Evaluating the effect of phenolic compounds as hydrogen acceptors when ruminal methanogenesis is inhibited in vitro - Part 2. Dairy goats.

Most mitigation strategies to reduce enteric methane (CH4) production in the rumen induce an excess of rumen dihydrogen (H2) that is expelled and consequently not redirected to the synthesis of metabolites that can be utilised by the ruminant. We hypothesised that phenolic compounds can be potential H2 acceptors when added to the diet, as they can be degraded to compounds that may be beneficial for the animal, using part of the H2 available when ruminal methanogenesis is inhibited. We performed four in vitro incubation experiments using rumen inoculum from Murciano-Granadina adult goats: Experiment 1 examined the inhibitory potential of Asparagopsis taxiformis (AT) at different concentrations (0, 1, 2, 3, 4 and 5% of the substrate on a DM basis) in 24 h incubations; Experiment 2 investigated the effect of a wide range of phenolic compounds (phenol, catechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, gallic acid and formic acid) at different doses (0, 2, 4, and 6 mM) on rumen fermentation for 24 h; Experiment 3 evaluated the combined effect of each phenolic compound at 6 mM with AT at 2% DM in sequential batch cultures for 5 days; and Experiment 4 examined the dose-response effect of phloroglucinol at different concentrations (0, 6, 16, 26 and 36 mM) combined with AT in sequential batch cultures for 5 days. Results from Experiment 1 confirmed that AT at 2% DM substantially inhibited CH4 production while significantly increasing H2 accumulation and decreasing the acetate:propionate ratio. Results from Experiment 2 showed that phenolic compounds did not negatively affect rumen fermentation at any dose. In Experiment 3, each phenolic compound at 6 mM combined with AT at 2% DM inhibited CH4 production. Phloroglucinol numerically decreased H2 accumulation and significantly increased total gas production (TGP), volatile fatty acid (VFA) production and the acetate:propionate ratio. In Experiment 4, phloroglucinol at increasing doses supplemented with AT at 2% DM significantly decreased H2 accumulation and the abundances of archaea, protozoa and fungi abundances, and increased TGP, total VFA production and the acetate:propionate ratio in a dose-dependent way. In conclusion, combined treatment with AT and phloroglucinol was successful to mitigate CH4 production while preventing the accumulation of H2, leading to an increase in acetate and total VFA production and therefore an improvement in rumen fermentation in goats.

Prediction of nitrogen excretion from data on dairy cows fed a wide range of diets compiled in an intercontinental database: A meta-analysis.

Manure nitrogen (N) from cattle contributes to nitrous oxide and ammonia emissions and nitrate leaching. Measurement of manure N outputs on dairy farms is laborious, expensive, and impractical at large scales; therefore, models are needed to predict N excreted in urine and feces. Building robust prediction models requires extensive data from animals under different management systems worldwide. Thus, the study objectives were (1) to collate an international database of N excretion in feces and urine based on individual lactating dairy cow data from different continents; (2) to determine the suitability of key variables for predicting fecal, urinary, and total manure N excretion; and (3) to develop robust and reliable N excretion prediction models based on individual data from lactating dairy cows consuming various diets. A raw data set was created based on 5,483 individual cow observations, with 5,420 fecal N excretion and 3,621 urine N excretion measurements collected from 162 in vivo experiments conducted by 22 research institutes mostly located in Europe (n = 14) and North America (n = 5). A sequential approach was taken in developing models with increasing complexity by incrementally adding variables that had a significant individual effect on fecal, urinary, or total manure N excretion. Nitrogen excretion was predicted by fitting linear mixed models including experiment as a random effect. Simple models requiring dry matter intake (DMI) or N intake performed better for predicting fecal N excretion than simple models using diet nutrient composition or milk performance parameters. Simple models based on N intake performed better for urinary and total manure N excretion than those based on DMI, but simple models using milk urea N (MUN) and N intake performed even better for urinary N excretion. The full model predicting fecal N excretion had similar performance to simple models based on DMI but included several independent variables (DMI, diet crude protein content, diet neutral detergent fiber content, milk protein), depending on the location, and had root mean square prediction errors as a fraction of the observed mean values of 19.1% for intercontinental, 19.8% for European, and 17.7% for North American data sets. Complex total manure N excretion models based on N intake and MUN led to prediction errors of about 13.0% to 14.0%, which were comparable to models based on N intake alone. Intercepts and slopes of variables in optimal prediction equations developed on intercontinental, European, and North American bases differed from each other, and therefore region-specific models are preferred to predict N excretion. In conclusion, region-specific models that include information on DMI or N intake and MUN are required for good prediction of fecal, urinary, and total manure N excretion. In absence of intake data, region-specific complex equations using easily and routinely measured variables to predict fecal, urinary, or total manure N excretion may be used, but these equations have lower performance than equations based on intake.

Short communication: Saliva and salivary components affect goat rumen fermentation in short-term batch incubations.

