Rumen fluid transplantation affects growth performance of weaned lambs by altering gastrointestinal microbiota,immune function and feed digestibility

Although rumen fluid transplantation (RT) has been developed to confer benefits for adult ruminants by altering gastrointestinal tract microbiota, the question remains whether RT can also benefit weaned lambs. Hence, in this study, thirty-eight pre-weaning lambs were randomly assigned to one of three treatment groups: control lambs (CON) received 25 ml of normal saline solution, and lambs in two RT groups received 25 ml of rumen fluid either from 3-month-old lambs (LT) or from one-year-old adult ewes (AT). The effects on their growth performance, nutrient digestibility, some blood parameters and gastrointestinal tract microbiota were monitored. There were differences (P < 0.05) in rumen bacterial composition between the groups at weaning, at 3 months and at 1 year. Rumen fluid transplantation decreased (P < 0.05) average daily feed intake, average daily gain in live weight and apparent digestibility of ether extract in the LT group, and it decreased (P < 0.05) apparent digestibility of NDF and ADF in the AT group. Rumen fluid transplantation also increased (P < 0.05) concentrations of serum immunoglobulin A in the AT group and increased (P < 0.05) serum concentrations of interleukin-6, interferon alpha and D-lactate in both LT and AT groups. Bacterial α-diversity in the rumen and rectum was not affected by RT (P > 0.05), but a bacterial community change was observed after RT, and the abundance of some dominant bacteria in both rumen and rectum changed after RT (P < 0.05). Analysis of correlations between the parameters indicated that the altered gastrointestinal microbiota and accelerated maturity of rumen microorganisms induced by RT caused some impairment of gastrointestinal integrity and immunity, which led to decreased feed intake, reduced feed digestibility and lower growth performance of the weaned lambs. In conclusion, rumen fluid transplantation altered the gastrointestinal microbiota causing adverse effects on feed intake, feed digestibility and growth performance of the weaned lambs.     

Next Generation Sequencing to Define Prokaryotic and Fungal Diversity in the Bovine Rumen

A combination of Sanger and 454 sequences of small subunit rRNA loci were used to interrogate microbial diversity in the bovine rumen of 12 cows consuming a forage diet. Observed bacterial species richness, based on the V1–V3 region of the 16S rRNA gene, was between 1,903 to 2,432 species-level operational taxonomic units (OTUs) when 5,520 reads were sampled per animal. Eighty percent of species-level OTUs were dominated by members of the order Clostridiales, Bacteroidales, Erysipelotrichales and unclassified TM7. Abundance of Prevotella species varied widely among the 12 animals. Archaeal species richness, also based on 16S rRNA, was between 8 and 13 OTUs, representing 5 genera. The majority of archaeal OTUs (84%) found in this study were previously observed in public databases with only two new OTUs discovered. Observed rumen fungal species richness, based on the 18S rRNA gene, was between 21 and 40 OTUs with 98.4–99.9% of OTUs represented by more than one read, using Good’s coverage. Examination of the fungal community identified numerous novel groups. Prevotella and Tannerella were overrepresented in the liquid fraction of the rumen while Butyrivibrio and Blautia were significantly overrepresented in the solid fraction of the rumen. No statistical difference was observed between the liquid and solid fractions in biodiversity of archaea and fungi. The survey of microbial communities and analysis of cross-domain correlations suggested there is a far greater extent of microbial diversity in the bovine rumen than previously appreciated, and that next generation sequencing technologies promise to reveal novel species, interactions and pathways that can be studied further in order to better understand how rumen microbial community structure and function affects ruminant feed efficiency, biofuel production, and environmental impact.     

