USDA-ARS Pasture Systems and Watershed Management Research Unit, Bldg 3702, Curtin Road, University Park, PA 16802, USA.
J Dairy Sci. 2010 Aug;93(8):3722-9. doi: 10.3168/jds.2009-2950.
Using a dual-flow continuous culture fermenter system, this study evaluated the effect of timing of corn silage supplementation on ruminal digestion and nutrient flows following a short and intensive orchardgrass herbage meal. Treatments included 28 g dry matter (DM) of corn silage added either 9h (9BH; 0700 h) or 1h (1BH; 1500 h) before adding 42 g DM orchardgrass herbage or no corn silage (control; 70 g DM herbage). Herbage was fed as follows: 66% of the total herbage meal at 1600 h, 22% at 1720 h, and the remaining 12% at 1840 h. Effluent was analyzed for organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF). Purine concentrations in effluent and bacterial isolates were used to estimate the partition of effluent N flow into bacterial and nonbacterial fractions, and to calculate true OM digestibility. Fermenters were sampled for pH, volatile fatty acids (VFA), and NH(3)-N at 0730, 1100, 1530, 1600, 1720, 1840, and 2000 h on d 10. Data were analyzed as a 3 x 4 Latin square experimental design. True digestibilities for OM (average of 78.5%) and CP (average of 84.6%), and apparent NDF digestibility (average of 82.7%) were not affected by treatment. Mean ruminal pH was lower for 9BH than for 1BH, averaging 5.6 and 6.5, respectively. Molar proportions of acetate were not affected by treatment. Propionate concentration was greater for 9BH than for 1BH, averaging 20.5 and 18.1mM, respectively. Diurnal patterns of pH, NH(3)-N, and acetate:propionate ratio were affected by treatment: 9BH had the lowest values for all measurements as the day progressed. The NH(3)-N concentration and effluent NH(3)-N flow were higher for 1BH (11.4 mg/100mL and 0.26 g/d, respectively) than for 9BH (8.8 mg/100mL and 0.20 g/d, respectively). Effluent NH(3)-N flow (as a % of total N flow) was the lowest for 9BH. Bacterial efficiency was not affected by treatments, with a mean of 10.5 g of N/kg of OM truly digested. Under the same resource allocation (pasture plus supplement), a simple change in timing of corn silage feeding (9 rather than 1h before an orchardgrass herbage meal) may alter ruminal fermentation pattern. These changes could increase the glucogenic nutrient supply and improve N utilization by reducing ammonia N losses.
利用双流量连续培养发酵罐系统，本研究评估了在短时间和高强度的草地草日粮后，玉米青贮补充的时间对瘤胃消化和养分流量的影响。处理包括添加 28 克干物质（DM）的玉米青贮，分别在添加 42 克 DM 草地草或不添加玉米青贮（对照；70 克 DM 草料）之前 9 小时（9BH；0700 h）或 1 小时（1BH；1500 h）。草料如下：1600 h 时喂 66%的总草料，1720 h 时喂 22%，1840 h 时喂 12%。流出物分析了有机物（OM）、粗蛋白（CP）和中性洗涤剂纤维（NDF）。流出物中的嘌呤浓度和细菌分离物用于估计流出物 N 流的细菌和非细菌部分的分配，并计算真实的 OM 消化率。发酵罐在第 10 天的 0730、1100、1530、1600、1720、1840 和 2000 h 时取样，用于测量 pH、挥发性脂肪酸（VFA）和 NH3-N。数据作为 3 x 4 拉丁方实验设计进行分析。OM（平均 78.5%）和 CP（平均 84.6%）的真实消化率以及表观 NDF 消化率（平均 82.7%）不受处理影响。9BH 的平均瘤胃 pH 低于 1BH，分别为 5.6 和 6.5。处理对乙酸的摩尔比例没有影响。丙酸浓度 9BH 高于 1BH，分别为 20.5 和 18.1mM。pH、NH3-N 和乙酸：丙酸比的昼夜模式受处理影响：随着时间的推移，9BH 的所有测量值均为最低值。1BH（11.4 mg/100mL 和 0.26 g/d）的 NH3-N 浓度和流出 NH3-N 流量高于 9BH（8.8 mg/100mL 和 0.20 g/d）。9BH 的流出 NH3-N 流量（占总 N 流量的%）最低。细菌效率不受处理影响，平均每消化 10.5 克 OM 消耗 1 克 N。在相同的资源分配（牧场加补充）下，简单改变玉米青贮的喂养时间（在草地草日粮前 9 小时而不是 1 小时）可能会改变瘤胃发酵模式。这些变化可以通过减少氨氮损失来增加生糖营养素的供应并提高氮的利用。
