Alipour Daryoush, Saleem Atef Mohamed, Sanderson Haley, Brand Tassilo, Santos Laize V, Mahmoudi-Abyane Mahdi, Marami Mohammad Reza, McAllister Tim Angus
Department of Animal Science, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
Department of Animal and Poultry Production, Faculty of Agriculture, South Valley University, Qena, Egypt.
Transl Anim Sci. 2020 Mar 6;4(2):txaa013. doi: 10.1093/tas/txaa013. eCollection 2020 Apr.
This study evaluated the effect of combinations of feed-grade urea and slow-release urea (SRU) on fermentation and microbial protein synthesis within two artificial rumens (Rusitec) fed a finishing concentrate diet. The experiment was a completely randomized, dose-response design with SRU substituted at levels of 0% (control), 0.5%, 1%, or 1.75% of dry matter (DM) in place of feed-grade urea, with four replicate fermenters per dosage. The diet consisted of 90% concentrate and 10% forage (DM basis). The experiment was conducted over 15 d, with 8 d of adaptation and 7 d of sampling. Dry matter and organic matter disappearances were determined after 48 h of incubation from day 9 to 12, and daily ammonia (NH) and volatile fatty acid (VFA) production were measured from day 9 to 12. Microbial protein synthesis was determined on days 13-15. Increasing the level of SRU quadratically affected total VFA (Q, = 0.031) and ammonia (Q, = 0.034), with a linear increment in acetate (L, = 0.01) and isovalerate (L, = 0.05) and reduction in butyrate (L, = 0.05). Disappearance of neutral detergent fiber (NDF) and acid detergent fiber (ADF) was quadratically affected by levels of SRU, plateauing at 1% SRU. Inclusion of 1% SRU resulted in the highest amount of microbial nitrogen associated with feed particles (Q, = 0.037). Responses in the efficiency of microbial protein synthesis fluctuated (L, = 0.002; Q, = 0.001) and were the highest for 1% SRU. In general, the result of this study showed that 1% SRU in combination with 0.6% urea increased NDF and ADF digestibility and total volatile fatty acid (TVFA) production.
本研究评估了饲料级尿素与缓释尿素（SRU）组合对两个饲喂育肥浓缩饲料日粮的人工瘤胃（瘤胃模拟系统）内发酵和微生物蛋白合成的影响。试验采用完全随机剂量反应设计，用SRU替代干物质（DM）的0%（对照）、0.5%、1%或1.75%的饲料级尿素，每个剂量有4个重复发酵罐。日粮由90%的浓缩饲料和10%的粗饲料（以干物质计）组成。试验持续15天，其中8天用于适应，7天用于采样。在第9天至12天培养48小时后测定干物质和有机物质消失量，在第9天至12天测定每日氨（NH）和挥发性脂肪酸（VFA）产量。在第13 - 15天测定微生物蛋白合成。增加SRU水平对总挥发性脂肪酸（二次项，P = 0.031）和氨（二次项，P = 0.034）有二次影响，乙酸（线性，P = 0.01）和异戊酸（线性，P = 0.05）呈线性增加，丁酸（线性，P = 0.05）减少。中性洗涤纤维（NDF）和酸性洗涤纤维（ADF）的消失量受SRU水平的二次影响，在1% SRU时达到平稳。添加1% SRU导致与饲料颗粒相关的微生物氮含量最高（二次项，P = 0.037）。微生物蛋白合成效率的反应波动（线性，P = 0.002；二次项，P = 0.001），1% SRU时最高。总体而言，本研究结果表明，1% SRU与0.6%尿素组合可提高NDF和ADF消化率以及总挥发性脂肪酸（TVFA）产量。