Response of rumen microbiota,and metabolic profiles of rumen fluid,liver and serum of goats to high-grain diets

Feeding ruminants a high-grain (HG) diet is a widely used strategy to improve milk yield and cost efficiency. However, it may cause certain metabolic disorders. At present, information about the effects of HG diets on the systemic metabolic profile of goats and the correlation of such diets with rumen bacteria is limited. In the present study, goats were randomly divided into two groups: one was fed the hay diet (hay; n = 5), while the other was fed HG diets (HG; n = 5). On day 50, samples of rumen contents, peripheral blood serum and liver tissues were collected to determine the metabolic profiles in the rumen fluid, liver and serum and the microbial composition in rumen. The results revealed that HG diets reduced (P < 0.05) the community richness and diversity of rumen microbiota, with an increase in the Chao 1 and Shannon index and a decrease in the Simpson index. HG diets also altered the composition of rumen microbiota, with 30 genera affected (P < 0.05). Data on the metabolome showed that the metabolites in the rumen fluid, liver and serum were affected (variable importance projection > 1, P <0.05) by dietary treatment, with 47, 10 and 27 metabolites identified as differentially metabolites. Pathway analysis showed that the common metabolites in the shared key pathway (aminoacyl-transfer RNA biosynthesis) in the rumen fluid, liver and serum were glycine, lysine and valine. These findings suggested that HG diets changed the composition of the rumen microbiota and metabolites in the rumen fluid, liver and serum, mainly involved in amino acid metabolism. Our findings provide new insights into the understanding of diet-related systemic metabolism and the effects of HG diets on the overall health of goats.     

Garlic skin induces shifts in the rumen microbiome and metabolome of fattening lambs

Garlic (Allium sativum L.) and its constituents have been shown to modify rumen fermentation and improve growth performance. Garlic skin, a by-product of garlic processing, contains similar bioactive components as garlic bulb. This study aimed to investigate the effects of garlic skin supplementation on growth performance, ruminal microbes, and metabolites in ruminants. Twelve Hu lambs were randomly assigned to receive a basal diet (CON) or a basal diet supplemented with 80 g/kg DM of garlic skin (GAS). The experiment lasted for 10 weeks, with the first 2 weeks serving as the adaptation period. The results revealed that the average daily gain and volatile fatty acid concentration were higher (P < 0.05) in lambs fed GAS than those in the CON group. Garlic skin supplementation did not significantly (P > 0.10) affect the α-diversity indices, including the Chao1 index, the abundance-based coverage estimator value, and the Shannon and Simpson indices. At the genus level, garlic skin supplementation altered the ruminal bacterial composition by increasing (P < 0.05) the relative abundances of Prevotella, Bulleidia, Howardella, and Methanosphaera and decreasing (P < 0.05) the abundance of Fretibacterium. Concentrations of 139 metabolites significantly differed (P < 0.05) between the GAS and the CON groups. Among them, substrates for rumen microbial protein synthesis were enriched in the GAS group. The pathways of pyrimidine metabolism, purine metabolism, and vitamin B6 metabolism were influenced (P < 0.05) by garlic skin supplementation. Integrated correlation analysis also provided a link between the significantly altered rumen microbiota and metabolites. Thus, supplementation of garlic skin improved the growth performance of lambs by modifying rumen fermentation through shifts in the rumen microbiome and metabolome.     

Composition, spatial distribution, and diversity of the bacterial communities in the rumen of cows fed different forages

The species composition, distribution, and biodiversity of the bacterial communities in the rumen of cows fed alfalfa or triticale were investigated using 16S rRNA gene clone library analyses. The rumen bacterial community was fractionated and analyzed as three separate fractions: populations in the planktonic, loosely attached to rumen digesta particles, and tightly attached to rumen digesta particles. Six hundred and thirteen operational taxonomic units (OTUs) belonging to 32 genera, 19 families, and nine phyla of the domain Bacteria were identified from 1014 sequenced clones. Four hundred and fifty one of the 613 OTUs were identified as new species. These bacterial sequences were distributed differently among the three fractions in the rumen digesta of cows fed alfalfa or triticale. Chao 1 estimation revealed that, in both communities, the populations tightly attached to particulates were more diverse than the planktonic and those loosely attached to particulates. S-Libshuff detected significant differences in the composition between any two fractions in the rumen of cows with the same diet and between the communities fed alfalfa and triticale diets. The species richness estimated for the communities fed alfalfa and triticale is 1027 and 662, respectively. The diversity of the rumen bacterial community examined in this study is greater than previous studies have demonstrated and the differences in the community composition between two high-fiber diets have implications for sample selection for downstream metagenomics applications.     

