瘤胃微生物体外驯化降解纤维素研究

实验先按照正交表L18(3^7）的设计对瘤胃微生物降解滤纸的营养和环境条件进行研究，发现在C/N为14.2/1、葡萄糖浓度低、乙酸浓度为800mg/L、无丙酸存在，温度为45℃、pH值为6.5的环境条件下，纤维素的降解校为彻底。在以上优化条件的基础上，进行了纤维降解及产酸情况的研究，发现纤维素降解的直接产物葡萄糖不会产生积累而很快就转化为挥发酸，而挥发酸会产生积累。挥发酸主要是乙酸、丙酸和丁酸三种，其中乙酸产量占到86%-93%。在纤维素降解产酸过程中，产气量并不大。     

Milk odd- and branched-chain fatty acids in relation to the rumen fermentation pattern

The objectives of this study were 1) to determine whether a relationship exists between molar proportions of volatile fatty acids in the rumen and milk odd-and branched-chain fatty acid concentrations (i.e., iso C13:0, anteiso C13:0, iso C14:0, C15:0, iso C15:0, anteiso C15:0, iso C16:0, C17:0, iso C17:0, anteiso C17:0, and cis-9 C17:1); and 2) to evaluate the accuracy of prediction of the latter equations using an independent data set. For development of the regression equations, individual cow data from 10 feeding experiments with rumen-fistulated dairy cows were used, resulting in a data set of 148 observations. Milk odd- and branched-chain fatty acids were closely related to the molar proportions of acetate (SE = 15.3 mmol/mol), propionate (SE = 14.7 mmol/mol), and butyrate (SE = 9.2 mmol/mol). These regression equations were further validated using data from the literature (n = 14). Evaluation of these prediction equations using the independent data set resulted in a root mean square prediction error of 3.0, 9.0, and 8.9% of the observed mean for acetate, propionate, and butyrate, respectively. In addition, less then 5% of the mean square prediction error was due to line bias. This suggests that the currently developed prediction equations based on milk odd- and branched-chain fatty acids show potential to predict molar proportions of individual volatile fatty acids in the rumen.     

Supplementation of pearl millet flour with soybean protein: effect of cooking on in vitro protein digestibility and essential amino acids composition

In vitro protein digestibility (IVPD) and amino acids profile of pearl millet (Dempy cultivar) supplemented with soybean protein (5–15%) were investigated. Supplementation of dempy flour with soybean protein steadily decreased IVPD with increasing the portion of soybean in the blend. The in vitro protein digestibilities of the cooked supplemented dempy flours were higher when compared with the raw ones, whereas the highest value was that of the 5% soybean protein. All essential amino acids of dempy flour were enriched on supplementation with soybean protein. The levels of amino acids increased with increasing the amount of soybean protein in the blend. Essential amino acids in dempy supplemented with 15% soybean are comparable to those in the FAO reference pattern. Supplementation increased significantly lysine to 1.5–2.4 folds. Essential amino acids content remained higher in the cooked composite flours when compared with the cooked native dempy flour.     

Effect of calcium salts of fatty acids on rumen function and the digestibility of rations by sheep

Experiments were conducted to determine the effects of supplementing chopped ryegrass hay with 0, 1.5, 3, 6 or 12% calcium salts of fatty acids (CaSFA; Megalac) on digestion in the rumen of cannulated cows and on nutrient digestibility by sheep. In-situ ruminal disappearances of dry matter (DM) and cell wall fractions (acid detergent fibre, ADF, and neutral detergent fibre, NDF) were measured by the nylon bag technique. The DM, ADF and NDF disappearances were reduced for diets containing CaSFA at the 1.5, 3 or 6% levels after 48 h of rumen exposure. For diets containing 12% CaSFA, irrespective of the time of rumen incubation, DM disappearance was decreased, while ADF and NDF breakdown was improved. CaSFA supplementation did not influence invitro fermentation characteristics (pH, volatile fatty acid patterns). A digestibility experiment with six mature sheep showed no difference in nitrogen digestibility between unsupplemented and CaSFA-supplemented diets. However, digestibilities of DM, ADF and NDF were higher relative to the basal for the 12% CaSFA: 63.1 versus 60.6%, 63.8 versus 58.7% and 67.4 versus 62.7%, respectively. Ether extract digestion was enhanced by increasing the level of CaSFA, the corresponding values being 49.1, 66.5, 78.6, 81.9 and 77.9% at 0, 1.5, 3, 6 and 12% CaSFA, respectively. Apparent digestibility of energy was higher for the 12% CaSFA than the control diet 68.8 versus 62.1%). Nitrogen and energy retention was improved due to the decreases in urine and faecal excretion, respectively.     

