Effectiveness of a Brief Point of Care Ultrasound Course at a National Nephrology Conference

The rising demand for point of care ultrasound (POCUS) instruction during nephrology fellowship has been limited due to a shortage of trained faculty and courses designed specifically for nephrologists. A hands-on POCUS pre-course was organized during the April 2023 National Kidney Foundation (NKF) Spring Clinical Meeting to address this challenge. The course consisted of pre-recorded lectures and a 4-hour hands-on workshop guided by multidisciplinary POCUS experts. The anonymous post-course survey received responses from 25 out of 39 participants, yielding a 64.1% response rate. On a scale of 0-10, confidence levels for acquiring kidney images rose from 2.6 + 2.3 (mean + SD) pre-workshop to 7.8 + 1.5 post-workshop (p<0.001). Similarly, a remarkable improvement in confidence for acquiring lung and cardiac images was seen as scores increased from 1.8 + 2.4 to 7.7 + 1.5 (p<0.001) and from 1.5 + 2.2 to 7.2 + 1.3 (p<0.001), respectively. Additionally, respondents reported a substantial improvement in their confidence to interpret kidney, lung, and cardiac POCUS images, with scores increasing from 4.5 + 2.2 to 7.7 + 1.1 (p<0.001), 2.3 + 2.4 to 7.6 + 1.5 (p<0.001), and 2 + 2 to 7.3 + 1.5 (p<0.001), respectively. Barriers to implementing POCUS use at institutions included a perceived lack of trained faculty, limited protected time for faculty, and insufficient support from division leadership. The NKF POCUS pre-course successfully improved participants' confidence in acquiring and interpreting basic POCUS images.

Point-of-care-Ultrasound (POCUS) Training Curriculum for Pediatric Nephrology: PCRRT-ICONIC Group Recommendations

BACKGROUND

Point of care ultrasound (POCUS) is commonly used in adult specialties, pediatric emergency medicine, and neonatal and pediatric critical care. Specifically, in the field of pediatric nephrology, POCUS plays a valuable role in the critical inpatient and outpatient settings. However, the lack of guidelines and a standardized curriculum for POCUS in pediatric nephrology has led to substantial discrepancies in both clinical practice and training.

METHODS

A multinational, multicenter survey regarding POCUS usefulness and training was sent to 225 pediatric nephrology residents, fellows, and physicians with expertise in pediatric nephrology. Based on the results, an ideal pediatric nephrology POCUS curriculum was formulated with a panel of experts from across the world. Eighteen experts were included, with each expert having greater than 10 years of experience in using POCUS in adult and pediatric nephrology. A Delphi method was utilized to further solidify guidelines regarding the content, curriculum, and vital skills of using POCUS in pediatric nephrology.

RESULTS

A total of 134 pediatric nephrology trainees, specialists, and faculty responded to the survey (59.6% completion rate). A total of 87.4% of respondents believe that formal POCUS training is either highly desirable or should be mandatory in pediatric nephrology fellowship programs. Identified barriers to receiving training included lack of an organized curriculum, lack of POCUS experts and Pediatric intensivists, lack of ultrasound equipment, lack of financial support, and lack of dedicated time during training. An expert panel was convened and a Delphi survey was conducted to formulate guidelines to overcome the barriers to pediatric nephrology POCUS and standardize the training process.

CONCLUSIONS

After collaborating with prominent pediatric nephrologists and global POCUS experts proposed a comprehensive POCUS training curriculum tailored specifically for pediatric nephrology trainees, with an appeal for all pediatric nephrology education programs to integrate POCUS instruction into their curricula.

Current opinion in quantitative lung ultrasound for the nephrologist

PURPOSE OF REVIEW

Volume overload mediates worse cardiovascular outcomes in patients with end-stage kidney disease (ESKD) on hemodialysis (HD), leading to increased acute care utilization. Understanding the presence of pulmonary congestion, which is often clinically silent, could be instrumental in predicting acute care needs and mitigating risks through appropriate therapy. This review provides an overview of the existing literature on lung ultrasound in ESKD patients.

RECENT FINDINGS

Quantitative lung ultrasound predicts adverse cardiovascular outcomes in ESKD patients on HD. The largest randomized controlled trial of a lung ultrasound-guided ultrafiltration strategy demonstrated control of pulmonary congestion without an increased risk of intradialytic hypotension, arrhythmia, or access thrombosis. Despite this, the study was negative in the incidence of the primary composite endpoint of all-cause death, nonfatal myocardial infarction, and decompensated heart failure. A post hoc analysis showed promise with reductions in recurrent acute care utilization and cardiovascular events. Recent research has focused on simplification of the 28-zone lung ultrasound, and abbreviated protocols have been shown to retain prognostic ability.