The Bovine Ruminal Fluid Metabolome

The rumen is a unique organ that serves as the primary site for microbial fermentation of ingested plant material for domestic livestock such as cattle, sheep and goats. The chemical composition of ruminal fluid is thought to closely reflect the healthy/unhealthy interaction between rumen microflora and diet. Just as diet and feed quality is important for livestock production, rumen health is also critical to the growth and production of high quality milk and meat. Therefore a detailed understanding of the chemical composition of ruminal fluid and the influence of diet on its composition could help improve the efficiency and effectiveness of farming and veterinary practices. Consequently we have undertaken an effort to comprehensively characterize the bovine ruminal fluid metabolome. In doing so, we combined NMR spectroscopy, inductively coupled plasma mass-spectroscopy (ICP-MS), gas chromatography-mass spectrometry (GC-MS), direct flow injection (DFI) mass spectrometry and lipidomics with computer-aided literature mining to identify and quantify essentially all of the metabolites in bovine ruminal fluid that can be routinely detected (with today’s technology). The use of multiple metabolomics platforms and technologies allowed us to substantially enhance the level of metabolome coverage while critically assessing the relative strengths and weaknesses of these techniques. Tables containing the set of 246 ruminal fluid metabolites or metabolite species, their concentrations, related literature reference and links to their known diet associations for the bovine rumen metabolome are freely available at http://www.rumendb.ca.     

Maternal and direct dietary polyphenol supplementation affect growth,carcass and meat quality of sheep and goats

The beneficial effects of polyphenol intake such as improved nitrogen retention make them interesting feed supplements for ruminants. In contrast, dietary polyphenols may have adverse effects on the bioavailability of nutrients and palatability of the feed which might impair growth performance. The beneficial and adverse effects might differ between different ruminant species as well as between direct intake and intake of polyphenol metabolites via suckling when supplemented to lactating dams. This study investigated the effects of maternal and direct polyphenol supplementation via grape seed extract in sheep and goats on growth, slaughter performance, meat quality and fatty acid profile. The diet of lactating East Friesian Dairy sheep (n = 11) and Saanen goats (n = 9) and of their lambs (n = 16) and kids (n = 13), respectively, was supplemented either with grape seed extract (dams: 7.4% and offspring: 5.6%, P) or without (C). This resulted in four groups per species, namely maternalC/offspringC, maternalC/offspringP, maternalP/offspringC, and maternalP/offspringP. In lambs but not in goats, maternalP increased average daily gain and improved slaughter performance whereas offspringP had no effect. Maternal and offspring diet did not affect physicochemical meat quality in lambs, but direct intake of grape seed extract increased rancid aroma of burger patties. In goat kids, both maternal and offspring diets slightly affected meat colour. While groups of meat fatty acids (FAs) were not affected by diet in both species, maternalP in lambs as well as maternalP and offspringP in goat kids increased the meat n–6 to n–3 FA ratio compared to the respective control groups. In goat kid but not in lamb meat, direct intake of polyphenols affected the proportions of several rumen biohydrogenation intermediates. In conclusion, grape seed extract can be applied in both the maternal and offspring diets in sheep and goats while maintaining or even improving offspring growth performance and carcass quality. Only few species-specific effects of grape seed extract supplementation were observed, and additive effects were scarce. Larger studies are required to confirm the observed species-specific growth response to maternalP during lactation. The underlying reasons for this differential response need to be further evaluated.     

