摘要
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.
摘要译文
反刍动物在粮食安全方面发挥着重要作用，但人们越来越关注牛对环境的影响，尤其是温室气体排放。这项研究的目的是检查腐殖质（HS）对瘤胃发酵，营养物质消化率，甲烷（CH 4）排放的影响，和牛肉小母牛的瘤胃微生物组饲喂大麦青贮饲料。该实验设计为复制的4×4拉丁方，使用8个瘤状插管Angus×Hereford小母牛（758±40。7千克初始BW）。给小母牛提供由60％大麦青贮饲料和40％浓缩物（基于DM）组成的基础日粮，其具有0-（对照），100-，200-或300-mg颗粒化HS / kg BW。每个时期为28天，适应时间为14天。在第15天在喂食后0,3,6和12小时采集瘤胃样品。从第18天到第22天收集总尿液和粪便。在第22天，在喂食后0和6小时采集血样。在第26天和第28天之间，将小母牛放置在开路呼吸室中以测量CH 4。使用留置pH记录仪在CH 4测量期间连续记录瘤胃pH。治疗期间摄入量相似（P \x3d 0.47）。氨氮浓度和瘤胃原生动物的数量平方应答（P \x3d 0.03），其中H100处理均增加，然后H300处理减少。HS的表观总消化道消化率（P \x3d 0.04）由HS线性增加，总N保留率（g / d，％N摄入量，g / kg BW sup 0.75 / sup）得到改善（P \x3d 0。04）与对照相比，HS。 HS对CH 4的产生没有影响（g / d; P \x3d 0.83）;然而，HS降低了Proteobacteria的相对丰度（P \x3d 0。04）并且增加了Synergistetes（P \x3d 0.01）和Euryarchaeota（P \x3d 0.04）的相对丰度。结果表明，含有高达300 mg / kg BW的HS可以提高N保留率和CP消化率，但对CH 4的生产没有影响。
Stephanie A Terry;Gabriel de Oliveira Ribeiro;Robert J Gruninger;Martin Hunerberg;Sheng Ping;Alex V Chaves;Jake Burlet;Karen Ann Beauchemin;Tim Angus McAllister. Effect of humic substances on rumen fermentation, nutrient digestibility, methane emissions, and rumen microbiota in beef heifers[J]. Journal of Animal Science, 2018,96(9): 3863–3877