Vallimont J E, Bargo F, Cassidy T W, Luchini N D, Broderick G A, Varga G A
Department of Dairy and Animal Science, The Pennsylvania State University, University Park, 16802, USA.
J Dairy Sci. 2004 Dec;87(12):4221-9. doi: 10.3168/jds.S0022-0302(04)73567-5.
A dual-effluent continuous-culture system was used to evaluate the effects of partially replacing cornstarch with sucrose in a total mixed ration on ruminal fermentation and N metabolism. The 4 treatments were 0 (control), 2.5, 5.0, and 7.5% sucrose and, respectively, 7.5 (control), 5.0, 2.5, and 0% cornstarch in a total mixed ration containing 20% corn silage and 40% alfalfa silage. Fermenters were fed 4 times a day during four 9-d periods with sampling beginning on d 6. Replacing cornstarch with sucrose did not alter ruminal pH (5.97), total volatile fatty acids (VFA) (104.4 mmol/L), or the acetate to propionate ratio (2.16); however, branched-chain volatile fatty acids were higher for the control treatment compared with the 7.5% sucrose treatment. Five hours postfeeding, sucrose treatments significantly altered molar proportions of all volatile fatty acids, and acetate-to-propionate and glucogenic-to-lipogenic ratios. Digestibility of dry matter and N were not affected by treatment, but digestibility of total non-structural carbohydrates was increased with sucrose treatments. A quadratic effect was noted for neutral detergent fiber (NDF) digestibility as sucrose replaced starch. A higher NDF digestibility (66.1 vs. 59.9%) was observed for the 7.5% sucrose treatment compared with the other 2 sucrose treatments. Levels of ammonia N were within an acceptable range to support microbial protein synthesis and did not differ among treatments (mean=9.23 mg/dL). Sucrose inclusion in the total mixed ration did not affect bacterial N synthesis. Results indicate that (at the levels tested in this study) inclusion of sucrose in the diet when rumen-degradable protein is adequate does not affect ruminal fermentation.
采用双流出连续培养系统，评估在全混合日粮中用蔗糖部分替代玉米淀粉对瘤胃发酵和氮代谢的影响。4种处理分别为：全混合日粮中蔗糖含量为0（对照）、2.5%、5.0%和7.5%，相应地，玉米淀粉含量分别为7.5%（对照）、5.0%、2.5%和0%，该全混合日粮含有20%的玉米青贮和40%的苜蓿青贮。在四个9天的周期内，每天给发酵罐喂食4次，从第6天开始取样。用蔗糖替代玉米淀粉不会改变瘤胃pH值（5.97）、总挥发性脂肪酸（VFA）（104.4 mmol/L）或乙酸与丙酸的比例（2.16）；然而，与7.5%蔗糖处理相比，对照处理的支链挥发性脂肪酸含量更高。喂食后5小时，蔗糖处理显著改变了所有挥发性脂肪酸的摩尔比例，以及乙酸与丙酸的比例和生糖与生脂的比例。干物质和氮的消化率不受处理的影响，但蔗糖处理可提高总非结构性碳水化合物的消化率。随着蔗糖替代淀粉，中性洗涤纤维（NDF）消化率呈现二次效应。与其他两种蔗糖处理相比，7.5%蔗糖处理的NDF消化率更高（66.1%对59.9%）。氨氮水平在支持微生物蛋白质合成的可接受范围内，各处理之间没有差异（平均值=9.23 mg/dL）。全混合日粮中添加蔗糖不影响细菌氮的合成。结果表明，（在本研究测试的水平下）当瘤胃可降解蛋白质充足时，日粮中添加蔗糖不会影响瘤胃发酵。