SUMMARY

Lung ultrasound is a valuable tool for nephrologists to diagnose and manage pulmonary congestion. However, its optimal integration with other hemodynamic parameters to formulate effective management strategies remains elusive. Future studies should address these gaps and find solutions to the training inadequacies in clinician-performed ultrasound.

Evaluation of circulating microRNA profiles in blood as potential candidate biomarkers in a subacute ruminal acidosis cow model - a pilot study

BACKGROUND

Subacute ruminal acidosis (SARA) is a metabolic disorder often observed in high-yielding dairy cows, that are fed diets high in concentrates. We hypothesized that circulating miRNAs in blood of cows could serve as potential candidate biomarkers to detect animals with metabolic dysbalances such as SARA. MicroRNAs (miRNAs) are a class of small non-coding RNAs, serving as regulators of a plethora of molecular processes. To test our hypothesis, we performed a pilot study with non-lactating Holstein-Friesian cows fed a forage diet (FD; 0% concentrate, n = 4) or a high-grain diet (HG; 65% concentrate, n = 4) to induce SARA. Comprehensive profiling of miRNA expression in plasma and leucocytes were performed by next generation sequencing (NGS). The success of our model to induce SARA was evaluated based on ruminal pH and was evidenced by increased time spent with a pH threshold of 5.8 for an average period of 320 min/d.

RESULTS

A total of 520 and 730 miRNAs were found in plasma and leucocytes, respectively. From these, 498 miRNAs were shared by both plasma and leucocytes, with 22 miRNAs expressed exclusively in plasma and 232 miRNAs expressed exclusively in leucocytes. Differential expression analysis revealed 10 miRNAs that were up-regulated and 2 that were down-regulated in plasma of cows when fed the HG diet. A total of 63 circulating miRNAs were detected exclusively in the plasma of cows with SARA, indicating that these animals exhibited a higher number and diversity of circulating miRNAs. Considering the total read counts of miRNAs expressed when fed the HG diet, differentially expressed miRNAs ( log₂ fold change) and known function, we have identified bta-miR-11982, bta-miR-1388-5p, bta-miR-12034, bta-miR-2285u, and bta-miR-30b-3p as potential candidates for SARA-biomarker in cows by NGS. These were further subjected to validation using small RNA RT-qPCR, confirming the promising role of bta-miR-30b-3p and bta-miR-2285.

CONCLUSION

Our data demonstrate that dietary change impacts the release and expression of miRNAs in systemic circulation, which may modulate post-transcriptional gene expression in cows undergoing SARA. Particularly, bta-miR-30b-3p and bta-miR-2285 might serve as promising candidate biomarker predictive for SARA and should be further validated in larger cohorts.

The Evolution of Cardiovascular Ultrasound: A Review of Cardiac Point-of-Care Ultrasound (POCUS) Across Specialties

The use of cardiac point-of-care ultrasound (POCUS) is now widespread in clinics, emergency departments, and all areas of the hospital. Users include medical trainees, advanced practice practitioners, and attending physicians in many specialties and sub-specialties. Opportunities to learn cardiac POCUS and requirements for training vary across specialties as does the scope of the cardiac POCUS examination. In this review, we describe both a brief history of how cardiac POCUS emerged from echocardiography and the state of the art across a variety of medical fields.

Nephrologist-performed point-of-care venous excess Doppler ultrasound (VExUS) in the management of acute kidney injury

Acute kidney injury (AKI) is frequently associated with alterations in fluid balance making accurate assessment of hemodynamics a vital component of patient management. Unfortunately, conventional parameters such as history, physical examination, vital signs, weight, natriuretic peptides have limitations in this regard. Point of care ultrasonography (POCUS) is a clinician-performed limited ultrasound study intended to answer focused clinical questions at the bedside. In the past several years, it has evolved as an extension of physical examination in various medical specialties. Herein, we describe a case of AKI where nephrologist-performed multi-organ POCUS aided in accurate diagnosis of fluid overload state. In addition, we describe how venous Doppler (VExUS) evaluation can be used to monitor the efficacy of decongestive therapy in real-time. Nephrologists should adopt a multi-parametric approach integrating all the pieces of hemodynamic puzzle when evaluating patients with AKI and fluid/electrolyte disorders.

