Development of 454 New Kompetitive Allele-Specific PCR (KASP) Markers for Temperate japonica Rice Varieties

Temperate japonica rice varieties exhibit wide variation in the phenotypes of several important agronomic traits, including disease resistance, pre-harvest sprouting resistance, plant architecture, and grain quality, indicating the presence of genes contributing to favorable agronomic traits. However, gene mapping and molecular breeding has been hampered as a result of the low genetic diversity among cultivars and scarcity of polymorphic DNA markers. Single nucleotide polymorphism (SNP)-based kompetitive allele-specific PCR (KASP) markers allow high-throughput genotyping for marker-assisted selection and quantitative trait loci (QTL) mapping within closely related populations. Previously, we identified 740,566 SNPs and developed 771 KASP markers for Korean temperate japonica rice varieties. However, additional markers were needed to provide sufficient genome coverage to support breeding programs. In this study, the 740,566 SNPs were categorized according to their predicted impacts on gene function. The high-impact, moderate-impact, modifier, and low-impact groups contained 703 (0.1%), 20,179 (2.7%), 699,866 (94.5%), and 19,818 (2.7%) SNPs, respectively. A subset of 357 SNPs from the high-impact group was selected for initial KASP marker development, resulting in 283 polymorphic KASP markers. After incorporation of the 283 markers with the 771 existing markers in a physical map, additional markers were developed to fill genomic regions with large gaps between markers, and 171 polymorphic KASP markers were successfully developed from 284 SNPs. Overall, a set of 1225 KASP markers was produced. The markers were evenly distributed across the rice genome, with average marker density of 3.3 KASP markers per Mbp. The 1225 KASP markers will facilitate QTL/gene mapping and marker-assisted selection in temperate japonica rice breeding programs.

Enteric methane emission, milk production, and composition of dairy cows fed 3-nitrooxypropanol

This study examined the effect of 3-nitrooxypropanol (3-NOP), an investigational substance, on enteric methane emission, milk production, and composition in Holstein dairy cows. Following a 3-wk covariate period, 48 multi- and primiparous cows averaging (± standard deviation) 118 ± 28 d in milk, 43.4 ± 8 kg/d milk yield, and 594 ± 57 kg of body weight were blocked based on days in milk, milk yield, and enteric methane emission and randomly assigned to 1 of 2 treatment groups: (1) control, no 3-NOP, and (2) 3-NOP applied at 60 mg/kg feed dry matter. Inclusion of 3-NOP was through the total mixed ration and fed for 15 consecutive weeks. Cows were housed in a freestall barn equipped with a Calan Broadbent Feeding System (American Calan Inc., Northwood, NH) for monitoring individual dry matter intake and fed ad libitum once daily. Enteric gaseous emissions (methane, carbon dioxide, and hydrogen) were measured using 3 GreenFeed (C-Lock Inc., Rapid City, SD) units. Dry matter intake, cow body weight, and body weight change were not affected by 3-NOP. Compared with the control group, 3-NOP applied at 60 mg/kg feed dry matter decreased daily methane emission, emission yield, and emission intensity by 26, 27, and 29%, respectively. Enteric emission of carbon dioxide was not affected, and hydrogen emission was increased 6-fold by 3-NOP. Administration of 3-NOP had no effect on milk and energy-corrected milk yields and feed efficiency, increased milk fat and milk urea nitrogen concentrations, and increased milk fat yield but had no other effects on milk components. Concentration of C6:0 and C8:0 and the sum of saturated fatty acids in milk fat were increased by 3-NOP. Total trans fatty acids and the sum of polyunsaturated fatty acids were decreased by 3-NOP. In this experiment, 3-NOP decreased enteric methane daily emission, yield, and intensity without affecting dry matter intake and milk yield, but increased milk fat in high-producing dairy cows.

