Production of volatile fatty acids in the rumen and cecum-colon of steers as affected by forage:concentrate and forage physical form

Cecum microbiota composition, fermentation characteristics, and immunometabolic biomarkers of Yunshang black goat fed varying dietary energy and protein levels

Introduction

Ruminants including goats have diverse microcosms of microbiota involved in diet digestion, absorption, and assimilation. Moreover, it is well known that changes in dietary regimens including nutrient levels result in varied gut microbiota composition, and ultimately, the performance and health of these animals.

Methods

The current study examined the effects of varying dietary energy and protein levels on the cecal fermentation, immune biomarkers, and microbiota characteristics of 80 male Yunshan Black Goats (6 months, ~35.82 ± 2.79 kg), divided into four diets: 1) High Energy-High Protein (HEHP), 2) High Energy-Low Protein (HELP), 3) Low Energy-High Protein (LEHP), and 4) Low Energy-Low Protein (LELP). Twenty goats (five from each treatment group) were randomly slaughtered after a 50-day feeding trial, and cecal digesta and tissue were sampled for microbial analysis.

Results

The cecal content revealed that the high-energy groups (HEHP, HELP) had lower pH levels than the LEHP group (p < 0.05) and significantly higher valeric and isovaleric acid concentrations in HEHP. Although species richness (Chao1 index) remained consistent, the HEHP group showed higher diversity (Shannon and Simpson indices) than LEHP (p < 0.05). Dominant phyla included Bacteroidetes and Firmicutes; LEHP and LELP had significantly higher Bacteroidetes abundance than HELP, while HELP had higher Firmicutes abundance than LEHP (p < 0.05). Verrucomicrobia abundance was lower in LEHP than in HELP and LELP (p < 0.05). At the genus level, 311 genera were identified, with Clostridium, Prevotella, unidentified_BS11, and others showing significant variation. The HELP group had lower unidentified_BS11 than LEHP and LELP, and higher unidentified_Ruminococcaceae, Clostridium, and Lachnospiraceae than LEHP (p < 0.05). VFA metabolism, absorption, cytokine expression, and tight junction protein mRNA in cecal tissue were also analyzed. Genes like MCT-1 and SLC16A4, linked to VFA absorption, positively correlated with Paludibacter, which was associated with immune markers (TLR-3, TLR-4, IFN-γ) and Occludin expression. In contrast, VFA-related genes and tight junction proteins negatively correlated with unidentified Fibrobacterales, suggesting a microbial role in adaptive immunity.

Conclusion

This study demonstrated that dietary energy and protein levels significantly influenced cecal fermentation, immune biomarkers, and microbiota composition in Yunshan Black Goats.

Linkages between rumen microbiome, host, and environment in yaks, and their implications for understanding animal production and management

Livestock on the Qinghai-Tibetan Plateau is of great importance for the livelihood of the local inhabitants and the ecosystem of the plateau. The natural, harsh environment has shaped the adaptations of local livestock while providing them with requisite eco-services. Over time, unique genes and metabolic mechanisms (nitrogen and energy) have evolved which enabled the yaks to adapt morphologically and physiologically to the Qinghai-Tibetan Plateau. The rumen microbiota has also co-evolved with the host and contributed to the host's adaptation to the environment. Understanding the complex linkages between the rumen microbiota, the host, and the environment is essential to optimizing the rumen function to meet the growing demands for animal products while minimizing the environmental impact of ruminant production. However, little is known about the mechanisms of host-rumen microbiome-environment linkages and how they ultimately benefit the animal in adapting to the environment. In this review, we pieced together the yak's adaptation to the Qinghai-Tibetan Plateau ecosystem by summarizing the natural selection and nutritional features of yaks and integrating the key aspects of its rumen microbiome with the host metabolic efficiency and homeostasis. We found that this homeostasis results in higher feed digestibility, higher rumen microbial protein production, higher short-chain fatty acid (SCFA) concentrations, and lower methane emissions in yaks when compared with other low-altitude ruminants. The rumen microbiome forms a multi-synergistic relationship among the rumen microbiota services, their communities, genes, and enzymes. The rumen microbial proteins and SCFAs act as precursors that directly impact the milk composition or adipose accumulation, improving the milk or meat quality, resulting in a higher protein and fat content in yak milk and a higher percentage of protein and abundant fatty acids in yak meat when compared to dairy cow or cattle. The hierarchical interactions between the climate, forage, rumen microorganisms, and host genes have reshaped the animal's survival and performance. In this review, an integrating and interactive understanding of the host-rumen microbiome environment was established. The understanding of these concepts is valuable for agriculture and our environment. It also contributes to a better understanding of microbial ecology and evolution in anaerobic ecosystems and the host-environment linkages to improve animal production.

Altered microbiota, antimicrobial resistance genes, and functional enzyme profiles in the rumen of yak calves fed with milk replacer

IMPORTANCE

Yaks, as ruminants inhabiting high-altitude environments, possess a distinct rumen microbiome and are resistant to extreme living conditions. This study investigated the microbiota, resistome, and functional gene profiles in the rumen of yaks fed milk or milk replacer (MR), providing insights into the regulation of the rumen microbiome and the intervention of antimicrobial resistance in yaks through dietary methods. The abundance of Prevotella members increased significantly in response to MR. Tetracycline resistance was the most predominant. The rumen of yaks contained multiple antimicrobial resistance genes (ARGs) originating from different bacteria, which could be driven by MR, and these ARGs displayed intricate and complex interactions. MR also induced changes in functional genes. The enzymes associated with fiber degradation and butyrate metabolism were activated and showed close correlations with Prevotella members and butyrate concentration. This study allows us to deeply understand the ruminal microbiome and ARGs of yaks and their relationship with rumen bacteria in response to different milk sources.

The effects of residual energy intake on nutrient use, methane emissions and microbial composition in dairy cows

For sustainable food production selection and breeding of feed efficient animals is crucial. The objective of this study was to evaluate whether multiparous dairy cows, ranked during their first lactation based on residual energy intake (REI) as efficient (low; L-REI) or inefficient (high; H-REI), differ in terms of nutrient use efficiency, methane emissions, rumen fermentation, and gut microbiota composition. Six L-REI and 6 H-REI cows were offered two diets with either a low or high proportion of concentrates (30 vs. 50% of DM) on two consecutive periods of 21 d. Gas exchanges, milk yield, feces and urine excretions were measured in open-circuit respiratory chambers. The results indicated that L-REI cows had higher methane yields (22.6 vs. 20.4 g/kg DM intake) and derived more energy (energy balance - 36.6 vs. - 16.9 MJ/d) and protein (N balance - 6.6 vs. 18.8 g/d) from the tissues to support similar milk yields compared to H-REI cows. Nutrient intake and digestibility were not affected by REI, and there were no interactions between REI and diet. Milk yield, milk production efficiency, and milk composition were not affected by REI except for milk urea concentration that was higher for L-REI cows (14.1 vs. 10.8 mg/100 ml). The rumen and fecal microbiota community structure and function were associated with both the diet and REI, but the diet effect was more pronounced. The current study identified several physiological mechanisms underlying the differences between high and low REI cows, but further studies are needed to distinguish the quantitative role of each mechanism.

Effects of particle size reduction of meadow hay on feed intake, performance, and apparent total tract nutrient digestibility in dairy cows

Forage-based diets are encouraged in organic dairy cattle production as this can increase the net human food supply, but their voluminous nature can limit dry matter intake (DMI) and performance. This study investigates the effects of a substantial particle size reduction of hay on dairy cows' feed intake, performance, and body characteristics, as well as on apparent total tract digestibility (ATTD). Eighteen lactating Holstein cows were allocated to two balanced feeding groups. The control group received long stem hay with a conventional particle size (CON), the experimental group received chopped hay (RED). Both groups were supplemented with concentrates (3.6 kg/d, DM basis). After 14 adaptation days, data were collected for 20 consecutive days. A covariate period of 21 days preceded the experimental feeding period. Particles retained on the 19-, 8- and 4-mm screens and on the pan of the Penn State Particle Separator accounted for 21%, 20%, 20% and 39% of the RED hay. CON hay consisted of 72% large particles, followed by 8%, 7% and 13% retained on the other screens. Average DMI levels of cows in the CON group reached 20.8 kg/d, with a nonsignificant increase (+1.05 kg/d) in the RED group (p = 0.28). Intakes of both NFC (+0.65 kg/d, p = 0.01) and CP (+0.28 kg/d, p = 0.05) were significantly greater in the RED group, resulting in a slightly increased milk yield (+0.8 kg energy corrected milk/d) (p = 0.45), likely because the ATTD decreased significantly when feeding RED hay. No impact was observed on energy balance (103.7 vs 103.9%, p = 0.95), feed conversion efficiency (kg ECM/kg DMI), or N use efficiency. Overall, the results indicate increases in intake of NFC and CP in the RED group when feeding a hay-based (>83%, DM basis) diet, but also a decrease in nutrient digestibility, likely due to increased passage rate, potentially because of the high fraction of hay particles < 4 mm. In conclusion, hay-based rations with a lower proportion of fine particles should be tested to exploit the potential of particle size reduction in terms of improving hay use efficiency.

Fermentation technology as a driver of human brain expansion

Brain tissue is metabolically expensive. Consequently, the evolution of humans' large brains must have occurred via concomitant shifts in energy expenditure and intake. Proposed mechanisms include dietary shifts such as cooking. Importantly, though, any new food source must have been exploitable by hominids with brains a third the size of modern humans'. Here, we propose the initial metabolic trigger of hominid brain expansion was the consumption of externally fermented foods. We define "external fermentation" as occurring outside the body, as opposed to the internal fermentation in the gut. External fermentation could increase the bioavailability of macro- and micronutrients while reducing digestive energy expenditure and is supported by the relative reduction of the human colon. We discuss the explanatory power of our hypothesis and survey external fermentation practices across human cultures to demonstrate its viability across a range of environments and food sources. We close with suggestions for empirical tests.

