Phage mediated horizontal transfer of the sopE1 gene increases enteropathogenicity of Salmonella enterica serotype Typhimurium for calves

Anaerobic fungi are an important component of the cellulolytic ruminal microflora. Ammonia alone as N source supports growth, but amino acid mixtures are stimulatory. In order to evaluate the extent of de novo synthesis of individual amino acids in Piromyces communis and Neocallimastix frontalis, isotope enrichment in amino acids was determined during growth on (15)NH(4)Cl in different media. Most cell N (0.78 and 0.63 for P. communis and N. frontalis, respectively) and amino acid N (0.73 and 0.59) continued to be formed de novo from ammonia when 1 g l(-1) trypticase was added to the medium; this concentration approximates the peak concentration of peptides in the rumen after feeding. Higher peptide/amino acid concentrations decreased de novo synthesis. Lysine was exceptional, in that its synthesis decreased much more than other amino acids when Trypticase or amino acids were added to the medium, suggesting that lysine synthesis might limit fungal growth in the rumen.     

不同精粗比底物下瘤胃真菌和纤维降解细菌共培养发酵特性及菌群变化

采用体外厌氧共培养技术,研究了瘤胃真菌和纤维降解细菌在不同精粗比(A组为全粗料,B组3∶7,C组5∶5,D组7∶3,E组为全精料)底物下菌群变化及其共培养发酵特性。结果表明:与0h相比,发酵至24h时B组和C组的厌氧真菌数量有较大幅度的上升,A组和D组则有所下降,E组未检测到真菌生长;纤维降解细菌随精粗比的增加呈上升趋势。发酵至48h时,各组均未检测到真菌生长;从A组到C组细菌数量呈上升趋势,此后急剧下降。DGGE结果表明,A、B和C组(精粗比低于5∶5)的DGGE图谱相似,有11条共有条带,但是当精粗比上升到7:3时,条带数目显著下降。随精料比例的增加,整个发酵期共培养系统中pH值显著下降(P<0.05)。整个发酵期间,共培养系统发酵产生的VFA主要为乙酸,丙酸和丁酸的量较少,乙酸与丙酸比值从A组到C组呈下降趋势,此后呈上升趋势。随精料比例的上升,发酵48h时总挥发性脂肪酸浓度从A组到C组呈上升趋势,此后呈下降趋势。发酵48h的羧甲基纤维素酶活和木聚糖酶活均以A组最高,而α-淀粉酶活从A组到D组逐渐增大,而E组最低,仅为B、C、D组的1/4~1/3。     

Digesta characteristics of dorsal,middle and ventral rumen of cows fed with different hay qualities and concentrate levels

The influence of fibre content of hay (H) and concentrate level (C) on local differences in the composition of ruminal digesta (ratio of solid to fluid digesta, DM, NDF, ADF and ADL content), particle size (MPL), specific gravity (SG) and fermentation (pH and concentrations of SCFA and bicarbonate) have been tested on two ruminally cannulated Friesian cows (520?kg BW) which were fed restricted, using individual cows as experimental units. Digesta samples were collected via cannula from three rumen layers: 5 to 10?cm (top) and 25?–?35?cm beneath the top of the particle mat (middle) and 5?–?10?cm above the rumen floor (bottom). For a main plot treatment (H·C), repeated samples were collected at four time intervals (1?h before and 2, 5 and 10?h after morning feeding) on each of two days. From top to bottom rumen the share of solid digesta mass (SM), DM and NDF contents of squeezed digesta fluid (SRF) and concentration of SCFA decreased (P?P?相似文献   

Ruminal degradability of 15N labelled ribonucleic acid in grass

The ruminal degradation of RNA in rye grass (Lolium perenne) was studied using the bag method. A non-lactating cow (BW 550?kg) fitted with a rumen cannula was used and fed twice daily at maintenance level with a chopped grass hay-based ration containing 30% ground barley. Rye grass, labelled during growth by fertilization with ¹⁵N₂-urea (9.5 atom% ¹⁵N, 20?g N/m²), was cut at seven stages of growth and maturity and freeze-dried. RNA-N represented 6 to 17% of total N. Labelled grass samples (milled to 5.0?mm screen, 5.0?±?0.1?g DM) were incubated in polyester bags (100?×?200?mm, pore size 50?μm) in the rumen for periods of 1, 3, 6, 9, 12, 24, and 48?h. Data of N and RNA disappearances from the bags were fitted to an exponential equation to estimate parameters of degradation. The effective degradability of RNA in the rumen averaged 90?±?4%, for N it was 11% units lower (P?R ²?=?0.92). Degradability of RNA (R ²?=?0.96) and N (R ²?=?0.93) decreased with increasing fibre content of grass. Increasing the fibre content by 1% diminished the degradability of RNA and N by 1.1% units and 2.4% units, respectively (P????1, a model calculation indicates that about 9 to 19% of duodenal RNA are of dietary origin in animals fed grass. This should be taken into account for the calculation of microbial N on the basis of RNA as marker.     

Effect of increasing dietary concentrate levels on microbial biotin metabolism in the artificial rumen simulation system (RUSITEC)

The effect of varying hay/barley‐proportions in the feed ration on biotin metabolism of rumen microbes was studied by means of the rumen simulation technique RUSITEC. The stepwise replacement of hay by barley decreased dietary biotin and the net output of biotin by the microbial metabolism. It is concluded that rumen microbes utilise more and/or synthesize less biotin with increasing proportions of dietary barley. These results indicate that a critical reconsideration of current views with regard to the supply and requirement of the high yielding dairy cow for biotin is necessary.     