Effect of fermentation and cooking on protein quality of maize (Zea mays L.) cultivars

Maize like other cereals shows qualitative and quantitative deficiency in protein content. Efforts were made to correct this by fortification, supplementation and fermentation. Two maize cultivars, Hudeiba 1 and Mugtama 45, were used to study the effect of fermentation followed by cooking on their protein quality. Maize flour was fermented for 32 h; samples were withdrawn at 8 h intervals. Results indicated that the proteins fractions albumins plus globulins were significantly (P < 0.05) increased in the fermented doughs. This is an indication of improvement in the protein quality of maize. Cooking resulted in significant (P < 0.05) changes in protein solubility. The essential amino acids particularly lysine increased from 1.82 to 2.06 and from 1.88 to 2.60 g/100 g (i.e. an increase of 11.6% and 27.7%) for Hudeiba 1 and Mugtama 45, respectively. The in vitro protein digestibility of cooked samples decreased significantly (P < 0.05); however, the negative effects of cooking were lower than those of unfermented cooked samples.     

Variations in methane yield and microbial community profiles in the rumen of dairy cows as they pass through stages of first lactation

Considerable interest exists both from an environmental and economic perspective in reducing methane emissions from agriculture. In ruminants, CH₄ is produced by a complex community of microorganisms that is established in early life but can be influenced by external factors such as feed. Although CH₄ emissions were thought to be constant once an animal reached maturity, recent studies have shown that CH₄ yield significantly increases from early to late lactation in dairy cows. The aim of this study was to test the hypothesis that increases in CH₄ yield over the lactation cycle are related to changes in rumen microbial community structure. Nine cows were monitored throughout their first lactation cycle. Methane and dry matter intake were measured to calculate CH₄ per dry matter intake (CH₄ yield) and ruminal fluid was collected during early, mid, and late lactation. A significant difference in bacterial and archaeal community structure during early and late lactation was observed. Furthermore, when ruminal short-chain fatty acid concentrations were measured, the ratio of acetate and butyrate to propionate was significantly higher in late lactation compared with early lactation. Propionate concentrations were higher in cows with low CH₄ yield during late lactation, but no differences were observed in bacterial or archaeal community structures. Prevotella dominated the rumen of cows followed by Succinclasticum; Treponema, Fibrobacter, Ruminococcus, and Bifidobacterium were also in high abundance relative to other bacterial genera. In general, positive correlations were stronger between the most relatively abundant bacterial genera and acetate and butyrate concentrations in the cows with high CH₄ and weaker between these genera and propionate concentration. This study indicates that increased CH₄ yield in late lactation is reflected in significant changes in microbial community structure.     

Technical note: In vitro total gas and methane production measurements from closed or vented rumen batch culture systems

This study compared measured gas production (GP) and computed CH₄ production values provided by closed or vented bottles connected to gas collection bags. Two forages and 3 concentrates were incubated. Two incubations were conducted, where the 5 feeds were tested in 3 replicates in closed or vented bottles, plus 4 blanks, for a total of 64 bottles. Half of the bottles were not vented, and the others were vented at a fixed pressure (6.8 kPa) and gas was collected into one gas collection bag connected to each bottle. Each bottle (317 mL) was filled with 0.4000 ± 0.0010 g of feed sample and 60 mL of buffered rumen fluid (headspace volume = 257 mL) and incubated at 39.0°C for 24 h. At 24 h, gas samples were collected from the headspace of closed bottles or from headspace and bags of vented bottles and analyzed for CH₄ concentration. Volumes of GP at 24 h were corrected for the gas dissolved in the fermentation fluid, according to Henry’s law of gas solubility. Methane concentration (mL/100 mL of GP) was measured and CH₄ production (mL/g of incubated DM) was computed using corrected or uncorrected GP values. Data were analyzed for the effect of venting technique (T), feed (F), interaction between venting technique and feed (T × F), and incubation run as a random factor. Closed bottles provided lower uncorrected GP (−18%) compared with vented bottles, especially for concentrates. Correction for dissolved gas reduced but did not remove differences between techniques, and closed bottles (+25 mL of gas/g of incubated DM) had a greater magnitude of variation than did vented bottles (+1 mL of gas/g of incubated DM). Feeds differed in uncorrected and corrected GP, but the ranking was the same for the 2 techniques. The T × F interaction influenced uncorrected GP values, but this effect disappeared after correction. Closed bottles provided uncorrected CH₄ concentrations 23% greater than that of vented bottles. Correction reduced but did not remove this difference. Methane concentration was influenced by feed but not by the T × F interaction. Corrected CH₄ production was influenced by feed, but not by venting technique or the T × F interaction. Closed bottles provide good measurements of CH₄ production but not of GP. Venting of bottles at low pressure permits a reliable evaluation of total GP and CH₄ production.     