The research about the role of saliva in ruminants has been mainly focused on its buffering capacity together with facilitation of the rumination process. However, the role of salivary bioactive components on modulating the activity of the rumen microbiota has been neglected until recently. This study developed an in vitro approach to assess the impact of different components in saliva on rumen microbial fermentation. Four different salivary fractions were prepared from four goats: (i) non-filtrated saliva (NFS), (ii) filtrated through 0.25 µm to remove microorganisms and large particles (FS1), (iii) centrifuged through a 30 kDa filter to remove large proteins, (FS2), and (iv) autoclaved saliva (AS) to keep only the minerals. Two experiments were conducted in 24 h batch culture incubations with 6 ml of total volume consisting of 2 ml of rumen fluid and 4 ml of saliva/buffer mix. In Experiment 1, the effect of increasing the proportion of saliva (either NFS or FS1) in the solution (0%, 16%, 33% and 50% of the total volume) was evaluated. Treatment FS1 promoted greater total volatile fatty acids (VFA) (+8.4%) and butyrate molar proportion (+2.8%) but lower NH3-N concentrations than NFS fraction. Replacing the bicarbonate buffer solution by increasing proportions of saliva resulted in higher NH3-N, total VFA (+8.0%) and propionate molar proportion (+11%). Experiment 2 addressed the effect of the different fractions of saliva (NFS, FS1, FS2 and AS). Saliva fractions led to higher total VFA and NH3-N concentrations than non-saliva incubations, which suggests that the presence of some salivary elements enhanced rumen microbial activity. Fraction FS1 promoted a higher concentration of total VFA (+7.8%) than the other three fractions, and higher propionate (+26%) than NFS and AS. This agrees with findings from Experiment 1 and supports that 'microbe-free saliva', in which large salivary proteins are maintained, boosts rumen fermentation. Our results show the usefulness of this in vitro approach and suggest that different salivary components can modulate rumen microbial fermentation, although the specific metabolites and effects they cause need further research.

Early life dietary intervention in dairy calves results in a long-term reduction in methane emissions.

Recent evidence suggests that changes in microbial colonization of the rumen prior to weaning may imprint the rumen microbiome and impact phenotypes later in life. We investigated how dietary manipulation from birth influences growth, methane production, and gastrointestinal microbial ecology. At birth, 18 female Holstein and Montbéliarde calves were randomly assigned to either treatment or control (CONT). Treatment was 3-nitrooxypropanol (3-NOP), an investigational anti-methanogenic compound that was administered daily from birth until three weeks post-weaning (week 14). Samples of rumen fluid and faecal content were collected at weeks 1, 4, 11, 14, 23, and 60 of life. Calves were tested for methane emissions using the GreenFeed system during the post-weaning period (week 11-23 and week 56-60 of life). Calf physiological parameters (BW, ADG and individual VFA) were similar across groups throughout the trial. Treated calves showed a persistent reduction in methane emissions (g CH4/d) throughout the post-weaning period up to at least 1 year of life, despite treatment ceasing three weeks post-weaning. Similarly, despite variability in the abundance of individual taxa across weeks, the rumen bacterial, archaeal and fungal structure differed between CONT and 3-NOP calves across all weeks, as visualised using sparse-PLS-DA. Similar separation was also observed in the faecal bacterial community. Interestingly, despite modest modifications to the abundance of rumen microbes, the reductive effect of 3-NOP on methane production persisted following cessation of the treatment period, perhaps indicating a differentiation of the ruminal microbial ecosystem or a host response triggered by the treatment in the early development phase.

A multi-stakeholder participatory study identifies the priorities for the sustainability of the small ruminants farming sector in Europe.

The European small ruminants (i.e. sheep and goats) farming sector (ESRS) provides economic, social and environmental benefits to society, but is also one of the most vulnerable livestock sectors in Europe. This sector has diverse livestock species, breeds, production systems and products, which makes difficult to have a clear vision of its challenges through using conventional analyses. A multi-stakeholder and multi-step approach, including 90 surveys, was used to identify and assess the main challenges for the sustainability of the ESRS to prioritize actions. These challenges and actions were identified by ESRS experts including farmers, cooperatives, breeding associations, advisers and researchers of six EU countries and Turkey. From the 30 identified challenges, the most relevant were economy-related challenges such as 'uncertainty of meat and milk prices', 'volatility of commodity prices', 'low farm income', 'high subsidy dependency' and 'uncertainty in future changes in subsidies' resulting in 'a sector not attractive to young farmers'. Most of these challenges were beyond the farmer's control and perceived as difficult to address. Challenges were prioritized using an index, calculated by multiplying the relevance and the feasibility to address measures. The identified challenges had a similar priority index across the whole sector with small differences across livestock species (sheep vs goats), type of products (meat vs dairy) and intensification levels (intensive vs semi-intensive vs extensive). The priorities were different, however, between socio-geographical regions (Southern vs Central Europe). Some of the top prioritized challenges were linked to aspects related to the production systems ('low promotion of local breeds' and 'slow adaptability of high producing breeds') and market practices ('unfair trade/lack of traceability'). The majority of the priority challenges, however, were associated with a deficient knowledge or training at farm level ('poor business management training', 'lack of professionalization', 'slow adoption of innovations'), academia ('researchers do not address real problems') and society as a whole ('low consumer education in local products', 'low social knowledge about farming', 'poor recognition of farming public services'). Thus, improved collaboration among the different stakeholders across the food chain with special implication of farmers, associations of producers, academia and governments is needed to facilitate knowledge exchange and capacity building. These actions can contribute to make ESRS economically more sustainable and to adapt the production systems and policy to the current and future societal needs in a more region-contextualized framework.

