降低反刍动物甲烷排放的研究进展

本文阐述了反刍动物瘤胃甲烷生成的生物学机制及影响反刍动物瘤胃甲烷生成的因素，并用产明了降低瘤胃甲烷产生的方法，最后对降低甲烷生成的前景作了展望。     

反刍动物甲烷排放的调控

近年来随着畜牧业的迅速发展,饲养家畜向大气中排放的废弃物逐年增加,其中反刍家畜的甲烷排放问题已经引起了很多学者的关注,有研究表明     

反刍动物甲烷排放现状及调控技术研究进展

甲烷是反刍动物消化代谢的产物。但反刍动物胃肠道发酵排放甲烷不仅造成了能量的损失,而且也是导致环境温室效应的重要因素之一。因此,如何调控反刍动物瘤胃甲烷气体的产生,从而减少其排放量,对提高饲料能量的利用效率和提高动物生产力以及改善环境具有重要意义。文章从反刍动物瘤胃甲烷气体的产生机理、影响甲烷合成的影响因子以及调控减排技术研究进展等方面做一详细综述。     

采用红外光谱技术检测反刍动物甲烷排放

反刍动物甲烷排放监测一直难以建立起精确的评估体系,其中一个重要原因是常用检测反刍动物甲烷排放的方法不够完善,另外检测仪器受外部环境的影响,难以保证其准确度和灵敏度。目前,红外光谱检测技术正在被广泛应用于反刍动物甲烷排放检测,一些基于红外光谱检测技术的最新检测方法,如甲烷激光检测(LMD)、傅里叶变换红外光谱检测(FTIR)、Green Feed(GF)系统和便携式自动开路气体量化系统(GQS)也得到广泛运用。与以往常用方法相比,红外光谱检测技术具有一定优势。本文根据现有文献,从红外光谱检测的原理、可靠性及与其他常见方法对比,论述了红外光谱检测方法在反刍动物甲烷排放中的应用现状和应用前景,旨在为精确检测反刍动物的甲烷排放提供参考。     

2020年荷斯坦奶牛甲烷排放研究进展

二氧化碳、甲烷、臭氧等都是造成温室效应的主要气体,其中同等质量甲烷导致的温室效应是二氧化碳的28～35倍。甲烷不仅仅影响环境,而且还增加奶牛的能量损耗,因此,控制甲烷排放有利于保护环境和提高奶牛生产性能。本文结合国内外近年来的研究成果,从饲喂方式、饲料种类、瘤胃代谢、基因标记技术等方面进行综述,旨在为奶牛养殖过程中控制甲烷排放提供理论依据和指导。     

瓦里关大气二氧化碳和甲烷本底浓度变化特征

利用1994年至2017年瓦里关全球大气本底站在线监测的CO_2和CH_4数据,分析其变化特征。结果表明:瓦里关地区大气CO_2年平均体积浓度呈逐年增加的趋势,年平均浓度从1994年的358.99ppm增加到2017年的406. 80ppm,期间CO_2浓度共增加了47.81ppm,增幅为13.32%,年平均增长率为1.99ppm·a-1。季节变化特征表现为冬春季偏高,夏秋季偏低。CH_4年平均体积浓度从1994年的1804.7ppb增长至2017年的1905. 7ppb, CH_4浓度共增加了101ppb,增幅为5.6%,年平均增长率约为4.43ppb·a-1。季节变化特征为冬春季偏低,夏秋季偏高。     