亚临界提取蜜桔皮精油成分分析及其微乳液制备

采用亚临界流体萃取法提取宜昌蜜桔皮精油,用顶空固相微萃取—气相色谱—质谱联用技术(SPME-GC-MS)分析蜜桔皮精油中挥发性成分及脂肪酸组成,用高速分散及超高压均质制备O/W型蜜桔皮精油微乳液,确定高稳定性微乳液的乳化剂最适用量、最适油水比和最佳均质条件。结果表明:亚临界流体萃取蜜桔皮精油,平均得率约1%。精油挥发性成分主要由烃类和酸类化合物组成,分别占总量的58.68%和40.34%;宜昌蜜桔皮精油脂肪酸中主要含不饱和脂肪酸,达77.35%,其中亚油酸含量占总脂肪酸含量的37.80%,饱和脂肪酸主要为棕榈酸,含量为14.18%。均一微乳液制备的最适乳化剂SE-15质量分数为6%,最适油水质量比为1:25,最佳均质条件为:压力50 MPa,均质4次。     

Host specificity of the ruminal bacterial community in the dairy cow following near-total exchange of ruminal contents

The purpose of this study was to examine the stability and host specificity of a cow's ruminal bacterial community following massive challenge with ruminal microflora from another cow. In each of 2 experiments, 1 pair of cows was selected on the basis of differences in ruminal bacterial community composition (BCC), determined by automated ribosomal intergenic spacer analysis (ARISA), a culture-independent “community fingerprinting” technique. Each pair of cows was then subjected to a 1-time exchange of >95% of ruminal contents without changing the composition of a corn silage/alfalfa haylage-based TMR. In experiment 1, the 2 cows differed (P < 0.01) in prefeed ruminal pH (mean = 6.88 vs. 6.14) and prefeed total VFA concentration (mean = 57 vs. 77 mM), averaged over 3 d. Following exchange of ruminal contents, ruminal pH and total VFA concentration in both cows returned to their preexchange values within 24 h. Ruminal BCC also returned to near its original profile, but this change required 14 d for 1 cow and 61 d for the other cow. In experiment 2, the 2 other cows differed in prefeed ruminal pH (mean = 6.69 vs. 6.20) and total VFA concentration (mean = 101 vs. 136 mM). Following exchange of ruminal contents, the first cow returned to its preexchange pH and VFA values within 24 h; the second cow's rumen rapidly stabilized to a higher prefeed pH (mean = 6.47) and lower prefeed VFA concentration (mean = 120 mM) that was retained over the 62-d test period. Both cows reached somewhat different BCC than before the exchange. However, the BCC of both cows remained distinct and were ultimately more similar to that of the preexchange BCC than of the donor animal BCC. The data indicate that the host animal can quickly reestablish its characteristic ruminal pH and VFA concentration despite dramatic perturbation of its ruminal microbial community. The data also suggest that ruminal BCC displays substantial host specificity that can reestablish itself with varying success when challenged with a microbial community optimally adapted to ruminal conditions of a different host animal.     

Effect of dried oregano (Origanum vulgare L.) plant material in feed on methane production,rumen fermentation,nutrient digestibility,and milk fatty acid composition in dairy cows

Essential oils (EO) from oregano may have antimicrobial properties, potentially representing a methane mitigation strategy suitable for organic production. This study aimed to (1) examine the potential of oregano in lowering enteric methane production of dairy cows fed differing levels of dried oregano (Origanum vulgare ssp. hirtum) plant material containing high levels of EO; (2) determine whether differing levels of dried oregano plant material of another subspecies (Origanum vulgare ssp. vulgare) with naturally low levels of EO in feed affected enteric methane production; and (3) evaluate the effect of various levels of the 2 oregano subspecies (containing high or low levels of EO) in feed on rumen fermentation, nutrient digestibility, and milk fatty acids. Each experiment had a 4 × 4 Latin square design using 4 lactating Danish Holstein dairy cows that had rumen, duodenal, and ileal cannulas and were fed 4 different levels of oregano. Experiment 1 used low EO oregano [0.12% EO of oregano dry matter (DM)] and evaluated a control (C) diet with no oregano and 3 oregano diets with 18 (low; L), 36 (medium; M), and 53 g of oregano DM/kg of dietary DM (high; H). Experiment 2 used high EO oregano (4.21% EO of oregano DM) with 0, 7, 14, and 21 g of oregano DM/kg of dietary DM for C, L, M, and H, respectively. Oregano was added to the diets by substituting grass/clover silage on a DM basis. Low or high EO oregano in feed did not affect dry matter intake (DMI) or methane production (grams per day, grams per kilogram of DMI, grams per kilogram of energy-corrected milk, and percentage of gross energy intake). Rumen fermentation was slightly affected by diet in experiment 1, but was not affected by diet in experiment 2. In both experiments, the apparent total-tract digestibility of DM, organic matter, and neutral detergent fiber decreased linearly and cubically (a cubic response was not observed for neutral detergent fiber) with increasing dietary oregano content, while milk fatty acids were slightly affected. In conclusion, dried oregano plant material with either high or low levels of EO did not lower the methane production of dairy cows over 4 consecutive days, and no substantial effects were observed on rumen fermentation or nutrient digestibility. This conclusion regarding methane production is in contrast with literature and requires further study.