Inoculation with rumen fluid in early life as a strategy to optimize the weaning process in intensive dairy goat systems.

Ruminants are born with an undeveloped physical, metabolic, and microbial rumen. Rumen development is limited under artificial rearing systems when newborn animals are separated from the dam, fed on milk replacer, and weaned at an early age. This study aims to evaluate the effects of early-life inoculation of young ruminants with rumen fluid from adult animals. Eighty newborn goat kids were randomly allocated to 1 of 4 experimental treatments and inoculated daily from d 1 to wk 11 with autoclaved rumen fluid (AUT), fresh rumen fluid obtained from adult goats fed either a forage diet (RFF) or concentrate-rich diet (RFC), or absence of inoculation (CTL). Goat kids were artificially reared with ad libitum access to milk replacer, starter concentrate, and forage hay. Blood was sampled weekly and rumen microbial fermentation was monitored at 5 (preweaning), 7 (weaning), and 9 wk of age (postweaning). Results indicated that inoculation with fresh rumen fluid accelerated the rumen microbial and fermentative development before weaning. As a result, RFC and RFF animals had higher solid feed intake (+73%), rumen concentrations of ammonia-N (+26%), total volatile fatty acids (+46%), butyrate (+50%), and plasma ß-hydroxybutyrate (+48%), and lower milk intake (-6%) than CTL and AUT animals at wk 5. Inoculation with fresh inoculum also promoted early rumen colonization by a complex and abundant protozoal community, whereas CTL animals remained protozoa free. Although all kids experienced moderate growth retardation during 1 wk after weaning, inoculation with fresh rumen fluid favored the weaning process, leading to 2.2 times higher weight gain than CTL and AUT animals during wk 8. Some of these advantages were retained during the postweaning period and RFF and RFC animals showed higher forage intake (up to +44%) than CTL and AUT animals with no detrimental effects on feed digestibility or stress levels. The superior microbial load of RFC compared with RFF inoculum tended to provide further improvements in terms of forage intake, plasma ß-hydroxybutyrate, and rumen protozoa, whereas AUT inoculation provided minor (if any) advantages with respect to CTL animals. Although no differences were noted on animal growth, this study suggests that early life inoculation of goat kids with rumen microbiota can represent an effective strategy to accelerate the rumen development, facilitating a smooth transition from milk to solid feed and to the potential implementation of early weaning strategies.

Rumen bacterial community responses to DPA, EPA and DHA in cattle and sheep: A comparative in vitro study.

The role of marine lipids as modulators of ruminal biohydrogenation of dietary unsaturated fatty acids may be explained by the effects of their n-3 polyunsaturated fatty acids (PUFA) on the bacterial community. However, the impact of individual PUFA has barely been examined, and it is uncertain which bacteria are truly involved in biohydrogenation. In addition, despite interspecies differences in rumen bacterial composition, we are not aware of any direct comparison of bovine and ovine responses to dietary PUFA. Therefore, rumen fluid from cannulated cattle and sheep were used as inocula to examine in vitro the effect of 20:5n-3 (EPA), 22:5n-3 (DPA), and 22:6n-3 (DHA) on the bacterial community. Amplicon 16 S rRNA sequencing suggested that EPA and DHA had a greater contribution to the action of marine lipids than DPA both in cattle and sheep. Certain effects were exclusive to each ruminant species, which underlines the complexity of rumen microbial responses to dietary fatty acids. Based on changes in bacterial abundance, Barnesiella, Prevotella, Paraprevotella, Hallela, Anaerovorax, Succiniclasticum, Ruminococcus and Ruminobacter may be involved in the ruminal response in biohydrogenation to the addition of marine lipids, but further research is necessary to confirm their actual role in ruminal lipid metabolism.

Invited review: Nitrogen in ruminant nutrition: A review of measurement techniques.

