Gastrointestinal Tract Of Ruminants Research Articles

296 Effects of dietary antimicrobials on the ruminant gastrointestinal tract microbiome

Abstract Monensin, tylosin, and chlortetracycline (CTC) are antimicrobials frequently employed in high grain feedlot cattle diets to inhibit liver abscesses and enhance growth. However, increased public concerns regarding antibiotic resistance have created a pressing need to develop alternative strategies. A more mechanistic understanding of how antimicrobial drugs effect the microbiome in the ruminant gastrointestinal tract (GIT) may help develop effective alternatives. Therefore, the objective of this study was to determine changes in the GIT microbiome of grain-fed feedlot steers after antimicrobial drug administration. Thirty individually housed Angus x Simmental steers [body weight (BW) = 355 ± 16.8 kg] previously fed a 56% forage diet were immediately transitioned to a 93% concentrate diet and assigned to one of three treatments (10 steers/treatment): 1) control, without antibiotics, 2) 75 mg of tylosin and 200 mg of monensin per animal per day (TYLMON), and 3) 70 mg of CTC per animal per day. Fecal samples were collected on d 0, 7, 14, 28, 56, 112, and at slaughter and digesta were obtained from the rumen, jejunum, and cecum at slaughter. DNA was extracted from samples, amplified via 16S PCR, and sequenced. Jejunal samples had the least alpha diversity compared with ruminal, cecal, or fecal samples (P < 0.001). There were no differences in measures of alpha diversity in the ruminal, jejunal, or cecal digesta at slaughter (P ≥ 0.10). However, overall measures of alpha diversity (Shannon entropy, observed features) in feces were greater in CTC-fed steers (P ≤ 0.009) as well as in TYLMON-fed steers (P ≤ 0.04) compared with control steers. Measures of alpha diversity for all treatments decreased in feces from d 0 to 7, then increased from d 7 to slaughter (time effect, (P ≤ 0.001). There were no differences in fecal alpha diversity between treatment groups on d 0 (P ≥ 0.50), but by d 28 both TYLMON and CTC treated steers had greater fecal alpha diversity compared with the control steers (P ≤ 0.05). With regard to differential abundance, Phascolarctobacterium and Prevotellaceae UCG-003 were more abundant in feces of control steers relative to antimicrobial treated steers (P < 0.05). Bifidobacterium, Dorea, CAG-56, and Erysipelotrichaceae UCG-003, were the 4 genera found to be in the greatest abundance in the feces of TYLMON-fed relative to control steers (P < 0.05). Akkermansia, Succinivibrio, and Turicbacter were the 3 genera found to be in the greatest abundance in the feces of CTC-fed compared with control steers (P < 0.05). Taken together, these data suggest that differences in the microbiome associated with dietary antimicrobial treatment occur to a greater extent in the lower sections of the GIT, and that these changes in the microbiome occur after 28 d of feeding.

A compendium of ruminant gastrointestinal phage genomes revealed a higher proportion of lytic phages than in any other environments

BackgroundRuminants are important livestock animals that have a unique digestive system comprising multiple stomach compartments. Despite significant progress in the study of microbiome in the gastrointestinal tract (GIT) sites of ruminants, we still lack an understanding of the viral community of ruminants. Here, we surveyed its viral ecology using 2333 samples from 10 sites along the GIT of 8 ruminant species.ResultsWe present the Unified Ruminant Phage Catalogue (URPC), a comprehensive survey of phages in the GITs of ruminants including 64,922 non-redundant phage genomes. We characterized the distributions of the phage genomes in different ruminants and GIT sites and found that most phages were organism-specific. We revealed that ~ 60% of the ruminant phages were lytic, which was the highest as compared with those in all other environments and certainly will facilitate their applications in microbial interventions. To further facilitate the future applications of the phages, we also constructed a comprehensive virus-bacteria/archaea interaction network and identified dozens of phages that may have lytic effects on methanogenic archaea.ConclusionsThe URPC dataset represents a useful resource for future microbial interventions to improve ruminant production and ecological environmental qualities. Phages have great potential for controlling pathogenic bacterial/archaeal species and reducing methane emissions. Our findings provide insights into the virome ecology research of the ruminant GIT and offer a starting point for future research on phage therapy in ruminants.CJAF8kS71Z3NBgTNJ_uZFeVideo

PSVIII-A-2 How Does the Duration of Low Feed Intake Affect the Ruminant Gastrointestinal tract?

