Effects of Different Formulations of Glyphosate on Rumen Microbial Metabolism and Bacterial Community Composition in the Rumen Simulation Technique System.

The use of the herbicide glyphosate and its formulations on protein-rich feedstuff for cattle leads to a considerable intake of glyphosate into the rumen of the animals, where glyphosate may potentially impair the 5-enolpyruvylshikimate-3-phosphate pathway of the commensal microbiota, which could cause dysbiosis or proliferation of pathogenic microorganisms. Here, we evaluated the effects of pure glyphosate and the formulations Durano TF and Roundup® LB plus in different concentrations on the fermentation pattern, community composition and metabolic activity of the rumen microbiota using the Rumen Simulation Technique (RUSITEC). Application of the compounds in three concentrations (0.1 mg/l, 1.0 mg/l or 10 mg/l, n = 4 each) for 9 days did not affect fermentation parameters such as pH, redox potential, NH3-N concentration and production of short-chain fatty acids compared to a control group. Microbial protein synthesis and the degradation of different feed fractions did not vary among the treatments. None of the used compounds or concentrations did affect the microbial diversity or abundance of microbial taxa. Metaproteomics revealed that the present metabolic pathways including the shikimate pathway were not affected by addition of glyphosate, Durano TF or Roundup® LB plus. In conclusion, neither pure glyphosate, nor its formulations Durano TF and Roundup® LB plus did affect the bacterial communities of the rumen.

How much does it cost? Teaching physiology of energy metabolism in mice using an indirect calorimetry system in a practical course for veterinary students.

In endothermic mammals total energy expenditure (EE) is composed of basal metabolic rate (BMR), energy spent for muscle activity, thermoregulation, any kind of production (such as milk, meat, or egg production), and the thermic effect of feeding. The BMR is predominantly determined by body mass and the surface-to-volume ratio of the body. The EE can be quantified by either direct or indirect calorimetry. Direct calorimetry measures the rate of heat loss from the body, whereas indirect calorimetry measures oxygen consumption and carbon dioxide production and calculates heat production from oxidative nutrient combustion. A deep and sustainable understanding of EE in animals is crucial for veterinarians to properly calculate and evaluate feed rations during special circumstances such as anesthesia or in situations with increased energy demands as commonly seen in high-yielding livestock. The practical class described in this article provides an experimental approach to understanding how EE can be measured and calculated by indirect calorimetry. Two important factors that affect the EE of animals (the thermic effect of feeding and the effect of ambient temperature) are measured. A profound knowledge about the energy requirements of animal life and its measurement is also relevant for education in general biology, animal and human physiology, and nutrition. Therefore, this teaching unit can equally well be implemented in other areas of life sciences.

Long-Term Mootral Application Impacts Methane Production and the Microbial Community in the Rumen Simulation Technique System.

Methane emissions by ruminants contribute to global warming and result in a loss of dietary energy for the animals. One possibility of reducing methane emissions is by dietary strategies. In the present trial, we investigated the long-term effects of Mootral, a feed additive consisting of garlic powder (Allium sativum) and bitter orange extracts (Citrus aurantium), on fermentation parameters and the microbial community in the rumen simulation technique (RUSITEC) system. The experiment lasted 38 days and was divided into three phases: an equilibration period of 7 days, a baseline period (BL) of 3 days, and experimental period (EP) of 28 days. Twelve fermentation vessels were divided into three groups (n = 4): control (CON), short-term (ST), and long-term (LT) application. From day 11 to day 27, 1.7 g of Mootral was added to the ST vessels; LT vessels received 1.7 g of Mootral daily for the entire EP. With the onset of Mootral application, methane production was significantly reduced in both groups until day 18. Thereafter, the production rate returned to the initial quantity. Furthermore, the short chain fatty acid fermentation profile was significantly altered by Mootral application; the molar proportion of acetate decreased, while the proportions of propionate and butyrate increased. Metabolomic analysis revealed further changes in metabolite concentrations associated with the Mootral supplementation period. The methyl coenzyme-M reductase gene copy number was reduced in the liquid and solid phase, whereas the treatment did not affect the abundance of bacteria. At the end of the BL, Methanomicrobia was the most abundant archaeal class. Mootral supplementation induced an increase in the relative abundance of Methanomassiliicoccales and a reduction in the relative abundance of Methanomicrobia, however, this effect was transient. Abundances of bacterial families were only marginally altered by the treatment. In conclusion, Mootral has the transient ability to reduce methane production significantly due to a selective effect on archaea numbers and archaeal community composition with little effect on the bacterial community.