Nitrogen is a component of essential nutrients critical for the productivity of ruminants. If excreted in excess, N is also an important environmental pollutant contributing to acid deposition, eutrophication, human respiratory problems, and climate change. The complex microbial metabolic activity in the rumen and the effect on subsequent processes in the intestines and body tissues make the study of N metabolism in ruminants challenging compared with nonruminants. Therefore, using accurate and precise measurement techniques is imperative for obtaining reliable experimental results on N utilization by ruminants and evaluating the environmental impacts of N emission mitigation techniques. Changeover design experiments are as suitable as continuous ones for studying protein metabolism in ruminant animals, except when changes in body weight or carryover effects due to treatment are expected. Adaptation following a dietary change should be allowed for at least 2 (preferably 3) wk, and extended adaptation periods may be required if body pools can temporarily supply the nutrients studied. Dietary protein degradability in the rumen and intestines are feed characteristics determining the primary AA available to the host animal. They can be estimated using in situ, in vitro, or in vivo techniques with each having inherent advantages and disadvantages. Accurate, precise, and inexpensive laboratory assays for feed protein availability are still needed. Techniques used for direct determination of rumen microbial protein synthesis are laborious and expensive, and data variability can be unacceptably large; indirect approaches have not shown the level of accuracy required for widespread adoption. Techniques for studying postruminal digestion and absorption of nitrogenous compounds, urea recycling, and mammary AA metabolism are also laborious, expensive (especially the methods that use isotopes), and results can be variable, especially the methods based on measurements of digesta or blood flow. Volatile loss of N from feces and particularly urine can be substantial during collection, processing, and analysis of excreta, compromising the accuracy of measurements of total-tract N digestion and body N balance. In studying ruminant N metabolism, nutritionists should consider the longer term fate of manure N as well. Various techniques used to determine the effects of animal nutrition on total N, ammonia- or nitrous oxide-emitting potentials, as well as plant fertilizer value, of manure are available. Overall, methods to study ruminant N metabolism have been developed over 150 yr of animal nutrition research, but many of them are laborious and impractical for application on a large number of animals. The increasing environmental concerns associated with livestock production systems necessitate more accurate and reliable methods to determine manure N emissions in the context of feed composition and ruminant N metabolism.

Early feed restriction of lambs modifies ileal epimural microbiota and affects immunity parameters during the fattening period.

Bacteria firmly attached to the gastrointestinal epithelium during the pre-weaning phase may show a significant impact on nutrient processing, immunity parameters, health and feed efficiency of lambs during post-weaning phases. Thus, the aim of this study was to describe the differences in the ileal epimural microbiota (e.g. total bacteria, Prevotella spp., Bifidobacterium spp. and Lactobacillus spp.) of fattening lambs promoted by early feed restriction during the suckling phase trying to elucidate some of the underlying mechanisms behind changes in feed efficiency during the fattening period. A total of 24 Merino lambs (average BW 4.81±0.256 kg) were used, 12 of them (ad libitum, ADL) kept permanently in individual pens with their mothers, whereas the other 12 lambs were separated from their dams for 9 h each day to be exposed to milk restriction (RES). After weaning (BW=15 kg) all the animals were penned individually, offered the same complete pelleted diet (35 g/kg BW per day) and slaughtered at a BW of 27 kg. During the fattening period, reduced gain : feed ratio (0.320 v. 0.261, P<0.001) was observed for the RES group. Moreover, increments of Prevotella spp. were detected in the ileal epimural microbiota of RES lambs (P<0.05). There were also higher numbers of infiltrated lymphocytes (T and B cells) in the ileal lamina propria (P<0.05), a higher M-cell labelling intensity in ileal Peyer's patches domes (P<0.05) and a trend towards a thickening of the submucosa layer when compared with the ADL group (P=0.057). Some other immunological parameters, such as an increased immunoglobulin A (IgA) production (pg IgA/µg total protein) and increments in CD45+ cells were also observed in the ileum of RES group (P<0.05), whereas transforming growth factor ß and toll-like receptor gene expression was reduced (P<0.05). In conclusion, early feed restriction during the suckling phase promoted changes in ileal epimural microbiota and several immunity parameters that could be related to differences in feed efficiency traits during the fattening period of Merino lambs.

Symposium review: Uncertainties in enteric methane inventories, measurement techniques, and prediction models.

Ruminant production systems are important contributors to anthropogenic methane (CH4) emissions, but there are large uncertainties in national and global livestock CH4 inventories. Sources of uncertainty in enteric CH4 emissions include animal inventories, feed dry matter intake (DMI), ingredient and chemical composition of the diets, and CH4 emission factors. There is also significant uncertainty associated with enteric CH4 measurements. The most widely used techniques are respiration chambers, the sulfur hexafluoride (SF6) tracer technique, and the automated head-chamber system (GreenFeed; C-Lock Inc., Rapid City, SD). All 3 methods have been successfully used in a large number of experiments with dairy or beef cattle in various environmental conditions, although studies that compare techniques have reported inconsistent results. Although different types of models have been developed to predict enteric CH4 emissions, relatively simple empirical (statistical) models have been commonly used for inventory purposes because of their broad applicability and ease of use compared with more detailed empirical and process-based mechanistic models. However, extant empirical models used to predict enteric CH4 emissions suffer from narrow spatial focus, limited observations, and limitations of the statistical technique used. Therefore, prediction models must be developed from robust data sets that can only be generated through collaboration of scientists across the world. To achieve high prediction accuracy, these data sets should encompass a wide range of diets and production systems within regions and globally. Overall, enteric CH4 prediction models are based on various animal or feed characteristic inputs but are dominated by DMI in one form or another. As a result, accurate prediction of DMI is essential for accurate prediction of livestock CH4 emissions. Analysis of a large data set of individual dairy cattle data showed that simplified enteric CH4 prediction models based on DMI alone or DMI and limited feed- or animal-related inputs can predict average CH4 emission with a similar accuracy to more complex empirical models. These simplified models can be reliably used for emission inventory purposes.