Abstract The objective of this study was to determine the effect of 5 and 10 d low feed intake (LF) on the ruminant gastrointestinal tract (GIT). Twelve rams and nine wethers were used in a randomized complete block design where they were blocked by castration status and BW. After 5 d of ad libitum feeding, lambs were either exposed to 0 (CON; 100% DMI; n = 7), 5 (LF5; 30% DMI; n = 7), or 10 d (LF10; 30% DMI; n = 7) of LF. At the end of the study, lambs were euthanized, the GIT was removed to determine the digesta and tissue weights by region and the weights of the liver, spleen, and kidneys were recorded. There were no castration × treatment interactions (P ≥ 0.32). Initial (P = 0.97) and final (P = 0.19) BW did not differ by treatment. The weight of the reticulo-ruminal tissue tended to be less (P = 0.06) for LF10 than CON, with LF5 being intermediate but not different. Ruminal digesta weight was not affected (P = 0.98). Omasal tissue weight did not differ among treatments (P = 0.24), but digesta weight tended (P = 0.07) to be greater for CON compared with LF10 and LF5. Abomasal tissue weight was reduced for LF10 (P = 0.04), with LF5 being intermediate but not different. Abomasal digesta weight was less for LF5 and LF10 than CON (P = 0.04). The weight of the duodenum tended (P = 0.08) to be greater for CON than LF10 and LF5, but digesta weight was not affected (P = 0.16). For the jejunum, tissue and digesta weight tended (P = 0.07) to be greater for CON than LF10, with LF5 being intermediate. The weight of the ileum tended to be the greatest for CON, intermediate for LF5, and the least for LF10 (P = 0.10), but digesta weight was not affected (P = 0.81). Cecal tissue weight was not affected by treatment (P = 0.89); whereas digesta weight was the greatest (P = 0.03) for LF10, the least for CON, and intermediate but not different for LF5. In contrast, colonic tissue weight was less for LF10 relative to LF5 and CON (P = 0.01) and digesta weight tended (P = 0.05) to be greater for CON than LF5 and LF10. Liver weight was reduced (P < 0.01) for both LF5 and LF10 relative to CON, but kidney and spleen weights were not affected (P ≥ 0.33). This study indicates that exposing ruminants to LF rapidly reduces the weights for regions of the GIT and liver. These changes likely implicate a reduced absorptive capacity of the GIT and a lesser metabolic capacity of the liver.

Immunomodulation by cannabidiol in bovine primary ruminal epithelial cells

BackgroundRuminant livestock experience a number of challenges, including high concentrate diets, weaning and transport, which can increase their risk of disorders such as ruminal acidosis, and the associated inflammation of the ruminal epithelium. Cannabidiol (CBD), a phytochemical from hemp (Cannabis sativa), is a promising target as a therapy for gastrointestinal inflammation, and may be extremely valuable as either a treatment or prophylactic. However, the effects of CBD in the the ruminant gastrointestinal tract have not been explored, in part due to the restrictions on feeding hemp to livestock. Therefore, the objective of this study was to investigate the immunomodulatory properties of CBD using a model of inflammation in primary ruminal epithelial cells (REC). In addition, CBD dose was evaluated for possible cytotoxic effects.ResultsNegative effects on cell viability were not observed when REC were exposed to 10 μM CBD. However, when the dose was increased to 50 μM for 24 h, there was a significant cytotoxic effect. When 10 μM CBD was added to culture media as treatment for inflammation induced with lipopolysaccharide (LPS), expression of genes encoding for pro-inflammatory cytokine IL1B was less compared to LPS exposure alone, and CBD resulted in a down-regulation of IL6. As a pre-treatment, prior to LPS exposure, REC had decreased expression of IL6 and CXCL10 while CBD was present in the media, but not when it was removed prior to addition of LPS.ConclusionsResults suggest that CBD may reduce cytokine transcription both during LPS-induced inflammation and when used preventatively, although these effects were dependent on its continued presence in the culture media. Overall, these experiments provide evidence of an immunomodulatory effect by CBD during a pro-inflammatory response in primary REC in culture.