Serum indoxyl sulfate concentrations associate with progression of chronic kidney disease in children

The uremic toxins indoxyl sulfate (IS) and p-cresyl sulfate (pCS) accumulate in patients with chronic kidney disease (CKD) as a consequence of altered gut microbiota metabolism and a decline in renal excretion. Despite of solid experimental evidence for nephrotoxic effects, the impact of uremic toxins on the progression of CKD has not been investigated in representative patient cohorts. In this analysis, IS and pCS serum concentrations were measured in 604 pediatric participants (mean eGFR of 27 ± 11 ml/min/1.73m2) at enrolment into the prospective Cardiovascular Comorbidity in Children with CKD study. Associations with progression of CKD were analyzed by Kaplan-Meier analyses and Cox proportional hazard models. During a median follow up time of 2.2 years (IQR 4.3-0.8 years), the composite renal survival endpoint, defined as 50% loss of eGFR, or eGFR <10ml/min/1.73m2 or start of renal replacement therapy, was reached by 360 patients (60%). Median survival time was shorter in patients with IS and pCS levels in the highest versus lowest quartile for both IS (1.5 years, 95%CI [1.1,2.0] versus 6.0 years, 95%CI [5.0,8.4]) and pCS (1.8 years, 95%CI [1.5,2.8] versus 4.4 years, 95%CI [3.4,6.0]). Multivariable Cox regression disclosed a significant association of IS, but not pCS, with renal survival, which was independent of other risk factors including baseline eGFR, proteinuria and blood pressure. In this exploratory analysis we provide the first data showing a significant association of IS, but not pCS serum concentrations with the progression of CKD in children, independent of other known risk factors. In the absence of comorbidities, which interfere with serum levels of uremic toxins, such as diabetes, obesity and metabolic syndrome, these results highlight the important role of uremic toxins and accentuate the unmet need of effective elimination strategies to lower the uremic toxin burden and abate progression of CKD.

Short communication: Short-term effect of 3-nitrooxypropanol on feed dry matter intake in lactating dairy cows

The objective of this study was to investigate the effect of 3-nitrooxypropanol (3-NOP), an enteric methane inhibitor under investigation, on short-term dry matter intake (DMI) in lactating dairy cows. Following a 1-wk adaptation period, 12 multiparous Holstein cows were fed a basal total mixed ration (TMR) containing increasing levels of 3-NOP during 5 consecutive, 6-d periods. The experiment was conducted in a tiestall barn. Feed bins were split in half by a solid divider, and cows simultaneously received the basal TMR supplemented with the following: (1) a placebo without 3-NOP or (2) 3-NOP included in the TMR at 30, 60, 90, or 120 mg/kg of feed dry matter (experimental periods 2, 3, 4, and 5, respectively). Cows received the control diet (basal TMR plus placebo premix) during experimental period 1. A premix containing ground corn grain, soybean oil, and dry molasses was used to incorporate 3-NOP in the ration. Cows were fed twice daily as follows: 60% of the daily feed allowance at 0800 h and 40% at 1800 h. Feed offered and refused was recorded at each feeding. During the morning feedings, each cow was offered either control or 3-NOP-treated TMR at 150% of her average intake during the previous 3 d. After collection of the evening refusals, cows received only the basal TMR without the premix until the next morning feeding. The test period for the short-term DMI data collection was defined from morning feeding to afternoon refusals collection during each day of each experimental period. Location (left or right) of the control and 3-NOP diets within a feed bin was switched every day during each period to avoid feed location bias. Dry matter intake of TMR during the test period was quadratically increased by 3-NOP compared with the control. Inclusion of 3-NOP at 120 mg/kg of feed dry matter resulted in decreased 10-h DMI compared with the lower 3-NOP doses, but was similar to the control. There was no effect of feed location (left or right) within feed bin on DMI. Data from this short-term study suggests that 3-NOP does not have a negative effect on DMI in lactating dairy cows.