Venous Excess Doppler Ultrasound for the Nephrologist: Pearls and Pitfalls

The role of venous congestion in abnormal kidney function is being increasingly recognized. It is well known that unresolved congestion is associated with adverse kidney and overall outcomes in patients with heart failure. Similarly, any condition that leads to elevated central venous pressure, such as pulmonary hypertension, can result in impaired kidney perfusion by increasing its afterload. Point-of-care ultrasonography (POCUS) enables the clinician to objectively assess hemodynamics at the bedside and, thereby, guide patient management. Lung POCUS has received widespread attention in the recent past because of the relative ease of the technique, but it reflects only left heart pressures and not venous congestion. Although inferior vena cava POCUS is used to estimate right atrial pressure, its isolated use cannot demonstrate organ congestion. Moreover, it is associated with several technical and conceptual limitations. Recently, venous excess Doppler ultrasound has emerged as a tool to assess venous congestion at the organ level in real time. Severe flow abnormalities in hepatic, portal, and kidney parenchymal veins have shown to predict the risk of congestive kidney injury. In addition, it helps to objectively monitor the efficacy of decongestive therapy. In this review, we provide a brief overview of various components of venous excess Doppler ultrasound and share our perspective on incorporating this novel tool in nephrology practice.

Quantitative Lung Ultrasonography for the Nephrologist: Applications in Dialysis and Heart Failure

Volume overload, and its attendant increase in acute care utilization and cardiovascular morbidity and mortality, represents a critical challenge for the practicing nephrologist. This is particularly true among patients with ESKD on HD, where predialysis volume overload and intradialytic and postdialytic hypovolemia account for almost a third of all cost for the Medicare dialysis benefit. Quantitative lung ultrasound is a tool for assessing the extent of extravascular lung water that outperforms physical exam and plain chest radiography. B-lines are vertical hyperechoic artifacts present in patients with increased extravascular lung water. B-lines have been shown to decrease dynamically during the hemodialysis treatment in proportion to ultrafiltration volume. Among patients with chronic heart failure, titration of diuretics on the basis of the extent of pulmonary congestion noted on lung ultrasonography has been shown to decrease recurrent acute care utilization. Early data from randomized controlled trials of lung ultrasound-guided ultrafiltration therapy among patients with ESKD on HD have shown promise for potential reduction in recurrent episodes of decompensated heart failure and cardiovascular events. Ultimately, lung ultrasound may predict those who are ultrafiltration tolerant and could be used to decrease acute care utilization and, thus, cost in this population.

Incidentalomas Among Healthy Nephrology Fellow Volunteers at POCUS Workshops: A Case Series

A radiographic incidental finding (sometimes called an incidentaloma) is defined as a structure that is unintentionally found during an exam for an unrelated indication. The increased use of routine abdominal imaging is associated with a rising incidence in incidentalomas of the kidney 1. In one meta-analysis, 75% of renal incidentalomas were benign 2. However, the overall prevalence of incidental carcinomas is low at 0.2% 3. With the growing uptake of POCUS, healthy volunteers for clinical demonstrations may find themselves with new findings despite a lack of symptoms 4. Having an incidentaloma discovered during the course of a nephrology POCUS workshop is a unique experience. Herein we report our experiences of having incidentalomas discovered during the course of POCUS demonstrations.

Nephrology Fellowship Clinician-Performed Ultrasound Curriculum

Fluid overload (FO) contributes significantly to the development of cardiovascular disease among patients with end-stage kidney disease (ESKD) on hemodialysis (HD), yet remains underappreciated due to limitations of the physical exam [1]. Lung ultrasound (US) is an established tool for quantification of FO [2]. Previous validation of quantitative lung US among nephrology attendings using a remote web-based lung ultrasound training has been demonstrated [3]. Interest in ultrasound education among nephrology fellows is high [4]. Clinician-performed ultrasound curricula for nephrology fellows have been described previously, however fellows’ competency in quantitative lung US has not been described [5]. In the present study we aimed to assess the current level of knowledge among nephrology fellows as well as the efficacy of a brief training course in quantitative lung US.

POCUS Allows for Rapid Elucidation of Acute Kidney Injury in a Patient with Progressive Multiple Myeloma

A 63-year-old man with past history of multiple myeloma recently started on a regimen of daratumumab, carfilzomib, and dexamethasone was referred to our emergency department for a rapidly rising serum creatinine as high as 10 mg/dL. He complained of fatigue, nausea, and poor appetite. Exam revealed hypertension, but no edema or rales. Labs were consistent with AKI without hypercalcemia or evidence of hemolysis or tumor lysis. Urinalysis and urine sediment were bland without proteinuria, hematuria, or pyuria. Initial concern was for hypovolemia or myeloma cast nephropathy. POCUS revealed no overt evidence of volume overload or depletion, instead revealing bilateral hydronephrosis. Bilateral percutaneous nephrostomies were placed with resolution of the AKI. Ultimately, referral imaging revealed interval progression of bulky retroperitoneal extramedullary plasmacytomas compressing the ureters bilaterally related to the underlying multiple myeloma.

