Department of Animal Sciences, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brazil.
Department of Agriculture, Nutrition, and Veterinary Sciences, University of Nevada, Reno, Nevada, United States of America.
PLoS One. 2018 Jun 21;13(6):e0199577. doi: 10.1371/journal.pone.0199577. eCollection 2018.
Five in vitro experiments were conducted with the following objectives: 1) To evaluate the ruminal fermentation of three different single ingredients: corn, glycerin, and starch (Exp. 1 and 2); 2) To assess effects of partially replacing corn with glycerin in beef cattle diets on ruminal fermentation pattern (Exp. 3 and 4); and 3) To evaluate the effects of glycerin inclusion on the extension of ruminal DM digestibility of feeds with high (orchard hay) and low (corn) fiber content (Exp. 5). For Exp. 1 and 2, two in vitro systems (24-bottle AnkomRF and 20-serum bottles) were used in four consecutive fermentation batches to evaluate gas production (GP), fermentation profiles, enteric methane (CH4), and carbon dioxide (CO2) of corn, glycerin, and starch. The 24 h total GP, acetate concentration, and acetate: propionate ratio decreased only when glycerin was added to the diet (P < 0.01). The 48-h total GP and metabolizable energy were greatest for corn (P < 0.01), and similar between glycerin and starch. The starch treatment had the lowest total volatile fatty acids concentration (P = 0.01). Glycerin had greatest CH4 production, lag time, and maximum gas volume of the first pool (P < 0.05). However, the maximum gas volume of the second pool was greatest for corn (P < 0.05), and similar between glycerin and starch. The starch treatment had the greatest specific rates of digestion for first and second pools (P < 0.05). Production of CO2 (mL/g) was greater for corn (P < 0.01), but similar for glycerin and starch. For Exp. 3 and 4, the same systems were used to evaluate four different levels of glycerin [0, 100, 200, and 300 g/kg of dry matter (DM)] replacing corn in beef cattle finishing diets. Glycerin levels did not affect 24 and 48 h total GP, CH4, and CO2 (P > 0.05). The inclusion of glycerin linearly decreased acetate concentration (P = 0.03) and acetate: propionate ratio (P = 0.04). For Exp. 5, two DaisyII incubators were used to evaluate the in vitro dry matter digestibility (IVDMD) of the following treatments: orchard hay; corn; orchard hay + glycerin; and corn + glycerin. Glycerin inclusion decreased orchard hay IVDMD (P < 0.01) but did not affect corn IVDMD (P > 0.05). We concluded that, under these experimental conditions, glycerin has similar energy efficiency when used in replacement of corn and included at up to 300 g/kg in beef cattle diets.
进行了五项体外实验，目的如下：1）评估三种不同单一成分（玉米、甘油和淀粉）的瘤胃发酵：实验 1 和 2；2）评估在肉牛日粮中部分用甘油替代玉米对瘤胃发酵模式的影响：实验 3 和 4；3）评估甘油添加对高纤维（果园干草）和低纤维（玉米）含量饲料瘤胃 DM 消化率的影响：实验 5。实验 1 和 2 中，使用了两种体外系统（24 瓶 AnkomRF 和 20 个血清瓶），在四个连续的发酵批次中评估玉米、甘油和淀粉的气体生成（GP）、发酵谱、肠道甲烷（CH4）和二氧化碳（CO2）。当甘油添加到日粮中时，24 小时总 GP、乙酸浓度和乙酸：丙酸比仅降低（P < 0.01）。玉米的 48 小时总 GP 和可代谢能最大（P < 0.01），甘油和淀粉之间相似。淀粉处理的总挥发性脂肪酸浓度最低（P = 0.01）。甘油的 CH4 产量、滞后时间和第一池最大气体体积最大（P < 0.05）。然而，第二池的最大气体体积最大的是玉米（P < 0.05），甘油和淀粉之间相似。淀粉处理的第一和第二池的特定消化率最大（P < 0.05）。玉米的 CO2 产量（mL/g）最大（P < 0.01），但甘油和淀粉相似。实验 3 和 4 中，使用相同的系统评估了甘油替代肉牛育肥日粮中玉米的四个不同水平[0、100、200 和 300 g/kg 干物质（DM）]。甘油水平对 24 和 48 小时总 GP、CH4 和 CO2 没有影响（P > 0.05）。甘油的添加线性降低了乙酸浓度（P = 0.03）和乙酸：丙酸比（P = 0.04）。实验 5 中，使用两台 DaisyII 孵育器评估了以下处理的体外干物质消化率（IVDMD）：果园干草；玉米；果园干草+甘油；和玉米+甘油。甘油的添加降低了果园干草的 IVDMD（P < 0.01），但对玉米的 IVDMD 没有影响（P > 0.05）。我们得出结论，在这些实验条件下，甘油在替代玉米时具有相似的能量效率，在肉牛日粮中添加高达 300 g/kg 时也是如此。
