Effect of defaunation and refaunation of the rumen on rumen fermentation and N-flow in the duodenum of sheep

In order to confirm earlier fragmentary results, the effect of defaunation and refaunation of the rumen on the fermentation pattern and flow of N-components in the proximal duodenum of two sheep was investigated. Defaunation had no effect on acetic acid as a proportion of the total volatile fatty acids in the rumen, while the proportions of propionic acid increased with a concomitant decrease in butyrate. Refaunation resulted in lower acetic acid and higher butyric acid proportions. The concentration of ammonia N in the rumen was clearly decreased after defaunation, already indicating an effect of the elimination of protozoa on nitrogen metabolism in the rumen. Defaunation also increased significantly the flow of total N, non ammonia N and individual and total amino acids in the proximal duodenum. Defaunation resulted in higher bacterial growth efficiency, significantly in one sheep, but the decrease after refaunation was statistically significant for both sheep. Determination of rumen digestibility of organic matter and acid detergent fibre (ADF) revealed lower values in the absence of the protozoa, while total digestibility was only influenced to a much lower extent. This indicated a shift of digestion from rumen to the lower digestive tract. Finally, earlier work is discussed in the light of the present findings.     

Diversity and fluctuation in ciliate protozoan population in the rumen of cattle

The purpose of this study was to investigate the diversity and fluctuation in the ciliate protozoan population in the rumen of cattle. DNA was extracted from the rumen of three ruminally cannulated, crossbred cattle and a polymerase chain reaction (PCR)‐derived clone library was constructed, using a specific primer set targeting 18S ribosomal RNA genes of ciliate protozoa. DNA fragments of seven selected clones were validated for standard DNA of the protozoa‐specific real‐time PCR assay. Furthermore, population fluctuation of ciliate protozoa and methanogens in the cattle rumen was determined by real‐time PCR. A total of 60 clones were sequenced, phylogenetically analyzed, and classified into 24 operational taxonomic units (OTUs) based on a 99% similarity criterion. More than 80% sequences were phylogenetically placed in the genus Entodinium. The rest of the sequences were placed in the genus Diploplastron (5%), Dasytricha (8.3%) and Isotricha (3.3%). The results suggest that Entodinium was the dominant group in the rumen of cattle used in this study. The ciliate protozoan population showed no significant change in numbers during the monitoring period and reached a peak at 3 h after feeding. Changes in the protozoa population were lower than those of the methanogens.     

Feed and water deprivation has a negative but transient effect on the rumen kinetics of Bos indicus steers

The effects on rumen kinetics after feed and water had been deprived for 72 hr were studied using four fistulated Bos indicus steers. The animals were assigned in a 2 × 4 crossover design with two treatments: feed and water ad libitum (control) and no feed and water for 72 hr (deprived) with four steers per treatment over two time periods. Feed and water deprivation caused decreases in the numbers of cellulolytic bacteria (1.4 vs. 0.4 cfu × 10⁶/ml; p = .001), live (23.7 vs. 0.8 × 10⁹/ml; p = .001), dead (12.7 vs. 0.5 × 10⁹/ml; p = .001) and total bacterial counts (36.4 vs. 1.4 × 10⁹/ml; p = .001) at day 0, compared with the control treatment. However, the deprived group had greater numbers of cellulolytic bacteria (2.7 vs. 50.1 cfu × 10⁶/ml; p = .001), live (18.3 vs. 42.2 × 10⁹/ml; p = .001), dead (6. 5 vs. 19.1 × 10⁹/ml; p = .001) and total bacterial counts (24.8 vs. 61.3 × 10⁹/ml; p = .001) from rumen fluid on day 4, compared with the control treatment. The numbers of protozoa in rumen fluid from the deprived group were less than (551.2 vs. 2.4 × 10³/ml; p = .001) the control group on day 0. However, the deprived treatment had fewer protozoa in rumen fluid than the control treatment on day 4 (p = .001) and day 9 (p = .001). Volatile fatty acids and in vitro gas production as functional measurements of rumen fluid followed the same trend as the bacterial and protozoa populations. These results indicate that feed and water deprivation would have a negative but transient effect on the rumen kinetics of Bos indicus steers.     