Severe neurological outcomes after very early bilateral nephrectomies in patients with autosomal recessive polycystic kidney disease (ARPKD)

To test the association between bilateral nephrectomies in patients with autosomal recessive polycystic kidney disease (ARPKD) and long-term clinical outcome and to identify risk factors for severe outcomes, a dataset comprising 504 patients from the international registry study ARegPKD was analyzed for characteristics and complications of patients with very early (≤ 3 months; VEBNE) and early (4–15 months; EBNE) bilateral nephrectomies. Patients with very early dialysis (VED, onset ≤ 3 months) without bilateral nephrectomies and patients with total kidney volumes (TKV) comparable to VEBNE infants served as additional control groups. We identified 19 children with VEBNE, 9 with EBNE, 12 with VED and 11 in the TKV control group. VEBNE patients suffered more frequently from severe neurological complications in comparison to all control patients. Very early bilateral nephrectomies and documentation of severe hypotensive episodes were independent risk factors for severe neurological complications. Bilateral nephrectomies within the first 3 months of life are associated with a risk of severe neurological complications later in life. Our data support a very cautious indication of very early bilateral nephrectomies in ARPKD, especially in patients with residual kidney function, and emphasize the importance of avoiding severe hypotensive episodes in this at-risk cohort.

Podocytes Produce and Secrete Functional Complement C3 and Complement Factor H

Podocytes are an important part of the glomerular filtration barrier and the key player in the development of proteinuria, which is an early feature of complement mediated renal diseases. Complement factors are mainly liver-born and present in circulation. Nevertheless, there is a growing body of evidence for additional sites of complement protein synthesis, including various cell types in the kidney. We hypothesized that podocytes are able to produce complement components and contribute to the local balance of complement activation and regulation. To investigate the relevant balance between inhibiting and activating sides, our studies focused on complement factor H (CFH), an important complement regulator, and on C3, the early key component for complement activation. We characterized human cultured podocytes for the expression and secretion of activating and regulating complement factors, and analyzed the secretion pathway and functional activity. We studied glomerular CFH and C3 expression in puromycin aminonucleoside (PAN) -treated rats, a model for proteinuria, and the physiological mRNA-expression of both factors in murine kidneys. We found, that C3 and CFH were expressed in cultured podocytes and expression levels differed from those in cultivated glomerular endothelial cells. The process of secretion in podocytes was stimulated with interferon gamma and located in the Golgi apparatus. Cultured podocytes could initiate the complement cascade by the splitting of C3, which can be shown by the generation of C3a, a functional C3 split product. C3 contributed to external complement activation. Podocyte-secreted CFH, in conjunction with factor I, was able to split C3b. Podocytes derived from a patient with a CFH mutation displayed impaired cell surface complement regulation. CFH and C3 were synthesized in podocytes of healthy C57Bl/6-mice and were upregulated in podocytes of PAN treated rats. These data show that podocytes produce functionally active complement components, and could therefore influence the local glomerular complement activation and regulation. This modulating effect should therefore be considered in all diseases where glomerular complement activation occurs. Furthermore, our data indicate a potential novel role of podocytes in the innate immune system.

Bone and Mineral Metabolism in Children with Nephropathic Cystinosis Compared with other CKD Entities

CONTEXT

Children with nephropathic cystinosis (NC) show persistent hypophosphatemia, due to Fanconi syndrome, as well as mineral and bone disorders related to chronic kidney disease (CKD); however, systematic analyses are lacking.

OBJECTIVE

To compare biochemical parameters of bone and mineral metabolism between children with NC and controls across all stages of CKD.

DESIGN

Cross-sectional multicenter study.

SETTING

Hospital clinics.

PATIENTS

Forty-nine children with NC, 80 CKD controls of the same age and CKD stage.

MAIN OUTCOME MEASURES

Fibroblast growth factor 23 (FGF23), soluble Klotho, bone alkaline phosphatase (BAP), tartrate-resistant acid phosphatase 5b (TRAP5b), sclerostin, osteoprotegerin (OPG), biochemical parameters related to mineral metabolism, and skeletal comorbidity.