PacBio and Illumina MiSeq Amplicon Sequencing Confirm Full Recovery of the Bacterial Community After Subacute Ruminal Acidosis Challenge in the RUSITEC System.

The impact of subacute rumen acidosis (SARA) on the rumen bacterial community has been frequently studied in in vivo trials. Here we investigated whether these alterations can be mirrored by using the rumen simulation technique (RUSITEC) as an in vitro model for this disease. We hypothezised that the bacterial community fully recovers after a subacute ruminal acidosis challenge. We combined a PacBio nearly full-length 16S rRNA gene analysis with 16S rRNA gene Illumina MiSeq sequencing of the V4 hypervariable region. With this hybrid approach, we aimed to get an increased taxonomic resolution of the most abundant bacterial groups and an overview of the total bacterial diversity. The experiment consisted of a control period I and a SARA challenge and ended after a control period II, of which each period lasted 5 d. Subacute acidosis was induced by applying two buffer solutions, which were reduced in their buffering capacity (SARA buffers) during the SARA challenge. Two control groups were constantly infused with the standard buffer solution. Furthermore, the two SARA buffers were combined with three different feeding variations, which differed in their concentrate-to-hay ratio. The induction of SARA led to a decrease in pH below 5.8, which then turned into a steady-state SARA. Decreasing pH values led to a reduction in bacterial diversity and richness. Moreover, the diversity of solid-associated bacteria was lower for high concentrate groups throughout all experimental periods. Generally, Firmicutes and Bacteroidetes were the predominant phyla in the solid and the liquid phase. During the SARA period, we observed a decrease in fibrolytic bacteria although lactate-producing and -utilizing families increased in certain treatment groups. The genera Lactobacillus and Prevotella dominated during the SARA period. With induction of the second control period, most bacterial groups regained their initial abundance. In conclusion, this in vitro model displayed typical bacterial alterations related to SARA and is capable of recovery from bouts of SARA. Therefore, this model can be used to mimic SARA under laboratory conditions and may contribute to a reduction in animal experiments.

Alterations in fermentation parameters during and after induction of a subacute rumen acidosis in the rumen simulation technique.

Subacute rumen acidosis (SARA) is a common problem in dairy cattle. High-concentrate rations lead to an accumulation of short-chain fatty acids (SCFA) in the rumen and a subsequent decrease in ruminal pH. As SARA impairs animal welfare and productivity, numerous in vivo studies are focusing on evaluation of prevention strategies. In vitro models can support this research and reduce animal numbers and experimental costs. We used different diets and buffer compositions to induce SARA in the rumen simulation technique (Rusitec) and investigated the recovery process. The experiment consisted of an equilibration period (7 days), a first control period, a SARA period and a second control period (5 days each). During the SARA period, SARA was induced by infusing SARA1 or SARA2 buffer with reduced bicarbonate (20 mmol/L and 25 mmol/L) and phosphate (both 10 mmol/L) contents compared to a modified McDougall's buffer (bicarbonate 97.9 mmol/L, phosphates 20 mmol/L). Additionally, we compared three feeding strategies, which differed in the concentrate-to-roughage ratio (30:70, 70:30, changing ratio: 30% concentrate in control periods and 70% concentrate in SARA period). During the SARA period, the pH decreased to a constant value below the SARA thresholds of pH 5.8 and 5.6, whereas lactate concentrations remained low. The total SCFA production rate declined 3 days after SARA induction, and the molar proportion of acetate decreased. The decrease in pH and SCFA production was more pronounced for SARA1 buffer. The high-concentrate diet reduced the molar proportion of acetate and increased NH3 -N concentrations. During the second control period, most parameters recovered. In conclusion, SARA conditions were successfully induced in the Rusitec. However, we observed a higher influence of buffer composition than of concentrate proportions on most biochemical parameters. Nearly all changes were reversible. This model can be applied to test acidosis prevention strategies prior to animal experiments.