瘤胃原虫对瘤胃营养物质代谢的影响研究进展

本文在广泛查阅有关瘤胃原虫对糖代谢包括淀粉和可溶性糖代谢及纤维素代谢、对蛋白质代谢和对瘤胃内甲烷代谢等的影响研究资料的基础上，分析、总结了瘤胃原虫对反刍动物营养物质代谢的影响机理，指出瘤胃原虫对反刍动物的营养代谢既有有利的方面，也有不利的方面。实际应用时可根据不同的日粮类型、家畜的生理状况、当地的饲养管理条件等实际情况因时控制瘤胃纤毛虫区系及种群密度，创造适宜的瘤胃内环境，充分发挥原虫在特定条件下的有利生理功能，从而提高反刍动物饲料利用率和生产性能。     

Fatty acid composition of ruminal bacteria and protozoa,and effect of defaunation on fatty acid profile in the rumen with special reference to conjugated linoleic acid in cattle

Objectives of this study were to compare fatty acid (FA) composition of ruminal bacterial (B) and protozoal (P) cells, and to investigate effect of protozoa on FA profile in the rumen of cattle. Three cows were used to prepare ruminal B and P cells. Four faunated and three defaunated cattle (half‐siblings) were used to study effect of protozoa on ruminal FA profile. Proportions of C16:0 and C18:0 in total fatty acids in B cells were 20.7% and 37.4%, whereas those in P cells were 33.4% and 11.6%, respectively. Proportions of trans‐vaccenic acid (VA) and cis‐9, trans‐11 conjugated linoleic acid (CLA) in B cells were 3.9% and 1.0%, and those in P cells were 5.5% and 1.6%, respectively, being higher in P cells. Proportions of C18:1, C18:2 and C18:3 in P cells were two to three times higher than in B cells. Proportions of unsaturated fatty acids, VA and CLA in B cells of faunated cattle were higher than those of defaunated. VA and CLA in the ruminal fluid of faunated were also 1.6 to 2.5 times higher than those of defaunated. This tendency was similar for cell‐free fraction of ruminal fluid. These results indicate that protozoa contribute greatly in VA and CLA production in the rumen.     

瘤胃原虫营养研究进展

瘤胃原虫是瘤胃微生物的重要组成部分。本文针对瘤胃原虫特点、作用、调控及瘤胃细菌和真菌间的相互作用作一综述。     

Effect of Saccharomyces cerevisiae on alfalfa nutrient degradation characteristics and rumen microbial populations of steers fed diets with different concentrate-to-forage ratios

Live yeast (Saccharomyces cerevisiae) constitutes an effective additive for animal production; its probiotic effect may be related to the concentrate-to-forage ratio (CTFR). The objective of this study was to assess the effects of S. cerevisiae (SC) on fiber degradation and rumen microbial populations in steers fed diets with different levels of dietary concentrate. Ten Simmental × Local crossbred steers (450 ± 50 kg BW) were assigned to a control group or an SC group. Both groups were fed the same basal diet but the SC group received SC supplementation (8 × 10⁹ cfu/h/d through the ruminal fistula) following a two-period crossover design. Each period consisted of four phases, each of which lasted 17 d: 10 d for dietary adaptation, 6 d for degradation study, and 1 d for rumen sample collection. From the 1^st to the 4^th phase, steers were fed in a stepwise fashion with increasing CTFRs, i.e., 30:70, 50:50, 70:30, and 90:10. The kinetics of dry matter and fiber degradation of alfalfa pellets were evaluated; the rumen microbial populations were detected using real-time PCR. The results revealed no significant (P > 0.05) interactions between dietary CTFR and SC for most parameters. Dietary CTFR had a significant effect (P < 0.01) on degradation characteristics of alfalfa pellets and the copies of rumen microorganism; the increasing concentrate level resulted in linear, quadratic or cubic variation trend for these parameters. SC supplementation significantly (P < 0.05) affected dry matter (DM) and neutral detergent fiber (NDF) degradation rates (c_DM, c_NDF) and NDF effective degradability (ED_NDF). Compared with the control group, there was an increasing trend of rumen fungi and protozoa in SC group (P < 0.1); copies of total bacteria in SC group were significantly higher (P < 0.05). Additionally, percentage of Ruminobacter amylophilus was significantly lower (P < 0.05) but percentage of Selenomonas ruminantium was significantly higher (P < 0.05) in the SC group. In a word, dietary CTFR had a significant effect on degradation characteristics of forage and rumen microbial population. S. cerevisiae had positive effects on DM and NDF degradation rate or effective degradability of forage; S. cerevisiae increased rumen total bacteria, fungi, protozoa, and lactate-utilizing bacteria but reduced starch-degrading and lactate-producing bacteria.     