RESULTS

Despite Fanconi syndrome medication, NC patients showed an 11-fold increased risk of short stature, bone deformities, and/or requirement for skeletal surgery compared with CKD controls. This was associated with a higher frequency of risk factors such as hypophosphatemia, hypocalcemia, low parathyroid hormone (PTH), metabolic acidosis, and a specific CKD stage-dependent pattern of bone marker alterations. Pretransplant NC patients in mild to moderate CKD showed a delayed increase or lacked an increase in FGF23 and sclerostin, and increased BAP, TRAP5b, and OPG concentrations compared with CKD controls. Post-transplant, BAP and OPG returned to normal, TRAP5b further increased, whereas FGF23 and PTH were less elevated compared with CKD controls and associated with higher serum phosphate.

CONCLUSIONS

Patients with NC show more severe skeletal comorbidity associated with distinct CKD stage-dependent alterations of bone metabolism than CKD controls, suggesting impaired mineralization and increased bone resorption, which is only partially normalized after renal transplantation.

[Kidney Cysts and Cystic Nephropathies in Children - A Consensus Guideline by 10 German Medical Societies]

This consensus-based guideline was developed by all relevant German pediatric medical societies. Ultrasound is the standard imaging modality for pre- and postnatal kidney cysts and should also exclude extrarenal manifestations in the abdomen and internal genital organs. MRI has selected indications. Suspicion of a cystic kidney disease should prompt consultation of a pediatric nephrologist. Prenatal management must be tailored to very different degrees of disease severity. After renal oligohydramnios, we recommend delivery in a perinatal center. Neonates should not be denied renal replacement therapy solely because of their age. Children with unilateral multicystic dysplastic kidney do not require routine further imaging or nephrectomy, but long-term nephrology follow-up (as do children with uni- or bilateral kidney hypo-/dysplasia with cysts). ARPKD (autosomal recessive polycystic kidney disease), nephronophthisis, Bardet-Biedl syndrome and HNF1B mutations cause relevant extrarenal disease and genetic testing is advisable. Children with tuberous sclerosis complex, tumor predisposition (e. g. von Hippel Lindau syndrome) or high risk of acquired kidney cysts should have regular ultrasounds. Even asymptomatic children of parents with ADPKD (autosomal dominant PKD) should be monitored for hypertension and proteinuria. Presymptomatic diagnostic ultrasound or genetic examination for ADPKD in minors should only be done after thorough counselling. Simple cysts are very rare in children and ADPKD in a parent should be excluded. Complex renal cysts require further investigation.

Twelve-month outcome in juvenile proliferative lupus nephritis: results of the German registry study

BACKGROUND

Children presenting with proliferative lupus nephritis (LN) are treated with intensified immunosuppressive protocols. Data on renal outcome and treatment toxicity is scare.

METHODS

Twelve-month renal outcome and comorbidity were assessed in 79 predominantly Caucasian children with proliferative LN reported to the Lupus Nephritis Registry of the German Society of Paediatric Nephrology diagnosed between 1997 and 2015.

RESULTS

At the time of diagnosis, median age was 13.7 (interquartile range 11.8-15.8) years; 86% showed WHO histology class IV, nephrotic range proteinuria was noted in 55%, and median estimated glomerular filtration rate amounted to 75 ml/min/1.73 m². At 12 months, the percentage of patients with complete and partial remission was 38% and 41%, respectively. Six percent of patients were non-responders and 15% presented with renal flare. Nephrotic range proteinuria at the time of diagnosis was associated with inferior renal outcome (odds ratio 5.34, 95% confidence interval 1.26-22.62, p = 0.02), whereas all other variables including mode of immune-suppressive treatment (e.g., induction treatment with cyclophosphamide (IVCYC) versus mycophenolate mofetil (MMF)) were not significant correlates. Complications were reported in 80% of patients including glucocorticoid toxicity in 42% (Cushingoid appearance, striae distensae, cataract, or osteonecrosis), leukopenia in 37%, infection in 23%, and menstrual disorder in 20%. Growth impairment, more pronounced in boys than girls, was noted in 78% of patients.