Evaluating lactation performance of multiparous dairy cattle to prepartum and/or postpartum supplementation of fat-embedded calcium gluconate

Prebiotic compounds may be supplemented in the diet to improve animal health and performance in a variety of ways. In dairy cattle, the transition from pregnancy through parturition and lactation represents a critical life stage with many concurrent stressors. The objectives of this study were to evaluate responses to the provision of a hindgut-targeted prebiotic compound (calcium gluconate; HFCG) when supplemented prepartum and/or postpartum in a 2 × 2 factorial design. One hundred and sixty-four multiparous Holstein cattle were enrolled and followed from approximately 21 d prior to calving until 100 d of lactation. Treatments were administered as a pelleted compound feed offered in the rotary milking parlor once daily prepartum and thrice daily postpartum. Information pertaining to milk production and body weight were automatically recorded by the milking equipment, and information pertaining to reproductive and health performance was recorded by farm staff. Cattle that received HFCG prepartum were confirmed pregnant approximately 21 d earlier (P = 0.024). Cattle that received HFCG both pre- and postpartum had 9% to 10% higher yields of milk protein, fat, and energy-corrected milk (P ≤ 0.037) from weeks 4 to 9 of lactation relative to those that received HFCG exclusively prepartum. Conversely, cattle that received HFCG exclusively postpartum had 9% to 10% higher yields of milk protein, fat, and energy-corrected milk (P ≤ 0.037) from weeks 9 to 14 of lactation relative to those that received exclusively the negative control in both periods. The mechanism underlying these responses remains unclear, however, we hypothesize that these responses are due to localized reductions in inflammation in the gut and/or signaling to extragastrointestinal tissues altering energy partitioning and balance.

Plasma metabolomics reveals major changes in carbohydrate, lipid, and protein metabolism of abruptly weaned beef calves

¹H NMR-based metabolomics was used to study the effect of abrupt weaning on the blood metabolome of beef calves. Twenty Angus calves (258 ± 5 kg BW; 5 to 6 months old) were randomly assigned to a non-weaned (NW) group that remained grazing with their dam or a weaned (W) group that underwent abrupt separation from their dam to a separate paddock on d 0 of the study. Body weight, behaviour, and blood samples for cortisol and metabolomics were measured at d 0, 1, 2, 7, and 14 of the study. On d 1 and 2, W calves spent less time grazing and ruminating, and more time vocalising and walking, had a greater concentration of cortisol, NEFA, 3-hydroxybutyrate, betaine, creatine, and phenylalanine, and lesser abundance of tyrosine (P < 0.05) compared to NW calves. Compared to NW calves at d 14, W calves had greater (P < 0.01) relative abundance of acetate, glucose, allantoin, creatinine, creatine, creatine phosphate, glutamate, 3-hydroxybutyrate, 3-hydroxyisobutyrate, and seven AA (alanine, glutamate, leucine, lysine, phenylalanine, threonine and valine) but lesser (P < 0.05) relative abundance of low density and very low-density lipids, and unsaturated lipids. Both PCA and OPLS-DA showed no clustering or discrimination between groups at d 0 and increasing divergence to d 14. Blood metabolomics is a useful tool to quantify the acute effects of stress in calves during the first 2 days after abrupt weaning, and longer-term changes in carbohydrate, lipid and protein metabolism due to nutritional changes from cessation of milk intake and greater reliance on forage intake.

Rumen Epithelial Development- and Metabolism-Related Genes Regulate Their Micromorphology and VFAs Mediating Plateau Adaptability at Different Ages in Tibetan Sheep

The rumen is an important hallmark organ of ruminants and plays an important role in the metabolism and immune barrier of Tibetan sheep on the Plateau. However, there are few studies on rumen development and metabolism regulation in Tibetan sheep at different ages. Here, we comprehensively analyzed the immune function, fermentation function, rumen epithelial micromorphology and transcriptome profile of Tibetan sheep at different ages. The results showed that the concentration of IgG decreased and the concentration of IgM increased with age (p < 0.05), and the highest concentration of IgA was observed at 1.5 and 3.5 years of age. In terms of rumen fermentation characteristics, VFAs of 4-month-old lambs were the highest, followed by VFAs and NH3-N of Tibetan sheep at 3.5 years of age. Hematoxylin-eosin staining and transmission electron microscopy section examination of rumen epithelial tissue showed that the rumen papilla width increased with age (p < 0.001), the thickness of the stratum corneum decreased, the cells in the stratum corneum showed accelerated migration and the thickness of the rumen muscle layer increased (p < 0.001). Desmosomal junctions between the layers of rumen epithelium increased at 1.5 and 3.5 years old, forming a compact barrier structure, and the basal layer had more mitochondria involved in the regulation of energy metabolism. RNA-seq analysis revealed that a total of 1006 differentially expressed genes (DEGs) were identified at four ages. The DEGs of Tibetan sheep aged 4 months and 6 years were mainly enriched in the oxidation−reduction process and ISG15-protein conjugation pathway. The 1.5 and 3.5-year-olds were mainly enriched in skeletal muscle thin filament assembly, mesenchyme migration and the tight junction pathway. WGCNA showed that DEGs related to rumen microbiota metabolite VFAs and epithelial morphology were enriched in “Metabolism of xenobiotics by cytochrome P450, PPAR signaling pathway, Butanoate metabolism pathways” and participated in the regulation of rumen epithelial immune and fermentation metabolism functions of Tibetan sheep at different ages. This study systematically revealed the regulatory mechanism of rumen epithelial development and metabolism in the plateau adaptation of Tibetan sheep, providing a new approach for the study of plateau adaptation.

Castration alters the cecal microbiota and inhibits growth in Holstein cattle

To determine the effects of castration on growth performance, serum hormone levels, cecal microbiota composition, and metabolites in cattle. A total of 18 Holstein bulls and steers were divided into bull and steer groups and randomly assigned to 3 pens (3 cattle per pen, and each cattle were separated by a fence) to determine the average daily gain (ADG), daily dry matter intake (DMI), and feed efficiency (G/F). After the finishing trial, six cattle per group were randomly slaughtered. Serum was collected to measure the hormone concentration, and the cecal content was collected to measure the pH, short-chain fatty acids, and digestive enzyme activities. Metagenome sequencing and untargeted metabolomics were used to investigate the microbiota composition, functional profiles, and differential metabolites of the cecal contents. We found that castration significantly decreased ADG, DMI, and G/F in cattle (P < 0.05). The serum testosterone, thyroxine, growth hormone (P < 0.05), and triiodothyronine (P < 0.01) concentrations significantly decreased in the steer group when compared to those of the bull group. The activities of cellulase, xylanase, pectinase, and β-glucosidase (P < 0.05) significantly decreased in the steer group, whereas the activities of lipase and α-amylase significantly increased. Moreover, castration significantly decreased the relative abundance of Ruminococcaceae_bacterium, Treponema_porcinum, Oscillibacter_sp. (P < 0.05), and Alistipes_senegalensis (P < 0.01), whereas the relative abundance of Phocaeicola_plebeius (P < 0.05) was significantly increased. Also, the relative abundance of Phocaeicola_plebeius was negatively correlated with testosterone levels, and the function of the cecal microbiota was enriched in the GH29 and GH97 families in the steer group. Metabolomic analysis indicated that castration increased the levels of L-valine, L-phenylalanine, L-aspartic acid, L-isoleucine, L-lysine, methionine, L-glutamic acid, and L-leucine, while decreasing the levels of α-ketoglutaric acid through the 2-oxocarboxylic acid metabolism pathway. In addition, α-ketoglutaric acid was negatively correlated with Oscillibacter_sp. (P < 0.01). Overall, castration can inhibit cattle growth by altering the composition of the cecal microbiota. Therefore, this study provides a theoretical and practical basis for improving the growth performance of steers.

Isolation and Characterization of Ruminal Yeast Strain with Probiotic Potential and Its Effects on Growth Performance, Nutrients Digestibility, Rumen Fermentation and Microbiota of Hu Sheep

Yeast strains are widely used in ruminant production. However, knowledge about the effects of rumen native yeasts on ruminants is limited. Therefore, this study aimed to obtain a rumen native yeast isolate and investigate its effects on growth performance, nutrient digestibility, rumen fermentation and microbiota in Hu sheep. Yeasts were isolated by picking up colonies from agar plates, and identified by sequencing the ITS sequences. One isolate belonging to Pichia kudriavzevii had the highest optical density among these isolates obtained. This isolate was prepared to perform an animal feeding trial. A randomized block design was used for the animal trial. Sixteen Hu sheep were randomly assigned to the control (CON, fed basal diet, n = 8) and treatment group (LPK, fed basal diet plus P. kudriavzevii, CFU = 8 × 10⁹ head/d, n = 8). Sheep were housed individually and treated for 4 weeks. Compared to CON, LPK increased final body weight, nutrient digestibility and rumen acetate concentration and acetate-to-propionate ratio in sheep. The results of Illumina MiSeq PE 300 sequencing showed that LPK increased the relative abundance of lipolytic bacteria (Anaerovibrio spp. and Pseudomonas spp.) and probiotic bacteria (Faecalibacterium spp. and Bifidobacterium spp.). For rumen eukaryotes, LPK increased the genera associated with fiber degradation, including protozoan Polyplastron and fungus Pichia. Our results discovered that rumen native yeast isolate P. kudriavzevii might promote the digestion of fibers and lipids by modulating specific microbial populations with enhancing acetate-type fermentation.

Rumen Microbial Predictors for Short-Chain Fatty Acid Levels and the Grass-Fed Regimen in Angus Cattle

The health benefits of grass-fed beef are well documented. However, the rumen microbiome features in beef steers raised in a grass-fed regimen have yet to be identified. This study examined the rumen microbiome profile in the feeding regimes. Our findings show that the rumen microbiome of the grass-fed cattle demonstrated greater species diversity and harbored significantly higher microbial alpha diversity, including multiple species richness and evenness indices, than the grain-fed cattle. Global network analysis unveiled that grass-fed cattle's rumen microbial interaction networks had higher modularity, suggesting a more resilient and stable microbial community under this feeding regimen. Using the analysis of compositions of microbiomes with a bias correction (ANCOM-BC) algorithm, the abundance of multiple unclassified genera, such as those belonging to Planctomycetes, LD1-PB3, SR1, Lachnospira, and Sutterella, were significantly enriched in the rumen of grass-fed steers. Sutterella was also the critical genus able to distinguish the two feeding regimens by Random Forest. A rumen microbial predictor consisting of an unclassified genus in the candidate division SR1 (numerator) and an unclassified genus in the order Bacteroidales (denominator) accurately distinguished the two feeding schemes. Multiple microbial signatures or balances strongly correlated with various levels of SCFA in the rumen. For example, a balance represented by the log abundance ratio of Sutterella to Desulfovibrio was strongly associated with acetate-to-propionate proportions in the rumen (R2 = 0.87), which could be developed as a valuable biomarker for optimizing milk fat yield and cattle growth. Therefore, our findings provided novel insights into microbial interactions in the rumen under different feed schemes and their ecophysiological implications. These findings will help to develop rumen manipulation strategies to improve feed conversion ratios and average daily weight gains for grass- or pasture-fed cattle production.