Reconstruction of corneal epithelium with cryopreserved corneal limbal stem cells in a rabbit model

The integrity and transparency of the cornea plays a key role in preserving vision. This paper reports a procedure to create an artificial sheet of corneal epithelium from cryopreserved limbal stem cells (LSCs) and to use this for corneal transplantation. Corneal LSCs were isolated from biopsy specimens of rabbit limbal lamellar and cryopreserved in liquid nitrogen at 2–4 passages. The cells were grown in culture medium for 12–14 days on top of a cell-free human amniotic membrane framed on a nitrocellulose sheet. The corneal epithelium generated was transplanted into the right eyes of 14 LSC deficient (LSCD) rabbits (seven experimental animals, seven controls) with corneal damage. The seven LSCD rabbits in the experimental group were transplanted with a corneal epithelial sheet generated from the cryopreserved corneal LSCs. Four LSCD rabbits were used as the vehicle control and were transplanted with a cell-free amniotic membrane, and the remaining three LSCD rabbits were negative controls without transplantation. Over a 2-month recovery period, 2/7 animals in the experimental group recovered completely, four recovered partially and one did not respond. In the control groups, three negative controls and three vehicle controls lost their vision completely, and one of the vehicle controls partially recovered transparency of the cornea Following treatment, corneal transparency of the experimental rabbits was significantly improved compared to controls (P < 0.05). The results indicated that cryopreserved corneal LSCs can repair damaged rabbit cornea, suggesting a possible new clinical approach to reconstruction of corneal epithelium.     

Pediococcus acidilactici isolated from the rumen of lambs with rumen acidosis, 16S rRNA identification and sensibility to monensin and lasalocid

A lactic-acid producing bacterium was isolated from the rumen of lambs with rumen acidosis. The cells were Gram-positive, nonmotile, nonsporing, catalase negative spherical, 1.5-2.0 μm in diameter, and occur in pairs and tetrads. Analysis of 16S ribosomal RNA indicated that the rumen bacterium was a strain of Pediococcus acidilactici with 99% of nucleotide homology. This bacterium was sensible to monensin and lasalocid at the unique dose tested of 300 ppm. The concentration of lactic acid and DM degradation decreased (P < 0.05) when monensin or lasalocid were added to the culture media after 24, 48 and 72 h of incubation. In contrast, total VFA concentration and pH were higher (P < 0.05) in the culture media added with the ionophores. Up to now S. bovis is considered the main ruminal bacterium related with rumen acidosis, but the importance of P. acidilactici should be also reconsidered in experimental studies focused on the control rumen acidosis.     

