In vitro gas formation and fermentation parameters using different substrates and pig faecal inocula affected by bile extract

The effect of bile extract on microbial gas formation and composition, production of volatile fatty acids (VFA) and methane and on reductive acetogenesis was studied in vitro. As substrates cellulose and potato starch in combination with graded levels of bile extract concentrations (0; 333; 666; 1333 mg/l) were incubated with a faecal suspension from pigs as microbial inoculum according to procedures of a modified “Hohenheim gas formation test” (HFT). Bile extract concentration of 1333 mg/l in the in vitro system reduced total gas production from cellulose significantly (p < 0.05) compared to incubation without bile extract. After 24 h of incubation, bile extract concentration of 1333 mg/l lead to a decrease in methane production from cellulose (p < 0.05) in comparison to incubation without bile extract. Increasing levels of bile extract reduced total production of VFA (p < 0.05) from cellulose. Furthermore, bile extract concentration of 1333 mg/l increased molar percentage of propionate from cellulose and starch after 24 h of incubation (p < 0.05). Bile extract concentration of 333 mg/l increased molar percentage of propionate from cellulose after 48 h of incubation (p < 0.05). The results may contribute to explain the differences in gas and methane production between the rumen and the hindgut of monogastric animals.     

不同纤维素与淀粉比率等氮纯化日粮瘤胃发酵挥发性脂肪酸产生量

本文采用持续动态瘤胃模拟装置 (RSI)研究了 6种不同纤维素和淀粉比率 (C S) ;0 .14、0 .4 4、0 .94、1.92、4 .75、15 .76等氮纯化日粮养分瘤胃发酵率及挥发性脂肪酸净产生量。结果显示 :随着日粮中C S的升高 ,72小时发酵后 ,纤维素发酵率由 75 .2 1%下降至 5 0 .2 9% ;对纯化日粮而言 ,有机物发酵率 (FOM OM ,% )在C S为 0 .4 4～ 4 .75时可以保持较高 (6 8%～ 72 % ) ;纯化日粮 72小时发酵后 ,净挥发性脂肪酸产生量 (VFA FOM ,mol g)与日粮可发酵纤维素和可发酵淀粉比率 (FC FS)间呈乘幂负相关 (VFA FOM ,mol g =4 .2 7) (FC FS) - 0 .1 41 6 ,r=- 0 .94 2 7) ,并在 3.4 0～ 5 .5 2之间浮动。表明 ,纯化日粮体外发酵养分发酵率及VFA产生量与日粮结构性碳水化合物与非结构性碳水化合物比率密切相关。     

不同纤维素与淀粉比率等氮纯化底物瘤胃发酵微生物蛋白质合成量

采用持续动态瘤胃模拟装置 (RSI)研究了 6种不同纤维素和淀粉比率 (C S) :0 .14、0 .44、0 .94、1.92、4.75、15 .76,等氮 ( 14.2 2 % ,风干物质基础 )纯化底物养分瘤胃发酵微生物组分及微生物蛋白质合成量。结果显示 :微生物有机物中氮的含量MN MOM在 5 5 0 %～ 6 64 %之间 ;微生物有机物中RNA含量 (RNA MOM ,% )不受日粮C S影响(P >0 0 5 ) ,仅发现微生物氮含量受到日粮碳水化合物比率影响 (P <0 0 5 )。 72小时发酵后 ,瘤胃微生物蛋白质合成效率与底物纤维素和淀粉比率成乘幂负相关关系 :MN RDN =0 .764 9(C S) - 0 .1 0 6 3,n =6,R =- 0 .93 1;MN FOM(g kg) =2 3 .88(C S) - 0 .0 988,n =6,R =- 0 .881。结果表明 ,在瘤胃可利用氮相同条件下 ,微生物蛋白合成效率取决于适宜的底物结构性碳水化合物和非结构性碳水化合物比率     