Integrative Volume Status Assessment

Volume status assessment is a critical but challenging clinical skill and is especially important for the management of patients in the emergency department, intensive care unit, and dialysis unit where accurate intravascular assessment is necessary to guide appropriate fluid management. Assessment of volume status is subjective and can vary from provider to provider, posing clinical dilemmas. Traditional non-invasive methods of volume assessment include assessment of skin turgor, axillary sweat, peripheral edema, pulmonary crackles, orthostatic vital signs, and jugular venous distension. Invasive assessments of volume status include direct measurement of central venous pressure and pulmonary artery pressures. Each of these has their own limitations, challenges, and pitfalls and were often validated based on small cohorts with questionable comparators. In the past 30 years, the increased availability, progressive miniaturization, and falling price of ultrasound devices has made point of care ultrasound (POCUS) widely available. Emerging evidence base and increased uptake across multiple subspecialities has facilitated the adoption of this technology. POCUS is now widely available, relatively inexpensive, free of ionizing radiation, and can help providers make medical decisions with more precision. POCUS is not intended to replace the physical exam, but rather to complement clinical assessment, guiding providers to give thorough and accurate clinical care to their patients. We should be mindful of the nascent literature supporting the use of POCUS and other limitations as uptake increases among providers and be wary not to use POCUS to substitute clinical judgement, but integrate ultrasonographic findings carefully with history and clinical examination.

Exploratory real-time kinetic analysis of the cytotoxicity induced by maize silage mycotoxins in a calf intestinal epithelial cell line

In a temperate climate, the mycotoxins deoxynivalenol (DON), nivalenol (NIV), enniatin B (ENN B), mycophenolic acid (MPA), roquefortine C (ROC) and zearalenone (ZEN) are often found in maize silage. Although rumen microbiota are able to degrade some mycotoxins (e.g. DON), others are known to stay mainly intact (e.g. ROC). In addition, mycotoxin degradation can be hampered by a low ruminal pH or decrease in rumen microbial activity. Hence, these mycotoxins can reach the small intestine and exert a cytotoxic effect on intestinal epithelial cells. In this study, a real-time kinetic analysis of the cytotoxicity of these six mycotoxins and some of their metabolites (α- and β-zearalenol, α- and β-ZOL) was performed in a calf small intestinal epithelial cell line (CIEB). Confluency as well as the cell death parameters apoptosis and necrosis were determined to evaluate the mycotoxin-induced cytotoxicity. A combination of Annexin-V green and Cytotox red staining was used to determine early and late apoptosis as well as necrosis. Six different concentrations were tested ranging from 0.78 to 12.5 μM. Compared to cells not exposed to mycotoxins, DON and NIV exert a fast toxic effect with DON being more toxic than NIV within the first hours of incubation, whereas the inverse was observed at 16 h of incubation. On the other hand, MPA and ZEN induced increased Annexin V green positive cells within several hours of incubation with higher toxicity over time. Increased Annexin V green and Cytotox red positive cells were seen for ROC only at the highest concentration tested. For ENN B, increased Annexin V green positive cells were observed only after 12 h and α- and β-ZOL did not show cytotoxic effects. Hence, mycotoxin exposure causes either severe (DON and NIV) or more limited (ZEN, ROC, MPA, and ENN B) risk of bovine intestinal epithelial damage.

Comprehensive Assessment of Fluid Status by Point-of-Care Ultrasonography

The management of complex fluid and electrolyte disorders is central to the practice of nephrologists. The sensitivity of physical examination alone to determine fluid status is limited, precluding accurate clinical decision making. Point-of-care ultrasonography (POCUS) is emerging as a valuable, noninvasive, bedside diagnostic tool for objective evaluation of physiologic and hemodynamic parameters related to fluid status, tolerance, and responsiveness. Rapid bedside sonographic evaluation can obtain qualitative data on cardiac function and quantitative data on pulmonary congestion. Advanced POCUS, including goal-directed Doppler echocardiography, provides additional quantitative information, including flow velocities and pressures across the cardiac structures. Recently, abnormal Doppler flow patterns in abdominal organs secondary to increased right atrial pressure have been linked to congestive organ damage, adding another component to the hemodynamic assessment. Integrating POCUS findings with clinical and laboratory data can further elucidate a patient's hemodynamic status. This drives decisions regarding crystalloid administration or, conversely, diuresis or ultrafiltration and allows tailored therapy for individual patients. In this article, we provide an overview of the focused assessment of cardiovascular function and pulmonary and venous congestion using POCUS and review relevant literature.