Change in body condition and carcass characteristics of cull ewes fed diets supplemented with rumen bypass fat

Thirty Malpura ewes (>6 years age) distributed into three groups of 10 each were maintained on concentrate supplemented with rumen protected fat at 0 (T₁), 20 (T₂) and 40 (T₃) g kg⁻¹ and chick pea straw for a period of three months. Towards the end of feeding experiment a metabolism trial was conducted on five representative ewes from each treatment. Blood and rumen liquor samples were analyzed at 0 and 90 days of feeding for blood biochemical and rumen metabolites. Five representative ewes were slaughtered at the initiation of the study and all the experimental ewes were slaughtered after termination of the experiment. The gain in weight (kg) and final body condition score was higher (P<0.05) in T₂ and T₃ as compared to T₁. The concentrate intake increased (P<0.05) with bypass fat (RBF) supplementation. The serum glucose and population of spirotrichs and total protozoa in rumen liquour sample increased (P<0.05) with concentrate as well as concentrate with RBF supplementation. Pre-slaughter weight, hot carcass weight, dressing percent, loin eye area, bone percent and carcass fat improved (P<0.05) with RBF supplementation. Composition of Longissimus dorsi muscle also revealed improvement when compared with 0 day composition. The feeding protocol also revealed higher returns by RBF supplementation. It is therefore concluded that RBF supplementation is advantageous in improving body conditions of cull ewes.     

GC analysis of essential oils in the rumen fluid after incubation of Thuja orientalis twigs in the Rusitec system

Methods for the chemical analysis of toxic plant substances in the rumen of ruminants are of importance for the diagnosis of intoxications with poisonous plants. The present work establishes a method to estimate monoterpene components of the essential oil of thuja (Thuja orientalis, Cupressaceae) in these types of samples. Alpha-thujone, which is regarded as the toxic principle, is present at a concentration of 50-60% in the essential oil. The rumen simulation technique (Rusitec) was used to simulate natural digestion. Chopped twigs of thuja were subjected to rumen content in a closed container with an overflow device. The flow of saliva was simulated by the continuous addition of a buffer solution. Samples for analysis were taken from the overflow at 24 and 48 h. A further sample was taken from the remaining liquid fraction of the rumen content in the container at 48 h. The essential oils were extracted with hexane and concentrated. A quantitative determination was done by capillary gas chromatography. Together in the three fractions analysed this resulted in total mean recoveries of 6.8% for alpha-thujone, 5.3% for beta-thujone, 18.9% for fenchone and 27.8% for camphor. The observation that the thujones were recovered to a lesser extent than other oil components is evidence of their fast decomposition in the rumen medium. Under these circumstances the calculated detection limit is 100-200 g thuja twigs in cows with rumen volumes of 60-100 litres. The main essential oil degradation products found in the rumen fluid of all three fractions in the Rusitec system were discovered to be iso-3-thujanol, neo-3-thujanol, carvomenthol and carvomenthone.     

混合牧草和配合饲料在滩羊瘤胃中的降解率比较

试验用尼龙袋法测定了35kg滩羊采食混合牧草和配合饲料中干物质(DM)、粗蛋白(CP)、酸性洗涤纤维(ADF)和中性洗涤纤维(NDF)在瘤胃内6h、12h、24h、36h、48h和72h的降解率。结果表明：混合牧草中CP降解率比配合饲料高出7．96个百分点，而配合饲料中DM、ADF和NDF降解率分别比混合牧草高出0．87、11．92和12．15个百分点。因此，牧区养羊时放牧与舍饲结合，两种饲料可得以互补，使有限的资源可以得到最大的合理利用，降低生产成本。     

不同发酵处理甘蔗渣在肉牛瘤胃中的降解特性研究

[目的]本试验旨在研究不同发酵处理甘蔗渣在肉牛瘤胃中的降解特性。[方法]试验选择3头安装永久性瘤胃瘘管的西门塔尔杂交公牛为试验动物,采用尼龙袋法测定未发酵甘蔗渣、发酵甘蔗渣1(添加0.3%乳酸杆菌(含量≥10×10⁸CFU/g)青贮发酵甘蔗渣)和发酵甘蔗2(添加0.3%菌种组合(菌种组合以酿酒酵母菌(含量≥4×10⁸CFU/g)、黑曲霉菌(含量≥2×10⁸CFU/g)、米曲霉菌(含量≥2×10⁸CFU/g)、乳酸杆菌(含量≥2×10⁸CFU/g)按2:1:1:1配制)和0.1%纤维素酶(酶活≥2万IU/g)进行菌酶协同发酵甘蔗渣)的干物质(DM)、粗蛋白质(CP)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)在瘤胃内的降解率。[结果]结果表明：1)干物质基础上,未发酵甘蔗渣和两种发酵甘蔗渣在DM和粗脂肪(EE)水平上差异不显著(P>0.05),而发酵甘蔗渣2的粗纤维(CF)、NDF、ADF和酸性木质素(ADL)水平显著低于未发酵甘蔗渣和发酵甘蔗渣1(P<0.05)...     

