High-retention membrane bioreactors for sugarcane vinasse treatment: Opportunities for environmental impact reduction and wastewater valorization.

Ethanol production has increased over the years, and Brazil ranking second in the world using sugarcane as the main raw material. However, 10-15 L of vinasse are generated per liter of ethanol produced. Besides large volumes, this wastewater has high polluting potential due to its low pH and high concentrations of organic matter and nutrients. Given the high biodegradability of the organic matter, the treatment of this effluent by anaerobic digestion and membrane separation processes results in the generation of high value-added byproducts such as volatile fatty acids (VFAs), biohydrogen and biogas. Membrane bioreactors have been widely evaluated due to the high efficiency achieved in vinasse treatment. In recent years, high retention membrane bioreactors, in which high retention membranes (nanofiltration, reverse osmosis, forward osmosis and membrane distillation) are combined with biological processes, have gained increasing attention. This paper presents a critical review focused on high retention membrane bioreactors and the challenges associated with the proposed configurations. For nanofiltration membrane bioreactor (NF-MBR), the main drawback is the higher fouling propensity due to the hydraulic driving force. Nonetheless, the development of membranes with high permeability and anti-fouling properties is uprising. Regarding osmotic membrane bioreactor (OMBR), special attention is needed for the selection of a proper draw solution, which desirably should be low cost, have high osmolality, reduce reverse salt flux, and can be easily reconcentrated. Membrane distillation bioreactor (MDBR) also exhibit some shortcomings, with emphasis on energy demand, that can be solved with the use of low-grade and residual heat, or renewable energies. Among the configurations, MDBR seems to be more advantageous for sugarcane vinasse treatment due to the lower energy consumption provided by the use of waste heat from the effluent, and due to the VFAs recovery, which has high added value.

Efficacy of plants extracts from the Cerrado against adult female of Dermacentor nitens (Acari: Ixodidae).

Dermacentor nitens tick is commonly found in the equine auditory canal, where it causes economic losses due to its direct damage, causing blood spoliation, stress, transmission of pathogens, and predisposition to myasis and secondary bacterial infection in its hosts. In this study we evaluated the effect of ethanolic extracts of Cerrado plants on biological parameters of engorged females of D. nitens. Ethanolic extracts were prepared from the leaves of Schinopsis brasiliensis, Piptadenia viridiflora, Ximenia americana, and Serjania lethalis at 25-150 mg mL-1. Groups of 10 engorged adult females were treated with these extracts and compared with a control containing distilled water and another control with organophosphate, using five replicates for each group. Compared with the control with water, S. lethalis and X. americana extracts at 100 and 150 mg mL-1 significantly inhibited the posture ability. Differently, extracts of S. brasiliensis and P. viridiflora were the most effective in inhibiting larval hatching. Extracts of X. americana and P. viridiflora showed effective inhibition of reproductive parameters of the tick, presenting dose-dependent effect with IC90 78.86 and 78.94 mg mL-1, respectively. Theses effective extracts contained low condensed tannin levels and their HPLC chromatograms revealed the presence of flavonoids. The efficacies of P. viridiflora and X. americana extracts were higher than 90% indicating that these extracts are promising as alternative agents for D. nitens control.

Multistimuli Response Micro- and Nanolayers of a Coordination Polymer Based on Cu2 I2 Chains Linked by 2-Aminopyrazine.

A nonporous laminar coordination polymer of formula [Cu2 I2 (2-aminopyrazine)]n is prepared by direct reaction between CuI and 2-aminopyrazine, two industrially available building blocks. The fine tuning of the reaction conditions allows obtaining [Cu2 I2 (2-aminopyrazine)]n in micrometric and nanometric sizes with same structure and composition. Interestingly, both materials show similar reversible thermo- and pressure-luminescent response as well as reversible electrical response to volatile organic solvents such as acetic acid. X-ray diffraction studies under different conditions, temperatures and pressures, in combination with theoretical calculations allow rationalizing the physical properties of this compound and its changes under physical stimuli. Thus, the emission dramatically increases when lowering the temperature, while an enhancement of the pressure produces a decrease in the emission intensity. These observations emerge as a direct consequence of the high structural flexibility of the Cu2 I2 chains which undergo a contraction in CuCu distances as far as temperature decreases or pressure increases. However, the strong structural changes observed under high pressure lead to an unexpected effect that produces a less effective CuCu orbital overlapping that justifies the decrease in the intensity emission. This work shows the high potential of materials based on Cu2 I2 chains for new applications.