Effects of ethyl-3-nitrooxy propionate and 3-nitrooxypropanol on ruminal fermentation, microbial abundance, and methane emissions in sheep.

The aim of this work was to investigate the effect of feeding ethyl-3-nitrooxy propionate (E3NP) and 3-nitrooxypropanol (3 NP), 2 recently developed compounds with potential antimethanogenic activity, in vitro and in vivo in nonlactating sheep on ruminal methane production, fermentation pattern, the abundance of major microbial groups, and feed degradability. Three experiments were conducted, 1 in vitro and 2 in vivo. The in vitro batch culture trial (experiment 1) tested 2 doses of E3NP and 3 NP (40 and 80 µL/L), which showed a substantial reduction of methane production (up to 95%) without affecting concentration of volatile fatty acids (VFA). The 2 in vivo trials were conducted over 16 d (experiment 2) and 30 d (experiment 3) to study their effects in sheep. In experiment 2, 6 adult nonpregnant sheep, with permanent rumen cannula and fed alfalfa hay and oats (60:40), were treated with E3NP at 2 doses (50 and 500 mg/animal per day). After 7, 14, and 15 d of treatment, methane emissions were recorded in respiration chambers and rumen fluid samples were collected for VFA analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. Methane production decreased by 29% compared with the control with the higher dose of E3NP on d 14 to 15. A decrease in the acetate:propionate ratio was observed without detrimental effects on dry matter intake. In experiment 3, 9 adult nonpregnant sheep, with permanent rumen cannula and fed with alfalfa hay and oats (60:40), were treated with E3NP or 3 NP at one dose (100mg/animal per day) over 30 d. On d 14 and d 29 to 30, methane emissions were recorded in respiration chambers. Rumen fluid samples were collected on d 29 and 30 for VFA analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. In addition, on d 22 and 23, samples of oats and alfalfa hay were incubated in the rumen of sheep to determine dry matter ruminal degradation over 24 and 48 h, respectively; no effect was observed (78.6, 78.3, and 78.8% of alfalfa and 74.2, 74.0, and 70.6% of oats in control, E3NP, and 3 NP groups, respectively). A reduction in methane production was observed for both additives at d 14 and d 29 to 30. In both treatments, the acetate:propionate ratio was significantly decreased. Likewise, total concentrations of the analyzed microbial groups in the rumen showed no difference among treatments and doses for both experiments. Both tested compounds showed promise as methane inhibitors in the rumen, with no detrimental effects on fermentation or intake, which would need to be confirmed in lactating animals.

In vitro-in vivo study on the effects of plant compounds on rumen fermentation, microbial abundances and methane emissions in goats.

Two in vitro and one in vivo experiments were conducted to investigate the effects of a selection of plant compounds on rumen fermentation, microbial concentration and methane emissions in goats. Treatments were: control (no additive), carvacrol (CAR), cinnamaldehyde (CIN), eugenol (EUG), propyl propane thiosulfinate (PTS), propyl propane thiosulfonate (PTSO), diallyl disulfide (DDS), a mixture (40 : 60) of PTS and PTSO (PTS+PTSO), and bromochloromethane (BCM) as positive control with proven antimethanogenic effectiveness. Four doses (40, 80, 160 and 320 µl/l) of the different compounds were incubated in vitro for 24 h in diluted rumen fluid from goats using two diets differing in starch and protein source within the concentrate (Experiment 1).The total gas production was linearly decreased (P<0.012) by all compounds, with the exception of EUG and PTS+PTSO (P≥ 0.366). Total volatile fatty-acid (VFA) concentration decreased (P≤ 0.018) only with PTS, PTSO and CAR, whereas the acetate:propionate ratio decreased (P≤ 0.002) with PTS, PTSO and BCM, and a tendency (P=0.064) was observed for DDS. On the basis of results from Experiment 1, two doses of PTS, CAR, CIN, BCM (160 and 320 µl/l), PTSO (40 and 160 µl/l) and DDS (80 and 320 µl/l) were further tested in vitro for 72 h (Experiment 2). The gas production kinetics were affected (P≤ 0.045) by all compounds, and digested NDF (DNDF) after 72 h of incubation was only linearly decreased (P≤ 0.004) by CAR and PTS. The addition of all compounds linearly decreased (P≤ 0.009) methane production, although the greatest reductions were observed for PTS (up to 96%), DDS (62%) and BCM (95%). No diet-dose interaction was observed. To further test the results obtained in vitro, two groups of 16 adult non-pregnant goats were used to study in vivo the effect of adding PTS (50, 100 and 200 mg/l rumen content per day) and BCM (50, 100 and 160 mg/l rumen content per day) during the 9 days on methane emissions (Experiment 3). The addition of PTS and BCM resulted in linear reductions (33% and 64%, respectively, P≤ 0.002) of methane production per unit of dry matter intake, which were lower than the maximum inhibition observed in vitro (87% and 96%, respectively). We conclude that applying the same doses in vivo as in vitro resulted in a proportional lower extent of methane decrease, and that PTS at 200 mg/l rumen content per day has the potential to reduce methane emissions in goats. Whether the reduction in methane emission observed in vivo persists over longer periods of treatments and improves feed conversion efficiency requires further research.

