Innate immunity and metabolomic responses in dairy cows challenged intramammarily with lipopolysaccharide after subacute ruminal acidosis

Subacute ruminal acidosis (SARA) is a prevalent metabolic disorder in dairy cows known to elicit local and systemic immune responses. We recently showed that cows experiencing SARA and challenged intramammarily with lipopolysaccharide (LPS) experienced stronger metabolic disturbances compared with cows without SARA. Therefore, we hypothesized that cows experiencing SARA have a modulated innate immune response and impaired plasma metabolome compared with healthy cows when experiencing an acute mastitis challenge. A total of 18 Simmental cows were subjected either to a Control (CON, n=6) or SARA (n=12) feeding regimen, receiving either 40% or 60% concentrates for 30 days. Thereafter, six SARA (SARA-LPS) and the CON (CON-LPS) cows were intramammarily challenged with 50 µg LPS from Escherichia coli (O26 : B6), while the remaining six SARA cows (SARA-PLA) received a placebo. Blood and milk samples were analyzed for acute phase proteins and a targeted ESI-LC-MS/MS-based metabolomics approach was performed in blood samples 24 h after the LPS challenge. The LPS infusion caused a strong increase in immune response variables, with a higher concentration of milk amyloid A 48 h after the LPS challenge in SARA-LPS compared with CON-LPS cows. Cows receiving the LPS infusion had a lower plasma concentration of several amino acids and lysophosphatidylcholines but without differences in SARA cows and healthy cows. In conclusion, our results revealed that an intramammary LPS infusion increased acute phase proteins and modulated the blood metabolome. While no systemic differences between SARA and healthy cows were observed, cows experiencing SARA showed a higher concentration of an acute phase protein at the local level of the mammary gland. Further research is required to elucidate the underlying mechanisms and to evaluate its clinical significance for udder health.     

Biochanin A improves fibre fermentation by cellulolytic bacteria

Aims

The objective was to determine the effect of the isoflavone biochanin A (BCA) on rumen cellulolytic bacteria and consequent fermentative activity.

Methods and Results

When bovine microbial rumen cell suspensions (n = 3) were incubated (24 h, 39°C) with ground hay, cellulolytic bacteria proliferated, short‐chain fatty acids were produced and pH declined. BCA (30 μg ml^?1) had no effect on the number of cellulolytic bacteria or pH, but increased acetate, propionate and total SCFA production. Addition of BCA improved total digestibility when cell suspensions (n = 3) were incubated (48 h, 39°C) with ground hay, Avicel, or filter paper. Fibrobacter succinogenes S85, Ruminococcus flavefaciens 8 and Ruminococcus albus 8 were directly inhibited by BCA. Synergistic antimicrobial activity was observed with BCA and heat killed cultures of cellulolytic bacteria, but the effects were species dependent.

Conclusions

These results indicate that BCA improves fibre degradation by influencing cellulolytic bacteria competition and guild composition.

Significance and Impact of the Study

BCA could serve as a feed additive to improve cellulosis when cattle are consuming high‐fibre diets. Future research is needed to evaluate the effect of BCA on fibre degradation and utilization in vivo.     

Rumen Ciliate Fauna of Alaskan Moose (Alces americana), Musk-Ox (Ovibos moschatus) and Dall Mountain Sheep (Ovis dalli)*

Total numbers, generic distribution and percentage species distribution were determined for the ciliate protozoa in rumen contents obtained from Alaskan moose (Alces americana), musk-ox (Ovibos moschatus) and Dall mountain sheep (Ovis dalli). The musk-ox has a fauna somewhat similar to that previously observed in reindeer and caribou. In contrast, only protozoa in the genus Entodinium were observed in moose, while Dall mountain sheep have a fauna unique among Alaskan ruminants studied to date. Other than Entodinium exiguum which was common to all animals, only 2 additional species of Entodinium, observed in the moose and musk-ox, occurred in more than one animal species. Four new species of protozoa are described, Entodinium dalli sp.n., Entodinium constrictum sp.n. and Polyplastron alaskum sp.n. from the Dall mountain sheep and Entodinium alces sp.n. from moose.     

Effect of variety and harvest date on nutritive value and ruminal degradability of ensiled maize ears

The nutritive value of whole crop forage maize is influenced by the proportion of ears and stover in the whole crop and by the nutrient composition and digestibility characteristics of the plant parts. An experiment investigating the impact of variety, harvest date and year on the nutritive value of ensiled maize ears was carried out in three consecutive years (2007, 2008 and 2010). Nine different maize varieties were harvested at three different maturity stages (50, 55 and 60% dry matter (DM) content in the ears). After harvest, ears and stover were ensiled separately and afterwards nutrient composition and ruminal nutrient degradability (organic matter (OM), crude protein (CP) and non-fibre carbohydrates (NFC)) were analysed. Variety had a significant influence on content of CP and effective ruminal degradability (ED) of OM at low passage rates, whereas ED of CP and NFC was not affected by variety. In contrast, harvest date and year significantly influenced nutrient composition and ruminal degradability of ensiled maize ears. The content of NFC increased and the content of fibre components as well as ED of OM, CP and NFC declined with processing maturity of the maize plants. At a passage rate of 5% h^?1, ED of OM declined from 75.9% to 68.4%, ED of CP from 82.5% to 73.8% and ED of NFC from 88.0% to 82.3% between the early and late harvest date. The results of this study indicate that the nutrient composition and ruminal degradability of ensiled maize ears are affected mainly by maturity stage at harvest and by year, whereas variety has only little influence.     