Quantitative studies of the in vitro production of pipecolic acid by rumen protozoa and its degradation by rumen bacteria

An in vitro study was conducted to quantitatively investigate the metabolism of pipecolic acid (Pip), a neuromodulator, by mixed rumen bacteria (B), mixed rumen protozoa (P), a combination of B and P (BP), species‐enriched rumen protozoal suspension (Polyplastron sp., Diploplastron sp., entodinia and Entodinium caudatum) and pure cultures of several isolates of rumen bacteria (Prevetolla bryantii, Prevetolla albensis, Streptococcus bovis, Veillonella parvula, Megasphaera elsdenii and Ruminococcus albus). Only P produced Pip from L‐lysine (1.0 mmol/L L‐Lys) at a rate of 83.5 ± 1.6 µmol/L/h and even in BP, Pip was produced from L‐Lys by P and increased at a rate of 31.2 ± 3.8 µmol/L/h. Pip production by P was highest when the substrate (L‐Lys) concentration was 6 mmol/L and then the rate was 580 ± 36 µmol/L/h. Pipecolic acid production by P suspension enriched with different species of protozoa showed that Polyplastron sp. had the highest Pip production rate of 0.907 ± 0.092 µmol/L/mg protozoal protein per h, and Diploplastron sp. had the lowest rate of 0.55 ± 0.13 µmol/L/mg protozoal protein per h. The addition of D‐Lys (1.0 mmol/L) as a substrate to the P suspension revealed that P were also able to produce Pip from D‐Lys, though at a lower rate (1/3) compared with L‐Lys (1.0 mmol/L), suggesting the presence of epimerases in P. It was confirmed that B were unable to produce Pip from L‐ or D‐Lys. Only B degraded Pip (1.0 mmol/L) after a lag phase at a rate of 56.0 ± 1.5 µmol/L/h. The B suspension was able to degrade D‐Lys, though the products were not identified. Pip degradation by pure culture of some species of rumen bacteria showed that P. bryantii and R. albus had the highest rate followed by P. albensis, S. bovis and M. elsdenii with a low rate of Pip degradation. Veillonella parvula showed no ability to degrade Pip. The results suggest that a fairly large proportion of rumen‐produced Pip is likely to be absorbed by the host animal before degradation by rumen bacteria.     

Monitoring cow comfort and rumen health indices in a cubicle-housed herd with an automatic milking system: a repeated measures approach

Background

Cow rumination and lying behaviour are potentially useful and interrelated indicators of cow health and welfare but there is conflicting evidence about how reliable these measures are. The objective of this study was to quantify the variation of indices of cow comfort and rumen health in a herd with an automatic milking system for which husbandry was relatively constant, in order to propose an alternative approach to optimising the use of these indices when continuous monitoring is not available. During a period of 28 days, standing index, cud chewing index and rumination index were observed.

Results

The daily mean standing index ranged between 9.0 and 18.0 per cent, cud chewing index between 43.5 and 74.0 per cent, and rumination index between 49.0 and 81.0 per cent. The point of lowest variation in the indices was determined as that with the lowest coefficient of variation. The coefficient of variation was lowest for data collected between 240 and 270 minutes after refreshing of the bedding material on the cubicles for both the standing index and rumination index, and for data collected between 120 and 150 minutes after refreshing of the bedding material on the cubicles for the cud chewing index.

Conclusions

In spite of relative constant husbandry practices in a herd with an automatic milking system, the variation in the standing index, cud chewing index and rumination index was still considerable. This suggests these measures should be repeated on several consecutive days, according to population size and wanted margin of error, to be representative and useful.     