Abundance of Amino Acid Transporters and mTOR Pathway Components in the Gastrointestinal Tract of Lactating Holstein Cows.

Data from non-ruminants indicate that amino acid (AA) transport into cells can regulate mTOR pathway activity and protein synthesis. Whether mTOR is expressed in the ruminant gastrointestinal tract (GIT) and how it may be related to AA transporters and the AA concentrations in the tissue is unknown. Ruminal papillae and the epithelia of the duodenum, jejunum, and ileum collected at slaughter from eight clinically healthy Holstein in mid-lactation were used. Metabolites and RNA were extracted from tissue for liquid chromatography-mass spectrometry and RT-qPCR analysis. The glycine and asparagine concentrations in the rumen were greater than those in the intestine (p < 0.05), but the concentrations of other AAs were greater in the small intestine than those in the rumen. Among the 20 AAs identified, the concentrations of glutamate, alanine, and glycine were the greatest. The mRNA abundances of AKT1 and MTOR were greater in the small intestine than those in the rumen (p < 0.05). Similarly, the SLC1A1, SLC6A6, SLC7A8, SLC38A1, SLC38A7, and SLC43A2 mRNA abundances were greater (p < 0.05) in the small intestine than those in the rumen. The mRNA abundances of SLC1A5, SLC3A2, and SLC7A5 were greater in the rumen than those in the small intestine (p < 0.05). Overall, the present study provides fundamental data on the relationship between mTOR pathway components and the transport of AAs in different sections of the gastrointestinal tract.

Identification of nematodes of the genus Teladorsagia parasites of ruminants with the help of species-specific markers based on ITS2 rDNA

The present study delves into a methodological framework aimed at establishing species-specific markers via the utilization of sequences derived from the internal transcribed spacer 2 (ITS2) region of nuclear ribosomal DNA. This method, in conjunction with polymerase chain reaction (PCR) testing, serves as a diagnostic tool for discerning species belonging to the genus Teladorsagia Andreeva et Satubaldin, 1954. These species, constituents of the subfamily Ostertagiinae (Nematoda: Trichostrongylidae), exhibit wide distribution within the gastrointestinal tracts of ruminants across the geographic expanse of Uzbekistan. The heart of this endeavor is the development of species-specific primers, a pioneering creation in its own right. These primers are crafted using sequences emanating from the ITS2 region of the ribosomal DNA, an innovative approach that facilitates the precise identification of morphospecies within the Teladorsagia genus. Notably, the primers exhibit a nucleotide length of 153 base pairs, an attribute instrumental in their capacity to accurately distinguish and diagnose eggs and larvae of three distinct morphspecies: T. circumcincta, T. trifurcata, and T. davtiani. The potential implications of this method are significant, with ramifications reverberating across the field of veterinary diagnostics. Through the application of these primers, practitioners and researchers alike can effectively ascertain the presence of specific Teladorsagia morphospecies in ruminant animals. This holds the promise of not only enhancing diagnostic precision but also contributing to the broader comprehension of the prevalence and distribution of these nematode species within the local ruminant populations.

Cultivation-independent genomes greatly expand taxonomic-profiling capabilities of mOTUs across various environments

