Witzig Maren, Lengowski Melanie B, Zuber Karin H R, Möhring Jens, Rodehutscord Markus
Institut für Nutztierwissenschaften, Universität Hohenheim, Stuttgart, Germany.
Institut für Nutztierwissenschaften, Universität Hohenheim, Stuttgart, Germany.
Anaerobe. 2018 Jun;51:99-109. doi: 10.1016/j.anaerobe.2018.04.016. Epub 2018 May 1.
Compared to grass silage (GS)-, corn silage (CS)-based diets appear to increase the efficiency of microbial protein synthesis (EMPS) in the rumen. Opposite results for the EMPS obtained in vitro have raised the question of whether an inadequate supply of amino N for microbes might explain the low EMPS. We examined the effects of supplementation with different N sources in CS on the EMPS and microbial populations in vitro. GS and CS were used as substrates for in vitro incubation. CS was non-supplemented or supplemented with urea, mixed amino acids (AA), peptone, or protein to adjust the N content to that of GS. Degradation of organic matter (OM) and crude protein (CP) revealed a positive effect of all N supplements, except protein. Additionally, N supplementation increased fiber degradation of CS. Peptone primarily stimulated hemicellulolytic activity and urea stimulated cellulolytic activity. The EMPS of CS was improved by all N supplements, with peptone and urea exhibiting the highest increase (57% and 54%, respectively), followed by AA mix (40%) and protein (11%) compared to that of CS alone (111 g microbial CP kg fermented OM). However, the level of EMPS detected with GS (200 g microbial CP kg fermented OM) was not achieved. Protozoal 18S rRNA gene copy numbers were negatively correlated with the EMPS, whereas no correlation was found between total bacteria and the EMPS. A stimulating effect of urea, AA mix, and peptone was detected for Ruminococcus albus and Prevotella bryantii, whereas Fibrobacter succinogenes was inhibited by N supplementation. This indicated that neither the amount of available N nor the N source was the only limiting factor in the low EMPS values of CS in vitro. Information is also provided on the stimulating effects of different N sources on several microbial species in mixed rumen culture.
与以青草青贮饲料（GS）为基础的日粮相比，以玉米青贮饲料（CS）为基础的日粮似乎能提高瘤胃中微生物蛋白质合成效率（EMPS）。体外获得的EMPS的相反结果引发了一个问题，即微生物可利用的氨基氮供应不足是否可以解释低EMPS。我们研究了在CS中添加不同氮源对体外EMPS和微生物种群的影响。GS和CS用作体外培养的底物。CS不添加或添加尿素、混合氨基酸（AA）、蛋白胨或蛋白质，以将氮含量调整到与GS相同的水平。有机物（OM）和粗蛋白（CP）的降解表明，除蛋白质外，所有氮补充剂都有积极作用。此外，添加氮提高了CS的纤维降解率。蛋白胨主要刺激半纤维素分解活性，尿素刺激纤维素分解活性。所有氮补充剂都提高了CS的EMPS，与单独的CS（111 g微生物CP/kg发酵OM）相比，蛋白胨和尿素的提高幅度最大（分别为57%和54%），其次是AA混合物（40%）和蛋白质（11%）。然而，未达到用GS检测到的EMPS水平（200 g微生物CP/kg发酵OM）。原生动物18S rRNA基因拷贝数与EMPS呈负相关，而总细菌与EMPS之间未发现相关性。检测到尿素、AA混合物和蛋白胨对白色瘤胃球菌和布氏普雷沃氏菌有刺激作用，而添加氮抑制了产琥珀酸丝状杆菌。这表明，可用氮的量和氮源都不是体外CS低EMPS值的唯一限制因素。还提供了不同氮源对混合瘤胃培养中几种微生物物种的刺激作用的信息。
