The University of Sydney, School of Life and Environmental Sciences, Sydney, New South Wales, Australia.
Lethbridge Research and Development Centre, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada.
J Anim Sci. 2018 Sep 7;96(9):3863-3877. doi: 10.1093/jas/sky265.
Ruminants play an important role in food security, but there is a growing concern about the impact of cattle on the environment, particularly regarding greenhouse gas emissions. The objective of this study was to examine the effect of humic substances (HS) on rumen fermentation, nutrient digestibility, methane (CH4) emissions, and the rumen microbiome of beef heifers fed a barley silage-based diet. The experiment was designed as a replicated 4 × 4 Latin square using 8 ruminally cannulated Angus × Hereford heifers (758 ± 40.7 kg initial BW). Heifers were offered a basal diet consisting of 60% barley silage and 40% concentrate (DM basis) with either 0- (control), 100-, 200- or 300-mg granulated HS/kg BW. Each period was 28 d with 14 d of adaptation. Rumen samples were taken on day 15 at 0, 3, 6, and 12 h postfeeding. Total urine and feces were collected from days 18 to 22. Blood samples were taken on day 22 at 0 and 6 h postfeeding. Between days 26 and 28, heifers were placed in open-circuit respiratory chambers to measure CH4. Ruminal pH was recorded continuously during the periods of CH4 measurement using indwelling pH loggers. Intake was similar (P = 0.47) across treatments. Concentration of ammonia-N and counts of rumen protozoa responded quadratically (P = 0.03), where both increased at H100 and then decreased for the H300 treatments. Apparent total tract digestibility of CP (P = 0.04) was linearly increased by HS and total N retention (g/d, % N intake, g/kg BW0.75) was improved (P = 0.04) for HS when compared with the control. There was no effect of HS on CH4 production (g/d; P = 0.83); however, HS decreased the relative abundance of Proteobacteria (P = 0.04) and increased the relative abundance of Synergistetes (P = 0.01) and Euryarchaeota (P = 0.04). Results suggest that HS included at up to 300 mg/kg BW may improve N retention and CP digestibility, but there was no impact on CH4 production.
反刍动物在食品安全中发挥着重要作用，但人们越来越关注牛对环境的影响，特别是温室气体排放。本研究的目的是研究腐殖质（HS）对瘤胃发酵、养分消化率、甲烷（CH4）排放和饲喂大麦青贮饲料的肉牛小母牛瘤胃微生物组的影响。该实验采用 8 头带有瘤胃套管的安格斯×赫里福德小母牛（758±40.7kg 初始体重），以可重复的 4×4 拉丁方设计进行。小母牛提供由 60%大麦青贮和 40%浓缩物（干物质基础）组成的基础日粮，添加 0-（对照）、100-、200-或 300-mg 粒状 HS/kgBW。每个周期为 28d，适应期为 14d。在饲喂后 0、3、6 和 12h 取第 15 天的瘤胃液样品。从第 18 天到第 22 天收集总尿液和粪便。在饲喂后 0 和 6h 取第 22 天的血液样品。在第 26 天到第 28 天期间，将小母牛放入闭路呼吸室以测量 CH4。在测量 CH4 的期间，使用植入式 pH 记录器连续记录瘤胃 pH。处理间的采食量相似（P=0.47）。氨氮浓度和瘤胃原虫计数呈二次曲线反应（P=0.03），H100 时两者均增加，然后 H300 处理时减少。HS 线性增加 CP 的表观全肠道消化率（P=0.04），与对照相比，总氮保留（g/d、%氮摄入、g/kgBW0.75）得到改善（P=0.04）。HS 对 CH4 产量（g/d；P=0.83）没有影响；然而，HS 降低了变形菌门的相对丰度（P=0.04），增加了互养菌门（P=0.01）和广古菌门（P=0.04）的相对丰度。结果表明，HS 添加量高达 300mg/kgBW 可能会提高氮保留和 CP 消化率，但对 CH4 产量没有影响。