BackgroundTaxonomic profiling is a fundamental task in microbiome research that aims to detect and quantify the relative abundance of microorganisms in biological samples. Available methods using shotgun metagenomic data generally depend on the deposition of sequenced and taxonomically annotated genomes, usually from cultures of isolated strains, in reference databases (reference genomes). However, the majority of microorganisms have not been cultured yet. Thus, a substantial fraction of microbial community members remains unaccounted for during taxonomic profiling, particularly in samples from underexplored environments. To address this issue, we developed the mOTU profiler, a tool that enables reference genome-independent species-level profiling of metagenomes. As such, it supports the identification and quantification of both “known” and “unknown” species based on a set of select marker genes.ResultsWe present mOTUs3, a command line tool that enables the profiling of metagenomes for >33,000 species-level operational taxonomic units. To achieve this, we leveraged the reconstruction of >600,000 draft genomes, most of which are metagenome-assembled genomes (MAGs), from diverse microbiomes, including soil, freshwater systems, and the gastrointestinal tract of ruminants and other animals, which we found to be underrepresented by reference genomes. Overall, two thirds of all species-level taxa lacked a reference genome. The cumulative relative abundance of these newly included taxa was low in well-studied microbiomes, such as the human body sites (6–11%). By contrast, they accounted for substantial proportions (ocean, freshwater, soil: 43–63%) or even the majority (pig, fish, cattle: 60–80%) of the relative abundance across diverse non-human-associated microbiomes. Using community-developed benchmarks and datasets, we found mOTUs3 to be more accurate than other methods and to be more congruent with 16S rRNA gene-based methods for taxonomic profiling. Furthermore, we demonstrate that mOTUs3 increases the resolution of well-known microbial groups into species-level taxa and helps identify new differentially abundant taxa in comparative metagenomic studies.ConclusionsWe developed mOTUs3 to enable accurate species-level profiling of metagenomes. Compared to other methods, it provides a more comprehensive view of prokaryotic community diversity, in particular for currently underexplored microbiomes. To facilitate comparative analyses by the research community, it is released with >11,000 precomputed profiles for publicly available metagenomes and is freely available at: https://github.com/motu-tool/mOTUs.EtaL3gdjB5XhyYuYaq3JvNVideo

Isolation and characterization of bacteriophage Ib_pec2 against shigatoxigenic Escherichia coli.

This study was aimed to isolate and characterize bacteriophage against drug-resistant, shigatoxigenic Escherichia coli (STEC), one of the zoonotic, food-borne organisms associated with ruminants, mainly cattle. STEC were isolated (n = 35) from neonatal calves, dairy workers, and the surrounding environment and their antimicrobial resistance pattern was studied. Out of the 35 isolates tested, 17 isolates were found to be multidrug resistant to important antibiotics like ampicillin, amoxicillin-clavulanate, ciprofloxacin, streptomycin, and tetracycline. Bacteriophage namely Ib_pec2 was isolated against one of the STEC isolates and its morphology, genetic and proteomic characterization was done. Morphological analysis by TEM revealed bacteriophages belonging to myoviridae family. The genetic characterization of g23 gene revealed that the bacteriophage belonged to Tequatrovirus of myoviridae family. Proteomic analysis was able to identify five proteins identical to Tequatrovirus of myoviridae family. One-step growth curve experiment revealed a latency period of 40 min and a burst size of 893 pfu/bacteria. Temperature and pH ranging from 40°C to 50°C, pH6-8, respectively. Phage could able to lyse majority of the STEC isolates. STEC are commensal organisms in the gastrointestinal tract of ruminants but are pathogenic in humans. Bacteriophages can be used as alternatives to antibiotics to control bacterial growth in ruminants and prevent its further spillage in the environment.

97 Immunology and the gut: The key to Animal Health

Abstract The gut immune system consists of three lines of defense systems: barriers, innate immunity and adaptive or acquired immunity that work together to give ruminant gastrointestinal tract (GIT) protection from disease. The gastrointestinal tract is the largest immune organ of the body. The mucosal barrier- the tight junctions and the “kill zone” along with the gut mucosa and maintaining an “anti-inflammatory” state are essential for “good gut health”. The microbiome- the microorganisms in the GIT, which has more cells than the entire animal’s body, is essential for immune development, immune response, and maximizing ruminant productivity. Homeostasis is an important function of the gut immune response to maintain health. Management of bovine GIT immune system is not a simple process. Stressors along with the intake of feed and hydration affect the microbiome and the intestinal epithelial cells resulting in important immune interactions. Nutraceuticals (i.e., probiotics, prebiotics, hen yolk IgY, essential oils, organic acids) aid in both microbiome stability “homeostasis” and immune function.