Microbial protein formation of different carbohydrates in vitro

The aim of this study was to investigate the microbial protein yield of different pure carbohydrates to contribute to a more precise prediction of the microbial protein formed in the rumen. In a first experiment, sucrose, wheat starch, microcrystalline cellulose and citrus pectin were incubated for 8 and 24 hr in the modified Hohenheim gas test (HGT) system (3 runs × 2 syringes) including gas production, ammonia and short‐chain fatty acid concentration measurements. Ammonia values were used for estimation of the microbial protein formation. In a second experiment, the same substrates were incubated for 96 hr in the HGT system (2 runs × 3 syringes) and gas production was measured after 2, 4, 6, 8, 12, 16, 24, 30, 36, 48, 60, 72 and 96 hr of incubation to obtain the fermentation kinetics and the time of half‐maximal gas production (t_1/2) of the substrates. The substrates differed considerably in their fermentation kinetics, and therefore, comparison on the basis of t_1/2 was chosen as the most meaningful. At t_1/2, microbial protein yield [g/kg dry matter] was higher for cellulose than for sucrose and pectin and higher for starch than for sucrose. The microbial protein expressed in g/L gas production was higher for starch and cellulose than for sucrose and pectin at t_1/2. Effects of carbohydrates related to ruminal pH may remain undetected in in vitro trials.     

利用体外法研究粗饲料的产气曲线及5种养分的发酵系数

利用自行设计的体外发酵产气装置，采用Jerson等     

In vitro fermentation of different starches by mixed micro-organisms from the sheep rumen

Fermentation characteristics of wheat, rye, maize and triticale starches by mixed micro-organisms from the sheep rumen were determined in an in vitro experiment. Starch was incubated with ruminal fluid for 2, 4, 6, 8, 10 and 12 h and various fermentation variables were determined. The rates of fermentation of the starches were not different (p > 0.05) from each other except for 2 and 4 h of incubation. Likewise, net ammonia production, sugar utilization, microbial biomass and the efficiency of microbial protein synthesis did not differ between the starches (p > 0.05). The proportions of sugar utilized were similar between the starches and approximately 75% of the starches were fermented during the 12-h incubation. The 12-h net concentrations of individual and total volatile fatty acids (VFA) were affected (p < 0.05) by the type of starch. The concentrations of acetate, propionate and butyrate and that of total VFA from wheat, maize and triticale incubations were higher (p < 0.05) than those from rye incubation. The results suggest that the type of starch subject to investigation had no measurable effects on fermentation variables determined in this study except for individual and total VFA concentrations.     

Effects of monensin, pyromellitic diimide and 2-bromoethanesulfonic acid on rumen fermentation in vitro

The effects of monensin, 2-bromoethanesulfonic acid (2-BES) and pyromellitic diimide (diimide) on gas and volatile fatty acid (VFA) production by the rumen microbiota were compared in mixed culture. Oat hay, a hay-concentrate mixture (48% hay, 43% concentrate) and a soluble carbohydrate mixture were used as substrates for microbial growth. The highest concentrations of diimide (10 ppm) and 2-BES (30 microM) decreased methanogenesis by 97 and 76%, respectively, while H2 accumulation was increased 30- and 20-fold, respectively. The effect of monensin on methanogenesis was less dramatic as 10 ppm decreased CH4 accumulation 16% and H2 did not accumulate. Diimide and 2-BES decreased the acetate:propionate ratio with the hay (P less than .05) and soluble carbohydrate mixture (P less than .025). The numbers of saccharolytic, cellulolytic and methanogenic bacteria from sheep fed a diet with diimide (60 ppm) did not differ significantly from sheep fed a control diet. Semicontinuous culture incubations indicated that the mixed rumen microbial population could adapt and degrade diimide after 24 h of incubation.     