A comparative study of four rumen buffering agents on productive performance,rumen fermentation and meat quality in growing lambs fed a total mixed ration

Controlling rumen fermentation using buffering agents could contribute to enhancing ruminant productivity and performance. This study was realized to investigate the effect of dietary supplementation of AcidBuf, sodium bicarbonate, calseapowder and WMC seaweed (Utva Lactuca extra) on the animal performance, volatile fatty acids, rumen pH, rumen histology and carcass characteristics of growing male Awassi lambs. A total of 60 lambs was divided into five groups. One group served as a control and fed only on a concentrate diet without any buffering, whereas the other four groups were fed the concentrate diet supplemented with 0.4% AcidBuf (Buf1), 0.4% AcidBuf plus sodium bicarbonate, 50 : 50 (Buf2), 0.4% calseapowder (Buf3) or 0.4% WMC Seaweed (Buf4) for 98 days. The feed conversion ratio was (P<0.05) improved in Buf2 compared to the control and other treatment groups. The propionic acid decreased, whereas butyric acid was increased in the treatment groups (P<0.05) compared to the control. The pH of the rumen fluid and the length of submucosa were (P<0.05) higher in Buf4 and Buf1, respectively, compared to the control. Hot and cold carcass weights were (P<0.05) higher in Buf4 compared to Buf1. Lean meat percentage and rib eye area were (P<0.05) higher in Buf4; while the fat percentage was (P<0.05) lower in Buf2 and Buf4 groups compared to the control. The lightness and yellowness of meat were (P<0.05) higher in Buf1 and Buf4 compared to the control. The meat pH was (P<0.05) higher in Buf3 and Buf4 compared to Buf2 (at 1 h) and control (at 24 h). The visceral depot fat (%) was reduced with Buf3 and Buf4 compared to the control. The results indicated that dietary supplementation of different buffering agents improved feed efficiency, rumen pH, carcass characteristics and decreased the body fat in growing Awassi lambs.     

Serum metabolomic fingerprints of lambs fed chitosan and its association with performance and meat quality traits

Chitosan (CHI) is a natural biopolymer with antimicrobial, anti-inflammatory, antioxidant and digestive modulatory effects, which can be used in the ruminant diet to replace antibiotics. The aim of this study was to evaluate the effects of CHI on lamb growth traits, nutrients digestibility, muscle and fatty deposition, meat fatty acid (FA) profile, meat quality traits and serum metabolome. Thirty 30-month-old male lambs, half Suffolk and half Dorper, with an average BW of 21.65 ± 0.86 kg, were fed in a feedlot system for a total of 70 days. The lambs were separated into two groups according to the diet: the control (CON) group which received the basal diet and the CHI group which received the basal diet with the addition of CHI as 2 g/kg of DM in the diet. Lambs supplemented with CHI had a greater (P< 0.05) final BW, DM intake, final body metabolic weight (P< 0.05) and lower residual feed intake than the CON group. Animals fed CHI had a greater (P< 0.05) starch digestibility at 14 and 28 days, average daily gain at 14, 42 and 56 days, greater feed efficiency at 28 days and feed conversation at 14 and 42 days in feedlot. Most of the carcass traits were not affected (P> 0.05) by the treatment; however, the CHI supplementation improved (P< 0.05) dressing and longissimus muscle area. The treatments had no effect (P> 0.05) on the meat colour and other quality measurements. Meat from the CHI-fed lambs had a greater concentration (P< 0.05) of oleic-cis-9 acid, linoleic acid, linolenic-trans-6 acid, arachidonic acid and eicosapentaenoic acid. According to the variable importance in projection score, the most important metabolites to differentiate between the CON and the CHI group were hippurate, acetate, hypoxanthine, arginine, malonate, creatine, choline, myo-inositol, 2-oxoglutarate, alanine, glycerol, carnosine, histidine, glutamate and 3-hydroxyisobutyrate. Similarly, fold change (FC) analysis highlighted succinate (FC = 1.53), arginine (FC = 1.51), hippurate (FC = 0.68), myo-inositol (FC = 1.48), hypoxanthine (FC = 1.45), acetate (FC = 0.73) and malonate (FC = 1.35) as metabolites significantly different between groups. In conclusion, the present data showed that CHI changes the muscle metabolism improving muscle mass deposition, the lamb’s performance and carcass dressing. In addition, CHI led to an alteration in the FA metabolism, changes in the meat FA profile and improvements in meat quality.     