Comprehensive Assessment of Fluid Status by Point-of-Care Ultrasonography

The management of complex fluid and electrolyte disorders is central to the practice of nephrologists. The sensitivity of physical examination alone to determine fluid status is limited, precluding accurate clinical decision making. Point-of-care ultrasonography (POCUS) is emerging as a valuable, noninvasive, bedside diagnostic tool for objective evaluation of physiologic and hemodynamic parameters related to fluid status, tolerance, and responsiveness. Rapid bedside sonographic evaluation can obtain qualitative data on cardiac function and quantitative data on pulmonary congestion. Advanced POCUS, including goal-directed Doppler echocardiography, provides additional quantitative information, including flow velocities and pressures across the cardiac structures. Recently, abnormal Doppler flow patterns in abdominal organs secondary to increased right atrial pressure have been linked to congestive organ damage, adding another component to the hemodynamic assessment. Integrating POCUS findings with clinical and laboratory data can further elucidate a patient's hemodynamic status. This drives decisions regarding crystalloid administration or, conversely, diuresis or ultrafiltration and allows tailored therapy for individual patients. In this article, we provide an overview of the focused assessment of cardiovascular function and pulmonary and venous congestion using POCUS and review relevant literature.

POCUS for Nephrologists: Basic Principles and a General Approach

Point-of-care ultrasonography (POCUS) has evolved as a valuable adjunct to physical examination in the recent past and various medical specialties have embraced it. However, POCUS training and scope of practice remain relatively undefined in nephrology. The utility of diagnostic POCUS beyond kidney and vascular access is under-recognized. Assessment of fluid status is a frequent dilemma faced by nephrologists in day-to-day practice where multiorgan POCUS can enhance the sensitivity of conventional physical examination. POCUS also reduces fragmentation of care, facilitates timely diagnosis, and expedites management. Although the need for further imaging studies is obviated in selected patients, POCUS is not meant to serve as an alternative to consultative imaging. In addition, the utility of POCUS depends on the skills and experience of the operator, which in turn depend on the quality of training. In this review, we discuss the rationale behind nephrologists performing POCUS, discuss patient examples to illustrate the basic principles of focused ultrasonography, and share our experience-based opinion about developing a POCUS training program at the institutional level.

Lung Ultrasound to Diagnose Pulmonary Congestion Among Patients on Hemodialysis: Comparison of Full Versus Abbreviated Scanning Protocols

RATIONALE & OBJECTIVE

Pulmonary congestion contributes to morbidity and mortality in patients with kidney failure on hemodialysis, but physical assessment is an insensitive approach to its detection. Lung ultrasound is useful for assessing the presence and severity of pulmonary congestion, but the most widely validated 28-zone study is cumbersome. We sought to compare abbreviated 4-, 6-, and 8-zone studies to 28-zone studies.

STUDY DESIGN

Diagnostic test study.

SETTING & PARTICIPANTS

Convenience sample of 98 patients with kidney failure on hemodialysis presenting to an emergency department in the United States.

TESTS COMPARED

4-, 6-, and 8-zone lung ultrasound studies versus a 28-zone lung ultrasound.

OUTCOME

Prediction of pulmonary congestion and 30-day mortality.

RESULTS

All patients completed a 28-zone lung ultrasound. Correlation coefficients (nonparametric Spearman) between each of the studies were high (all values > 0.84). Bland-Altman analysis showed good agreement. Each of the short-form studies discriminated well with area under the receiver-operator characteristic curve > 0.83 for no-to-mild versus moderate-to-severe pulmonary congestion. During a median follow-up period of 778 days, 46 (47%) died. Patients with moderate-to-severe pulmonary congestion on lung ultrasound had a 30-day mortality rate similar to that observed among patients with no-to-mild pulmonary congestion (OR, 0.95 [95% CI, 0.70-1.29]).

LIMITATIONS

Single-center study conducted in an emergency care setting, convenience sample of patients, and lack of long-term follow-up data.

CONCLUSIONS

Among hemodialysis patients presenting to an emergency department, 4-, 6-, or 8-zone lung ultrasounds were comparable to 28-zone studies for the assessment of pulmonary congestion. The mortality rates did not differ between those with no-to-mild and moderate-to-severe pulmonary congestion.