CONCLUSIONS

In this cohort of juvenile proliferative LN, renal outcome at 12 months was good irrespectively if patients received induction treatment with MMF or IVCYC, but glucocorticoid toxicity was very high underscoring the need for corticoid sparing protocols. Graphical abstract.

Role of bilateral corticobulbar tracts in dysphagia after middle cerebral artery stroke

BACKGROUND AND PURPOSE

The corticobulbar tract is a potential neural pathway involved in swallowing. The frontal operculum, insular cortex, corona radiata and internal capsule, which are frequently involved in middle cerebral artery (MCA) strokes, are locations in which lesions cause dysphagia. However, it is unclear whether the locations are linked to the corticobulbar tract or whether corticobulbar tract integrity is associated with dysphagia severity. This study aimed to assess the association between corticobulbar tract integrity and dysphagia severity after MCA stroke.

METHODS

Thirty dysphagic patients after MCA stroke and 27 healthy controls were examined. Diffusion tensor imaging (DTI)-derived parameters of the corticobulbar tract were compared between patient and control groups. Next, patients were divided into mild and moderate-to-severe dysphagia groups, and DTI-derived parameters of the corticobulbar tract were compared between the subgroups. Logistic regression analysis was used to determine the association between corticobulbar tract integrity and dysphagia severity.

RESULTS

The tract volume (TV) of the affected corticobulbar tract was lower in dysphagic patients than in healthy controls (P < 0.001). According to dysphagia severity, TV of the unaffected corticobulbar tract was higher in the mild dysphagia group than in the moderate-to-severe dysphagia group (P = 0.012). TV of the unaffected corticobulbar tract was independently associated with dysphagia severity according to the logistic regression model (adjusted odds ratio 0.817, 95% confidence interval 0.683-0.976).

CONCLUSIONS

The corticobulbar tract was affected after MCA stroke and may be associated with dysphagia. A higher corticobulbar TV in the unaffected hemisphere was indicative of better swallowing function in dysphagic patients after MCA stroke.

B-Flow Sonography vs. Color Doppler Sonography for the Assessment of Vascularity in Pediatric Kidney Transplantation

OBJECTIVE

 To compare B-flow sonography (BFS) with color Doppler sonography (CDS) for imaging of kidney transplant vascularization in children.

PATIENTS AND METHODS

 All children receiving a kidney transplantation who underwent a protocol-based ultrasound examination (Loqiq 9, GE Medical Systems, Milwaukee, WI, USA) using the BFS and CDS technique with equal settings and probe position between January 2013 and January 2016 were retrospectively assessed (n = 40). The obtained datasets were visually graded according to the following criteria: (I) delineation of the renal vascular tree (Grade 1 - clear demarcation of interlobar, together with arcuate and interlobular vessels; Grade 2 - clear demarcation of interlobar and cortical vessels, but no distinction of interlobular from arcuate vessels; Grade 3 - only clear demarcation of interlobar vessels, Grade 4 - insufficient demarcation) (II) delineation of cortical vessel density in ventral, lateral, and dorsal part of the transplant, (III) smallest vessel-capsule distance, and (IV) maximum cortical vessel count. Comparison between methods was performed using Fisher's exact and paired sample t-tests.

RESULTS

 Applying a curved transducer (C1-6), BFS showed superior delineation of the renal vascular tree (p < 0.001), a lower vessel-capsule distance (p < 0.001), a higher cortical vessel count (p < 0.001), and a higher cortical vessel density in the superficial cortex (p = 0.01) than CDS. In the dorsal and lateral aspects of the transplant, cortical vessel density was lower with BFS (both p < 0.001). Using a linear high-resolution transducer (ML 6-15), no significant differences between the methods were found.

CONCLUSION

 Improved imaging of kidney transplant vascularization can be achieved in children by adding BFS to a standard protocol. The BFS technique is especially beneficial for overall assessment of the renal vascular tree together with the extent of cortical vascularization on curved array images.