Milk production and composition responds to dietary neutral detergent fiber and starch ratio in dairy cows

This study was designed to investigate whether dietary neutral detergent fiber (NDF) : starch ratio could be considered as a nutritional indicator to evaluate carbohydrate composition and manipulate milk production and composition synthesis. Eight primiparous dairy cows were assigned to four total mixed rations with NDF : starch ratios of 0.86, 1.18, 1.63 and 2.34 from T1 to T4 in a replicated 4 × 4 Latin square design. Dry matter intake and milk production were decreased from T1 to T4. Digestibility of dry matter, organic matter, NDF and crude protein were linearly decreased from T1 to T4. As NDF : starch ratio increased, milk protein content and production, and milk lactose content and production were linearly reduced. However, milk fat content was linearly increased from T1 to T4. Quadratic effect was observed on milk fat production with the highest level in T3. Averaged rumen pH was linearly increased from T1 to T4, and subacute rumen acidosis occurred in T1. Ruminal propionate and butyrate concentration were linearly decreased, and microbial crude protein and metabolizable protein decreased from T1 to T4. It is concluded that NDF : starch ratio can be considered as a potential indicator to evaluate dietary carbohydrate composition and manipulate milk production and composition synthesis.     

饲粮中结构性碳水化合物与非结构性碳水化合物的不同比例对降解后白酒糟体外发酵特性的影响

本文旨在研究添加可溶性淀粉对降解后的白酒糟体外发酵特性的影响,并确定影响发酵的最佳结构性碳水化合物(SC)与非结构性碳水化合物(NSC)的比例.采用黄孢原毛平革菌发酵白酒糟20 d,以降解其木质素含量.在体外发酵各组中添加可溶性淀粉使SC/NSC比分别为1.66、2.06、2.46、2.86、3.26和3.66.每组设5个重复.结果表明,通过黄孢原毛平革菌发酵,白酒糟中酸性洗涤木质素的含量降低了16.4%(P＜0.01),而粗蛋白质含量提高了6.04%(P＜0.01).在体外发酵试验中,随着可溶性淀粉添加量的增加,累计产气量显著增加(P＜0.01).增加可溶性淀粉添加量改变SC/NSC比可显著影响微生物蛋白(MCP)、总挥发性脂肪酸(TVFA)和氨氮(NH3-N)浓度(P＜0.01).通过SC/NSC比(x)与MCP(y)的回归分析(y=-0.826x2+3.947x+1.189)得出,体外发酵最佳SC/NSC比为2.39.添加可溶性淀粉提高了丙酸在TVFA中的比例(P＜0.05),而降低了乙酸与丙酸比例(P＜0.05).由结果可知,添加可溶性淀粉可提高降解后白酒糟的消化率,并得出体外发酵最佳SC/NSC比为2.39.     

不同油脂对瘤胃微生物体外产气及其区系动态变化的影响

本试验利用3头瘤胃瘘管山羊提供瘤胃液,以淀粉、纤维素、酪蛋白为底物进行体外培养,研究花生油、菜油、玉米油和豆油等对瘤胃发酵产气及微生物活力状况的影响。结果表明:培养液36 h总产气量在20.61～39.67mL,除花生油组与对照组差异不显著外(P>0.05),其他油脂组都显著低于对照组(P<0.05);随着培养时间的延长各组产气量呈现波动变化。培养液总脱氢酶以豆油组最高,显著高于对照组;并依次显著高于玉米油、花生油、菜籽油等组(P<0.05)。另外,培养液原虫DNA、细菌DNA、微生物DNA、原虫/细菌区系比例的均值与对照组,以及油脂组间差异都不显著(P>0.05),但随着培养时间的延长,微生物DNA在各时间点都以豆油与玉米油组的较高;原虫DNA一般在16 h达到最高,而细菌DNA则在8 h或16 h最高,并显著高于1 h或4 h的量(P<0.05、P<0.01),且各个试验组在培养过程中随时间的动态变化模式也不尽相同。总体看来,不同油脂对瘤胃微生物体外产气及区系动态变化的影响不同。     

The influence of cellulose and various starches in feed on nitrogen metabolism in growing swine

In N-balance experiments with a total of 49 female fattening pigs with a live weight between 33 and 47 kg the influence of cellulose supplements (exchanger principle) and changing quotas of maize starch and maize soak starch in semisynthetic feed mixtures on parameters of N-utilization was studied. The results show that there may be a positive influence of the supplement of cellulose on total N utilization (b-value, Gebhardt, 1963). One can conclude that, apart from a shift of the ways of N-excretion through faeces and urine, the utilization of products of microbial protein synthesis for N-retention is possible to a nutrition-physiologically relevant degree. The influence of the kind of starch on N-utilization was small.     