Short-term screening of multiple phytogenic compounds for their potential to modulate chewing behavior, ruminal fermentation profile, and pH in cattle fed grain-rich diets

In cattle, proper rumen functioning and digestion are intimately linked to chewing behavior. Yet, high grain feeding impairs chewing activity, increasing the risk of subacute ruminal acidosis and dysfermentation. This study aimed to screen 9 different phytogenic compounds for their potential to modulate chewing activity, meal size, rumino-reticular short-chain fatty acids (SCFA), and pH during consumption in a first daily meal and shortly thereafter in cattle fed a grain-rich diet. Treatments were control (total mixed ration without phytogenic) or addition of a phytogenic compound at a low or high dose. Phytogenic compounds and doses (all in mg/kg) were angelica root (6.6 and 66), capsaicin (10 and 100), gentian root (6.6 and 66), garlic oil (0.3 and 3), ginger extract (40 and 400), L-menthol (6.7 and 67), mint oil (15.3 and 153), thyme oil (9.4 and 94), and thymol (5 and 50), for the low and high groups, respectively. Before the start of the screening experiment, cows were fed to reach subacute ruminal acidosis conditions, confirmed with the time of ruminal pH <5.8 being 655 ± 148.2 min/d. During the screening experiment, the treatments were offered in a controlled meal (2.5 kg of DM for 4 h) as part of the daily diet with 65% concentrate. Each treatment was tested in 4 of the 9 cannulated Holstein cows using an incomplete Latin square design. Ruminal and reticular fluids were sampled before and after each treatment, and data collected before the meal were used as covariates. Chewing and ruminal pH were monitored during the treatment, followed by 2 h of complete feed restriction, and then 4 h of ad libitum feed intake without phytogenic. Data showed that supplementation of angelica root tended to linearly increase rumination time immediately after the first meal when feed was restricted (27.3, 41.9, and 42.6 ± 5.99 min for control, low and high groups, respectively). Capsaicin increased eating time (43.6, 49.4, and 66.4 ± 4.93 min) during consumption but did not affect ruminal total SCFA or mean ruminal pH. Garlic oil reduced the concentration of reticular total SCFA (75.7, 71.3, and 60.1 mM) and tended to decrease ruminal acetate-to-propionate ratio (2.50, 1.78, and 1.87 ± 0.177) with no effect on ruminal pH. The L-menthol affected reticular total SCFA quadratically (76.1, 64.9, and 81.0 ± 4.22%), and ruminal pH responded quadratically when feed was reintroduced ad libitum (6.0, 6.3, and 6.1 ± 0.07). Mint oil did not affect chewing or total SCFA during consumption, but the low dose increased ruminal pH (6.5, 6.7, and 6.5 ± 0.08). Thyme oil tended to lower the severity of ruminal acidosis. Overall, phytogenic compounds demonstrated distinct dose-dependent effects to beneficially influence chewing behavior, modulate fermentation, and mitigate ruminal acidosis in dairy cows under a high-grain challenge diet.

Distinct serum metabolomic signatures of multiparous and primiparous dairy cows switched from a moderate to high-grain diet during early lactation

INTRODUCTION

Feeding of high-grain diets is common in cows during early lactation, but increases the odds of metabolic derailments, which can likely be detected as undesirable shifts in the serum metabolome signature.

OBJECTIVES

The present study aimed to identify the metabolic signatures of the serum metabolome of early lactation dairy cows switched from a moderate to a high-grain diet.

METHODS

Targeted ESI-LC-MS/MS-based metabolomics was used to characterize metabolic alterations in the serum of early lactation multiparous (MP, n = 16) and primiparous (PP, n = 8) Simmental cows, according to parity and feeding phase. Data were analysed using different data mining approaches.

RESULTS

Carnitine, acetylcarnitine, propionoylcarnitine, amino acid related compounds cis-4-hydroxyproline, trans-4-hydroxyproline, proline betaine, lysophosphatidylcholine PC a C16:1 and phosphatidylcholine PC ae C36:0 were identified as the key metabolites distinguishing MP from PP cows. A different serum metabolite composition during moderate and high-grain diet was also evident. Notably, cows fed high grain diet had higher serum concentrations of primary bile acids and triglycerides, but lower levels of conjugated bile acids and carboxylic acids during the first week in grain. Amino acids valine, cystine and taurine together with lysophosphatidylcholine PC a C26:0 and several phosphatidylcholines were classified as important features for cluster separation.