KEY POINTS

  · Depiction of vascular tree and ventral cortical vessels is improved by BFS.. · The dorso-lateral cortex was better represented with CDS because of higher penetration.. · Additional monitoring with BFS improves the monitoring of transplant viability..

CITATION FORMAT

· Dammann E, Groth M, Schild R et al. B-Flow Sonography vs. Color Doppler Sonography for the Assessment of Vascularity in Pediatric Kidney Transplantation. Fortschr Röntgenstr 2021; 193: 49 - 60.

QTL mapping for pre-harvest sprouting resistance in japonica rice varieties utilizing genome re-sequencing

Pre-harvest sprouting (PHS) leads to serious economic losses because of reductions in yield and quality. To analyze the quantitative trait loci (QTLs) for PHS resistance in japonica rice, PHS rates on panicles were measured in 160 recombinant inbred lines (RILs) derived from a cross between the temperate japonica varieties Odae (PHS resistant) and Unbong40 (PHS susceptible) under two different environmental conditions—field (summer) and greenhouse (winter) environments. Genome re-sequencing of the parental varieties detected 266,773 DNA polymorphisms including 248,255 single nucleotide polymorphisms and 18,518 insertions/deletions. We constructed a genetic map comprising 239 kompetitive allele-specific PCR and 49 cleaved amplified polymorphic sequence markers. In the field environment, two major QTLs, qPHS-3^FD and qPHS-11^FD, were identified on chromosomes 3 and 11, respectively, whereas three major QTLs, qPHS-3^GH, qPHS-4^GH, and qPHS-11^GH, were identified on chromosomes 3, 4, and 11, respectively, in the greenhouse environment. qPHS-11^GH and qPHS-11^FD had similar locations on chromosome 11, suggesting the existence of a gene conferring stable PHS resistance effects under different environmental conditions. The QTLs identified in this study can be used to improve the PHS resistance of japonica varieties, and they may improve our understanding of the genetic basis of PHS resistance.

Epidemiology of and Risk Factors for BK Polyomavirus Replication and Nephropathy in Pediatric Renal Transplant Recipients: An International CERTAIN Registry Study

BACKGROUND

BK polyomavirus-associated nephropathy (BKPyVAN) constitutes a serious cause of kidney allograft failure, but large-scale data in pediatric renal transplant recipients and a comprehensive analysis of specific risk factors are lacking.

METHODS

We analyzed the data of 313 patients in the Cooperative European Pediatric Renal Transplant Initiative Registry, with an observation period of 3.3 years (range, 1-5). The net state of immunosuppressive therapy was assessed by the modified Vasudev score.

RESULTS

Presumptive BKPyVAN (defined as sustained [>3 wk] high-level BK viremia >10 copies/mL) within 5 years posttransplant occurred in 49 (15.8%) of 311 patients, and biopsy-proven BKPyVAN in 14 (4.5%) of 313. BKPyV viremia was observed in 115 (36.7%) of 311 patients, of whom 11 (9.6%) of 115 developed viremia late, that is, after the second year posttransplant. In 6 (12.5%) of 48 patients with high-level viremia and in 3 (21.4%) of 14 with BKPyVAN, this respective event occurred late. According to multivariable analysis, BKPyV viremia and/or BKPyVAN were associated not only with a higher net state of immunosuppression (odds ratio [OR], 1.3; P < 0.01) and with tacrolimus-based versus ciclosporin-based immunosuppression (OR, 3.6; P < 0.01) but also with younger recipient age (OR, 1.1 per y younger; P < 0.001) and obstructive uropathy (OR, 12.4; P < 0.01) as primary renal disease.

CONCLUSIONS

Uncontrolled BKPyV replication affects a significant proportion of pediatric renal transplant recipients and is associated with unique features of epidemiology and risk factors, such as young recipient age, obstructive uropathy, and overall intensity of immunosuppressive therapy. BKPyV surveillance should be considered beyond 2 years posttransplant in pediatric patients at higher risk.