In vitro fermentation characteristics of different carbohydrate sources in two dog breeds (German shepherd and Neapolitan mastiff)

Few studies have been published on the normal intestinal biota of canines unlike the wealth of information regarding livestock animal species. The in vitro gas production technique (IVGPT) including measurements of accumulating gas during fermentation and end‐product determinations allows obtaining a complete picture of microbial activity kinetics. The aim of this study was to study the in vitro fermentation characteristics of different carbohydrate sources using inocula from two dog breeds (German Shepherd and Neapolitan mastiff). Faeces sampled from rectum of two GS and NM adult dogs, fed the same dry food, were used as inocula. The samples, diluted and filtered, were incubated at 39 °C under anaerobic condition with nine substrates different for carbohydrate composition (rice, corn, potato, spelt, pure cellulose, beet pulp, wheat bran, inulin and fructo‐oligosaccharide). Gas production was recorded 17 times using a manual pressure transducer. After 48 h, the fermentation was stopped and fermenting liquor was analysed for pH and volatile fatty acids (VFA). Organic matter digestibility (OMD) was calculated as difference after burning the residuals. OMD, gas production and end‐products were significantly correlated with chemical composition of substrates, in particular carbohydrate fractions (total dietary fibre and starch), confirming the effectiveness of the IVGPT in evaluating dog feeds. Concerning the comparison between breeds significant differences (p < 0.01) were found for OMD, gas production, fermentation kinetic parameters and end‐products, suggesting a different pathway of fermentation and consequently, a different anaerobic population.     

利用体外产气法和CNCPS法对不同生育期虉草营养价值的评价研究

为了评定不同生育期虉草的营养价值,分析体外产气法和CNCPS法两种营养评价方法的相关性。采用体外产气法测定抽穗期、开花期、灌浆期、乳熟期4个生育期虉草的体外发酵产气量、发酵参数(a、b、c)、DM消化率、NDF和ADF降解率,用康奈尔净碳水化合物和蛋白质体系(cornell net carbohydrate and protein system,CNCPS)分析方法测定相应组分,评价其营养价值,并比较研究两种方法评价结果的相关性。结果表明,体外发酵至72 h结束,累计总产气量和产气参数a以开花期最高(122.68 和4.46 mL),显著高于各组(P<0.05),且从抽穗期、灌浆期、乳熟期有降低的趋势;抽穗期和开花期的DM消化率、NDF和ADF降解率分别显著高于灌浆期和乳熟期(P<0.05)。随着虉草生育期的延长,CP和SOLP呈递减趋势,即抽穗期和开花期显著高于灌浆期和乳熟期(P<0.05);NDF、ADF和ADL呈递增趋势,但NDFIP、ADFIP呈递减趋势。灌浆期和乳熟期的CHO含量显著高于抽穗期和开花期(P<0.05),而CA和CNSC含量则相反,且CC含量同样以灌浆期与乳熟期较高;蛋白质组分中,PA与CA及CC与PC组分呈现同样的趋势。虉草CNSC、CA、CB₁、CB₂、PA、PB₃组分含量与不同时间点产气量呈显著或极显著的相关性(P<0.05或P<0.01)。因此,开花期虉草营养价值最高,其次为抽穗期、灌浆期和乳熟期,产气法和CNCPS评价牧草具有相关性,用体外产气量估测牧草CNCPS组分是可行的。     

Fermentation of animal components in strict carnivores: a comparative study with cheetah fecal inoculum

