment differences (P > 0.23) for IVDMD. In Exp. 3, two diets that varied in bulk density of SFC and roughage concentration (335 g/L SFC with 6% alfalfa hay vs. 386 g/L SFC with 10% alfalfa hay) were compared for their effects on the pattern of feed intake and the acid-base balance in Holstein steers (12/treatment). No differences (P > 0.10) between treatments were noted for blood gases or urine pH; however, day effects (P < 0.02) were detected for blood pH, partial pressure of CO(2), and urine pH, which generally decreased (P < 0.05) with an increasing time on feed. The 2 treatments had little effect on the pattern of feed intake within the sampling days, with the exception that the 386 g/L SFC with 10% alfalfa hay diet increased (P < 0.05) the percentage of total DMI consumed at 1 and 6 h after feeding on d 14. Within the ranges of bulk density and roughage level studied, 335 g/L SFC with 6% alfalfa hay yielded the optimal animal performance, with limited effects on in vitro fermentation and the acid-base balance.
本试验旨在评估蒸汽压片玉米（SFC）的不同容重和饲粮中粗饲料水平对肥育牛生产性能和胴体特性的影响。试验 1 选用 128 头肉牛采用 2×2 完全因子设计，研究 SFC 容重（335 或 386 g/L）和粗饲料浓度（6%或 10%粉碎紫花苜蓿干草，DM 基础）对生产性能和胴体特性的影响。SFC 容重和粗饲料浓度对生产性能数据没有互作影响。从 0 到试验结束，饲喂 335 g/L SFC 的肉牛的总体增重/饲料（G/F）比饲喂 386 g/L SFC 的肉牛高（P = 0.04），在整个饲养期的所有 35 d 间隔内，较轻的 SFC 薄片重量都表现出改善 G/F 的趋势（P < 0.10）。从 0 到 35 d（P = 0.03）和从 0 到 70 d（P = 0.05），饲喂 6%粗饲料的肉牛干物质采食量比饲喂 10%粗饲料的肉牛低，但整个饲养期的干物质采食量没有差异。与饲喂 10%粉碎紫花苜蓿干草作为粗饲料来源相比，饲喂 6%粉碎紫花苜蓿干草有改善总体 G/F 的趋势（P = 0.09）。处理对胴体测量的影响一般不显著（P > 0.20）。试验 2 研究了 SFC 容重（283、335 或 386 g/L）和 6%或 10%粉碎紫花苜蓿干草对体外干物质消化率（IVDMD）和体外 pH 的影响，在 6、12、18 和 24 h 体外发酵时测定。在体外发酵缓冲能力较弱的系统中，随着 SFC 容重的增加，pH 值在 6 和 12 h 时升高（P < 0.01），而 IVDMD 则降低（P < 0.03）。相反，在正常缓冲能力的系统中，处理间 IVDMD 没有差异（P > 0.23）。试验 3 比较了两种不同 SFC 容重和粗饲料浓度（335 g/L SFC 与 6%紫花苜蓿干草 vs. 386 g/L SFC 与 10%紫花苜蓿干草）的饲粮对荷斯坦肉牛采食模式和酸碱平衡的影响（12 头/处理）。处理间血液气体或尿液 pH 无差异（P > 0.10）；然而，血液 pH、CO2 分压和尿液 pH 存在日效应（P < 0.02），这通常随着采食时间的延长而降低（P < 0.05）。在采样日内，2 种饲粮对采食模式的影响不大，例外的是在第 14 天，饲喂 386 g/L SFC 与 10%紫花苜蓿干草的饲粮增加了（P < 0.05）第 1 和第 6 h 的总干物质采食量的比例。在研究的 SFC 容重和粗饲料水平范围内，饲喂 335 g/L SFC 与 6%紫花苜蓿干草可获得最佳的动物生产性能，对体外发酵和酸碱平衡的影响有限。