2-Hydroxy-4-(Methylthio) Butanoic Acid Isopropyl Ester Supplementation Altered Ruminal and Cecal Bacterial Composition and Improved Growth Performance of Finishing Beef Cattle

The objective of this study was to evaluate the effects of isopropyl ester of 2-hydroxy-4-(methylthio)-butyrate acid (HMBi) on ruminal and cecal fermentation, microbial composition, nutrient digestibility, plasma biochemical parameters, and growth performance in finishing beef cattle. The experiment was conducted for 120 days by a complete randomized block design. Sixty 24-month-old Angus steers (723.9 ± 11.6 kg) were randomly assigned to one of the flowing three treatments: basal diet (the concentrate: 7.6 kg/head·d-1, the rice straw: ad libitum) supplemented with 0 g/d MetaSmart® (H0), a basal diet supplemented with 15 g/d of MetaSmart® (H15), and a basal diet supplemented with 30 g/d of MetaSmart® (H30). Results showed that the average daily gain (ADG) increased linearly (P = 0.004) and the feed conversion ratio (FCR) decreased linearly (P < 0.01) with the increasing HMBi supplementation. Blood urea nitrogen (BUN) concentration significantly decreased in the H30 group (P < 0.05) compared with H0 or H15. The ruminal pH value tended to increase linearly (P = 0.086) on day 56 with the increased HMBi supplementation. The concentrations of ammonia-nitrogen (NH3-N), propionate, isobutyrate, butyrate, isovalerate, valerate, and total volatile fatty acid (VFA) were linearly decreased in the cecum (P < 0.05). The results of Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) showed that the abundance of most pathways with a significant difference was higher in the rumen and lower in the cecum in the H30 group compared to the H0 group, and those pathways were mainly related to the metabolism of amino acids, carbohydrates, and lipids. Correlation analysis showed that ADG was positively associated with the ratio of firmicutes/bacteroidetes both in the rumen and cecum. Additionally, the abundance of Lachnospiraceae, Saccharofermentans, Lachnospiraceae_XPB1014_group, and Ruminococcus_1 was positively correlated with ADG and negatively correlated with FCR and BUN in the rumen. In the cecum, ADG was positively correlated with the abundances of Peptostreptococcaceae, Romboutsia, Ruminococcaceae_UCG-013, and Paeniclostridium, and negatively correlated with the abundances of Bacteroidaceae and Bacteroides. Overall, these results indicated that dietary supplementation of HMBi can improve the growth performance and the feed efficiency of finishing beef cattle by potentially changing bacterial community and fermentation patterns of rumen and cecum.

Feedlot diets containing different starch levels and additives change the cecal proteome involved in cattle's energy metabolism and inflammatory response

Diets for feedlot cattle must be a higher energy density, entailing high fermentable carbohydrate content. Feed additives are needed to reduce possible metabolic disorders. This study aimed to analyze the post-rumen effects of different levels of starch (25%, 35%, and 45%) and additives (monensin or a blend of essential oils and exogenous α-amylase) in diets for Nellore feedlot cattle. The cecum tissue proteome was analyzed via two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and then differentially expressed protein spots were identified with liquid chromatography–tandem mass spectrometry (LC–MS/MS). The use of blends of essential oils associated with α-amylase as a feed additive promoted the upregulation of enzymes such as triosephosphate isomerase, phosphoglycerate mutase, alpha-enolase, beta-enolase, fructose-bisphosphate aldolase, pyruvate kinase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), l-lactate dehydrogenase B, l-lactate dehydrogenase A chain, l-lactate dehydrogenase, and ATP synthase subunit beta, which promote the degradation of carbohydrates in the glycolysis and gluconeogenesis pathways and oxidative phosphorylation, support pyruvate metabolism through the synthesis of lactate from pyruvate, and participate in the electron transport chain, producing ATP from ADP in the presence of a proton gradient across the membrane. The absence of proteins related to inflammation processes (leukocyte elastase inhibitors) in the cecum tissues of animals fed essential oils and amylase may be because feed enzymes can remain active in the intestine and aid in the digestion of nutrients that escape rumen fermentation; conversely, the effect of monensin is more evident in the rumen and less than 10% results in post-ruminal action, corroborating the hypothesis that ionophore antibiotics have a limited effect on the microbiota and intestinal fermentation of ruminants. However, the increase in starch in these diets promoted a downregulation of enzymes linked to carbohydrate degradation, probably caused by damage to the cecum epithelium due to increased responses linked to inflammatory injuries.

Rumen and lower gut microbiomes relationship with feed efficiency and production traits throughout the lactation of Holstein dairy cows

Fermentation of dietary nutrients in ruminants' gastrointestinal (GI) tract is an essential mechanism utilized to meet daily energy requirements. Especially in lactating dairy cows, the GI microbiome plays a pivotal role in the breakdown of indigestible plant polysaccharides and supply most AAs, fatty acids, and gluconeogenic precursors for milk synthesis. Although the contribution of the rumen microbiome to production efficiency in dairy cows has been widely researched over the years, variations throughout the lactation and the lower gut microbiome contribution to these traits remain poorly characterized. Therefore, we investigated throughout lactation the relationship between the rumen and lower gut microbiomes with production efficiency traits in Holstein cows. We found that the microbiome from both locations has temporal stability throughout lactation, yet factors such as feed intake levels played a significant role in shaping microbiome diversity. The composition of the rumen microbiome was dependent on feed intake. In contrast, the lower gut microbiome was less dependent on feed intake and associated with a potentially enhanced ability to digest dietary nutrients. Therefore, milk production traits may be more correlated with microorganisms present in the lower gut than previously expected. The current study's findings advance our understanding of the temporal relationship of the rumen and lower gut microbiomes by enabling a broader overview of the gut microbiome and production efficiency towards more sustainable livestock production.

Effects of whole corn high-grain diet feeding on ruminal bacterial community and epithelial gene expression related to VFA absorption and metabolism in fattening lambs

The objective of this study was to investigate the effects of whole corn high-grain diet feeding on growth performance, ruminal bacterial community, and epithelial morphology and gene expression related to VFA absorption and metabolism in fattening lambs. Fourteen male (castrated) lambs were randomly assigned to either a group fed a ground corn high-grain diet (50.4% grain; HGC, n = 7) or a group fed a whole corn high-grain diet (50.4% grain; HWC, n = 7). After 7 wk of feeding, HWC group increased the average daily gain (ADG) (P = 0.036) and decreased the feed: gain value (P = 0.010) significantly. HWC group had a greater crude protein apparent digestibility (P = 0.028) in the third week and dry matter and neutral detergent fiber apparent digestibility (P < 0.05) in the seventh week. Pyrosequencing of the 16S ribosomal RNA gene revealed that HWC feeding increased the relative abundance of genera Anaerovibrio, Schwartzia and Unclassified Veillonellaceae in the rumen content and Howardella, Schwartzia and Unclassified Veillonellaceae in the rumen epithelia (P<0.05), while decreased the proportion of Lachnospira and Unclassified Synergistaceae in the rumen content and Anaerovorax, Papillibacter, Ruminococcus, Fibrobacter, Unclassified Lachnospiraceae, Unclassified Bacteroidales and Unclassified Prevotellaceae in the rumen epithelia (P < 0.05). HWC group increased the rumen papilla length (P = 0.001) and surface area (P = 0.002). Furthermore, HWC diet feeding up-regulated the relative mRNA expression of putative anion transporter isoform 1 (PAT1) (P = 0.032) in the rumen epithelia. In summary, compared with ground corn high-grain diet feeding, whole corn high-grain diet feeding improved animal performance, changed ruminal bacterial composition and diversity, and increased VFA absorption of epithelial papilla in fattening lambs. These findings provided theoretical guidance for the actual application of whole corn high-grain diet in ruminants.

Maternal butyrate supplementation affects the lipid metabolism and fatty acid composition in the skeletal muscle of offspring piglets

Maternal sodium butyrate (SB) intake has important effects on offspring growth and development. This study aimed to investigate the impacts of maternal SB supplementation during gestation and lactation on fatty acid composition and lipid metabolism in the offspring skeletal muscle of pigs. Twenty sows (Yorkshire, parity 2 to 3) were assigned to the control group (diets without SB, n = 10) and SB group (diets with 0.1% SB, n = 10). The results showed maternal SB supplementation throughout gestation and lactation increased (P < 0.05) body weight of offspring piglets at weaning. The concentrations of triglyceride in plasma and milk were enhanced (P < 0.05). Maternal SB induced (P < 0.05) lipid accumulation with increased expression of peroxisome proliferator activated receptor γ (PPARγ) by enrichment of the acetylation of H3 acetylation K27 (H3K27) in offspring skeletal muscle. Meanwhile, the concentrations of C18:2n-6, C18:3n-3, total polyunsaturated fatty acid (PUFA), n-6 PUFA and n-3 PUFA decreased (P < 0.05) in skeletal muscle of weaning piglets derived from SB sows. Together, these results showed that maternal SB supplementation could influence offspring growth performance, lipid metabolism and fatty acid composition of the skeletal muscle.