Nutritional intervention in early life to manipulate rumen microbial colonization and methane output by kid goats postweaning.

The growing interest in reducing methane (CH4) emissions from ruminants by dietary means is constrained by the complexity of the microbial community in the rumen of the adult animal. The aim of this work was to study whether intervention in early life of goat kids has an impact on methane emissions and the microbial ecosystem in the rumen and whether the effects persist postweaning. Sixteen doe goats giving birth to 2 kids each were randomly split into 2 experimental groups: 8 does were treated (D+) with bromochloromethane (BCM) after giving birth and over 2 mo, and the other 8 does were not treated (D-). In both groups of does, 1 kid per doe was treated with BCM (k+) for 3 mo, and the other was untreated (k-), resulting in 4 experimental groups: D+k+, D+k-, D-k+, and D-k-. Methane emissions were recorded, and ruminal samples were collected from kids at 2 mo of age (weaning, W) and 1 (W+1) and 4 (W+4) mo later. At W+1 mo, CH4 emissions by k+ kids were 52% and 59% less than untreated kids (in D+ and D- groups, respectively). However, at W+4 mo, only D+k+ kids remained lower (33%) emitters and exhibited greater daily BW gain (146 g/d) compared with the other 3 groups (121.8 g/d). The analysis of the archaeal community structure by Denaturing Gradient Gel Electrophoresis (DGGE)showed a strong effect of BCM treatment on does and kids that persisted only in D+k+ kids. The study showed that the application of BCM during early life of kids modified the archaeal population that colonized the rumen, which resulted in decreased CH4 emissions around weaning. The effect is influenced by the treatment applied to the doe and persisted 3 mo later in D+k+ kids.

Comparative study of fermentation and methanogen community structure in the digestive tract of goats and rabbits.

Methane is the most important anthropogenic contribution to climate change after carbon dioxide and represents a loss of feed energy for the animal, mainly for herbivorous species. However, our knowledge about the ecology of Archaea, the microbial group responsible for methane synthesis in the gut, is very poor. Moreover, it is well known that hindgut fermentation differs from rumen fermentation. The composition of archaeal communities in fermentation compartments of goats and rabbits were investigated using DGGE to generate fingerprints of archaeal 16S rRNA gene. Ruminal contents and faeces from five Murciano-Granadina goats and caecal contents of five commercial White New Zealand rabbits were compared. Diversity profile of methanogenic archaea was carried out by PCR-DGGE. Quantification of methanogenic archaea and the abundance relative to bacteria was determined by real-time PCR. Methanogenic archaeal species were relatively constant across species. Dendrogram from DGGE of the methanogen community showed one cluster for goat samples with two sub-clusters by type of sample (ruminal and faeces). In a second cluster, samples from rabbit were grouped. No differences were found either in richness or Shannon index as diversity indexes. Although the primer sets used was developed to investigate rumen methanogenic archaeal community, primers specificity did not affect the assessment of rabbit methanogen community structure. Rumen content showed the highest number or methanogenic archaea (log10 9.36), followed by faeces (log10 8.52) and showing rabbit caecum the lower values (log10 5.52). DGGE profile showed that pre-gastric and hindgut fermenters hold a very different methanogen community. Rabbits hold a microbial community of similar complexity than that in ruminants but less abundant, which agrees with the type of fermentation profile.

Impact of oxalic acid on rumen function and bacterial community in sheep.