Isolation and characterization of bacteriophage Ib_pec2 against Shigatoxigenic E.coli

The current study aimed to isolate and characterize bacteriophage against drug resistant, Shiga toxigenic E.coli, one of the zoonotic, food-borne organisms associated with ruminants, mainly cattle. STEC were isolated (n=35) from neonatal calves, dairy workers and the surrounding environment and their antimicrobial resistance pattern was studied. Out of the 35 isolates tested, 17 isolates were found to be multi-drug resistant to important antibiotics like as ampicillin, amoxicillin-clavulanate, ciprofloxacin, streptomycin and tetracycline. Bacteriophage namely Ib_pec2 was isolated against NM—18-040 isolate and its morphology, genetic and proteomic characterization was done. Morphological analysis by TEM revealed bacteriophage belonging to myoviridae family. The genetic characterization of g23 gene revealed that the bacteriophage belonged to Tequatrovirus of myoviridae family. SDS-PAGE analysis of structural proteins followed by LC-MS/MS analysis could able to identify five proteins identical to Tequatrovirus of myoviridae family. One step growth curve experiments revealed a latency period of 40 mins and a burst size of 893 PFU/ bacteria. Temperature and pH ranging from 40-50°C, pH 7-8, respectively were ideal for phage survival and multiplication. Phage was able to lyse 22 out of 35 STEC isolates. Thus, the study could able to characterize Ib_pec2 which could be used in control of STEC in the near future. STEC is a commensal organism in the gastrointestinal tract of ruminants but pathogenic in humans. Bacteriophages can be used as alternatives to antibiotics to control its growth in ruminants and prevent its further spillage in the environment.

Unraveling aerobic cultivable cellulolytic microorganisms within the gastrointestinal tract of sheep (Ovis aries) and their evaluation for cellulose biodegradation.

Anaerobic cellulolytic microbes in the gastrointestinal tract (GT) of ruminants have been well-documented; however, knowledge of aerobic microbes with cellulolytic activities in the ruminant GT is comparably limited. Here, we unraveled aerobic cultivable cellulolytic microbes in the GT of Ujimqin sheep (Ovis aries) and evaluated the cellulolytic potential of the promising isolates. Twenty-two strains were found to possess cellulose-degrading potential by Congo-red staining and phylogenetic analysis of the 16S rDNA/ITS sequence revealed that all strains belonged to nine genera, i.e., Bacillus, Streptomyces, Pseudomonas, Lactobacillus, Brachybacterium, Sanguibacter, Rhizobium, Fusarium, and Aspergillus. Strains with high cellulolytic activity were selected to further evaluate the activities of various enzymes in lignocellulosic alfalfa hay (Medicago sativa). Among them, isolate Bacillus subtilis RE2510 showed the highest potential for cellulose degradation, considering the high endoglucanase (0.1478 ± 0.0014 IU mL-1), exoglucanase (0.1735 ± 0.0012 IU mL-1), and β-glucosidase (0.3817 ± 0.0031 IU mL-1) after 10-day incubation with alfalfa hay. A significant destruction effect of the cellulose structure and the attachment of B. subtilis RE2510 to the hay were also revealed using a scanning electron microscope. This study expands our knowledge of aerobic cellulolytic isolates from the GT of sheep and highlights their potential application as a microbial additive in the aerobic process of cellulose bioconversion.

Biochemical and Structural Characterization of a Novel Bacterial Tannase From Lachnospiraceae bacterium in Ruminant Gastrointestinal Tract.

Tannases are a family of esterases that catalyze the hydrolysis of ester and depside bonds present in hydrolyzable tannins to release gallic acid. Here, a novel tannase from Lachnospiraceae bacterium (TanALb) was characterized. The recombinant TanALb exhibited maximal activity at pH 7.0 and 50°C, and it maintained more than 70% relative activity from 30°C to 55°C. The activity of TanALb was enhanced by Mg2+ and Ca2+, and was dramatically reduced by Cu2+ and Mn2+. TanALb is capable of degrading esters of phenolic acids with long-chain alcohols, such as lauryl gallate as well as tannic acid. The Km value and catalytic efficiency (k cat /Km) of TanALb toward five substrates showed that tannic acid (TA) was the favorite substrate. Homology modeling and structural analysis indicated that TanALb contains an insertion loop (residues 341–450). Based on the moleculer docking and molecular dynamics (MD) simulation, this loop was observed as a flap-like lid to interact with bulk substrates such as tannic acid. TanALb is a novel bacterial tannase, and the characteristics of this enzyme make it potentially interesting for industrial use.