牛至精油缓解反刍动物瘤胃甲烷排放的研究进展

反刍动物温室气体的排放量占畜禽温室气体总排放量的80%,甲烷作为瘤胃微生物代谢的副产物，不仅对环境造成严重危害还降低了反刍动物的饲料能量利用率。植物提取物凭借其调节瘤胃微生物群落的功效在甲烷减排领域成为研究热点之一。牛至精油是从牛至中提取的一种含多种生物活性物质的植物提取物，以麝香草酚和香芹酚为主效因子，具有改善瘤胃内环境、改变瘤胃微生物组成、调控瘤胃发酵等生物学功能，在反刍动物养殖领域的应用前景十分广阔。关于牛至精油降低甲烷的作用效果已在多种动物上进行研究，结果表明牛至精油能通过调节瘤胃微生物及其代谢来降低瘤胃甲烷排放，但对其作用机制的研究还不够深入。作者以反刍动物为对象，对牛至精油通过调节瘤胃中细菌、古菌以及原虫的丰度和组成，调控瘤胃代谢，抑制二氧化碳还原途径和乙酸发酵途径，达到改善甲烷排放的作用机制进行综述，以期为牛至精油在饲料中的应用提供参考。     

瘤胃中添加剂的甲烷减排作用及甲烷厌氧氧化北大核心CSCD

反刍动物每年排放甲烷(CH_(4))约1亿t,是全球变暖的重点关注对象。在瘤胃发酵过程中产生CH_(4)会造成2%~12%的能量损失。目前,有多种饲料添加剂能从不同角度降低CH_(4)排放量,但都存在一定缺陷;而甲烷厌氧氧化作为自然环境中重要的甲烷汇亦有可能在瘤胃中存在。本文综述了不同饲料添加剂对CH_(4)减排的作用以及甲烷厌氧氧化在瘤胃中存在的可能性,以期为反刍动物CH4减排提供新思路。     

猪场中季节、排风措施和猪粪混合物的清除等因素对甲烷释放的影响

全球大约有60％的甲烷的排放与人类的活动有关，比如农业领域、煤的燃料和垃圾的处理。而农业领域甲烷排放的一个很重要的组成部分就是猪场里猪粪混合物的甲烷的排放。总的来说，影响室内猪粪混合物甲烷排放的因素主要有氧气和挥发性物质的量、pH值、垫物的温度、贮存时间和抑制性物质。有关猪舍内猪粪混合物甲烷释放的调查开始于有两个阶段，分别是1999年10月-2001年2月和2003年2月-2004年7月。季节对甲烷的排放量有很大的影响，比如在夏季的堆肥期。然而，室内温度并引申到排风措施对甲烷释放的重要影响，仅仅发生在室内平均温度25℃以上的情况下。而且，甲烷的释放会由于在堆肥期和接下来的清除期之间猪粪混合物的完全清除而减少。     

淡水甲烷排放

<正>一个国际科学家小组研究表明,因为淡水区域的甲烷排放,内陆吸收的温室气体低于原来的想象。该研究小组成员爱荷华州立大学生态、进化和微生物学系教授John Downing,认为内陆水释放的甲烷高于原来的估计,该项研究发表在《科学》杂志上。研究表明淡水     

Effect of Terminalia chebula and Allium sativum on in vivo methane emission by sheep

A study was conducted to evaluate some plant parts (already tested for their antimethanogenic activity in in vitro gas production test in the authors’ laboratory) as feed additive to combat methane emission from sheep. Sixteen male sheep with average body weight of 29.96 ± 1.69 kg (22 months of age) were divided into four groups in a randomized block design. The animals were fed on a diet containing forage to concentrate ratio of 1:1. The concentrate fraction composed (in parts) of maize grain, 32; wheat bran, 45; deoiled soybean meal, 20; mineral mixture, 2 and common salt, 1. The four treatments were control (without additive), seed pulp of Terminalia chebula (Harad), bulb of Allium sativum (Garlic) and a mixture (Mix) of the latter two in equal proportions at the rate of 1% of dry matter (DM) intake. There was no effect on DM intake due to the inclusion of these feed additives. The digestibilities of DM and organic matter tended to be higher (p < 0.1) in the groups with T. chebula and A. sativum, whereas, neutral detergent fibre (NDF), acid detergent fibre (ADF) and cellulose digestibilities were higher (p < 0.05) in all the three experimental groups compared with control. The nitrogen balance and plane of nutrition were not affected by inclusion of any of the feed additives. Methane emission (L/kg digested DM intake) as estimated by open circuit respiration chamber and methane energy loss as per cent of digestible energy intake tended to be lower in T. chebula (p = 0.09) and Mix (p = 0.08) groups compared with control. The data indicated that T. chebula showed antimethanogenic activity, whereas both T. chebula and A. sativum improved nutrient digestibility. Therefore, these two plants appear to be suitable candidates for use as feed additive to mitigate methane emission and to improve nutrient utilization by sheep.     