Oxalic acid (OA) is a secondary compound occurring in a wide range of plants consumed by ruminants, especially in saline lands or in arid and semi-arid regions. However, its impact on the rumen microbial community and its changes over time, as well as the potential consequences on ruminal function, remain unknown. To examine this impact, five ewes fitted with a ruminal cannula and fed low-quality grass hay were dosed daily with 0.6 mmol of OA/kg body weight through the cannula for 14 days. On days 0 (before the start), 4, 7 and 14 of the administration period, samples of ruminal digesta were collected throughout the day (0, 3, 6 and 9 h after the morning feeding) for analysis of the bacterial community and fermentation parameters (pH, ammonia and volatile fatty acid (VFA) concentrations). In addition, two feedstuffs were incubated in situ using the nylon bag technique to estimate ruminal degradation. Terminal restriction fragment length polymorphism was employed to monitor the dynamics of total bacteria, and quantitative real-time PCR was used to investigate the abundance of the oxalate-degrading Oxalobacter formigenes. Neither pH nor total VFA concentrations were affected. Nevertheless, OA dosing altered molar proportions of most individual VFA and ammonia concentrations (P < 0.001). The dry matter disappearance of alfalfa hay was reduced on days 7 and 14 and that of barley straw only on day 7 (P < 0.01). These slight changes were related to others observed in the relative frequency of a number of terminal restriction fragments. Variations in the ruminal microbiota occurred rapidly with OA administration, which did not modify the bacterial diversity significantly but altered the structure of the community. However, many of these changes were reversed by the end of the experiment, with no significant differences between days 0 and 14 of dosing. These results suggest a rapid adaptation of the rumen bacterial community linked to the estimated increase in the abundance of O. formigenes (from 0.002% to 0.007% of oxc gene in relation to the total bacteria 16S rDNA; P < 0.01), which is assumed to be responsible for oxalate breakdown.

Biodiversity and fermentative activity of caecal microbial communities in wild and farm rabbits from Spain.

In order to study the microbial caecal ecosystem of wild and domestic rabbits through the fermentation characteristics and concentration and diversity of bacterial and archaeal communities, caecal samples from sixteen wild rabbits (WR) were contrasted with two groups (n = 4) of farm rabbits receiving low (LSF) or high (HSF) soluble fibre diets from 28 (weaning) to 51 days of age. DNA was extracted for quantifying bacteria and Archaea by qPCR and for biodiversity analysis of microbial communities by DGGE. Samples from WR had lower caecal pH and ammonia and higher volatile fatty acids concentration than farm animals. Lower acetate and higher butyrate proportions were detected in WR. Bacterial and archaeal DGGE profiles were clearly different between wild and farm rabbits, and diet-affected population of farm rabbits. Similarity index of bacteria was lower than 0.40 among WR, and 0.52 among farm rabbits. In conclusion, caecal fermentation characteristics differ between wild and farm rabbits, which harbour clearly different bacterial and archaeal communities. In farm rabbits, diversity is influenced by the dietary level of soluble fibre.

Effect of bromochloromethane on methane emission, rumen fermentation pattern, milk yield, and fatty acid profile in lactating dairy goats.

Several technologies have been tested to reduce enteric methanogenesis, but very few have been successfully used in practical conditions for livestock. Furthermore, the consequences of reduced rumen methane production on animal performance and milk quality are poorly understood. The aim of this work was to investigate the effect of feeding bromochloromethane (BCM), a halogenated aliphatic hydrocarbon with potential antimethanogenic activity, to dairy goats on rumen methane production, fermentation pattern, the abundance of major microbial groups, and on animal performance and milk composition. Eighteen goats were allocated to 2 experimental groups of 9 animals each: treated (BCM+) or not (BCM-) with 0.30 g of BCM/100 kg of body weight per day. The BCM was administered per os in 2 equal doses per day from parturition to 2 wk postweaning (10 wk). After weaning, methane emissions were recorded over 2 consecutive days (d 57 and 58 on treatment) in polycarbonate chambers. On d 59, individual rumen fluid samples were collected for volatile fatty acid (VFA) analysis and quantification of bacterial, protozoal, and archaeal numbers by real-time PCR. On d 69 and 70, daily milk production was recorded and samples were collected for determination of fat, protein, lactose, casein, and total solids concentration by infrared spectrophotometry, and fatty acid composition by gas chromatography. Treatment with BCM reduced methane production by 33% (21.6 vs. 14.4 L/kg of DMI) compared with nontreated animals, although it did not affect the abundance of rumen bacteria, protozoa, and total methanogenic archaea. The observed improvement in the efficiency of digestive processes was accompanied by a 36% increase in milk yield, probably due to the more propionic type of rumen fermentation and an increase in VFA production. The increase in milk yield was not accompanied by any changes in the concentrations or yields of fat, protein, or lactose. Despite the substantial decrease in methane production, only minor changes in milk fatty acid profile were observed, suggesting that ruminal biohydrogenation pathways were not affected. Compounds that influence terminal biochemical pathways for methane production deserve further development for future application in the dairy goat sector.

Technical note: The persistence of microbial-specific DNA sequences through gastric digestion in lambs and their potential use as microbial markers.

