Miller D N, Varel V H
US Meat Animal Research Center, ARS, USDA, Clay Center, NE 68933-0166, USA.
J Anim Sci. 2002 Sep;80(9):2214-22.
Very little is known about the biochemical origin of cattle feedlot odors and the environmental factors controlling their production. The tie between diet and manure composition is well established, but the effect of different manure compositions on odorous chemical production is unknown. This study describes the effect of starch, casein, and cellulose substrate additions to slurries of fresh (< 24 h) and aged cattle manure (> 1 d) on the anaerobic production of fermentation products and the consumption of substrates relative to no addition treatments. Aged cattle manure accumulated more VFA (245 to 290 mM) than the fresh manure (91 to 181 mM) irrespective of substrate additions (P < 0.001). In fresh manures, VFA concentrations were increased (P < 0.01) over no addition treatments when carbohydrate (starch or cellulose) was added, whereas starch and protein treatments to aged manure increased VFA content relative to no addition treatments (P < 0.001). Branched-chain VFA and aromatic compounds accumulated only in the aged manure (no addition and protein treatments), indicating that some protein fermentation occurred in those treatments. Based upon substrate loss, starch fermentation was the dominant process in both manures and all treatments with losses exceeding 18.6 g/L. Protein fermentation occurred only in the aged manure, specifically the no addition and protein treatments, when starch was no longer available. The production of odorous compounds from manure was controlled by substrate availability and pH, with pH related to lactate accumulation. We believe that calcareous soil and lactate-consuming microorganisms in the aged manure slurries minimized slurry acidification and resulted in greater accumulations of odorous products. Substrate additions had little effect on the overall accumulation of odor compounds in manure but had profound effects on odor compound composition. We propose that modifying cattle diets to limit starch and protein excretion would profoundly affect the production and accumulation of odor compounds in feedlots.
关于肉牛饲养场气味的生化来源以及控制其产生的环境因素，人们了解甚少。日粮与粪便成分之间的联系已得到充分证实，但不同粪便成分对有气味化学物质产生的影响尚不清楚。本研究描述了在新鲜（<24小时）和陈旧（>1天）牛粪浆中添加淀粉、酪蛋白和纤维素底物对发酵产物厌氧产生以及相对于不添加处理底物消耗的影响。无论添加何种底物，陈旧牛粪积累的挥发性脂肪酸（VFA）（245至290 mM）都比新鲜牛粪（91至181 mM）多（P<0.001）。在新鲜牛粪中，添加碳水化合物（淀粉或纤维素）时，VFA浓度相对于不添加处理有所增加（P<0.01），而在陈旧牛粪中，淀粉和蛋白质处理相对于不添加处理增加了VFA含量（P<0.001）。支链VFA和芳香族化合物仅在陈旧牛粪（不添加和蛋白质处理）中积累，表明这些处理中发生了一些蛋白质发酵。基于底物损失，淀粉发酵是两种牛粪以及所有处理中的主要过程，损失超过18.6 g/L。只有在陈旧牛粪中，特别是不添加和蛋白质处理中，当淀粉不再可用时才会发生蛋白质发酵。粪便中有气味化合物的产生受底物可用性和pH值控制，pH值与乳酸积累有关。我们认为，陈旧牛粪浆中的钙质土壤和消耗乳酸的微生物使浆体酸化最小化，并导致有气味产物的积累增加。底物添加对粪便中有气味化合物的总体积累影响不大，但对气味化合物组成有深远影响。我们建议，调整肉牛日粮以限制淀粉和蛋白质排泄将深刻影响饲养场中有气味化合物的产生和积累。