Measurement of enteric methane from ruminants using a hand-held laser methane detector

Abstract

This study investigated the effectiveness of the proprietary laser methane detector (LMD) in enteric methane monitoring from individual dairy cows and sheep. Three experiments were carried out. First, the relationship between LMD and indirect open-circuit respiration calorimetric chamber measurements was tested. Sensitivity and specificity for cows were 95.4% and 96.5%. For sheep, sensitivity was 93.8% and specificity was 78.7%. Second, the effect of cow's activity on enteric methane emissions was investigated. During drinking and feeding, cows produced significantly more (p<0.001) methane emissions than when idle. Third, effect of different micrometeorological factors on LMD measurements under outdoor grazing conditions was investigated. Wind speed, relative humidity, pressure and wind direction relative to methane point-source had significant effect on methane measurements (p<0.001) under outdoor conditions. With further validation, the LMD has potential to provide reliable estimates from ruminants and hence provide a useful technique for on-farm monitoring and decision support for greenhouse gas mitigation strategies.     

Influence of protein fermentation and carbohydrate source on in vitro methane production

Incubations were carried out with batch cultures of ruminal micro‐organisms from sheep to analyse the influence of the N source on in vitro CH₄ production. The two substrates were mixtures of maize starch and cellulose in proportions of 75:25 and 25:75 (STAR and CEL substrates, respectively), and the three nitrogen (N) sources were ammonia (NH₄Cl), casein (CA) and isolated soya bean protein (SP). Five isonitrogenous treatments were made by replacing non‐protein‐N (NPN) with CA or SP at levels of 0 (NPN), 50 (CA50 and SP50, respectively) and 100% (CA100 and SP100) of total N. All N treatments were applied at a rate of 35 mg of N/g of substrate organic matter and incubations lasted 16.5 h. With both proteins, N source × substrate interactions (p = 0.065 to 0.002) were detected for CH₄ production and CH₄/total VFA ratio. The increases in CH₄ production observed by replacing the NPN with protein‐N were higher (p < 0.05) for STAR than for CEL substrate, but the opposite was observed for the increases in volatile fatty acid (VFA) production. As a consequence, replacing the NPN by increased levels of CA or SP led to linear increases (p < 0.05) in CH₄/total VFA ratio with STAR, whereas CH₄/total VFA ratio tended (p < 0.10) to be decreased with CEL substrate. Increasing the amount of both proteins decreased linearly (p < 0.05) ammonia‐N concentrations, which may indicate an incorporation of amino acids and peptides into microbial protein without being first deaminated into ammonia‐N. In incubations with the tested N sources as the only substrate, the fermentation of 1 mg of CA or SP produced 1.24 and 0.60 μmol of CH₄ respectively. The results indicate the generation of CH₄ from protein fermentation, and that the response of CH₄ production to protein‐N supply may differ with the basal substrate.     

Potential of tannin‐rich plants,Leucaena leucocephala,Glyricidia sepium and Manihot esculenta,to reduce enteric methane emissions in sheep