Maresin 1 Promotes Wound Healing and Socket Bone Regeneration for Alveolar Ridge Preservation

Tooth extraction results in alveolar bone resorption and is accompanied by postoperative swelling and pain. Maresin 1 (MaR1) is a proresolving lipid mediator produced by macrophages during the resolution phase of inflammation, bridging healing and tissue regeneration. The aim of this study was to examine the effects of MaR1 on tooth extraction socket wound healing in a preclinical rat model. The maxillary right first molars of Sprague-Dawley rats were extracted, and gelatin scaffolds were placed into the sockets with or without MaR1. Topical application was also given twice a week until complete socket wound closure up to 14 d. Immediate postoperative pain was assessed by 3 scores. Histology and microcomputed tomography were used to assess socket bone fill and alveolar ridge dimensional changes at selected dates. The assessments of coded specimens were performed by masked, calibrated examiners. Local application of MaR1 potently accelerated extraction socket healing. Macroscopic and histologic analysis revealed a reduced soft tissue wound opening and more rapid re-epithelialization with MaR1 delivery versus vehicle on socket healing. Under micro-computed tomography analysis, MaR1 (especially at 0.05 μg/μL) stimulated greater socket bone fill at day 10 as compared with the vehicle-treated animals, resulting in less buccal plate resorption and a wider alveolar ridge by day 21. Interestingly, an increased ratio of CD206⁺:CD68⁺ macrophages was identified in the sockets with MaR1 application under immunohistochemistry and immunofluorescence analysis. As compared with the vehicle therapy, local delivery of MaR1 reduced immediate postoperative surrogate pain score panels. In summary, MaR1 accelerated extraction wound healing, promoted socket bone fill, preserved alveolar ridge bone, and reduced postoperative pain in vivo with a rodent preclinical model. Local administration of MaR1 offers clinical potential to accelerate extraction socket wound healing for more predictable dental implant reconstruction.

Dose-response effect of 3-nitrooxypropanol on enteric methane emissions in dairy cows

This experiment was designed to test the effect of inclusion rate of 3-nitrooxypropanol (3-NOP), a methane inhibitor, on enteric methane emissions in dairy cows. The study was conducted with 49 multiparous Holstein cows in a randomized complete block design in 2 phases; phase 1 was with 28 cows, and phase 2 with 21 cows. Cows were fed a basal total mixed ration ad libitum and were blocked based on days in milk, milk yield, and enteric methane emissions during a 14-d covariate period. Treatments were control (no 3-NOP) and 40, 60, 80, 100, 150, and 200 mg of 3-NOP/kg of feed dry matter. Following a 14-d adaptation period, enteric gaseous emissions (methane, carbon dioxide, and hydrogen) were measured using the GreenFeed system (C-Lock Inc., Rapid City, SD) over a 3-d period. Compared with the control, inclusion rate of 3-NOP quadratically decreased daily enteric methane emissions from 22 to 40%. Maximum mitigation effect was achieved with the 3 highest 3-NOP doses (with no statistical difference among 100, 150, and 200 mg/kg). The decrease in methane emission yield and emission intensity ranged from 16 to 36% and from 25 to 45%, respectively. Emissions of hydrogen quadratically increased 6- to 10-fold, compared with the control; the maximum increase was with 150 mg/kg 3-NOP. Treatment did not affect daily emissions of carbon dioxide, but a linear increase in carbon dioxide emission yield was observed with increasing 3-NOP doses. Dry matter intake and milk yield of the cows was not affected by 3-NOP. Milk fat concentration and yield were increased by 3-NOP due to increased concentration of de novo synthetized short-chain fatty acids in milk. Inclusion of 3-NOP also tended to increase milk urea nitrogen but had no other effects on milk components. In this short-term experiment, 3-NOP decreased enteric methane emissions without affecting dry matter intake or milk yield and increased milk fat in dairy cows. Maximum mitigation effect was achieved at 100 to 200 mg/kg of feed dry matter.