The natural diet of felids contains highly digestible animal tissues but also fractions resistant to small intestinal digestion, which enter the large intestine where they may be fermented by the resident microbial population. Little information exists on the microbial degradability of animal tissues in the large intestine of felids consuming a natural diet. This study aimed to rank animal substrates in their microbial degradability by means of an in vitro study using captive cheetahs fed a strict carnivorous diet as fecal donors. Fresh cheetah fecal samples were collected, pooled, and incubated with various raw animal substrates (chicken cartilage, collagen, glucosamine-chondroitin, glucosamine, rabbit bone, rabbit hair, and rabbit skin; 4 replicates per substrate) for cumulative gas production measurement in a batch culture technique. Negative (cellulose) and positive (casein and fructo-oligosaccharides; FOS) controls were incorporated in the study. Additionally, after 72 h of incubation, short-chain fatty acids (SCFA), including branched-chain fatty acids (BCFA), and ammonia concentrations were determined for each substrate. Glucosamine and glucosamine-chondroitin yielded the greatest organic matter cumulative gas volume (OMCV) among animal substrates (P < 0.05), whereas total SCFA production was greatest for collagen (P < 0.05). Collagen induced an acetate production comparable with FOS and a markedly high acetate-to-propionate ratio (8.41:1) compared with all other substrates (1.67:1 to 2.97:1). Chicken cartilage was rapidly fermentable, indicated by a greater maximal rate of gas production (R(max)) compared with all other substrates (P < 0.05). In general, animal substrates showed an earlier occurrence for maximal gas production rate compared with FOS. Rabbit hair, skin, and bone were poorly fermentable substrates, indicated by the least amount of OMCV and total SCFA among animal substrates (P < 0.05). The greatest amount of ammonia production among animal substrates was measured after incubation of collagen and rabbit bone (P < 0.05). This study provides the first insight into the potential of animal tissues to influence large intestinal fermentation in a strict carnivore, and indicates that animal tissues have potentially similar functions as soluble or insoluble plant fibers in vitro. Further research is warranted to assess the impact of fermentation of each type of animal tissue on gastro-intestinal function and health in the cheetah and other felid species.     

发酵玉米蛋白粉对奶牛瘤胃体外发酵特性及微生物菌群的影响

本试验旨在研究全混合日粮（TMR）中添加发酵玉米蛋白粉（fermented corn gluten meal,FCGM）对奶牛瘤胃体外发酵特性及微生物菌群的影响。选用3头体重（600±25）kg,安装永久性瘤胃瘘管的荷斯坦奶牛作为瘤胃液供体,发酵底物为TMR,分为对照组和3个试验组,各组分别在发酵液中添加0、0.3、0.6、0.9 g/L FCGM（干物质基础）,每个处理3个重复。记录体外发酵12、24、36和48 h产气量,测定体外发酵12、24和48 h发酵液pH、体外干物质消失率（IVDMD）、纤维素酶活性、氨态氮（NH₃-N）、挥发性脂肪酸（VFA）和菌体蛋白浓度,并测定体外发酵24 h发酵液中瘤胃微生物菌群相对丰度。结果显示：①添加不同水平FCGM组的体外产气量（除12 h外）、慢速产气部分、潜在产气部分和有效产气速率均显著或极显著高于对照组（P < 0.05;P < 0.01）;②与对照组相比,添加不同水平FCGM处理组的发酵液pH显著或极显著低于对照组,纤维素酶活性、菌体蛋白、挥发性脂肪酸、氨态氮含量和体外干物质消失率均显著或极显著升高（P < 0.05;P < 0.01）,且0.9 g/L FCGM组达到最高。③添加0.6和0.9 g/L FCGM组发酵液中白色瘤胃球菌、黄色瘤胃球菌、产琥珀酸丝状杆菌、牛链球菌、普雷沃氏菌、溶纤维丁酸弧菌、嗜淀粉瘤胃杆菌、真菌和原虫相对丰度均显著高于对照组（P < 0.05）,且0.9 g/L FCGM组达到最高,而产甲烷菌相对丰度显著低于对照组（P < 0.05）,且0.9 g/L FCGM组达到最低。综上所述,TMR中添加FCGM可提高体外发酵产气量,增加发酵液内纤维素酶活性、VFA、NH3-N及菌体蛋白含量,提高瘤胃内某些纤维降解菌、蛋白降解菌、淀粉降解菌、真菌和原虫相对丰度,降低产甲烷菌相对丰度,调节瘤胃微生物菌群结构,改善瘤胃发酵,其中以添加0.9 g/L FCGM为宜。     