维生素A对秸杆NDF瘤胃降解率的影响

试验采用3×3拉丁方设计,肉牛日粮中维生素A含量分别为1180国际单位、18680国际单位和36180国际单位,通过对瘤胃挥发性脂肪酸浓度和玉米秸秆NDF降解率的测定,结果表明维生素A36180国际单位较维生素A1180国际单位组能显著提高瘤胃中乙酸浓度和玉米秸杆NDF有效降解率(p＜0.05).     

Nutritive value of forage species grown in the warm temperate climate of Australia for dairy cows: Herbs and grain crops

The objective of this study was to quantify the nutritive characteristics of 6 grain crops and 4 herb forages over 4 seasons, when all species were grown at the same site, under the same climatic and edaphic conditions, and with soil moisture and nutrient availability being non-limiting to growth. The forages grown were maize (Zea mays), sorghum (Sorghum bicolor), millet (Pennisetum americana), wheat (Triticum aestivum), triticale (Triticum × secale), oats (Avena sativa), fodder radish (Raphanu sativa), rape (Brassica rapa), chicory (Cachorium intybus) and plantain (Plantago lanceolata). The in sacco degradation characteristics of organic matter (OM) and crude protein of herbages were measured in the rumen of cannulated sheep in order to calculate the availability of effective rumen degradable protein (ERDP), rumen by pass protein, metabolisable protein (MP) and the synchrony index (I_s), which describes the efficiency of utilization of degradable nitrogen (N) and OM for microbial protein synthesis (MPS) in the rumen.In this study, all grain crops except maize had a ERDP/fermentable metabolizable energy (FME) ratio varying from 14 for millet to 23 for wheat, well above the ratio of 11 required for optimum MPS in the rumen of dairy cows. In contrast, maize had the lowest ERDP/FME ratio of 3, indicating that ERDP would be limiting MPS in the rumen. The availability of MP varied from 58 g/kg DM in maize to 153 g/kg DM in wheat and all forage species except maize were be able to meet the MP requirement of high-producing dairy cows (30 L/milk/day) provided they were able to consume 11 to13 kg DM/cow/day of the forage.The availability of MP from herbs varied from 95 g/kg DM in fodder radish to 163 g/kg DM in plantain, which would be sufficient for high-producing cows, however, most dairy cows could not consume sufficient forage to achieve these high levels of production due to very high nitrate content in rape (mean of 11.1 g/kg DM) and fodder radish (mean of 8 g/kg DM).     

Quantitative comparisons of select cultured and uncultured microbial populations in the rumen of cattle fed different diets

Background: The number and diversity of uncultured ruminal bacterial and archaeal species revealed by 16S rRNA gene (rrs) sequences greatly exceeds that of cultured bacteria and archaea. However, the significance of uncultured microbes remains undetermined. The objective of this study was to assess the numeric importance of select uncultured bacteria and cultured bacteria and the impact of diets and microenvironments within cow rumen in a comparative manner. Results: Liquid and adherent fractions were obtained from the rumen of Jersey cattle fed hay alone and Holstein cattle fed hay plus grain. The populations of cultured and uncultured bacteria present in each fraction were quantified using specific real-time PCR assays. The population of total bacteria was similar between fractions or diets, while total archaea was numerically higher in the hay-fed Jersey cattle than in the hay-grain-fed Holstein cattle. The population of the genus Prevotella was about one log smaller than that of total bacteria. The populations of Fibrobacter succinogenes, Ruminococcus flavefaciens, the genus Butyrivibrio, and R. albus was at least one log smaller than that of genus Prevotella. Four of the six uncultured bacteria quantified were as abundant as F. succinogenes, R. flavefaciens and the genus Butyrivibrio. In addition, the populations of several uncultured bacteria were significantly higher in the adherent fractions than in the liquid fractions. These uncultured bacteria may be associated with fiber degradation. Conclusions: Some uncultured bacteria are as abundant as those of major cultured bacteria in the rumen. Uncultured bacteria may have important contribution to ruminal fermentation. Population dynamic studies of uncultured bacteria in a comparative manner can help reveal their ecological features and importance to rumen functions.     