Evaluation of Molly model predictions of ruminal fermentation, nutrient digestion, and performance by dairy cows consuming ryegrass-based diets

Several studies have been conducted to improve grazing management and supplementation in pasture-based systems. However, it is necessary to develop tools that integrate the available information linking the representation of biological processes with animal performance for use in decision making. The objective of this study was to evaluate the precision and accuracy of the Molly cow model predictions of ruminal fermentation, nutrient digestion, and animal performance by cows consuming pasture-based diets to identify model strengths and weaknesses, and to derive new digestive parameters when relevant. Model modifications for adipose tissue, protein synthesis in lean body mass and viscera representation were included. Data used for model evaluations were collected from 25 publications containing 115 treatment means sourced from studies conducted with lactating dairy cattle. The inclusion criteria were that diets contained ≥45% perennial ryegrass (Lolium perenne L.), and that dry matter intake, dietary ingredient composition, and nutrient digestion observations were reported. Animal performance and N excretion variables were also included if they were reported. Model performance was assessed before and after model reparameterization of selected digestive parameters, global sensitivity analysis was conducted after reparameterization, and a 5-fold cross evaluation was performed. Although rumen fermentation predictions were not significantly improved, rumen volatile fatty acids absorption rates were recalculated, which improved the concordance correlation coefficient (CCC) for rumen propionate and ammonia concentration predictions but decreased CCC for acetate predictions. Similar degradation rates of crude protein were observed for grass and total mixed ration diets, but rumen-undegradable protein predictions seemed to be affected by the solubility of the protein source as was the intestinal digestibility coefficient. Ruminal fiber degradation was greater after reparameterization, driven primarily by hemicellulose degradation. Predictions of ruminal and fecal outflow of neutral detergent fiber and acid detergent fiber, as well as total fecal output predictions, improved significantly after reparameterization. Blood urea N and urinary N excretion predictions resulted in similar accuracy using both sets of model parameters, whereas fecal N excretion predictions were significantly improved after reparameterization. Body weight and body condition score predictions were greatly improved after model modifications and reparameterization. Before reparameterization, yield predictions for daily milk, milk fat, milk protein, and milk lactose were greatly overestimated (mean bias of 61.0, 58.7, 73.7, and 64.6% of mean squared error, respectively). Although this problem was partially addressed by model modifications and reparameterization (mean bias of 3.2, 1.1, 1.7, and 0.4% of mean squared error, respectively), CCC values were still small. The ability of the model to predict grass digestion and animal performance in dairy cows consuming pasture-based diets was improved, demonstrating the applicability of this model to these productive systems. However, the failure to predict grass digestion based on standard model inputs without reparameterization indicates there are still fundamental challenges in characterizing feeds for this model.

Metatranscriptomic analyses reveal ruminal pH regulates fiber degradation and fermentation by shifting the microbial community and gene expression of carbohydrate-active enzymes

Background

Volatile fatty acids (VFA) generated from ruminal fermentation by microorganisms provide up to 75% of total metabolizable energy in ruminants. Ruminal pH is an important factor affecting the profile and production of VFA by shifting the microbial community. However, how ruminal pH affects the microbial community and its relationship with expression of genes encoding carbohydrate-active enzyme (CAZyme) for fiber degradation and fermentation are not well investigated. To fill in this knowledge gap, six cannulated Holstein heifers were subjected to a continuous 10-day intraruminal infusion of distilled water or a dilute blend of hydrochloric and phosphoric acids to achieve a pH reduction of 0.5 units in a cross-over design. RNA-seq based transcriptome profiling was performed using total RNA extracted from ruminal liquid and solid fractions collected on day 9 of each period, respectively.

Results

Metatranscriptomic analyses identified 19 bacterial phyla with 156 genera, 3 archaeal genera, 11 protozoal genera, and 97 CAZyme transcripts in sampled ruminal contents. Within these, 4 bacteria phyla (Proteobacteria, Firmicutes, Bacteroidetes, and Spirochaetes), 2 archaeal genera (Candidatus methanomethylophilus and Methanobrevibacter), and 5 protozoal genera (Entodinium, Polyplastron, Isotricha, Eudiplodinium, and Eremoplastron) were considered as the core active microbes, and genes encoding for cellulase, endo-1,4-beta- xylanase, amylase, and alpha-N-arabinofuranosidase were the most abundant CAZyme transcripts distributed in the rumen. Rumen microbiota is not equally distributed throughout the liquid and solid phases of rumen contents, and ruminal pH significantly affect microbial ecosystem, especially for the liquid fraction. In total, 21 bacterial genera, 4 protozoal genera, and 6 genes encoding CAZyme were regulated by ruminal pH. Metabolic pathways participated in glycolysis, pyruvate fermentation to acetate, lactate, and propanoate were downregulated by low pH in the liquid fraction.

Conclusions

The ruminal microbiome changed the expression of transcripts for biochemical pathways of fiber degradation and VFA production in response to reduced pH, and at least a portion of the shifts in transcripts was associated with altered microbial community structure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-021-00092-6.

Influence of forage level and corn grain processing on whole-body urea kinetics, and serosal-to-mucosal urea flux and expression of urea transporters and aquaporins in the ovine ruminal, duodenal, and cecal epithelia

The objectives were to determine the effects of forage level and grain processing on whole-body urea kinetics, N balance, serosal-to-mucosal urea flux (Jsm-urea), and messenger ribonucleic acid (mRNA) abundance of urea transporter-B (UT-B; SLC14a1) and aquaporins (AQP) in ovine ruminal, duodenal, and cecal epithelia. Thirty-two wether lambs were blocked by body weight into groups of four and assigned to one of four diets (n = 8) in a 2 × 2 factorial design. Dietary factors were forage level (30% [LF] vs. 70% [HF]) and corn grain processing (whole-shelled [WS] vs. steam-flaked [SF]). Four blocks of lambs (n = 4) were used to determine urea kinetics and N balance using 4-d [15N15N]-urea infusions with concurrent fecal and urine collections. Lambs were killed after 23 d of dietary adaptation. Ruminal, duodenal, and cecal epithelia were collected to determine Jsm-urea and mRNA abundance of UT-B and AQP. Lambs fed LF had greater intakes of dry matter (DMI; 1.20 vs. 0.86 kg/d) and N (NI; 20.1 vs. 15.0 g/d) than those fed HF (P < 0.01). Lambs fed SF had greater DMI (1.20 vs. 0.86 kg/d) and NI (20.6 vs. 14.5 g/d) than those fed WS (P < 0.01). As a percentage of NI, total N excretion was greater in lambs fed HF compared with those fed LF (103% vs. 63.0%; P < 0.01) and was also greater in lambs fed WS compared with those fed SF (93.6% vs. 72.1%; P = 0.02). Retained N (% of NI) was greater in lambs fed LF compared with those fed HF (37.0% vs. -2.55%; P < 0.01). Lambs fed SF had a greater (P = 0.02) retained N (% of NI; 28.0% vs. 6.50%) compared with those fed WS. Endogenous urea production (UER) tended (P = 0.09) to be greater in lambs fed HF compared with those fed LF. As a proportion of UER, lambs fed HF had a greater urinary urea-N loss (0.38 vs. 0.22) and lower urea-N transferred to the gastrointestinal tract (GIT; 0.62 vs. 0.78) or urea-N used for anabolism (as a proportion of urea-N transferred to the GIT; 0.12 vs. 0.26) compared with lambs fed LF (P < 0.01). Ruminal Jsm-urea was unaffected by diet. Duodenal Jsm-urea was greater (P < 0.01) in lambs fed HF compared with LF (77.5 vs. 57.2 nmol/[cm2 × h]). Lambs fed LF had greater (P = 0.03) mRNA expression of AQP3 in ruminal epithelia and tended (P = 0.06) to have greater mRNA expression of AQP3 in duodenal epithelia compared with lambs fed HF. Expression of UT-B mRNA was unaffected by diet. Our results showed that feeding more ruminally available energy improved N utilization, partly through a greater proportion of UER being transferred to the GIT and being used for anabolic purposes.

Transcriptomic analyses suggest a dominant role of insulin in the coordinated control of energy metabolism and ureagenesis in goat liver

BACKGROUND

The ureagenesis plays a central role in the homeostatic control of nitrogen metabolism. This process occurs in the liver, the key metabolic organ in the maintenance of energy homeostasis in the body. To date, the understanding of the influencing factors and regulators of ureagenesis in ruminants is still poor. The aim of this study was to investigate the relationship between energy metabolism and ureagenesis and detect the direct regulators of ureagenesis in the liver by using RNA-seq technology.

RESULTS

Eighteen four-month-old male goats were divided into two groups randomly and received a diet containing 10% (LNFC group, n = 9) or 30% non-fiber carbohydrate (MNFC group, n = 9), respectively, for four weeks. The global gene expression analysis of liver samples showed that, compared with a LNFC diet, the MNFC diet promoted the expression of genes required for synthesis of fatty acid and glycerol, whereas it suppressed those related to fatty acid oxidation, gluconeogenesis from amino acids and ureagenesis. Additionally, gene expression for rate-limiting enzymes of ureagenesis were highly correlated to the gene expression of key enzymes of both fatty acid synthesis and glycerol synthesis (Spearman correlation coefficient > 0.8 and p < 0.05). In the differentially expressed signaling pathways related to the endocrine system, the MNFC diet activated the insulin and PPAR signaling pathway, whereas it suppressed the leptin-JAK/STAT signaling pathway, compared with the LNFC diet. Reverse transcription quantitative PCR analyses of 40 differentially expressed genes confirmed the RNA-seq results (R² = 0.78).

CONCLUSION

Our study indicated that a dietary NFC-induced increase of energy supply promoted lipid anabolism and decreased ureagenesis in the caprine liver. By combining our results with previously published reports, insulin signaling can be suggested to play the dominant role in the coordinated control of hepatic energy metabolism and ureagenesis.

Bacterial community and metabolome shifts in the cecum and colon of captive sika deer (Cervus nippon) from birth to post weaning

Ruminant productivity is associated with the gastrointestinal tract bacterial community, which matures progressively with animal growth. However, knowledge of the bacteriome and metabolome dynamics in cecum and colon during the early lives of neonatal ruminants is limited. Thus, we examined the bacteriome and metabolomes of the cecum and colon in neonatal sika deer at days 1, 42 and 70. The bacterial diversity and richness in the cecum and colon increased with age, and the bacterial community significantly changed across three time points. For cecum and colon, the proportions of Bacteroides spp., Escherichia-Shigella, Clostridium sensu stricto 1, Lachnoclostridium spp. and Lactobacillus spp. were predominated at day 1 and decreased with age, while the proportions of Ruminococcaceae UCG 005, Ruminococcaceae UCG 010, Rikenellaceae RC9 and Prevotellaceae UCG 003 were predominated at days 42 and 70 and increased with age. The concentrations of creatine and serine were significantly decreased, whereas the concentrations of total short-chain volatile fatty acids, pelargonic acid and leucine were increased in both the cecum and colon during development. These data document the development of the bacterial community and the metabolites in the cecum and colon of sika deer, and suggest a possible importance of ecology niche on gut development.