Effects of replacing dietary starch with neutral detergent–soluble fibre on ruminal fermentation,microbial synthesis and populations of ruminal cellulolytic bacteria using the rumen simulation technique (RUSITEC)

A rumen simulation technique (RUSITEC) apparatus with eight 800 ml fermenters was used to investigate the effects of replacing dietary starch with neutral detergent–soluble fibre (NDSF) by inclusion of sugar beet pulp in diets on ruminal fermentation, microbial synthesis and populations of ruminal cellulolytic bacteria. Experimental diets contained 12.7, 16.4, 20.1 or 23.8% NDSF substituted for starch on a dry matter basis. The experiment was conducted over two independent 15‐day incubation periods with the last 8 days used for data collection. There was a tendency that 16.4% NDSF in the diet increased the apparent disappearance of organic matter (OM) and neutral detergent fibre (NDF). Increasing dietary NDSF level increased carboxymethylcellulase and xylanase activity in the solid fraction and apparent disappearance of acid detergent fibre (ADF) but reduced the 16S rDNA copy numbers of Ruminococcus albus in both liquid and solid fractions and R. flavefaciens in the solid fraction. The apparent disappearance of dietary nitrogen (N) was reduced by 29.6% with increased dietary NDSF. Substituting NDSF for starch appeared to increase the ratios of acetate/propionate and methane/volatile fatty acids (VFA) (mol/mol). Replacing dietary starch with NDSF reduced the daily production of ammonia‐N and increased the growth of the solid‐associated microbial pellets (SAM). Total microbial N flow and efficiency of microbial synthesis (EMS), expressed as g microbial N/kg OM fermented, tended to increase with increased dietary NDSF, but the numerical increase did not continue as dietary NDSF exceeded 20.1% of diet DM. Results suggested that substituting NDSF for starch up to 16.4% of diet DM increased digestion of nutrients (except for N) and microbial synthesis, and further increases (from 16.4% to 23.8%) in dietary NDSF did not repress microbial synthesis but did significantly reduce digestion of dietary N.     

Dietary carbohydrates affect caecal fermentation and modify nitrogen excretion patterns in rats. II. Studies with diets differing in protein quality.

In 2 two-factorial experiments, each conducted on 80 growing male rats, the effects of substituting 10% raw potato starch (PS), pectins (PEC), or cellulose (CEL) for wheat starch (WS) and the addition of tannic acid to WS (WSTA) were studied using diets differing in protein quality. Casein unsupplemented or supplemented with DL-methionine and gluten unsupplemented or supplemented with lysine, methionine and tryptophan were used as protein sources in Experiment 1 and 2, respectively. Parameters indicative of caecal fermentation intensity (pH, acetic, propionic and butyric acid contents, digesta and tissue weight) and of protein metabolism (urea blood concentration, faecal and urinary nitrogen excretion) were determined. Ten-day balance experiments were preceded by a 10-day adaption period to respective carbohydrates given in a diet containing balanced protein. In both experiments the type of carbohydrates affected the caecal concentration of individual and total SCFA and other parameters of fermentation intensity. Pectins and potato starch were fermented more intensively than cellulose. Faecal N excretion was increased by all carbohydrates substituted for cereal starch, and by tannic acid. Urinary excretion was greater on CEL than on PEC and WSTA containing casein and on other diets containing gluten. In both experiments urinary N excretion was the lowest on PEC diets. Protein quality had the greatest effect on apparent biological value and net protein utilization but all indices of protein utilization were also affected by carbohydrates. It is concluded that not only the amount of N excreted in faeces but also in urine is affected by the type and fermentability of carbohydrates.     

Effect of dietary medium chain triacylglycerols on plasma triacylglycerol levels in horses.