Fibrolytic Bacteria Isolated from the Rumen of North American Moose (Alces alces) and Their Use as a Probiotic in Neonatal Lambs

Fibrolytic bacteria were isolated from the rumen of North American moose (Alces alces), which eat a high-fiber diet of woody browse. It was hypothesized that fibrolytic bacteria isolated from the moose rumen could be used as probiotics to improve fiber degradation and animal production. Thirty-one isolates (Bacillus, n = 26; Paenibacillus, n = 1; and Staphylococcus, n = 4) were cultured from moose rumen digesta samples collected in Vermont. Using Sanger sequencing of the 16S rRNA gene, culturing techniques, and optical densities, isolates were identified and screened for biochemical properties important to plant carbohydrate degradation. Five isolates were selected as candidates for use as a probiotic, which was administered daily to neonate lambs for 9 weeks. It was hypothesized that regular administration of a probiotic to improve fibrolysis to neonate animals through weaning would increase the developing rumen bacterial diversity, increase animal production, and allow for long-term colonization of the probiotic species. Neither weight gain nor wool quality was improved in lambs given a probiotic, however, dietary efficiency was increased as evidenced by the reduced feed intake (and rearing costs) without a loss to weight gain. Experimental lambs had a lower acetate to propionate ratio than control lambs, which was previously shown to indicate increased dietary efficiency. Fibrolytic bacteria made up the majority of sequences, mainly Prevotella, Butyrivibrio, and Ruminococcus. While protozoal densities increased over time and were stable, methanogen densities varied greatly in the first six months of life for lambs. This is likely due to the changing diet and bacterial populations in the developing rumen.     

Maternal versus artificial rearing shapes the rumen microbiome having minor long-term physiological implications

Increasing productivity is a key target in ruminant science which requires better understanding of the rumen microbiota. This study investigated how maternal versus artificial rearing shapes the rumen microbiota using 24 sets of triplet lambs. Lambs within each sibling set were randomly assigned to natural rearing on the ewe (NN); ewe colostrum for 24 h followed by artificial milk feeding (NA); and colostrum alternative and artificial milk feeding (AA). Maternal colostrum feeding enhanced VFA production at weaning but not thereafter. At weaning, lambs reared on milk replacer had no rumen protozoa and lower microbial diversity, whereas natural rearing accelerated the rumen microbial development and facilitated the transition to solid diet. Differences in the rumen prokaryotic communities disappear later in life when all lambs were grouped on the same pasture up to 23 weeks of age. However, NN animals retained higher fungal diversity and abundances of Piromyces, Feramyces and Diplodiniinae protozoa as well as higher feed digestibility (+4%) and animal growth (+6.5%) during the grazing period. Nevertheless, no correlations were found between rumen microbiota and productive outcomes. These findings suggest that the early life nutritional intervention determine the initial rumen microbial community, but the persistence of these effects later in life is weak.     

An Integrated Metabolomic and Microbiome Analysis Identified Specific Gut Microbiota Associated with Fecal Cholesterol and Coprostanol in Clostridium difficile Infection

Clostridium difficile infection (CDI) is characterized by dysbiosis of the intestinal microbiota and a profound derangement in the fecal metabolome. However, the contribution of specific gut microbes to fecal metabolites in C. difficile-associated gut microbiome remains poorly understood. Using gas-chromatography mass spectrometry (GC-MS) and 16S rRNA deep sequencing, we analyzed the metabolome and microbiome of fecal samples obtained longitudinally from subjects with Clostridium difficile infection (n = 7) and healthy controls (n = 6). From 155 fecal metabolites, we identified two sterol metabolites at >95% match to cholesterol and coprostanol that significantly discriminated C. difficile-associated gut microbiome from healthy microbiota. By correlating the levels of cholesterol and coprostanol in fecal extracts with 2,395 bacterial operational taxonomic units (OTUs) determined by 16S rRNA sequencing, we identified 63 OTUs associated with high levels of coprostanol and 2 OTUs correlated with low coprostanol levels. Using indicator species analysis (ISA), 31 of the 63 coprostanol-associated bacteria correlated with health, and two Veillonella species were associated with low coprostanol levels that correlated strongly with CDI. These 65 bacterial taxa could be clustered into 12 sub-communities, with each community containing a consortium of organisms that co-occurred with one another. Our studies identified 63 human gut microbes associated with cholesterol-reducing activities. Given the importance of gut bacteria in reducing and eliminating cholesterol from the GI tract, these results support the recent finding that gut microbiome may play an important role in host lipid metabolism.     