Short-Chain Fatty Acids Regulate the Immune Responses via G Protein-Coupled Receptor 41 in Bovine Rumen Epithelial Cells

The rumen immune system often suffers when challenging antigens from lysis of dead microbiota cells in the rumen. However, the rumen epithelium innate immune system can actively respond to the infection. Previous studies have demonstrated G protein-coupled receptors 41 (GPR41) as receptors for short chain fatty acids (SCFAs) in human. We hypothesized that SCFAs, the most abundant microbial metabolites in rumen, may regulate the immune responses by GPR41 in bovine rumen epithelial cells (BRECs). Therefore, the objective of study was to firstly establish an immortal BRECs line and investigate the regulatory effects of SCFAs and GPR41 on innate immunity responses in BRECs. These results showed that long-term BRECs cultures were established by SV40T-induced immortalization. The concentrations of 20 mM SCFAs significantly enhanced the levels of GPR41, IL1β, TNFα, chemokines, and immune barrier genes by transcriptome analysis. Consistent with transcriptome results, the expression of GPR41, IL1β, TNFα, and chemokines were markedly upregulated in BRECs treated with 20 mM SCFAs by qRT-PCR compared with control BRECs. Remarkably, the GPR41 knockdown (GPR41KD) BRECs treated with 20 mM SCFAs significantly enhanced the proinflammatory cytokines IL1β and TNFα expression compared with wild type BRECs treated with 20 mM SCFAs, but reduced the expression of CCL20, CXCL2, CXCL3, CXCL5, CXCL8, CXCL14, Occludin, and ZO-1. Moreover, GPR41 mRNA expression is positively correlated with CCL20, CXCL2, CXCL3, CXCL8, CXCL14, and ZO-1. These findings revealed that SCFAs regulate GPR41-mediated levels of genes involved in immune cell recruitment and epithelial immune barrier and thereby mediate protective innate immunity in BRECs.

Using artificial neural networks to predict pH, ammonia, and volatile fatty acid concentrations in the rumen

The objectives of this study were (1) to predict ruminal pH and ruminal ammonia and volatile fatty acid (VFA) concentrations by developing artificial neural networks (ANN) using dietary nutrient compositions, dry matter intake, and body weight as input variables; and (2) to compare accuracy and precision of ANN model predictions with that of a multiple linear regression model (MLR). Data were collected from 229 published papers with 938 treatment means. The data set was randomly split into a training data set containing 70% of the observations and a test data set with the remaining observations. A series of ANN with a range of 1 to 9 artificial neurons in 1 hidden layer were examined, and the best one was selected to compare with the best-fitted MLR model. The performance of model predictions was evaluated by root mean square errors (RMSE) and concordance correlation coefficients (CCC) using cross-evaluations with 100 iterations. When using the ANN to predict ruminal pH and concentrations of ammonia, total VFA, acetate, propionate, and butyrate, the RMSE were 4.2, 41.4, 20.9, 22.3, 32.9, and 29.7% of observed means, respectively. The RMSE for the MLR were 4.2, 37.8, 18.3, 19.9, 29.8, and 26.6% of the observed means. The CCC for ruminal pH, ruminal concentrations of ammonia, total VFA, acetate, propionate, and butyrate were 0.57, 0.49, 0.45, 0.40, 0.52, and 0.40, using the ANN, and 0.37, 0.48, 0.40, 0.29, 0.43, and 0.35, using the MLR. Evaluations of the MLR and the ANN indicated that these 2 model forms exhibited similar prediction errors, with 4.2, 39.6, 19.6, 21.1, 31.3, and 28.1% of observed means for pH, ammonia, total VFA, acetate, propionate, and butyrate. Although the ANN increased the precision of predictions related to ruminal metabolism, it failed to improve the accuracy compared with the linear regression model.

Form of calf diet and the rumen. I: Impact on growth and development

Preweaning diet is known to affect rumen tissue appearance at the gross level. The objectives of this experiment were to investigate effects of different preweaning diets on the growth and development of the rumen epithelium and on putative rumen epithelial stem and progenitor cell measurements at the gene and cell levels. Neonatal Holstein bull calves (n = 11) were individually housed and randomly assigned to 1 of 2 diets. The diets were milk replacer only (MRO; n = 5) or milk replacer with starter (MRS; n = 6). Diets were isoenergetic (3.87 ± 0.06 Mcal of metabolizable energy per day) and isonitrogenous (0.17 ± 0.003 kg/d of apparent digestible protein). Milk replacer was 22% crude protein, 21.5% fat (dry matter basis). The textured calf starter was 21.5% crude protein (dry matter basis). Water was available ad libitum and feed and water intake were recorded daily. Putative stem and progenitor cells were labeled by administering a thymidine analog (5-bromo-2'-deoxyuridine, BrdU; 5 mg/kg of body weight in sterile saline) for 5 consecutive days and allowed a 25-d washout period. Calves were killed at 43 ± 1 d after a 6 h exposure to a defined concentration of volatile fatty acids. We obtained rumen tissue from the ventral sac and used it for immunohistochemical analyses of BrdU (putative stem and progenitor cells) and Ki67 (cell proliferation), gene expression analysis, and morphological measurements via hematoxylin and eosin staining. Epithelial stem and progenitor cell gene markers of interest, analyzed by real-time quantitative PCR, were β1-integrin, keratin-14, notch-1, tumor protein p63, and leucine-rich repeat-containing G protein-coupled receptor 5. Body growth did not differ by diet, but empty reticulorumens were heavier in MRS calves (MRS: 0.67 ± 0.04 kg; MRO: 0.39 ± 0.04 kg). The percentage of label-retaining BrdU basale cells was higher in MRO calves than in MRS calves (2.0 ± 0.3% vs. 0.3 ± 0.2%, respectively). We observed a higher percentage of basale cells undergoing proliferation in MRS calves than in MRO calves (18.4 ± 2.6% vs. 10.8 ± 2.8%, respectively). Rumen epithelial gene expression was not affected by diet, but the submucosa was thicker in MRO calves and the epithelium and corneum/keratin layers were thicker in MRS calves. Presumptive stem and progenitor cells in the rumen epithelium were identifiable by their ability to retain labeled DNA in the long term, changed proliferative status in response to diet, and likely contributed to observed treatment differences in rumen tissue thickness.

Unveiling the relationships between diet composition and fermentation parameters response in dual-flow continuous culture system: a meta-analytical approach

The objective of this study was to investigate the functional form of the relationship between diet composition (dietary crude protein [CP] and neutral detergent fiber [NDF]) and amount of substrate (fermenter dry matter intake [DMI]) with microbial fermentation end products in a dual-flow continuous culture system. A meta-analysis was performed using data from 75 studies. To derive the linear models, the MIXED procedure was used, and for nonlinear models, the NLMIXED procedure was used. Significance levels to fit the model assumed for fixed and random effects were P ≤ 0.05. Independent variables were dietary NDF, CP, and fermenter DMI, whereas dependent variables were total volatile fatty acids (VFA) concentration; molar proportions of acetate, propionate, and butyrate; true ruminal digestibilities of organic matter (OM), CP, and NDF; ammonia nitrogen (NH₃-N) concentration and flows of NH₃-N; non-ammonia nitrogen; bacterial-N; dietary-N; and efficiency of microbial protein synthesis (EMPS). Ruminal digestibilities of OM, NDF, and CP decreased as fermenter DMI increased (P < 0.04). Dietary NDF and CP digestibilities were quadratically associated (P < 0.01). Total VFA linearly increased as DMI increased (P < 0.01), exponentially decreased as dietary NDF increased (P < 0.01), and was quadratically associated with dietary CP (P < 0.01), in which total VFA concentration was maximized at 18% dietary CP. Molar proportion of acetate exponentially increased (P < 0.01) as dietary NDF increased. Molar proportion of propionate linearly increased and exponentially decreased as DMI and dietary NDF increased, respectively (P < 0.01). Bacterial-N quadratically increased and dietary-N exponentially increased as DMI increased (P < 0.01). Flows of bacterial-N and dietary-N linearly decreased as dietary NDF increased (P < 0.02), and dietary-N flow was maximized at 18% CP. The EMPS linearly increased as dietary CP increased (P < 0.02) and was not affected by DMI or dietary NDF (P > 0.05). In summary, increasing fermenter DMI increased total VFA concentration and molar proportion of propionate, whereas, dietary NDF increased the molar proportion of acetate. Dietary CP increased bacterial-N flow and was positively associated with NH₃-N concentration. Overall, the analysis of this dataset demonstrates evidences that the dual-flow continuous culture system provides valuable estimates of ruminal digestibility, VFA concentration, and nitrogen metabolism.

Heterogeneous development of methanogens and the correlation with bacteria in the rumen and cecum of sika deer (Cervus nippon) during early life suggest different ecology relevance

BACKGROUND

Enteric methane from the ruminant livestock is a significant source in global greenhouse gas emissions, which is mainly generated by the methanogens inhabiting the rumen and cecum. Sika deer (Cervus nippon) not only produces less methane than bovine, but they also harbor a distinct methanogen community. Whereas, knowledge of methanogens colonization in the rumen and cecum of sika deer is relatively still unknown, which could provide more insights to the manipulation of gut microbiota during early life.

RESULTS

Here, we examined the development of bacteria and methanogens in the rumen and cecum of juvenile sika deer from birth to post-weaning (1 day, 42 days and 70 days, respectively) based on next generation sequencing. The results showed that the facultative anaerobic bacteria were decreased and the cellulolytic bacteria were increased. However, methanogens established soon after birth thrived through the whole developmental period, indicating a different succession process than bacteria in the GIT, and the limited role of age and dietary change on GIT methanogens. We also found Methanobrevibacter spp. (Mean relative abundance = 44.2%) and Methanocorpusculum spp. (Mean relative abundance = 57.5%) were dominated in the rumen and cecum, respectively. The methanogens also formed specific correlations with bacteria under different niches, suggesting a role of ecology niche on methanogen community.

CONCLUSIONS

This study contributes to our knowledge about the microbial succession in GIT of sika deer, that may facilitate the development of targeted strategies to improve GIT function of sika deer.