CONCLUSIONS

Our study greatly expands earlier observations on dietary effects on serum metabolome composition of cows. The altered metabolomic fingerprints clearly distinguishable by diet and cow parity hold potential to be used as early diagnostic tools for cows experiencing grain-induced metabolic disturbances.

Distinct responses in feed sorting, chewing behavior, and ruminal acidosis risk between primiparous and multiparous Simmental cows fed diets differing in forage and starch levels

During early lactation, both primiparous (PP) and multiparous (MP) cows are commonly fed diets rich in starch and low in forages to support their high energy requirements. Yet, the PP cows experience this dietary challenge for the first time, which might result in higher odds for them to develop rumen and systemic health disorders. The primary objective of this study was to evaluate the effect of decreasing the amount of forages in the diet on chewing and sorting behaviors and rumen and systemic health variables in PP and MP dairy cows. Twenty-four lactating Simmental cows [8 PP, average dry matter intake (DMI) of 19.1 ± 1.1 kg/d; 16 MP, average DMI of 22.5 ± 1.1 kg/d] with a body weight of 737 ± 90 kg and 50 ± 22 days in milk were used in this study. Cows were first fed a total mixed ration with 60% forage and 40% concentrate [on a dry matter (DM) basis] considered marginal in forages for 2 wk. Then, cows were switched to a diet low in forages with 40% forage and 60% concentrate (on a DM basis) for 4 wk. Reticular pH was measured continuously with wireless pH-sensors inserted into the reticulum to calculate the subacute ruminal acidosis (SARA) index. Chewing activity was measured with noseband-sensor halters, and feed sorting was measured weekly. Blood samples were collected weekly and analyzed for metabolic and inflammation markers. Switching PP and MP cows from a marginal to low-forage diet decreased the time spent eating and ruminating per kilogram of DM. Primiparous cows chewed longer per kilogram of DMI than MP cows. Also, the PP cows sorted more pronounced for longer particles and against fine particles than MP cows did. Despite higher rumination activity per kilogram of DMI and the adaptive sorting behavior, the PP cows spent on average 4.6 h/d longer below a pH of 5.8 and had a higher SARA index (i.e., area pH <5.8/DMI) than MP cows, especially during the first week of the low-forage diet (9.5 vs. 4.8). The concentration of liver enzymes increased with the low-forage diet, which was especially pronounced in the PP cows. In conclusion, this study demonstrated greater susceptibility of PP cows to SARA and liver damage than MP cows fed the same diets. Although PP cows demonstrated greater chewing and ruminating activity per kilogram of DMI, as well as adapted sorting behavior in favor of large particles during the low-forage high-starch feeding, they developed more severe signs of SARA. This suggests higher forage fiber requirements for PP cows and the need for improved feeding strategies to mitigate rumen fermentation disorders during early lactation in these cows.

Deoxynivalenol-3-sulphate is the major metabolite of dietary deoxynivalenol in eggs of laying hens

Previous studies reported very low carry-over of dietary deoxynivalenol (DON) into eggs of laying hens. However, recent studies showed that DON is extensively metabolised to DON-3-sulphate (DON-3S) in chickens. We therefore hypothesised that DON-3S might also be a major DON metabolite in eggs of laying hens fed with DON contaminated diet. The aim of the work was to develop, validate and apply an LC-MS/MS based method for determination of DON, deepoxy-DON (DOM), DON-3S, and DOM-3-sulphate (DOM-3S) in freeze-dried eggs of laying hens. Laying hens were allocated to three treatment groups (negative control (NC); DON low (3.8 mg/kg DON in feed); DON high (7.5 mg/kg DON in feed)) and eggs were collected in the 5th, 7th and 10th week of the trial. DON-3S was identified as the major DON metabolite in eggs for the first time with average concentrations in fresh eggs <0.74 ng/g in the NC, 4.4-6.4 ng/g in the DON low group and 7.9-9.7 ng/g in the DON high group. DON-3S was also the major DON metabolite in chicken plasma, with average concentrations of 6.8±4.1 and 10±7 ng/ml in the DON low and DON high group, respectively. Experiments with intestinal explants indicated that DON-3S is in part already formed in intestinal mucosa cells. Considering the carry-over factor of 0.001, the European guidance value of DON in poultry feed (5 mg/kg), the tolerable daily intake of DON (1 μg/kg body weight and day) and the average egg consumption in Europe (0.5 egg/day/person), there is no significant health risk due to carry-over of DON or DON-3S into eggs, even if the per se non-toxic metabolite DON-3S might be hydrolysed back to free DON in the gut of the egg consumer.