Rumen Methanogenic Genotypes Differ in Abundance According to Host Residual Feed Intake Phenotype and Diet Type

Methane is an undesirable end product of rumen fermentative activity because of associated environmental impacts and reduced host feed efficiency. Our study characterized the rumen microbial methanogenic community in beef cattle divergently selected for phenotypic residual feed intake (RFI) while offered a high-forage (HF) diet followed by a low-forage (LF) diet. Rumen fluid was collected from 14 high-RFI (HRFI) and 14 low-RFI (LRFI) animals at the end of both dietary periods. 16S rRNA gene clone libraries were used, and methanogen-specific tag-encoded pyrosequencing was carried out on the samples. We found that Methanobrevibacter spp. are the dominant methanogens in the rumen, with Methanobrevibacter smithii being the most abundant species. Differences in the abundance of Methanobrevibacter smithii and Methanosphaera stadtmanae genotypes were detected in the rumen of animals offered the LF compared to the HF diet while the abundance of Methanobrevibacter smithii genotypes was different between HRFI and LRFI animals irrespective of diet. Our results demonstrate that while a core group of methanogen operational taxonomic units (OTUs) exist across diet and phenotype, significant differences were observed in the distribution of genotypes within those OTUs. These changes in genotype abundance may contribute to the observed differences in methane emissions between efficient and inefficient animals.     

Establishment and development of ruminal hydrogenotrophs in methanogen-free lambs

The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid concentrations for lambs lacking ruminal methanogens were lower but not markedly dissimilar from those for conventional lambs reared on the same diet. A high population density (10(7) to 10(8) cells g(-1)) of ruminal acetogens slowly developed in methanogen-free lambs. Sulfate- and fumarate-reducing bacteria were present, but their population densities were highly variable. In methanogen-free lambs, the hydrogen capture from fermentation was low (28 to 46%) in comparison with that in lambs containing ruminal methanogens (>90%). Reductive acetogenesis was not a significant part of ruminal fermentation in conventional lambs but contributed 21 to 25% to the fermentation in methanogen-free meroxenic animals. Ruminal H(2) utilization was lower in lambs lacking ruminal methanogens, but when a methanogen-free lamb was inoculated with a methanogen, the ruminal H(2) utilization was similar to that in conventional lambs. H(2) utilization in lambs containing a normal ruminal microflora was age dependent and increased with the animal age. The animal age effect was less marked in lambs lacking ruminal methanogens. Addition of fumarate to rumen contents from methanogen-free lambs increased H(2) utilization. These findings provide the first evidence from animal studies that reductive acetogens can sustain a functional rumen and replace methanogens as a sink for H(2) in the rumen.     