BioWorma as an Aid for Controlling Ruminant Nematode Parasites

Abstract Nematode-trapping fungi are biological control agents used against the larval stages of gastrointestinal nematodes in livestock feces. These fungi are normal soil inhabitants where they feed on a variety of non-parasitic soil nematodes. Of the various fungi tested, Duddingtonia flagrans spores (BioWorma, International Animal Health Products, Australia) have been shown to survive passage through the gastrointestinal tract of ruminants. After defecation, the spores germinate and grow in the feces to form sticky, sophisticated traps/loops which are able to trap the developing larval stages in the fecal environment. This form of control has been successfully applied under field conditions and is an environmentally safe biological approach for forage-based feeding systems. BioWorma has recently been approved for use in the United States. The primary delivery system is mixing BioWorma into supplement feedstuffs daily where each animal has the opportunity to consume an adequate amount of the mixture. To achieve optimum control of larvae during the transmission season (May–October), BioWorma needs to be fed for a period of no shorter than 60 days, starting at the beginning of the grazing season (especially young after weaning). Feeding BioWorma to dams during late pregnancy and lactation will also help to reduce pasture contamination, especially for growing young that will graze the same pasture. Another delivery system is mixing BioWorma into loose mineral supplement where animals will consume it free choice. The mineral needs to be kept covered and dry. The spores cannot be incorporated into pellets as the heat of the pelleting process will kill the spores. One drawback in using BioWorma is the relatively high cost. Research is being conducted to evaluate other delivery schemes that could be more cost effective. This product is the only control method that targets nematodes on pasture, where a majority of the total population reside.

Cellulolytic and xylanolytic faecal bacteria from tedong bonga, [Toraja buffalo, Bubalus bubalis carabanesis

The gastrointestinal tract of ruminants contains a considerable number of microbes that can utilize lignocellulosic biomass from plants. In this study, faecal samples of a local white spotted swamp buffalo or tedong bonga from North Toraja, South Sulawesi [Bubalus bubalis carabanesis] were investigated to aimed bacterial isolate that are capable of degrading both cellulose and xylan. Direct isolation and enrichment methods were performed by using selective medium containing 1% carboxymethyl cellulose [CMC] or xylan in the isolation process. Plate screening and enzyme quantification indicate that 11 out of 25 isolates have double actions of cellulase and xylanase with the range of 0.18-0.30 U/ml and 0.10-1.56 U/ml, respectively. Further, molecular identification using 16S rRNA gene for four selected isolates shows that three strains [KBX04, KBX07 and KBX08] were identical to Bacillus altitudinis 41KF2bT [100%] while another strain [KBX03] were identical to Cellulomonas flavigena DSM 20109T [99%]. We demonstrated that faeces from ruminants are a promising source for lignocellulose degrading bacteria that could be used for biomass conversion.

The effects of phytochemicals on methanogenesis: insights from ruminant digestion and implications for industrial biogas digesters management

The overarching objective of this review is to compare methanogenesis in ruminant gut systems and industrial digesters that employ plants, crops and their processing residues or by-products as feedstocks. An important consideration is the presence of phytochemicals in these feedstocks, with the understanding that depending on the type and quantities, these phytochemicals affect the activity of biomass degrading microorganisms to varying extents. This review aims to evaluate currently available knowledge on the effects of phytochemicals in ruminants’ methanogenesis as well as industrial anaerobic digestion processes. Technology and scale up in industrial fermentation have always benefited from our understanding of natural biological processes as such, knowledge from the process of methanogenesis in the gastrointestinal tract of ruminants can be used to make inferences about the performance of industrial digester systems for biogas production. This is particularly important when the same feedstock is used in both systems. Thus, in this review, comparisons of the two methane generating systems are discussed with an emphasis on phytochemical inhibitory effects on microorganisms that are involved in anaerobic digestion.