Postruminal digestion of starch infused into the abomasum of heifers with or without exogenous amylase administration

The effect of an exogenous amylase on postruminal digestion of starch infused into the abomasum of cattle was studied. Four rumen-cannulated heifers were fed 5.5 kg DM/d of a diet without starch, and assigned randomly to a crossover design. The experiment consisted of 2 periods lasting 23 d each with 10 d for adaptation to the diet followed by 13 d of abomasal infusion and sample collection. During the first 3 d of each infusion phase, isotonic saline solution was infused (1 liter/h) for measurement of baseline values in feces, followed by daily infusions of 880 g DM corn starch (1 kg/10 liters of water) without or with the addition of 2% of amylase. Titanium dioxide (10 g/d) was ruminally administered for estimation of fecal excretion. Digestion of starch in small intestine was calculated as the difference between the amounts of infused starch, disappeared from hindgut and fecal excretion. The apparent disappearance of starch from the hindgut was estimated based on the increment of microbial nitrogen (N) excretion due to starch infusion (1 g microbial N/100 g fermented starch) compared to baseline values. The concentration of purine bases in feces was used to estimate excretion of microbial N. Microbial N excretion increased with starch infusion (P < 0.05) but was not influenced by amylase (P = 0.81). Starch disappearance from the small intestine was not improved by amylase (P = 0.78) and averaged 85%. Amylase affected neither blood concentration of glucose (P = 0.80) nor of insulin (P = 0.26), but glucagon was lower without (P < 0.0001) than with amylase. The infusion of starch increased fecal excretion of total VFA (acetate, propionate, and butyrate) by 53% (P < 0.05), which indicates increased carbohydrate fermentation in the hindgut and incomplete digestion of starch in the small intestine. However, the excretion of total VFA was not affected by amylase (P = 0.66). Lactate excretion was higher at the second day of starch infusion (P < 0.05) without than with amylase, which suggests lower flow of starch from the small intestine to the hindgut due to a possible effect of amylase addition in animals not adapted to starch digestion. However, lactate excretion returned near to baseline values within 2 d, which was probably due to increase of lactate-utilizing bacteria and the adaptation of the microbial population in the hindgut. Further studies with higher starch levels and addition of amylase are recommended.

Scrophularia striata Extract Supports Rumen Fermentation and Improves Microbial Diversity in vitro Compared to Monensin

In the search for natural alternatives to antibiotic feed additives, we compared the efficacy of two doses of Scrophularia striata extract [S. striata-Low at 40 and S. striata-High at 80 mg g^-1 dry matter (DM)] with monensin (monensin) and a negative control in the modulation of rumen fermentation, methane production and microbial abundance in vitro. Microbes were investigated using qPCR and 16S rRNA targeted sequencing. Data showed that the addition of S. striata increased production of total short chain fatty acids (SCFA) in comparison to both monensin and control (P = 0.04). The addition of S. striata increased acetate production, and increased propionate at the higher dosage (P < 0.001). Supplementation of S. striata lowered methane production (P < 0.001) compared to control but with no effect compared to monensin. Ammonia concentration decreased by 52% (P < 0.001) with S. striata-High supplementation (4.14 mmol L^-1) compared to control, which was greater than that of monensin (36%). The diversity of rumen bacteria was reduced (P < 0.001) for monensin and S. striata for both the number of observed OTUs and the Chao1 index. Quantitative analysis of Protozoa showed a decrease in the monensin treatment (P = 0.05) compared to control. Archaea copy numbers decreased equally in both S. striata-High and monensin treatments compared to the control group. Supplementation with S. striata increased relative abundances of Fibrobacteres (P < 0.001) and Planctomycetes (P = 0.001) in comparison to both the control and monensin treatments. Significant negative correlations were observed between the abundances of Bacteroides, Fusobacterium, and Succinivibrio genera and methane (r > -0.71; P ≤ 0.001). The abundance of Fibrobacter genera and total SCFA (r = 0.86), acetate (r = 0.75), and valerate (r = -0.51; P < 0.001) correlated positively. These results suggest that S. striata supplementation at 80 mg g^-1 DM inclusion, similar to monensin, supports rumen fermentation, lowers methane and ammonia production. However, S. striata supported rumen fermentation toward higher total SCFA and propionate production, while unlike monensin still supported a diverse rumen microbiome and an increase in cellulolytic bacteria such as Fibrobacter.

Modulation of ruminal and intestinal fermentation by medicinal plants and zinc from different sources

Two experiments were conducted on sheep to determine the effect of dietary supplementation with zinc and a medicinal plant mixture on haematological parameters and microbial activity in the rumen and large intestine. In Experiment 1, 24 male lambs were randomly divided into four groups: One group was fed an unsupplemented basal diet (control), and three groups were fed a diet supplemented with 70 mg Zn/kg diet in the form of Zn sulphate (ZnSO₄ ), a Zn-chelate of glycine hydrate (Zn-Gly) or a Zn-proteinate (Zn-Pro), for five months. The ruminal content was collected separately from each lamb, and batch cultures of ruminal fluid were incubated in vitro with mixture of medicinal plants (Mix) with different roughage:concentrate ratios (800:200 and 400:600, w/w). Bioactive compounds in Mix were quantified by UPLC/MS/MS. In Experiment 2, four sheep were fed a diet consisting of meadow hay and barley grain (400:600, w/w), with Zn-Gly (70 mg Zn/kg diet), Mix (10% replacement of meadow hay) or Zn-Gly and Mix (Zn-Gly-Mix) as supplements in a Latin square design. Mix decreased total gas (p < 0.001) and methane (p < 0.01) production in vitro. In Experiment 1, caecal isobutyrate and isovalerate concentrations varied among the dietary treatments (p < 0.01). The isovalerate concentration of the zinc-supplemented groups in the distal colon was higher (p < 0.001) compared with the control. In Experiment 2, the molar proportion of isobutyrate was the highest in the faeces of the sheep fed the diet with Zn-Gly-Mix (p < 0.01). The plasma zinc concentration was higher in the groups fed a diet supplemented with zinc (p < 0.001). The haematological profile and antioxidant status did not differ between the dietary groups (p > 0.05). The diets containing medicinal plants and organic zinc thus helped to modulate the characteristics of fermentation in ruminants.

The particulate passage rate, nutrient composition and fermentation characteristics across gastrointestinal tracts in lactating dairy cows fed three different forage source diets

This study was conducted to investigate the particulate passage rate, nutrient characteristics and fermentation parameters across the gastrointestinal tract (GIT) in lactating dairy cows fed cereal straws in comparison with alfalfa hay. Eighteen multiparous Holstein cows were randomly assigned to one of three experimental diets consisting of 55% concentrate, 15% corn silage and 30% different forage sources as follows (% of dry matter [DM]): (i) 23% alfalfa hay and 7% Chinese wild rye hay (AH); (ii) 30% corn stover (CS); and (iii) 30% rice straw (RS). The Cr-mordanted corn silage-neutral detergent fibre was used to estimate the passage flow at week 14. After 14-week feeding, the animals were slaughtered to collect the gastrointestinal digesta. Dietary forage sources had little effect on the fractional passage rates in the rumen (range from 5.05 to 6.25%/hr) or hindgut (range from 4.49 to 5.24%/hr). Total volatile fatty acid (VFA) concentration in the caecum was highest, followed by the rumen, colon and rectum, and the lowest in the abomasum and duodenum, indicating that the large intestines, especially caecum, are the important positions for carbohydrate degradation. Greater proportion of propionate and butyrate and lower acetate were found in the AH compared to CS or RS in colon, but higher acetate in abomasum was found in the cows fed CS or RS compared to AH. In conclusion, cereal straw diets did not change the particulate passage rate in the rumen and hindgut which might be mainly due to the similar DM intake among these three diets. Different forage source diets significantly changed VFA proportion in the abomasum and colon, indicating the existence of different digestion or absorption rates in these tracts among the experimental diets.

Dietary modulation of endogenous host defense peptide synthesis as an alternative approach to in-feed antibiotics

Traditionally, antibiotics are included in animal feed at subtherapeutic levels for growth promotion and disease prevention. However, recent links between in-feed antibiotics and a rise in antibiotic-resistant pathogens have led to a ban of all antibiotics in livestock production by the European Union in January 2006 and a removal of medically important antibiotics in animal feeds in the United States in January 2017. An urgent need arises for antibiotic alternatives capable of maintaining animal health and productivity without triggering antimicrobial resistance. Host defense peptides (HDP) are a critical component of the animal innate immune system with direct antimicrobial and immunomodulatory activities. While in-feed supplementation of recombinant or synthetic HDP appears to be effective in maintaining animal performance and alleviating clinical symptoms in the context of disease, dietary modulation of the synthesis of endogenous host defense peptides has emerged as a cost-effective, antibiotic-alternative approach to disease control and prevention. Several different classes of small-molecule compounds have been found capable of promoting HDP synthesis. Among the most efficacious compounds are butyrate and vitamin D. Moreover, butyrate and vitamin D synergize with each other in enhancing HDP synthesis. This review will focus on the regulation of HDP synthesis by butyrate and vitamin D in humans, chickens, pigs, and cattle and argue for potential application of HDP-inducing compounds in antibiotic-free livestock production.

Maternal butyrate supplementation induces insulin resistance associated with enhanced intramuscular fat deposition in the offspring

Maternal nutrition is important for the risk of the offspring to develop insulin resistance and adiposity later in life. The study was undertaken to determine effects of maternal butyrate supplementation on lipid metabolism and insulin sensitivity in the offspring skeletal muscle. The offspring of rats, fed a control diet or a butyrate diet (1% sodium butyrate) throughout gestation and lactation, was studied at weaning and at 60 days of age. The offspring of dams fed a butyrate diet had higher HOMA-insulin resistance and impaired glucose tolerance. This was associated with elevated mRNA and protein expressions of lipogenic genes and decreased amounts of lipolytic enzyme. Simultaneously, enhanced acetylation of histone H3 lysine 9 and histone H3 lysine 27 modification on the lipogenic genes in skeletal muscle of adult offspring was observed. Higher concentration of serum insulin and intramuscular triglyceride in skeletal muscle of offspring from the butyrate group at weaning were accompanied by increasing levels of lipogenic genes and enrichment of acetylation of histone H3 lysine 27. Maternal butyrate supplementation leads to insulin resistance and ectopic lipid accumulation in skeletal muscle of offspring, indicating the importance of short chain fatty acids in the maternal diet on lipid metabolism.