Untersuchungen zur Methodik der Stoffwechselversuche an Kälbern

The digestible (DE) and metabolizable energy (ME) of full‐fat and defatted rubber seed meals (FRS and DRS) were determined with weanling albino rats fed diets in which the meals replaced either 20 or 40% glucose monohydrate in the reference diet. The nutritive value of both FRS and DRS included at 10, 20 and 30% of the diet as substitutes for groundnut meal and yellow maize was studied with 56, 28‐day‐old albino rats of the Wistar strain. The trial lasted 28 days. Nutrient digestion and nitrogen retention were studied at the end of the second week on test. The DE and ME for FRS were on average 24.7±1.30 and 21.7±0.80 hy/g dry matter and those for DRS were 15.3±0.97 and 13.8 ±0.46 hy/g dry matter.

Incorporation of rubber seed meals at increasing levels in the diet significantly depressed gains and worsened feed/gain ratio (P< 0.01), the diet containing 30% FRS or 20 and 30% DRS being significantly iferior to the control and the diet with 10% FRS or DRS. Significantly (P < 0.01) superior gains but not feed intake and efficiency were obtained for FRS compared to DRS.

Percent intake ‐N retained also decreased with increasing rubber seed levels in the diet. Except for the significantly (P < 0.05) higher crude fibre digestibility of the control diet compared with those containing 20 or 30% FRS or DRS, the digestibilities of other nutrients were not significantly different.     

Ammonia Assimilation in Rumen Bacteria: A Review

In the rumen bacteria, ammonia as the end product of nitrogen is incorporated into carbon skeleton (α-ketoglutarate) to yield glutamine and glutamate which are important nitrogen donors in nitrogenous compounds metabolism in cells. The enzymes glutamine synthetase, glutamate synthetase, and glutamate dehydrogenase are involved in these processes. Some experimental results have proven that the global nitrogen regulation system may participate in the regulation of assimilation of ammonia in rumen bacteria. This review offers a current perspective on the pathways and key enzymes of ammonia assimilation in rumen bacteria with the possible molecular regulation strategy, while points out the further research direction.     

Isolation of previously uncultured rumen bacteria by dilution to extinction using a new liquid culture medium

A new anaerobic medium that mimics the salts composition of rumen fluid was used in conjunction with a dilution method of liquid culture to isolate fermentative bacteria from the rumen of a grass-fed sheep. The aim was to inoculate a large number of culture tubes each with a mean of < 1 culturable cell, which should maximize the number of cultures that develop from a single bacterium. This minimizes the effort that has to be put into purifying the resultant cultures. Of 1000 tubes, 139 were growth positive. Of the 93 that were able to be subcultured, 54 (58%) appeared to be pure cultures. The phylogenetic placements of these 54 cultures, together with another 6 cultures obtained from a preliminary study, were determined. Using a criterion of < 93% 16S rRNA gene sequence identity to a previously named bacterium as a proxy for defining a new genus, 27 (45%) of the 60 cultures belonged to 14 potentially novel genera. Many of these had 16S rRNA genes that shared > 97% sequence identity to genes of uncultured bacteria detected in various gastrointestinal environments. This strategy has therefore allowed us to cultivate many novel rumen bacteria, opening the way to overcoming the lack of cultures of many of the groups detected using cultivation-independent methods.     

为动物类专业本科生讲授瘤胃微生物知识点的体会

瘤胃微生物与反刍动物的共生关系是动物类专业本科生必须掌握的重要知识。我们采取问题导向教学方法,使学生较好地掌握瘤胃微生物在反刍动物生长发育中的作用,积极培养学生在科学饲养反刍动物、正确防治瘤胃疾病以及未来开展反刍动物相关研究的素质和能力。     

Inclusion of cocoa by-product in the diet of dairy sheep: Effect on the fatty acid profile of ruminal content and on the composition of milk and cheese

In this study, we hypothesized that dietary cocoa bean shell (CBS) as a partial replacer of human edible cereal grains in the diet of lactating ewes may affect performance and milk and cheese composition. Twenty Comisana lactating ewes allotted into control (CTRL; n = 10) or cocoa (CBS; n = 10) group received alfalfa hay ad libitum and 800 g of conventional (CTRL) or experimental (CBS) concentrate containing 11.7% CBS to partially replace corn and barley of the CTRL concentrate. Milk yield and composition did not differ between groups, and only urea concentration was lower in CBS milk. Dietary CBS increased cheese fat and reduced protein percentage in CBS group. Fatty acid composition of rumen content partially reflected that of the ingested diet, with total saturated fatty acids (SFA), total monounsaturated fatty acids (MUFA), 16:0, 18:0 and 18:1c9 greater in the CBS group. Moreover, all the identified trans- and cis-18:1 isomers were greater in CBS rumen content. Milk and cheese showed a similar fatty acid composition. Total MUFAs were greater in milk and cheese of CBS, mainly due to the proportion of 18:1c9, and conversely, total polyunsaturated fatty acids (PUFA), PUFAn-6 and PUFAn-6-to-PUFAn-3 ratio was greater in CTRL group. Concluding, the inclusion of CBS in the diet of lactating ewes within the limit imposed by the current legislation did not cause detrimental effects on animal performance and milk composition. Interestingly, dietary CBS reduced milk urea concentration probably due to the phenols contained in CBS concentrate. However, our results support that biohydrogenation was weakly impaired by dietary CBS. Finally, CBS negatively affected cheese nutritional characteristics due to lower protein and greater fat content, but improved fat health indexes in milk and cheese.