Качество клетчатки и эффективность ее использования в рационах голштин-холмогорских коров

Abstract. The purpose of the research is to determine the optimal level of fibre and its fractions, neutral detergent fibre (NDF) and acid detergent fibre (ADF), in the ration of cows with milk yield 6–7 thousand kg according to the period of the physiological cycle. The scientific and economic experiment was carried out with two groups of cows, control and test, 10 animals in each other, during the whole period of lactation. The ration of control group cows corresponded to the economic one. The analysis of the crude fibre in feeds doesn't identify a reasonably accurate content of the fibre and its fractions. Therefore, the research includes the elaborated method of fractionation of structural carbohydrates (Van Soest et al.). As a result of the research, the optimal level of the crude fibre and its fractions (NDF and ADF) was determined in the cow rations according to the periods of the physiological cycle. It was established that the level of the crude fibre should be 20.5 %; NDF – 40.0 %; ADF – 25.0 % during the first phase of lactation (14–100 days). For the period of the second phase of lactation (101–200 days) the content of the crude fiber – 22,5 %, NDF – 41,3 %, and ADF – 26,3 %. For the period of the third phase of lactation (201–305 days) the level of the crude fibre should be 25,0 %; NDF – 45,5 %; ADF – 25,4 %. The novelty of the research is that we determined the requirements of the milk cows for the crude fibre, NDF and ADF according to the physiological periods in the conditions of the Arctic region. Separation of the fibre into fractions makes it possible to reveal more fully its composition, and consequently to show more precisely digesting of each fraction in the gastrointestinal tract of ruminants and to determine the role of fibre in providing of animals by energy.

The decisive role of the abomasal acidic medium in the mineral absorption in gastrointestinal tract of ruminants

The abomasum represents the “true stomach” of the ruminants and presents a significantly acid pH, which is decisive to the chemical processes that occur with mineral salts. Indeed, the pH value of the chemical medium affects decisively the precipitation or solubilization of ions as well as its complexation, which are determinant factors to the ionic absorption in the gastrointestinal tract (GIT) of the respective animal species. However, the importance of the acid medium to the metallic complexes and/or coordination compounds is not always adequately explained and emphasized in the literature focused on animal nutrition. The understanding of the relevance of the cations complexation for molecules and macromolecules present in the digesta as well as the decisive influence of the acid medium in this process constitutes fundamental aspects to the search of more efficient nutritional strategies to a higher absorption of the mineral salts that are intrinsic in the food eaten or added in the complete diet. In this way, the present approach constitutes relevant pre-requisite to viabilized new diets and/or protocols of management aiming to a lower mineral salt’s loss in the fecal matter. The biochemical and physiological relevance of several ions in the mineral salts and its great impact in the cost of the animal diet denotes the real value of a greater study and focus to this area by animal nutritionists and other researchers of similar areas.

Effects of different molecular weights of chitosan on methane production and bacterial community structure in vitro

As a new feed additive, chitosan has been shown in recent years to have a certain role in reducing methane emissions from the gastrointestinal tracts of ruminants. However, the effects of chitosan with different molecular weights on rumen fermentation, methane production and bacterial community structure are not yet clear. A basal diet without chitosan served as the control (CTL), and the treatment diets were supplemented with chitosan with different molecular weights: 1 000 (1K), 3 000 (3K), 5 000 (5K), 50 000 (5W) and 200 000 (20W) dry matter (DM). Six fermentation units per treatment were established. Gas chromatography was used to measure the concentrations of methane, H2 and volatile fatty acids (VFAs). The bacterial 16S rRNA genes were sequenced with an Illumina MiSeq platform and analysed to reveal the relative abundances of bacterial community taxa. The results showed that the propionate proportion was significantly increased by the addition of chitosan with different molecular weights (P<0.05), while methane production and the acetate proportion were significantly decreased (P<0.05). The relative abundances of Rikenellaceae_RC9_gut_group and Prevotellaceae_UCG_003 were significantly increased in the 3K chitosan group compared with the CTL group, whereas the relative abundance of Ruminococcaceae_NK4A214_group was significantly decreased (P<0.05). Correlation analyses of the relative abundances of the bacterial genera showed that Prevotella was positively related to propionate production (P<0.05). In conclusion, 3K chitosan could reduce methane production by replacing fibrolytic bacteria (Firmicutes and Fibrobacteres) with amylolytic bacteria (Bacteroidetes and Proteobacteria) in the bacterial community structure.