Supplementing phytogenic compounds or autolyzed yeast modulates ruminal biogenic amines and plasma metabolome in dry cows experiencing subacute ruminal acidosis

Subacute ruminal acidosis (SARA) causes ruminal dysbiosis, thereby increasing the risk of systemic metabolic disorders in cattle. We recently showed that supplementation with phytogenic compounds (PHY) or autolyzed yeast (AY) counteracted negative effects of SARA by improving ruminal pH and microbiome. This study investigated the effects of an intermittent SARA challenge on the ruminal concentration of biogenic amines (BA) and lipopolysaccharides (LPS), as well as on the blood metabolome. We also evaluated effects of PHY and AY on the latter variables. Eight rumen-cannulated nonlactating Holstein cows were arranged in an incomplete 4 × 3 Latin square design with 4 experimental runs and 3 treatment groups. During each run, cows were switched from an all-forage diet (baseline) to an intermittent concentrate-challenge diet with a forage:concentrate ratio of 35:65 (dry matter basis) to induce SARA for 1 (SARA1) or 2 (SARA2) wk, separated by 1 wk of forage-only feeding. The 3 treatment groups were no additive as control, PHY, or AY. During baseline, SARA1 and SARA2 rumen fluid samples were collected for analysis of BA and LPS. Blood samples were taken during baseline and SARA1 for a targeted metabolomics approach. High-concentrate feeding caused a 9-fold increase in ruminal LPS during SARA1 and an 11-fold increase in SARA2 compared with the baseline. Elevated concentrations of ruminal BA were found during both SARA periods, with histamine showing the strongest increase during SARA1. Moreover, a decrease in phosphatidylcholines, lysophosphatidylcholines, sphingomyelines, and several AA in the blood during SARA1 were detected. Supplementation of PHY decreased concentrations of LPS (-43%), histamine (-66%), pyrrolidine (-38%), and spermine (-54%) in SARA1 and cadaverine in SARA2 (-50%). Moreover, cows that received PHY had higher concentrations of cholesterol (+26%), several AA, and phosphatidylcholines in SARA1 compared with control cows. For AY, decreases in ruminal ethanolamine (-21%), methylamine (-52%), histamine (-54%), spermidine (-44%), and spermine (-80%) in SARA1 were observed, whereas in the blood an increase in tryptophan was noticed. In conclusion, the SARA was associated with markedly increased concentrations of LPS and BA in the rumen fluid and undesirable shifts in the plasma metabolome. Supplementation of PHY and AY counteracted some of these changes and therefore may help in attenuating negative effects of high-concentrate feeding in dairy cattle.

Technical note: Changes in rumen mucosa thickness measured by transabdominal ultrasound as a noninvasive method to diagnose subacute rumen acidosis in dairy cows

Feeding high-grain diets leads to the release and accumulation of short-chain fatty acids in the rumen. The subsequent prolonged decline in ruminal pH can lead to subacute ruminal acidosis (SARA). Accumulation of short-chain fatty acids can cause proliferation of rumen papillae to increase absorption surface, subsequently leading to a thickening of the rumen mucosa. The aim of this study was to evaluate the appropriateness of continuous measurements of the rumen mucosa thickness (RMT) as a diagnostic tool for SARA in dairy cows compared with continuous measurements of ruminal pH. The study used 6 lactating Simmental cows switched from a moderate-grain (MG) diet with 40% concentrate (dry matter basis) for 1 wk to a high-grain (HG) diet with 60% concentrate (dry matter basis) for 4 wk. Reticuloruminal pH was recorded with indwelling sensors throughout the trial. Rumen mucosa thickness was measured by transabdominal ultrasound at 4 d during the MG diet and 23 d during the HG diet. Mean RMT increased from 4.7 ± 0.19 mm in the MG diet to 5.3 ± 0.17 mm in the HG diet, whereas daily mean reticular pH decreased from 6.8 ± 0.01 in the MG diet to 6.5 ± 0.01 in the HG diet. Older cows (>3 lactations) had increased RMT, associated with higher reticular pH throughout the experiment. The higher RMT and pH level in older cows underlines their lesser susceptibility to SARA during high-grain feeding. In conclusion, RMT can successfully be measured using linear ultrasound probes, commonly used by veterinary practitioners as rectal probes. By combining noninvasive RMT measurements with the lactation number of the individual cows in a herd, this study suggests that RMT is a viable option for diagnosing SARA. Further research, using a larger number of cows with different lactations numbers, is needed to establish a cut-off RMT indicating the risk of SARA.