The hypothesis tested was that the feeding of medium chain triacylglycerols (MCT) to horses would raise the level of plasma triacylglycerols by increasing the availability of glucose as lipogenic substrate, implying that the MCT effect would be greater with glucose in the diet instead of cellulose. A Latin square experiment was carried out with 4 horses and 4 dietary treatments. The experimental periods lasted 21 d. Blood samples were taken 16 h after feeding. The diets consisted of hay and experimental concentrates, differing in fat source (MCT or soybean oil) and carbohydrate source (corn starch plus glucose or cellulose). The dietary variables, MCT or soybean oil, provided on average 27% of total dietary net energy, while glucose plus constarch or cellulose provided 33%. The feeding of MCT versus soybean oil raised the level of plasma triacylglycerols significantly from 196.7 +/- 30.2 to 427.3 +/- 85.7 mmol/l and that of VLDL cholesterol from 0.028 +/- 0.01 to 0.069 +/- 0.01 mmol/ml. As based on analysis of variance, for the four experimental diets there was no significant effect of carbohydrate source and no fat-carbohydrate interaction. Thus, the hypothesis was rejected. When the diets contained soybean oil, cellulose versus starch plus glucose produced significantly greater increase plasma triacylglycerols. This carbohydrate effect was not seen when horses were fed the MCT diets. The experimental concentrates did not differently influence the concentrations of plasma glucose, total serum cholesterol, phospholipids, insulin, free fatty acids and the activity of post-heparin lipoprotein lipase. We suggest that the MCT-induced increase in plasma triacylglycerols is related to an increase in hepatic VLDL secretion, with the extra substrate for increased synthesis of triacylglycerols being the acetyl-CoA derived from the hepatic oxidation of medium chain fatty acids.     

低淀粉饲粮条件下不同瘤胃降解淀粉水平对体外瘤胃发酵的影响

本试验旨在研究玉米作为淀粉来源的低淀粉饲粮条件下不同瘤胃降解淀粉(RDS)水平对体外瘤胃发酵的影响。以3头安装有永久性瘤胃瘘管的健康荷斯坦奶牛作为瘤胃液供体,各组分别以不同RDS水平饲粮作为发酵底物,体外产气法测定培养48 h时产气量和瘤胃发酵参数以及24 h时瘤胃微生物区系变化。结果表明:1)随着饲粮RDS水平的提高,体外培养48 h时产气量、潜在产气部分和产气速率呈线性升高(P0.05),快速发酵部分产气量呈线性下降(P0.05),干物质消失率呈线性升高(P0.05);2)随着饲粮RDS水平的提高,体外培养48 h时发酵液微生物蛋白、乙酸、丙酸、丁酸和总挥发性脂肪酸浓度呈线性升高(P0.05),pH和氨态氮浓度没有显著变化(P0.05);3)随着饲粮RDS水平的提高,体外培养24 h时发酵液中白色瘤胃球菌和嗜淀粉瘤胃杆菌的相对数量呈线性升高(P0.05),黄色瘤胃球菌、琥珀酸丝状杆菌、溶纤维丁酸弧菌、牛链球菌和溶淀粉琥珀酸单胞菌的相对数量没有显著变化(P0.05)。综合考虑,低淀粉饲粮条件下提高RDS水平有利于瘤胃发酵。     

ATP in the metabolism of ruminants]

The ATP yield from the carbohydrates of anaerobically living microorganisms in the rumen amounts to only 5-10% of the ATP yield of the intermediary metabolism in the presence of oxygen. Vital functions and thus microbial protein synthesis are due to protein degradation in the rumen. The ATP yield in the intermediary metabolism of ruminants is mainly achieved from propionate and microbial protein by means of gluconeogenesis because the absorption of glucose from digested starch is very low. The relationships between ATP yield in the rumen and the processes of glucose provision for the production of lactose as well as the protein content of the milk are shown. As important processes of ATP production in microorganisms from easily soluble carbohydrates take place in silage preparations before feed intake, the corresponding consequences for the metabolism of high-performance cows fed with silage are shown.