An in vivo trial was conducted in sheep to investigate the effect of three tropical tannin‐rich plants (TRP) on methane emission, intake and digestibility. The TRP used were leaves of Glyricidia sepium, Leucaena leucocephala and Manihot esculenta that contained, respectively, 39, 75 and 92 g condensed tannins/kg DM. Methane was determined with the sulphur hexafluoride tracer technique. Eight rumen‐cannulated sheep of two breeds (four Texel, four Blackbelly) were used in two 4 × 4 Latin square designs. Four experimental diets were tested. They consisted in a tropical natural grassland hay based on Dichanthium spp. fed alone (C) or in association with G. sepium (G), L. leucocephala (L) or M. esculenta (M) given as pellets at 44% of the daily ration. Daily organic matter intake was higher in TRP diets (686, 984, 1054 and 1186 g/day for C, G, L and M respectively; p < 0.05) while apparent organic matter total tract digestibility was not affected (69.9%, 62.8%, 65.3% and 64.7% for C, G, L and M respectively; p > 0.05). Methane emission was 47.1, 44.9, 33.3 and 33.5 g/kg digestible organic matter intake for C, G, L and M, respectively, and was significantly lower (p < 0.05) for L and M than for G and C. Our results confirm the potential of some TRP to reduce methane production. The strong decrease in methane and the increase in intake with TRPs may be due to their presentation as pellets.     

Effect of divergence in residual methane emissions on feed intake and efficiency,growth and carcass performance,and indices of rumen fermentation and methane emissions in finishing beef cattle

Residual expressions of enteric emissions favor a more equitable identification of an animal’s methanogenic potential compared with traditional measures of enteric emissions. The objective of this study was to investigate the effect of divergently ranking beef cattle for residual methane emissions (RME) on animal productivity, enteric emissions, and rumen fermentation. Dry matter intake (DMI), growth, feed efficiency, carcass output, and enteric emissions (GreenFeed emissions monitoring system) were recorded on 294 crossbred beef cattle (steers = 135 and heifers = 159; mean age 441 d (SD = 49); initial body weight (BW) of 476 kg (SD = 67)) at the Irish national beef cattle performance test center. Animals were offered a total mixed ration (77% concentrate and 23% forage; 12.6 MJ ME/kg of DM and 12% CP) ad libitum with emissions estimated for 21 d over a mean feed intake measurement period of 91 d. Animals had a mean daily methane emissions (DME) of 229.18 g/d (SD = 45.96), methane yield (MY) of 22.07 g/kg of DMI (SD = 4.06), methane intensity (MI) 0.70 g/kg of carcass weight (SD = 0.15), and RME 0.00 g/d (SD = 0.34). RME was computed as the residuals from a multiple regression model regressing DME on DMI and BW (R² = 0.45). Animals were ranked into three groups namely high RME (>0.5 SD above the mean), medium RME (±0.5 SD above/below the mean), and low RME (>0.5 SD below the mean). Low RME animals produced 17.6% and 30.4% less (P < 0.05) DME compared with medium and high RME animals, respectively. A ~30% reduction in MY and MI was detected in low versus high RME animals. Positive correlations were apparent among all methane traits with RME most highly associated with (r = 0.86) DME. MY and MI were correlated (P < 0.05) with DMI, growth, feed efficiency, and carcass output. High RME had lower (P < 0.05) ruminal propionate compared with low RME animals and increased (P < 0.05) butyrate compared with medium and low RME animals. Propionate was negatively associated (P < 0.05) with all methane traits. Greater acetate:propionate ratio was associated with higher RME (r = 0.18; P < 0.05). Under the ad libitum feeding regime deployed here, RME was the best predictor of DME and only methane trait independent of animal productivity. Ranking animals on RME presents the opportunity to exploit interanimal variation in enteric emissions as well as providing a more equitable index of the methanogenic potential of an animal on which to investigate the underlying biological regulatory mechanisms.     

Effect of α-cyclodextrin-allyl isothiocyanate on ruminal microbial methane production in vitro