Two groups of 5 lambs were euthanized at the weaning (T45) and fattening stages (T90) to evaluate the use of microbial ribosomal DNA (rDNA) sequences as potential microbial markers in relation to purine bases (PB) as a conventional marker. Both microbial markers originated similar microbial N concentrations (mg/g of DM), although T45 showed decreased values compared with the T90 group when either PB or rDNA were considered (P = 0.02). The survival of microbial rDNA was determined in 3 digestive sites (omasum, abomasum, and duodenum), but no substantial differences were observed, indicating that rDNA maintains the molecular stability along the sampling sites analyzed. Contrarily PB concentration increased successively along the digestive tract (P < 0.05), likely as a consequence of the endogenous PB secretion. Undegraded milk PB may also explain the overestimation of the microbial N concentration (2.8 times greater) using PB than rDNA sequences. Abomasum was the sampling site where the best agreement between PB and rDNA estimations was observed. Protozoal N concentration was irrelevant in T45 animals, although substantial in T90 lambs (18% of microbial N). In conclusion, bacterial 16S and protozoal 18S rDNA sequences may persist through the gastric digestive tract and their utilization as a highly specific microbial marker should not be neglected.

The effect of the feed-to-buffer ratio on bacterial diversity and ruminal fermentation in single-flow continuous-culture fermenters.

Eight single-flow continuous-culture fermenters were used in a completely randomized block design with a 2 × 4 factorial arrangement of treatments to investigate the effects of the feed-to-buffer ratio (F/B) on ruminal fermentation, the diversity and community structure of bacteria, nutrient digestibility, and N metabolism. Four diets with forage-to-concentrate ratios of 70:30 or 30:70 with alfalfa or grass hay as forage were supplied to fermenters twice per day at 2 different F/B (23.5 and 35 g of DM/L). The dilution rate was kept constant (5.3%) among all fermenters by infusing the same volume of buffer. An increase in the total volatile fatty acid (VFA) concentration and a decrease in the average pH were observed with an increased F/B. In addition, the molar proportions of all individual VFA found in fermenters differed, depending on the F/B. A terminal restriction fragment length polymorphism analysis showed that the community structure and diversity of bacteria were highly influenced by the F/B. Both diversity and the number of peaks in the electropherograms were lower in most fermenters receiving diets at a high F/B, whereas the similarity percentage of the bacterial communities across diets was higher as the F/B increased. Moreover, the high reduction of neutral detergent fiber digestibility (15.3% ± 3.65) in fermenters with high F/B suggested a pH-related decrease in the cellulolytic bacterial community as the F/B increased. The crude protein degradation found in fermenters receiving diets with a high F/B was lower compared with that from fermenters with a low F/B. The VFA concentration and purine bases flow response patterns to diets were similar to in vivo conditions only in the case of fermenters with a low F/B. The results suggested that the community structure and diversity of bacteria, as well as the in vitro fermentation parameters, may be affected by the F/B that is used, most likely through a pH effect. In addition, several fermentation parameters showed different response patterns to diets according to the F/B used. Therefore, the amount of feed supplied to single-flow continuous-culture fermenters in which pH is not under control should be carefully chosen according to the volume of buffer infused for the purpose of simulating ruminal fermentation.

Description of development of rumen ecosystem by PCR assay in milk-fed, weaned and finished lambs in an intensive fattening system.

This study examined the reticulo-rumen characteristics of the microbial community and its fermentative characteristics in milk-fed, at weaning and finished lambs in a conventional fattening system. Five lambs were assigned to each of three groups: milk-fed lambs slaughtered at 30 days (T30), weaned lambs slaughtered at 45 days (T45) and 'finished lambs' slaughtered at 90 days (T90). At slaughter, rumen size, fermentation parameters (pH, volatile fatty acids and microbial enzyme activity) and protozoal counts were recorded. Quantitative PCR was used to quantify the genes encoding 16S and 18S ribosomal DNA of the rumen bacterial and protozoal populations, respectively, and the sequential colonization of the rumen by cellulolytic (Ruminococcus albus, Ruminococcus flavefaciens) and amylolytic (Prevotella ruminicola, Streptococcus bovis) bacteria, and protozoa (Entodinium sp.). Denaturing gradient gel electrophoresis was used to study the development of rumen microbiota biodiversity. Intake of solid food before weaning caused a significant increase in rumen weight (p < 0.0001) and bacterial DNA (p < 0.05) and volatile fatty acid analysis concentration (p < 0.01), whereas pH declined. In milk-fed lambs, cellulolytic bacteria were evident after 30 days. Thereafter, in the 45-day and 90-day groups, the proportions of R. flavefaciens decreased and R. albus increased. Amylolytic bacteria were present in milk-fed lambs; the proportion of P. ruminicola increased in fattening lambs and S. bovis was the least abundant species. Protozoal concentrations were irregular; milk-fed lambs had a significant number of protozoa species from Entodinium and subfamily Isotrichiidae, but they disappeared at weaning. Lamb rumen were refaunated in some individuals at 90 days (Entodinium and subfamily Diplodiniinae spp.), although individual concentrations were variable.