Replication of PTPRC as genetic biomarker of response to TNF inhibitors in patients with rheumatoid arthritis.

Genetic biomarkers could be useful for orienting treatment of patients with rheumatoid arthritis (RA), but none has been convincingly validated yet. Putative biomarkers include 14 single nucleotide polymorphisms that have shown association with response to TNF inhibitors (TNFi) in candidate gene studies and that we assayed here in 755 RA patients. Three of them, in the PTPRC, IL10 and CHUK genes, were significantly associated with response to TNFi. The most significant result was obtained with rs10919563 in PTPRC, which is a confirmed RA susceptibility locus. Its RA risk allele was associated with improved response (B=0.33, P=0.006). This is the second independent replication of this biomarker (P=9.08 × 10(-8) in the combined 3003 RA patients). In this way, PTPRC has become the most replicated genetic biomarker of response to TNFi. In addition, the positive but weaker replication of IL10 and CHUK should stimulate further validation studies.

Effect of condensed corn distillers solubles concentration on lactation performance of Holstein cows.

Forty-eight Holstein cows (32 multiparous and 16 primiparous) in mid to late lactation averaging 219±71 days in milk and 30.5±6.6 kg/d of 3.5% fat-corrected milk were used in a 56-d completely randomized design experiment to evaluate condensed corn distillers solubles (CCDS) inclusion in high-fiber total mixed rations (TMR). Inclusion rates evaluated were 0, 6.6, 13.2, and 19.8% CCDS as a percentage of dry matter (DM). Distiller solubles substituted for soybean meal, corn grain, and whole cottonseed such that diets were similar in protein (16.6%) and fat (4.50%). Water was added to 0, 6.6, and 13.2% CCDS treatments so that final TMR DM concentrations (47.8%) were similar across diets. The forage portion of the diet was kept constant at 19.6% annual ryegrass hay and 26.0% sorghum baleage. Diet in vitro true digestibility tended to increase as CCDS addition increased, but neutral detergent fiber digestibility trended lower in CCDS diets. Percent P (0.39, 0.55, 0.69, and 0.73%) and S (0.32, 0.35, 0.39, and 0.42%) in TMR increased as CCDS concentration increased. Milk yield (23.5, 24.7, 25.5, and 24.8 kg/d of 3.5% fat-corrected milk) was similar for control and CCDS diets. Milk fat (3.88, 3.73, 3.78, and 3.68%), protein (3.28, 3.27, 3.31, and 3.31%), and lactose (4.61, 4.66, 4.69, and 4.77) percentages were similar across diets. Milk urea nitrogen (16.60, 15.58, 15.43, and 14.75 mg/dL) declined with increasing CCDS addition. Animal activity, body weight, body condition scores, and locomotion scores were not influenced by CCDS. Day 28 poststudy locomotion scores were similar across diets. Ruminal acetate concentrations did not differ among diets, but propionate and butyrate concentrations were elevated in rumen fluid of cows receiving 19.6% CCDS. Although rumen fluid pH values were similar (6.5, 6.4, 6.3, and 6.2), the two highest CCDS diets exhibited depressed acetate:propionate ratios relative to controls. The results from this study indicate that CCDS may be included in high-fiber TMR for lactating dairy cows at up to nearly 20% of diet DM; however, caution is recommended because high CCDS P concentrations may create Ca:P imbalances and excess P may be introduced into the environment.

Short communication: Substituting dry distillers grains with solubles and rumen-protected amino acids for soybean meal in late-lactation cows' diets based on corn silage or ryegrass silage.