The objective of the present study was to investigate the effects of α‐cyclodextrin‐allyl isothiocyanate (CD‐AI) on ruminal microbial methane production and rumen fermentation of corn starch, soluble potato starch or hay plus concentrate (1.5:1) by mixed rumen microorganisms. Diluted rumen fluid (30 mL) was incubated anaerobically at 38°C for 6 and 24 h with or without CD‐AI (0, 0.4, 0.8, 1.6 and 3.2 g/L). The pH of the medium was unchanged by CD‐AI in all substrates. The molar proportion of acetate was decreased and propionate was increased with a corresponding decrease in acetate : propionate ratio (P < 0.05). Total volatile fatty acids and butyrate were increased (P < 0.05). Ammonia‐N was decreased (P < 0.05). Except with soluble potato starch, numbers of protozoa were unchanged after 6 h. As concentration of CD‐AI increased from 0 to 3.2 g/L, fermentation of corn starch, soluble potato starch and hay plus concentrate resulted in decreased (P < 0.05) methane production of 49–100% (6 h) and 14–100% (24 h); 39–100% (6 h) and 16–100% (24 h); and 45–100% (6 h) and 17–100% (24 h), respectively. When hay plus concentrate was used as substrate, methanogenic bacteria were decreased (P < 0.05) with 0.8 g/L of CD‐AI after 6 h. Excluding the lower dose level (0.4 g/L) of CD‐AI, digestibility of neutral detergent fiber of hay plus concentrate was decreased (P < 0.05) after 24 h. A suitable level of CD‐AI could therefore be used as a supplement to inhibit methane production and improve rumen fermentation without detrimental effects on fiber digestion.     

添加5种植物酚类化合物对高精料底物瘤胃体外发酵及产甲烷的影响

甲烷排放是全球变暖和气候变化的主要影响因素之一,而瘤胃微生物发酵会排放大量甲烷,因此减少反刍动物排放甲烷已引起广泛关注。本试验旨在采用人工瘤胃体外发酵技术,研究在精粗比为65∶35的条件下,添加不同浓度(0、0.05%、0.10%、0.20%)的单宁酸、对羟基苯甲酸、鞣花酸、丁香酸及芦丁对瘤胃体外发酵参数及甲烷产量的影响。结果表明,与空白对照相比,在体外条件下,添加0.05%及以上的单宁显著降低NH₃-N水平(P<0.05),添加0.20%的单宁显著降低发酵终点pH(P<0.05),并显著提高48 h累积产气量和乙丙比(P<0.05)。添加0.10%及以上浓度的对羟基苯甲酸可显著降低NH₃-N和乙酸浓度并提高累积产气量(P<0.05);除乙酸外,对挥发性脂肪酸的产生无显著影响(P>0.05)。添加鞣花酸后显著降低CH₄产生和乙丙比(P<0.05);当添加水平达到0.10%后TVFA(总挥发性脂肪酸)显著下降(P<0.05),达到0.20%后pH和NH₃-N显著下降(P<0.05)。添加丁香酸后NH₃-N和累积产气量显著下降(P<0.05);当添加水平达到0.10%后,CH₄和TVFA显著增加(P<0.05)。添加芦丁显著降低NH₃-N并增加TVFA(P<0.05),当添加水平达到0.10%时,乙丙比显著下降(P<0.05);达到0.20%时pH下降而累积产气量显著增加(P<0.05)。由此可见,添加一定水平的酚酸和芦丁能降低NH₃-N浓度,增加产气量;丁香酸和芦丁可增加TVFA水平,而鞣花酸降低TVFA水平;仅鞣花酸能抑制甲烷产生,而丁香酸促进甲烷的产生。     

Effects of pure plant secondary metabolites on methane production,rumen fermentation and rumen bacteria populations in vitro