Influence of aFusarium culmorum inoculation of wheat onin sacco dry matter degradation of wheat straw and wheat chaff

The aim of this study was to investigate the effect of aFusarium culmorum inoculation of wheat on thein sacco dry matter degradation (DG) of wheat straw and wheat chaff in dairy cows. The ruminal disappearance of dry matter was measured with thein situ nylon bag technique. Samples of wheat straw and wheat chaff from non-inoculated andFusarium-inoculated wheat were used to examine the ruminal dry matter degradability. Samples were subjected to ruminal incubation in two dairy cous fitted with a permanent rumen fistula and incubated for 4, 8, 16, 24, 48, 72, 96 and 120 h. To describe the degradation kinetics, the equation by Ørskov and McDonald (1979) was used. DG rates obtained for contaminates straw and chaff were higher compared to the corresponding rates of the non-contaminated samples, which is assumed to be due to the activity of fungal enzymes. It can be concluded that an infection of wheat withF. culmorum may have an influence on the dry matter degradation of straw and chaff.     

Changes in microbial community structure, methanogenesis and rumen fermentation in response to saponin-rich fractions from different plant materials

Aims:  Investigation of the effects of saponin-rich fractions on rumen fermentation, methane production and the microbial community.
Methods and Results:  Saponins were extracted from Carduus , Sesbania and Knautia leaves and fenugreek seeds. Two levels of saponin-rich fractions with a substrate were incubated using the Hohenheim gas method. Methane was measured using an infrared-based methane analyser and microbial communities using quantitative PCR. On addition of saponin-rich fractions, methane and short-chain fatty acid production was not affected. The protozoal counts decreased by 10–39%. Sesbania saponins decreased methanogen population by 78%. Decrease in ruminal fungal population (20–60%) and increase in Fibrobacter succinogenes (21–45%) and Ruminococcus flavefaciens (23–40%) were observed.
Conclusions:  The saponins evaluated possessed anti-protozoal activity; however, this activity did not lead to methane reduction. Fenugreek saponins seemed to have potential for increasing rumen efficiency. The saponins altered the microbial community towards proliferation of fibre-degrading bacteria and inhibition of fungal population.
Significance and Impact of the Study:  The uni-directional relationship between protozoal numbers and methanogenesis, as affected by saponins, is not obligatory. All saponins might not hold promise for decreasing methane production from ruminants.     

In sacco rumen disappearance of condensed tannins, fiber, and nitrogen from herbaceous native Texas legumes in goats

Condensed tannins (CT) can play a role in rumen protein and fiber degradability, especially in legumes high in CT. In order to better understand their potential role in ruminant nutrition, three legume species native to Texas, Acacia angustissima var. hirta (prairie acacia) (288.0 g/kg neutral detergent fiber (NDFom), 40.9 g/kg N), Desmodium paniculatum (panicled tick-clover) (479.7 g/kg NDFom, 24.8 g/kg N), and Lespedeza procumbens (trailing bush-clover) (401.0 g/kg NDFom, 21.7 g/kg N) were studied to determine in sacco disappearance rates of key nutritional components compared to that of Medicago sativa (alfalfa) (226.8 g/kg NDFom, 34.6 g/kg N). Herbage was incubated in rumen-cannulated goats fed a basal diet of Sorghum bicolor×S. sudanense (sorghum-Sudan) hay, with disappearance measured at 0, 4, 8, 16, 28, 48 and 96 h. Among the native legumes, the highest CT concentrations were measured in prairie acacia (263 g CT/kg DM foliage) and the lowest (120 g CT/kg DM) in trailing bush-clover. The lowest concentrations of acid detergent fiber (ADFom), NDFom, and sulfuric acid lignin (lignin(sa)) were measured in prairie acacia, the first two fractions being comparable to alfalfa. Proportion remaining was calculated for CT, ADFom, lignin(sa), NDFom, and N for 0, 24 and 48 h of rumen incubation. Disappearance parameters were measured for ADFom, lignin(sa), NDFom and N for the three native legumes and compared to alfalfa. Alfalfa had the highest disappearance of all degradable fractions except lignin(sa). Potential disappearance (PD) fraction for ADFom, lignin(sa) and N were lower for the native legumes versus alfalfa. No differences in N proportion remaining at 24 and 48 h occurred in the native legumes despite differences in protein-bound CT proportion remaining at those same times. Of the native legumes studied, prairie acacia shows the greatest potential for contributing rumen-escape protein, suggesting it may be a candidate for further development as a pasture and rangeland renovation legume.     

Influence of the maize silage to grass silage ratio and feed particle size of rations for ruminants on the community structure of ruminal Firmicutes in vitro

Aims: To investigate the effect of the forage source and feed particle size (FPS) in ruminant rations on the composition of the ruminal Firmicutes community in vitro. Methods and Results: Three diets, varying in maize silage to grass silage ratio and FPS, were incubated in a rumen simulation system. Microbial samples were taken from the liquid fermenter effluents. Microbial community analysis was performed by 16S rRNA‐based techniques. Clostridia‐specific single‐strand conformation polymorphism profiles revealed changes of the community structure in dependence on both factors tested. The coarse grass silage–containing diets seemed to enhance the occurrence of different Roseburia species. As detected by real‐time quantitative PCR, Ruminococcus albus showed a higher abundance with decreasing FPS. A slightly lower proportion of Bacilli was found with increasing grass silage to maize silage ratio by fluorescence in situ hybridization (FISH). In contrast, a slightly higher proportion of bacterial species belonging to the Clostridium‐clusters XIV a and b was detected by FISH with increasing grass silage contents in the diet. Conclusions: The ruminal Firmicutes community is affected by the choice of the forage source and FPS. Significance and Impact of the Study: This study supplies fundamental knowledge about the response of ruminal microbial communities to changing diets. Moreover, the data suggest a standardization of grinding of feeds for in vitro studies to facilitate the comparison of results of different laboratories.