Excess protein in dairy cattle diets increases production costs and contributes to environmental pollution. The objective of the present study was to evaluate the effect of feeding dry distillers grains with solubles (DDGS) supplemented with rumen-protected Lys and Met in place of solvent-extracted soybean meal on the performance of late-lactation cows. Two experiments were carried out, with each using 24 late-lactating dairy cows distributed among 4 pens. In trial 1, corn silage was the main forage source. Control (HP1) total mixed ration (TMR) contained 16.3% crude protein (CP) with soybean meal as the main protein source. Treatment TMR (LP1) had 13.7% CP when soybean meal was replaced with DDGS and rumen-protected Lys and Met. Forage in trial 2 was ryegrass silage; control TMR (HP2; 15.4% CP) contained soybean meal and rumen-protected Met, whereas treatment TMR (LP2; 13.8% CP) contained DDGS and rumen-protected Lys and Met. Trials were analyzed as crossover design using the MIXED procedure of SAS (SAS Institute Inc., Cary NC) with cow as sampling unit and pen as the experimental unit. Treatments were similar in dry matter intake (21.0 and 20.4 kg/cow per day for HP1 and LP1, respectively) and milk yield (20.7 and 20.5 kg/cow per day for HP1 and LP1, respectively) during trial 1. Milk composition was similar between treatments, averaging 4.22, 3.73, 4.54, and 9.15, respectively, for fat, protein, lactose, and solids nonfat. Milk urea nitrogen decreased from 17.2 mg/dL for HP1 to 9.93 mg/dL for LP1. In trial 2, no significant differences were observed for dry matter intake (21.4 and 20.9 kg/cow per day for HP2 and LP2, respectively), milk yield (28.1 and 26.6 kg/d for HP2 and LP2, respectively), fat yield (0.99 vs. 0.92 kg/d for HP2 and LP2, respectively), protein yield (0.94 vs. 0.86 kg/d for HP2 and LP2, respectively) and lactose yield (1.37 vs. 1.28 for HP2 and LP2, respectively). Milk urea nitrogen decreased from 9.88 mg/dL with HP2 to 6.39 mg/dL with the LP2 treatment. Milk N efficiency tended to be higher for LP treatments in trial 1, but not in trial 2. Low milk urea N suggested nitrogen losses to the environment may be lower when cows were fed diets based on DDGS in both trials. The studies indicated that DDGS with rumen-protected Lys and Met could substitute solvent-extracted soybean meal in low-protein corn silage- and ryegrass silage-based diets for late-lactation dairy cows averaging 20.6 or 27.4 kg of milk/d, respectively.

Antimutagenic action of the triterpene betulinic acid isolated from Scoparia dulcis (Scrophulariaceae).

The mutagenic and antimutagenic activities of triterpene betulinic acid {3b-3-hydroxy-lup-20(29)-en-28-oic} isolated from the roots of Scoparia dulcis (Scrophulariaceae) were analyzed using the somatic mutation and recombination test (SMART) in the wings of Drosophila melanogaster. The mutagenic potential of betulinic acid was evaluated at 3 different concentrations (1.64, 3.28, and 6.57 mM). Antimutagenic activity evaluation was performed by co-treatment trials in which the flies received betulinic acid at 3 different concentrations in addition to 10 mM pro-mutagenic urethane. The results demonstrated that betulinic acid was not capable of causing DNA damage. However, the frequency of small single spots, large spots, and twin spots was significantly reduced. In the high bioactivation cross, betulinic acid was significantly active and exerted enhanced antimutagenic activity, possibly as a desmutagen.

Protective effects of the antileishmanial extract of Tephrosia cinerea (L.) Pers. (Fabaceae) against cyclophosphamide-induced damage.

Tephrosia cinerea L. (Pers.) is a tropical species that exhibits antileishmanial activity in Leishmania amazonensis promastigote cultures and is commonly used to treat infections, inflammations, ulcers, nervous conditions, and diarrhea. However, no studies have investigated its effects on genetic material. Therefore, we evaluated the genotoxic potential, antigenotoxic potential, and cytotoxic effects of hydroalcoholic extracts of T. cinerea leaves. In an in vitro genotoxicity study, human peripheral blood leukocytes were treated for 3, 24 (comet assay), or 48 h (cell death assay) with 22, 44, or 88 µg/mL plant extract. In the in vivo assay, Swiss mice were treated with 500, 1000, or 2000 mg extract/kg body weight by intraperitoneal injection and were evaluated 24 h later. Antigenotoxicity was investigated in pre- and post-treatment assays in which the animals received the plant extract (2000 mg/kg) 24 h before or after receiving cyclophosphamide (50 mg/kg), respectively. The extract had no genotoxic effects in the in vitro or in vivo assays. However, the extract reduced apoptotic cell death and induced necrotic cell death at concentrations that presented leishmanicidal activity in vitro. The extract also had an antigenotoxic effect, reducing the levels of genomic damage that were caused by cyclophosphamide in Swiss mice by more than 80%.