In this study, the effects of seven pure plant secondary metabolites (PSM s) on rumen fermentation, methane (CH₄) production and rumen bacterial community composition were determined. Two in vitro trials were conducted. In trial 1, nine concentrations of 8‐hydroxyquinoline, α‐ terpineol, camphor, bornyl acetate, α‐ pinene, thymoquinone and thymol were incubated on separate days using in vitro 24‐hr batch incubations. All compounds tested demonstrated the ability to alter rumen fermentation parameters and decrease CH₄ production. However, effective concentrations differed among individual PSM s. The lowest concentrations that reduced (p  <  .05) CH₄ production were as follows: 8 mg/L of 8‐hydroxyquinoline, 120 mg/L of thymoquinone, 240 mg/L of thymol and 480 mg/L of α‐ terpineol, camphor, bornyl acetate and α‐ pinene. These concentrations were selected for use in trial 2. In trial 2, PSM s were incubated in one run. Methane was decreased (p  <  .05) by all PSM s at selected concentrations. However, only 8‐hydroxyquinoline, bornyl acetate and thymoquinone decreased (p  <  .05) CH₄ relative to volatile fatty acids (VFA s). Based on denaturing gradient gel electrophoresis analysis, different PSM s changed the composition of bacterial communities to different extents. As revealed by Ion Torrent sequencing, the effects of PSM s on relative abundance were most pronounced in the predominant families, especially in Lachnospiraceae , Succinivibrionaceae , Prevotellaceae , unclassified Clostridiales and Ruminococcaceae . The CH ₄ production was correlated negatively (?.72; p  <  .05) with relative abundance of Succinivibrionaceae and positively with relative abundance of Ruminococcaceae (.86; p  <  .05). In summary, this study identified three pure PSM s (8hydroxyquinoline, bornyl acetate and thymoquinone) with potentially promising effects on rumen CH₄ production. The PSM s tested in this study demonstrated considerable impact on rumen bacterial communities even at the lowest concentrations that decreased CH₄ production. The findings from this study may help to elucidate how PSM s affect rumen bacterial fermentation.     

In vitro gas and methane production in rumen fluid from dairy cows fed grass silages differing in plant maturity,compared to in vivo data

The relationship between in vitro rumen CH₄ production of grass silages, using the gas production technique, and in vivo data obtained with the same cows and rations in respiration chambers was investigated. Silages were made from grass harvested in 2013 on May 6th, May 25th, July 1st and July 8th. The grass silages were used to formulate four different rations which were fed to 24 cows in early and late lactation, resulting in a slightly different dry matter intake (DMI; 16.5 kg/day vs. 15.4 kg/day). The experimental rations consisted of 70% grass silage, 10% maize silage, and 20% concentrates on a dry matter basis. Cows were adapted to the rations for 17 days before rumen fluid was collected via oesophageal tubing, and in vitro gas and CH₄ production were analysed. In vitro total gas and CH₄ production of the (ensiled) grass expressed as ml/g OM decreased with advancing maturity of the grass. The in vitro CH₄ production after 48 hr of incubation expressed in ml/g OM did not correlate with the in vivo CH₄ production expressed in g/kg organic matter intake or g/kg DMI (R² = .00–.18, p ≥ .287). The differences in CH₄ emission per unit of intake observed in vivo were rather small between the different rations, which also contributed to the observed poor relationship. Utilizing stepwise multiple regression improved the correlation only slightly. In vitro gas and CH₄ production varied based on whether donor cows were previously adapted to the respective ration or not, suggesting that careful adaption to the experimental diet should be envisaged in in vitro gas and CH₄ production experiments.     

Effect of substituting soybean meal with euglena (Euglena gracilis) on methane emission and nitrogen efficiency in sheep

This study evaluated methane (CH₄) emission, intake, digestibility, and nitrogen efficiency in sheep fed diets containing replacement levels (0%, 33%, 50%, and 67% of soybean meal with euglena). In this experiment, four Corriedale wether sheep with an initial body weight of 53.8 ± 4.6 were arranged in a 4 × 4 Latin square design. This experiment lasted 84 days, divided into four experimental periods. Each period lasted 21 days, which consists of 14 days of adaptation to the diets, 5 days to collect samples, and 2 days to collect gas emission from sheep. Methane emission expressed as L/kg DM intake or g/kg DM intake reduced by up to 37% and the energy loss via CH₄ (% of GE intake) reduced by up to 34%. No differences (p > 0.05) were observed in DM and OM intake and whole tract apparent DM digestibility due to substitution of soybean meal with euglena. The total CP loss reduced significantly (linear, p < 0.001) and CP efficiency increased linearly (p = 0.03) with increasing concentration of euglena. As a result, nitrogen balance and average daily weight gain remained unchanged despite higher nitrogen concentration in soybean supplemented group. In conclusion, substitution of soybean meal with euglena reduced methane emission without affecting the performance of animals.