Bovine Host Genetic Variation Influences Rumen Microbial Methane Production with Best Selection Criterion for Low Methane Emitting and Efficiently Feed Converting Hosts Based on Metagenomic Gene Abundance

Methane produced by methanogenic archaea in ruminants contributes significantly to anthropogenic greenhouse gas emissions. The host genetic link controlling microbial methane production is unknown and appropriate genetic selection strategies are not developed. We used sire progeny group differences to estimate the host genetic influence on rumen microbial methane production in a factorial experiment consisting of crossbred breed types and diets. Rumen metagenomic profiling was undertaken to investigate links between microbial genes and methane emissions or feed conversion efficiency. Sire progeny groups differed significantly in their methane emissions measured in respiration chambers. Ranking of the sire progeny groups based on methane emissions or relative archaeal abundance was consistent overall and within diet, suggesting that archaeal abundance in ruminal digesta is under host genetic control and can be used to genetically select animals without measuring methane directly. In the metagenomic analysis of rumen contents, we identified 3970 microbial genes of which 20 and 49 genes were significantly associated with methane emissions and feed conversion efficiency respectively. These explained 81% and 86% of the respective variation and were clustered in distinct functional gene networks. Methanogenesis genes (e.g. mcrA and fmdB) were associated with methane emissions, whilst host-microbiome cross talk genes (e.g. TSTA3 and FucI) were associated with feed conversion efficiency. These results strengthen the idea that the host animal controls its own microbiota to a significant extent and open up the implementation of effective breeding strategies using rumen microbial gene abundance as a predictor for difficult-to-measure traits on a large number of hosts. Generally, the results provide a proof of principle to use the relative abundance of microbial genes in the gastrointestinal tract of different species to predict their influence on traits e.g. human metabolism, health and behaviour, as well as to understand the genetic link between host and microbiome.     

Feed efficiency and the liver proteome of fattening lambs are modified by feed restriction during the suckling period

The present study was designed to describe the effects of early feed restriction of Merino lambs on feed efficiency during the fattening period by examining ruminal microbiota and fermentation parameters, gastrointestinal morphology, digestibility or liver proteome. In total, 24 male Merino lambs were randomly assigned to two experimental treatments (n=12 per treatment). Lambs of the first group (ad libitum (ADL)) were kept permanently with the dams, whereas the other 12 lambs (restricted (RES)) were milk restricted. When lambs reached a live BW (LBW) of 15 kg, all the animals were offered the same complete pelleted diet (35 g dry matter/kg LBW per day) until slaughter at a LBW of 27 kg. The RES lambs showed poorer feed efficiency during the fattening period when compared with the ADL group (feed to gain ratio, 3.69 v. 3.05, P<0.001). No differences were observed in ruminal microbiota, fermentation parameters or apparent digestibility. However, the proportion of the small intestine and the length of ileal villi were reduced in the RES lambs. In total, 26 spots/proteins were identified in the liver proteomic profile, with significant differences (P<0.05) between experimental treatments, suggesting a higher catabolism of proteins and a reduction in β-oxidation of fatty acids in RES lambs when compared with the ADL animals. In conclusion, early feed restriction of Merino lambs during the suckling period promotes long-term effects on the small intestine and the proteomic profile of the liver, which may influence the metabolic use of nutrients, thus negatively affecting feed efficiency during the fattening phase.     

Establishment and Development of Ruminal Hydrogenotrophs in Methanogen-Free Lambs

The aim of this work was to determine whether reductive acetogenesis can provide an alternative to methanogenesis in the rumen. Gnotobiotic lambs were inoculated with a functional rumen microbiota lacking methanogens and reared to maturity on a fibrous diet. Lambs with a methanogen-free rumen grew well, and the feed intake and ruminal volatile fatty acid concentrations for lambs lacking ruminal methanogens were lower but not markedly dissimilar from those for conventional lambs reared on the same diet. A high population density (10⁷ to 10⁸ cells g⁻¹) of ruminal acetogens slowly developed in methanogen-free lambs. Sulfate- and fumarate-reducing bacteria were present, but their population densities were highly variable. In methanogen-free lambs, the hydrogen capture from fermentation was low (28 to 46%) in comparison with that in lambs containing ruminal methanogens (>90%). Reductive acetogenesis was not a significant part of ruminal fermentation in conventional lambs but contributed 21 to 25% to the fermentation in methanogen-free meroxenic animals. Ruminal H₂ utilization was lower in lambs lacking ruminal methanogens, but when a methanogen-free lamb was inoculated with a methanogen, the ruminal H₂ utilization was similar to that in conventional lambs. H₂ utilization in lambs containing a normal ruminal microflora was age dependent and increased with the animal age. The animal age effect was less marked in lambs lacking ruminal methanogens. Addition of fumarate to rumen contents from methanogen-free lambs increased H₂ utilization. These findings provide the first evidence from animal studies that reductive acetogens can sustain a functional rumen and replace methanogens as a sink for H₂ in the rumen.     