Modification of pillared layered clays for scavenging radiostrontium from acidic aqueous environments

A Pillared Layered Clay (PILC), code-named FREZEN, has been developed as a potential antidote for trapping radiostrontium in the gastrointestinal tract of ruminants. The ion exchange behaviour of FREZEN has been studied, with particular emphasis on Sr+2 exchange in acidic solutions. As for most sorbents and ion ex­ changers, strontium uptake by FREZEN remains sufficiently good over a pH range of 5-11, but a sharp diminution is observed at pH values below 4. Furthermore, at lower pH values, hydronium ions (H3O+) successfully compete with strontium cations already uptaken by FREZEN. An extended "back-exchange" effect, charac­terized by fast kinetics, is thus observed. In order to impede the diffusion and prevalence of Η3Ο+, a modification of the microporous space in FREZEN has been carried out via intercalation of suitable organic molecules. Work currently underway reveals that this approach is capable of improving the performance properties of the PILC. Experimental results with glycerol as the intercalated organic agen will be presented and discussed.

Evaluation of two commercially-available Salmonella vaccines on Salmonella in the peripheral lymph nodes of experimentally-infected cattle.

Background:Salmonella is a common inhabitant of the ruminant gastrointestinal tract, where it often resides asymptomatically and may be shed into the feces. More recently it was discovered that Salmonella may be contained within the peripheral, non-mesenteric lymph nodes, where it is impervious to in-plant pathogen control interventions and may serve as a source of Salmonella-contamination of ground beef. Over the past 10 years considerable research effort has been expended at understanding how this pathogen gets to these lymph nodes, the duration of infection, and, most importantly, screening and developing potential intervention strategies that may be employed on farm prior to the animal being presented for slaughter.Methods:Utilizing an experimental model of Salmonella inoculation of bovine peripheral lymph nodes (PLNs), two pilot vaccine experiments were conducted to evaluate two Salmonella vaccines: Salmonella Newport Bacterial Extract (Experiment I) and Endovac-Bovi® (Experiment II) on preventing Salmonella acquisition by these nodes. In Experiment I, 4 months following the booster vaccination, 30 steers were inoculated with three Salmonella serotypes intradermally: Newport, Montevideo, and Anatum administered to the right legs, left legs, and to the caudal thorax and abdomen, respectively. Cattle were inoculated every other day over the course of five days (three total inoculation events) and 6 and 12 days following the final Salmonella inoculation, 16 and 14 head in each treatment were euthanized, respectively. In Experiment II, 12 head of Holstein steers were utilized. Seven days following the booster and weekly thereafter for 3 weeks (four total inoculation events), cattle were inoculated as above and euthanized 7 days following final inoculation. Right and left sub-iliac, popliteal and pre-scapular lymph nodes were collected in each experiment, weighed and cultured for Salmonella.Results:In Experiment I, no treatment differences were observed in Salmonella prevalence 6 days post-inoculation (necropsy 1). However, in vaccinated cattle at the second necropsy, a reduction (p = 0.05) in Salmonella prevalence was observed in the sub-iliac and pre-scapular lymph nodes as well as when all nodes were evaluated collectively (p = 0.04). In Experiment II, the vaccine reduced (p = 0.03) Salmonella prevalence in the right popliteal and tended (p = 0.09) to decrease prevalence in both popliteal lymph nodes.Conclusion:Under these experimental conditions, the data generated provide evidence of a partial vaccine effect on Salmonella within PLNs and indicate that further research may be warranted.