The Structural and Functional Capacity of Ruminal and Cecal Microbiota in Growing Cattle Was Unaffected by Dietary Supplementation of Linseed Oil and Nitrate

Microorganisms in the digestive tract of ruminants differ in their functionality and ability to use feed constituents. While cecal microbiota play an important role in post-rumen fermentation of residual substrates undigested in the rumen, limited knowledge exists regarding its structure and function. In this trial we investigated the effect of dietary supplementation with linseed oil and nitrate on methane emissions and on the structure of ruminal and cecal microbiota of growing bulls. Animals were allocated to either a CTL (control) or LINNIT (CTL supplemented with 1.9% linseed and 1.0% nitrates) diet. Methane emissions were measured using the GreenFeed system. Microbial diversity was assessed using amplicon sequencing of microbial genomic DNA. Additionally, total RNA was extracted from ruminal contents and functional mcrA and mtt genes were targeted in amplicon sequencing approach to explore the diversity of functional gene expression in methanogens. LINNIT had no effect on methane yield (g/kg DMI) even though it decreased methane production by 9% (g/day; P < 0.05). Methanobrevibacter- and Methanomassiliicoccaceae-related OTUs were more abundant in cecum (72 and 24%) compared to rumen (60 and 11%) irrespective of the diet (P < 0.05). Feeding LINNIT reduced the relative abundance of Methanomassiliicoccaceae mcrA cDNA reads in the rumen. Principal component analysis revealed significant differences in taxonomic composition and abundance of bacterial communities between rumen and cecum. Treatment decreased the relative abundance of a few Ruminococcaceae genera, without affecting global bacterial community structure. Our research confirms a high level of heterogeneity in species composition of microbial consortia in the main gastrointestinal compartments where feed is fermented in ruminants. There was a parallel between the lack of effect of LINNIT on ruminal and cecal microbial community structure and functions on one side and methane emission changes on the other. These results suggest that the sequencing strategy used here to study microbial diversity and function accurately reflected the absence of effect on methane phenotypes in bulls treated with linseed plus nitrate.

Supplementing the maternal diet of rats with butyrate enhances mitochondrial biogenesis in the skeletal muscles of weaned offspring

The present study aimed to investigate the effects of maternal dietary butyrate supplementation on energy metabolism and mitochondrial biogenesis in offspring skeletal muscle and the possible mediating mechanisms. Virgin female rats were randomly assigned to either control or butyrate diets (1 % butyrate sodium) throughout gestation and lactation. At the end of lactation (21 d), the offspring were killed by exsanguination from the abdominal aorta under anaesthesia. The results showed that maternal butyrate supplementation throughout gestation and lactation did not affect offspring body weight. However, the protein expressions of G-protein-coupled receptors (GPR) 43 and 41 were significantly enhanced in offspring skeletal muscle of the maternal butyrate-supplemented group. The ATP content, most of mitochondrial DNA-encoded gene expressions, the cytochrome c oxidase subunit 1 and 4 protein contents and the mitochondrial DNA copy number were significantly higher in the butyrate group than in the control group. Meanwhile, the protein expressions of type 1 myosin heavy chain, mitochondrial transcription factor A, PPAR-coactivator-1α (PGC-1α) and uncoupling protein 3 were significantly increased in the gastrocnemius muscle of the treatment group compared with the control group. These results indicate for the first time that maternal butyrate supplementation during the gestation and lactation periods influenced energy metabolism and mitochondrial biogenesis through the GPR and PGC-1α pathways in offspring skeletal muscle at weaning.

Efficiency and rumen responses in younger and older Holstein heifers limit-fed diets of differing energy density

The objective of this study was to evaluate the effects of limit feeding diets of different predicted energy density on the efficiency of utilization of feed and nitrogen and rumen responses in younger and older Holstein heifers. Eight rumen-cannulated Holstein heifers (4 heifers beginning at 257 ± 7 d, hereafter "young," and 4 heifers beginning at 610 ± 16 d, hereafter "old") were limit-fed high [HED; 2.64 Mcal/kg of dry matter (DM), 15.31% crude protein (CP)] or low (LED; 2.42 Mcal/kg of DM, 14.15% CP) energy density diets according to a 4-period, split-plot Latin square design with 28-d periods. Diets were limit-fed to provide isonitrogenous and isoenergetic intake on a rumen empty body weight (BW) basis at a level predicted to support approximately 800 g/d of average daily gain. During the last 7d of each period, rumen contents were subsampled over a 24-h period, rumen contents were completely evacuated, and total collection of feces and urine was made over 4d. Intakes of DM and water were greater for heifers fed LED, although, by design, calculated intake of metabolizable energy did not differ between age groups or diets when expressed relative to rumen empty BW. Rumen pH was lower, ammonia (NH3-N) concentration tended to be higher, and volatile fatty acids (VFA) concentration was not different for HED compared with LED and was unaffected by age group. Rumen content mass was greater for heifers fed LED and for old heifers, so when expressing rumen fermentation responses corrected for this difference in pool size, NH3-N pool size was not different between diets and total moles of VFA in the rumen were greater for heifers fed LED, whereas these pool sizes were greater for old heifers. Total-tract digestibility of potentially digestible neutral detergent fiber (NDF) was greater in heifers fed LED and for young heifers, whereas the fractional rate of ruminal passage and digestion of NDF were both greater in heifers fed LED. Digestibility of N was greater for heifers fed HED, but was unaffected by age group, whereas the efficiency of N retention was greater for heifers fed HED and for young heifers. Manure output was reduced in heifers fed HED, but the effect was largest in old heifers. Results confirm previous studies in which young heifers utilize N more efficiently than old heifers, primarily through greater efficiency of postabsorptive metabolism. Results also support the concept of limit feeding HED diets as a potential means to reduce manure excretion and increase nitrogen efficiency.

Short-chain fatty acids enhance adipocyte differentiation in the stromal vascular fraction of porcine adipose tissue

BACKGROUND

Short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate, are the main products of microbial fermentation in the gut and might mediate some of the effects of gut microbiota and nutrition on development, metabolism, and pathogenesis of obesity and other diseases.

OBJECTIVE

The objective of this study was to determine the effects of SCFAs on adipocyte differentiation and the underlying mechanism.

METHODS

The stromal vascular fraction (SVF) of the porcine subcutaneous fat was used as the preadipocyte model. Adipocyte differentiation was assessed by Oil Red O staining and gene expression analysis of adipocyte markers. Chromatin immunoprecipitation was used to assess the histone acetylation amounts at the peroxisome proliferator-activated receptor γ (PPARG) and CCAAT/enhancer binding protein α (CEBPA) promoters.

RESULTS

Compared with control, propionate and butyrate enhanced the formation of adipocytes by 10-20% and mRNA expression of adipocyte markers by 20-200% in porcine SVF undergoing adipocyte differentiation. Compared with control, short-term treatment of propionate and butyrate enhanced PPARG and CEBPA mRNA expression in porcine SVF by 50-100%. Neither free fatty acid receptor (FFAR) 2 nor FFAR3 mRNA was detectable in porcine SVF before or during differentiation. Neither a cAMP analogue nor an activator of AMP-activated protein kinase (AMPK) affected propionate- or butyrate-enhanced expression of PPARG or CEBPA mRNA. Trichostatin A, a specific inhibitor of histone deacetylases (HDACs), enhanced the formation of adipocytes in porcine SVF by nearly 100% and the expression of PPARG and CEBPA mRNAs by 150% and 50%, respectively. Butyrate increased whereas propionate had no significant effect on histone H3 acetylation at the CEBPA promoter in porcine SVF.

CONCLUSIONS

Propionate and butyrate enhance adipocyte differentiation in porcine SVF. These effects are unlikely mediated through FFAR2, FFAR3, cAMP, or AMPK. The effect of butyrate may be partially mediated by its HDAC inhibitory activity, whereas that of propionate is independent of its HDAC inhibitory activity.

Volatile fatty acid profile for grass hay or alfalfa hay fed to alpacas (Vicugna pacos)

The purpose of this study was to determine the diurnal composition and concentration of volatile fatty acids (VFA) and to determine VFA composition and concentration differences between stomach compartment 1 (C1) and caecum of alpacas fed grass and alfalfa hay. The study was divided into two experiments. In Experiment 1 (EXP 1), 10 male alpacas (3+ years old, 65 kg BW) were divided into two groups, housed in drylot pens, provided ad libitum water and fed alfalfa (AH) or grass hay (GH) for 30 days. The alpacas were slaughtered and the digestive tract collected, divided into sub-tract sections, weighed and digesta sampled for pH, dry matter (DM) and NDF. Volatile fatty acid composition and concentration were determined on C1 and caecal material. Four adult male (3+ years old, 60 kg BW), C1 fistulated alpacas were housed in metabolism crates and divided into two forage groups for Experiment 2 (EXP 2). Alpacas were fed the forages as in EXP 1. Diurnal C1 VFA samples were drawn at 1, 3, 6, 9, 12, 18 and 24 h post-feeding. There were no differences between forages for tract weight, C1 and caecum digesta DM or NDF. Differences were noted (p < 0.05) for pH between forages and sub-tract site. Volatile fatty acids concentrations were different (p < 0.05) for forage and site, and total VFA was higher for AH than GH (110.6 and 79.1 mm) and C1 than caecum (40.7 and 27.6 mm). Proportion of VFA was significant (p < 0.05) for forage and site, C1 acetate highest for GH (84.8 vs. 74.0 mm) and caecum acetate 83.7 and 76.2 mm for GH and AH respectively. These data demonstrate the level of VFA produced in C1 and the caecum of alpacas and the diurnal VFA patterns. Composition of VFA is similar to other ruminant species.

Avaliação morfológica do abomaso e ceco-cólon de bovinos

A morfofisiologia relacionada à absorção de ácidos graxos voláteis (AGV) ao longo do trato gastrintestinal de ruminantes não é totalmente caracterizada. Desse modo, os objetivos deste trabalho foram mensurar a extensão da superfície de absorção e determinar o índice mitótico (IM) do abomaso, do ceco e da alça proximal do cólon ascendente (APCA). Dez bovinos mestiços adultos tiveram seu estômago e intestino grosso removidos imediatamente após o abate. A área total da superfície de absorção foi mensurada por meio de digitalização e análise de imagens. Cortes histológicos foram feitos para determinação do IM. A superfície absortiva do abomaso, 0,58m², foi menor (P<0,01) do que a do rúmen, 6,53m², e a do omaso, 2,31m². A superfície absortiva do ceco e da APCA, 0,23m², correspondeu a 3,5% da superfície do rúmen e a 10% da superfície do omaso. O IM observado foi 0,48%; 0,14%; 0,36% e 0,41% para as regiões de pregas espirais, pilórica, ceco e APCA, respectivamente. Observou-se correlação positiva entre a massa tecidual do abomaso e a área de superfície de absorção, aspecto também observado no ceco-APCA. Foi possível estabelecer regressões para facilitar a mensuração da superfície absortiva do abomaso e do ceco-APCA.

