Kim S C, Adesogan A T, Arthington J D
Department of Animal Sciences, University of Florida-IFAS, Gainesville 32611, USA.
J Anim Sci. 2007 Oct;85(10):2548-55. doi: 10.2527/jas.2007-0059. Epub 2007 May 25.
Our objectives were to compare the effects of sources of supplemental N on ruminal fermentation of dried citrus pulp (DCP) and performance of growing steers fed DCP and bahiagrass (Paspalum notatum) hay. In Exp. 1, fermentation of DCP alone was compared with that of isonitrogenous mixtures of DCP and solvent soybean meal (SBM), expeller soybean meal (SoyPLUS; SP), or urea (UR). Ground (1 mm) substrates were incubated in buffered rumen fluid for 24 h, and IVDMD and fermentation gas production kinetics and products were measured. Nitrogen supplementation increased (P < 0.10) ruminally fermentable fractions, IVDMD, pH, and concentrations of NH3 and total VFA, but reduced the rate of gas production (P < 0.10) and the lag phase (P < 0.01). Supplementation with UR vs. the soy-based supplements increased ruminally fermentable fractions (P < 0.05) and concentrations of total VFA (P < 0.10) and NH3 (P < 0.01), but these measures were similar (P > 0.10) between SBM and SP. In Exp. 2, 4 steers (254 kg) were fed bahiagrass hay plus DCP, or hay plus DCP supplemented with CP predominantly from UR, SBM, or SP in a 4 x 4 Latin square design, with four 21-d periods, each with 7 d for DMI and fecal output measurement. Nitrogen-supplemented diets were formulated to be isonitrogenous (11.9% CP), and all diets were formulated to be isocaloric (66% TDN). Intake and digestibility of DM, N, and ADF were improved (P < 0.05) by N supplementation. Compared with UR, the soy-based supplements led to greater (P < 0.05) DM and N intakes and apparent N and ADF digestibilities. Plasma glucose and urea concentrations increased (P < 0.10) with N supplementation and were greater (P < 0.01) for the soy-based supplements than for UR. Intake, digestibility, and plasma metabolite concentrations were similar (P > 0.1) for SBM and SP. In Exp. 3, 24 steers (261 kg) were individually fed bahiagrass hay plus DCP (control), or hay plus DCP supplemented with CP predominantly from UR or SBM. Over 56 d, DMI and ADG were greatest (P < 0.05) in steers fed SBM. Nitrogen supplementation increased (P < 0.05) DMI, ADG, and G:F. However, SBM supplementation produced greater (P < 0.05) DMI and ADG and similar (P > 0.05) G:F compared with UR supplementation. We conclude that supplemental N is important to optimize ruminal function and performance of growing steers fed forage diets supplemented with DCP. Diets with supplemental N mainly from SBM improved diet digestibility and animal performance beyond that achieved by UR.
我们的目标是比较补充氮源对干柑橘渣（DCP）瘤胃发酵的影响，以及对饲喂DCP和巴哈雀稗（Paspalum notatum）干草的生长阉牛生产性能的影响。在试验1中，将单独的DCP发酵与DCP与溶剂豆粕（SBM）、压榨豆粕（SoyPLUS；SP）或尿素（UR）的等氮混合物的发酵进行比较。将粉碎（1毫米）的底物在缓冲瘤胃液中孵育24小时，并测定体外干物质消化率（IVDMD）、发酵气体产生动力学和产物。补充氮增加了（P < 0.10）瘤胃可发酵部分、IVDMD、pH值以及NH₃和总挥发性脂肪酸（VFA）的浓度，但降低了气体产生速率（P < 0.10）和延滞期（P < 0.01）。与基于大豆的补充剂相比，补充UR增加了瘤胃可发酵部分（P < 0.05）、总VFA浓度（P < 0.10）和NH₃浓度（P < 0.01），但SBM和SP之间这些指标相似（P > 0.10）。在试验2中，4头阉牛（254千克）按照4×4拉丁方设计，分别饲喂巴哈雀稗干草加DCP，或加主要来自UR、SBM或SP的粗蛋白（CP）补充的DCP，共4个21天周期，每个周期有7天用于测定干物质采食量（DMI）和粪便产量。补充氮的日粮配方为等氮（11.9% CP），所有日粮配方为等热卡（66%总可消化养分，TDN）。补充氮提高了（P < 0.05）干物质、氮和酸性洗涤纤维（ADF）的采食量和消化率。与UR相比，基于大豆的补充剂使干物质和氮采食量以及表观氮和ADF消化率更高（P < 0.05）。血浆葡萄糖和尿素浓度随补充氮而增加（P < 0.10），基于大豆的补充剂比UR更高（P < 0.01）。SBM和SP的采食量、消化率和血浆代谢物浓度相似（P > 0.1）。在试验3中，24头阉牛（261千克）分别单独饲喂巴哈雀稗干草加DCP（对照），或加主要来自UR或SBM的CP补充的DCP。在56天内，饲喂SBM的阉牛的DMI和平均日增重（ADG）最高（P < 0.05）。补充氮增加了（P < 0.05）DMI、ADG和料重比（G:F）。然而，与补充UR相比，补充SBM产生了更高的（P < 0.05）DMI和ADG，且G:F相似（P > 0.05）。我们得出结论，补充氮对于优化饲喂补充DCP的牧草日粮的生长阉牛的瘤胃功能和生产性能很重要。主要来自SBM的补充氮的日粮比UR更能提高日粮消化率和动物生产性能。