Quantitative comparisons of select cultured and uncultured microbial populations in the rumen of cattle fed different diets

ABSTRACT: BACKGROUND: The number and diversity of uncultured ruminal bacterial and archaeal species revealed by 16S rRNA gene (rrs) sequences greatly exceeds that of cultured bacteria and archaea. However, the significance of uncultured microbes remains undetermined. The objective of this study was to assess the numeric importance of select uncultured bacteria and cultured bacteria and the impact of diets and microenvironments within cow rumen in a comparative manner. RESULTS: Liquid and adherent fractions were obtained from the rumen of Jersey cattle fed hay alone and Holstein cattle fed hay plus grain. The populations of cultured and uncultured bacteria present in each fraction were quantified using specific real-time PCR assays. The population of total bacteria was similar between fractions or diets, while total archaea was numerically higher in the hay-fed Jersey cattle than in the hay-grain-fed Holstein cattle. The population of the genus Prevotella was about one log smaller than that of total bacteria. The populations of Fibrobacter succinogenes, Ruminococcus flavefaciens, the genus Butyrivibrio, and R. albus was at least one log smaller than that of genus Prevotella. Four of the six uncultured bacteria quantified were as abundant as F. succinogenes, R. flavefaciens and the genus Butyrivibrio. In addition, the populations of several uncultured bacteria were significantly higher in the adherent fractions than in the liquid fractions. These uncultured bacteria may be associated with fiber degradation. CONCLUSIONS: Some uncultured bacteria are as abundant as those of major cultured bacteria in the rumen. Uncultured bacteria may have important contribution to ruminal fermentation. Population dynamic studies of uncultured bacteria in a comparative manner can help reveal their ecological features and importance to rumen functions.     

A note on the effect of dietary proportions of kale (Brassica oleracea) and grass silage on rumen pH and volatile fatty acid concentrations in dry dairy cows

The objective of this study was to evaluate the effect of varying proportions of dietary kale on rumen pH and volatile fatty acid production. Four pregnant dry dairy cows permanently fitted with ruminal cannulae were randomly assigned to four kale: grass silage dietary proportions (0:100, K0; 60:40, K60; 85:15, K85 and 100:0, K100) on a dry matter basis in a 4 × 4 Latin Square design with four 20 day periods. Cows were acclimatised for 15 days, followed by a five-day period of experimental sampling and measurement. Internal pH meters were installed to continuously monitor rumen pH while rumen liquor collection tubes were used to sample rumen liquor for volatile fatty acid analysis at 0, 4, 8 and 12 h after feeding on each sampling day. Cows on treatment K85 had a lower (P < 0.001) ruminal pH compared to cows on treatments K100, K60 or K0 (6.26, 6.32, and 6.32 vs. 5.91, respectively). While a gradual decrease in rumen pH was observed over an eight-hour period for K85 before recovery, offering K100 did not reduce rumen pH below 6.0 or induce acidosis. Increasing the dietary proportion of kale did not affect (P > 0.05) acetate:propionate ratio production (3.71, 3.65, 3.86, 3.78 mmol L^− 1 for K0, K60, K85 and K100, respectively). Offering cows K60 had increased (P < 0.05) rumen VFA concentration (71.67 mmol L^− 1) relative to K0 (53.45 mmol L^− 1), while offering K85 and K100 had no affect on rumen VFA concentration (61.74 and 59.35 mmol L^− 1) (Table 2). Offering dry cows K100 relative to K0 reduced dry matter intake by 17.5% (7.32 vs. 8.87 kg DM day^− 1, respectively) which may be associated with the presence of S-methyl-L-cysteine sulphoxide which can cause haemolytic anaemia and depressed DM intake. The results suggest that increasing the dietary proportion of kale was associated with a progressive decrease in dry matter intake but with minimal effects on rumen pH, total volatile fatty acid concentration and individual volatile fatty acid proportions.