Characterization of the Core Rumen Microbiome in Cattle during Transition from Forage to Concentrate as Well as during and after an Acidotic Challenge

This study investigated the effect of diet and host on the rumen bacterial microbiome and the impact of an acidotic challenge on its composition. Using parallel pyrosequencing of the V3 hypervariable region of 16S rRNA gene, solid and liquid associated bacterial communities of 8 heifers were profiled. Heifers were exclusively fed forage, before being transitioned to a concentrate diet, subjected to an acidotic challenge and allowed to recover. Samples of rumen digesta were collected when heifers were fed forage, mixed forage, high grain, during challenge (4 h and 12 h) and recovery. A total of 560,994 high-quality bacterial sequences were obtained from the solid and liquid digesta. Using cluster analysis, prominent bacterial populations differed (P≤0.10) in solid and liquid fractions between forage and grain diets. Differences among hosts and diets were not revealed by DGGE, but real time qPCR showed that several bacteria taxon were impacted by changes in diet, with the exception of Streptococcus bovis. Analysis of the core rumen microbiome identified 32 OTU''s representing 10 distinct bacterial taxa including Bacteroidetes (32.8%), Firmicutes (43.2%) and Proteobacteria (14.3%). Diversity of OTUs was highest with forage with 38 unique OTUs identified as compared to only 11 with the high grain diet. Comparison of the microbial profiles of clincial vs. subclinical acidotic heifers found a increases in the relative abundances of Acetitomaculum, Lactobacillus, Prevotella, and Streptococcus. Increases in Streptococcus and Lactobacillus likely reflect the tolerance of these species to low pH and their ability to proliferate on surplus fermentable carbohydrate. The acetogen, Acetitomaculum may thereforeplay a role in the conversion of lactate to acetate in acidotic animals. Further profiling of the bacterial populations associated with subclinical and clinical acidosis could establish a microbial fingerprint for these disorders and provide insight into whether there are causative microbial populations that could potentially be therapeutically manipulated.     

A comparative analysis of carcass and meat traits,and rumen bacteria between Chinese Mongolian sheep and Dorper × Chinese Mongolian crossbred sheep

Mutton is one of the most widely consumed meats globally. The Chinese Mongolian sheep (MS) breed is an indigenous breed of sheep characterised by high-quality meat and strong adaptability. Dorper × Chinese Mongolian crossbred sheep (DS) is an improved breed with a rapid growth rate and high mutton yield found in parts of China. The rumen microbiota is known to play a key role in shaping host nutrition and health. However, the carcass traits and meat nutritional qualities of DS and MS remain poorly defined, as does how rumen microbes affect these characteristics. The objective of this study was to compare carcass profiles, rumen bacterial communities, and meat nutritional qualities between MS and DS and clarify the associations between rumen microbiota and meat nutritional composition. We found that DS had a faster growth rate and better carcass traits than MS, including BW, carcass weight, meat weight, and loin-eye area. We further found that metabolite and rumen bacterial community composition differed between the two sheep breeds. First, compared with MS, DS had lower contents of some sweet amino acids, monounsaturated fatty acids, n-3 polyunsaturated fatty acids, and beneficial metabolites. Secondly, MS and DS had distinct rumen bacterial compositions, and these differential bacteria were related to carcass traits as well as to contents of meat amino acids, free fatty acids, and other metabolites. Taken together, our data showed that DS had better carcass characteristics but lower meat nutritional quality, parameters that were associated with differences in rumen bacterial community composition. These findings may benefit future breeding strategies aimed at improving sheep carcass performance and meat quality worldwide.