Short communication: Presence of G protein-coupled receptor 43 in rumen epithelium but not in the islets of Langerhans in cattle

Volatile fatty acids (VFA) are the major products of microbial fermentation in the rumen. Besides serving as substrates for energy generation, VFA are known to stimulate rumen development, increase serum insulin and glucagon concentrations, and regulate gene expression in cattle and sheep. The mechanisms underlying these regulatory effects of VFA are unknown, but the recent discovery that VFA can bind to G protein-coupled receptor 43 (GPR43) and 41 (GPR41) suggests that the regulatory effects of VFA may be mediated by these receptors. As a step toward testing this possibility, we determined whether GPR43 was expressed in bovine rumen wall and the pancreatic islets of Langerhans. Polyclonal antibody against a bovine GPR43 peptide was generated. The specificity of the antibody for bovine GPR43 was confirmed by Western blot analysis of recombinant bovine GPR43 protein. Immunohistochemical analyses using this antibody revealed the presence of GPR43-immunoreactive cells in the epithelium, but not in the other layers of cattle rumen wall. The same immunohistochemical analyses did not reveal GPR43-immunoreactive cells in the islets of Langerhans or the surrounding exocrine tissue of cattle pancreas. These data support the possibility that the effect of VFA on rumen epithelial growth in cattle is directly mediated by GPR43 in the rumen epithelial cells and that the effect of VFA on pancreatic secretion of insulin and glucagon in cattle is unlikely to be directly mediated by GPR43.

Effects of subacute ruminal acidosis challenges on fermentation and endotoxins in the rumen and hindgut of dairy cows

The effects of a grain-based subacute ruminal acidosis (SARA) challenge (GBSC) and an alfalfa-pellet SARA challenge (APSC) on fermentation and endotoxins in the rumen and in the cecum, as well as on endotoxins in peripheral blood, were determined. Six nonlactating Holstein cows with cannulas in the rumen and cecum were used in the study. A 3×3 Latin square arrangement of treatments with 4-wk experimental periods was adopted. During the first 3 wk of each experimental period, all cows received a diet containing 70% forages [dry matter (DM) basis]. In wk 4 of each period, cows received 1 of the following 3 diets: the 70% forage diet fed during wk 1 to 3 (control), a diet in which 34% of the dietary DM was replaced with grain pellets made of 50% ground wheat and 50% ground barely (GBSC), or a diet in which 37% of dietary DM was replaced with pellets of ground alfalfa (APSC). Rumen pH was monitored continuously using indwelling pH probes, and rumen fluid, blood, cecal digesta, and fecal grab samples were collected immediately before feed delivery at 0900 h and at 6 h after feed delivery on d 3 and 5 of wk 4. The time for which rumen pH was below 5.6 was 56.4, 225.2, and 298.8 min/d for the control, APSC, and GBSC treatments, respectively. Compared with the control, SARA challenges resulted in similar reductions in cecal digesta pH, which were 7.07, 6.86, and 6.79 for the control, APSC, and GBSC treatments, respectively. Compared with the control, only GBSC increased starch content in cecal digesta, which averaged 2.8, 2.6, and 7.4% of DM for the control, APSC, and GBSC, respectively. Free lipopolysaccharide endotoxin (LPS) concentration in rumen fluid increased from 10,405 endotoxin units (EU)/mL in the control treatment to 30,715 and 168,391 EU/mL in APSC and GBSC, respectively. Additionally, GBSC increased the LPS concentration from 16,508 to 118,522 EU/g in wet cecal digesta, and from 12,832 to 93,154 EU/g in wet feces. The APSC treatment did not affect LPS concentrations in cecal digesta and feces. All concentrations of LPS in blood plasma were below the detection limit of >0.05 EU/mL of the technique used. Despite the absence of LPS in blood, only GBSC increased the concentration of LPS-binding protein in blood plasma, which averaged, 8.9, 9.5, and 12.1mg/L for the control, APSC, and GBSC treatments, respectively. This suggests that GBSC caused translocation of LPS from the digestive tract but that LPS was detoxified before entering the peripheral blood circulation. The higher LPS concentration in cecal digesta in the GBSC compared with the APSC suggests a higher risk of LPS translocation in the large intestine in GBSC than in APSC.

Ruminant Nutrition Symposium: Productivity, digestion, and health responses to hindgut acidosis in ruminants

Microbial fermentation of carbohydrates in the hindgut of dairy cattle is responsible for 5 to 10% of total-tract carbohydrate digestion. When dietary, animal, or environmental factors contribute to abnormal, excessive flow of fermentable carbohydrates from the small intestine, hindgut acidosis can occur. Hindgut acidosis is characterized by increased rates of production of short-chain fatty acids including lactic acid, decreased digesta pH, and damage to gut epithelium as evidenced by the appearance of mucin casts in feces. Hindgut acidosis is more likely to occur in high-producing animals fed diets with relatively greater proportions of grains and lesser proportions of forage. In these animals, ruminal acidosis and poor selective retention of fermentable carbohydrates by the rumen will increase carbohydrate flow to the hindgut. In more severe situations, hindgut acidosis is characterized by an inflammatory response; the resulting breach of the barrier between animal and digesta may contribute to laminitis and other disorders. In a research setting, effects of increased hindgut fermentation have been evaluated using pulse-dose or continuous abomasal infusions of varying amounts of fermentable carbohydrates. Continuous small-dose abomasal infusions of 1 kg/d of pectin or fructans into lactating cows resulted in decreased diet digestibility and decreased milk fat percentage without affecting fecal pH or VFA concentrations. The decreased diet digestibility likely resulted from increased bulk in the digestive tract or from increased digesta passage rate, reducing exposure of the digesta to intestinal enzymes and epithelial absorptive surfaces. The same mechanism is proposed to explain the decreased milk fat percentage because only milk concentrations of long-chain fatty acids were decreased. Pulse-dose abomasal fructan infusions (1 g/kg of BW) into steers resulted in watery feces, decreased fecal pH, and increased fecal VFA concentrations, without causing an inflammatory response. Daily 12-h abomasal infusions of a large dose of starch (~4 kg/d) have also induced hindgut acidosis as indicated by decreased fecal pH and watery feces. On the farm, watery or foamy feces or presence of mucin casts in feces may indicate hindgut acidosis. In summary, hindgut acidosis occurs because of relatively high rates of large intestinal fermentation, likely due to digestive dysfunction in other parts of the gut. A better understanding of the relationship of this disorder to other animal health disorders is needed.

Rumen fluid inhibits proliferation and stimulates expression of cyclin-dependent kinase inhibitors 1A and 2A in bovine rumen epithelial cells

It has been known for decades that microbial fermentation within the rumen is critical to postnatal rumen epithelial growth and maturation in ruminants, but the underlying mechanism is largely unknown. In this study, we determined the effect of rumen fluid, which should contain all products from rumen fermentation, on growth of rumen epithelial cells in vitro. Addition of 10% rumen fluid from cows to the culture medium inhibited (P < 0.05), whereas addition of 6.5 mM acetate, 2.5 mM propionate, or 1 mM butyrate had no effect (P > 0.1) on, the proliferation of rumen epithelial cells isolated from newborn calves. Flow cytometric assays showed that 10% rumen fluid inhibited (P < 0.05) the transition of rumen epithelial cells from the G1 phase to the S phase during the cell cycle. Real-time RT-PCR analyses of mRNA for key cell cycle regulators indicated that 10% rumen fluid did not change (P > 0.1) the expression of cyclin D1, D2, D3, E1, or E2 mRNA or that of cyclin-dependent kinase inhibitor 1B or 2B mRNA, but increased (P < 0.05) the expression of cyclin-dependent kinase inhibitors 1A and 2A mRNA in rumen epithelial cells. These mRNA data support the possibility that rumen fluid inhibits proliferation of rumen epithelial cells in vitro by increasing the expression of cyclin-dependent kinase inhibitors 1A and 2A. The result that rumen fluid inhibits proliferation of bovine rumen epithelial cells in culture indicates that rumen fermentation does not stimulate the postnatal rumen epithelial growth in cattle by directly stimulating proliferation of rumen epithelial cells.

Identification and characterization of the bovine G protein-coupled receptor GPR41 and GPR43 genes

Volatile fatty acids (VFA), including acetate, propionate, and butyrate, are not only a primary source of energy, but also regulate rumen development, insulin and glucagon secretion, and other physiological processes in cattle and sheep. The mechanism underlying the regulatory effects of VFA is unknown. Recent "reverse pharmacology" studies identified human G protein-coupled receptors GPR41 and GPR43 as receptors for short-chain fatty acids. It is possible that proteins similar to human GPR41 and GPR43 mediate the regulatory effects of VFA in cattle. In this study, we determined first, whether the bovine genome contains genes similar to the human GPR41 and GPR43 genes; second, whether and where these genes are expressed in cattle; and third, if the proteins encoded by these genes can be activated by acetate, propionate, and butyrate. A search of GenBank revealed bovine genomic sequences and expressed sequence tags highly similar to the human GPR41 and GPR43 DNA and cDNA sequences. The protein-coding and 5' untranslated regions of the bovine GPR41 and GPR43 mRNA were cloned and sequenced from spleen tissue. Based on these sequences, the bovine GPR41 gene contains 3 exons and its transcription is initiated at 2 leader exons, generating 2 GPR41 mRNA variants differing in the 5' untranslated region. The bovine GPR43 gene contains 2 exons and transcription of this gene is initiated from a single start site. The amino acid sequences deduced from the bovine GPR41 and GPR43 mRNA sequences are more than 75% identical to those of the human GPR41 and GPR43 and are predicted to encode 7 transmembrane domains, typical of G protein-coupled receptors. Both bovine GPR41 and GPR43 mRNA were detected in a variety of tissues including rumen and pancreas. In a cell system, interaction of the overexpressed bovine GPR41 or GPR43 protein with acetate, propionate, or butyrate inhibited luciferase reporter expression from a cyclic AMP-responsive promoter, suggesting that the bovine GPR41 and GPR43 proteins couple to Galpha(i/11). In total, these results demonstrate that the bovine genome encodes functional GPR41 and GPR43 genes and suggest that GPR41 and GPR43 may play a role in the regulatory effects of VFA in cattle.

Surgery of the bovine large intestine

Cecal dilatation in cows and large intestinal atresia in neonatal calves are the most important diseases of the bovine large intestine amenable to surgical correction under field conditions. Clinical symptoms, diagnostic steps, surgical and medical treatment, etiopathogenesis, and prognosis are discussed. Surgery for correction of cecal dilatation, with and without retroflexion or torsion, can be performed under field conditions. In contrast, only anal reconstruction after atresia ani or colostomy in the case of atresia coli are amenable to field surgery; more complicated bypass procedures with anastomosis for atresia coli are best performed in hospital settings. Correcting intestinal atresia is not recommended because of animal welfare and breeding hygiene issues; it should be undertaken for salvage purposes only.