Evaluation of genotoxic and cytotoxic effects of antileishmanial extract from Julocroton triqueter (Euphorbiaceae).

Julocroton triqueter extracts have antileishmanial activity; however, the effect on genetic stability has not been studied. We evaluated genotoxic and cell death induction potential (in vitro and in vivo) of J. triqueter var. triqueter hydroalcoholic extracts, as well as their antigenotoxic potential in vivo. The in vitro genotoxic studies were performed using human leukocytes at four different concentrations. For the in vivo tests, Swiss mice were treated with 125, 250 or 500 mg/kg of extract injected intraperitoneally. Antigenotoxic effects of the extract were measured before and after cyclophosphamide treatment. An absence of genotoxic effects was observed both in vitro and in vivo. In the antigenotoxic studies, no significant difference was observed between the treatments and the positive control, indicating that the extracts did not protect against damage caused by cyclophosphamide. Hydroalcoholic extracts of J. triqueter did not provoke DNA damage at concentrations and doses normally used for antileishmanial treatment; however, they reduced apoptotic cell death and induced necrotic cell death.

Sugarcane vinasse as organo-mineral fertilizers feedstock: Opportunities and environmental risks.

Fertigation using sugarcane vinasse is expected in the sugar and alcohol industries; however, its indiscriminate practice can trigger soil salinization and contamination of water sources. This review article appraises the vinasse use as a precursor material in producing organo-mineral fertilizers. Vinasse use could be an alternative for the increased demand for organo-mineral fertilizers. In that case, the vinasse reuse would be maintained but through controlled practices and lower environmental impact. The state-of-art points to possible advantages associated with the vinasse conversion into organo-mineral fertilizers, such as ease of transport and handling, low variability in its composition, and lower risks of soil and water resources contamination. It has been summarized and critically discussed the past ten years (2011-2021, total number papers revised: 175) of research data about vinasse composition, along with the limitations to be overcome in the near future to enable the application of organo-mineral fertilizers. Possible nutrients supplementation beyond those already present in vinasse composition would depend on the crop requirement, and the impact on the soil biota and integrity should be better understood. The aspects discussed along the manuscript would be aligned with circular economy principles, converting a residue (vinasse) into a potential resource for agricultural activities, including sugar and alcohol industries. After all, although promising, obtaining organo-mineral fertilizers from vinasse must be empirically validated and its feasibility proven by comparative studies between fertigation and the use of organo-mineral fertilizers.

Wien effect in interfacial water dissociation through proton-permeable graphene electrodes.

Strong electric fields can accelerate molecular dissociation reactions. The phenomenon known as the Wien effect was previously observed using high-voltage electrolysis cells that produced fields of about 107 V m-1, sufficient to accelerate the dissociation of weakly bound molecules (e.g., organics and weak electrolytes). The observation of the Wien effect for the common case of water dissociation (H2O [Formula: see text] H+ + OH-) has remained elusive. Here we study the dissociation of interfacial water adjacent to proton-permeable graphene electrodes and observe strong acceleration of the reaction in fields reaching above 108 V m-1. The use of graphene electrodes allows measuring the proton currents arising exclusively from the dissociation of interfacial water, while the electric field driving the reaction is monitored through the carrier density induced in graphene by the same field. The observed exponential increase in proton currents is in quantitative agreement with Onsager's theory. Our results also demonstrate that graphene electrodes can be valuable for the investigation of various interfacial phenomena involving proton transport.

Forage conservation efficiency and lactation response to bahiagrass conserved as barn-stored hay, outdoor-stored hay, or baleage.

A study was conducted to determine the effect of conserving bahiagrass as outdoor-stored hay (OSH), barn-stored hay (BSH), or baleage (BAL) on storage losses and lactation performance by Holstein cows. For baleage production, bahiagrass forage was cut and allowed to dry for 20 h in windrows, baled (1.2 × 1.4 m), and individually wrapped with white stretch film. Forage cut on the same day was dried to hay stage, baled (1.2 × 1.6 m round bales), and stored either outdoors (OSH) or in an enclosed hay barn (BSH). Bales were core sampled and weighed at harvest and again following a 6-mo storage period. At the end of the storage period, 30 multiparous mid-lactation Holstein cows [39.2 ± 5.6 kg of 3.5% fat-corrected milk and 142 ± 27 d in milk (DIM)] were stratified according to milk yield and DIM and randomly assigned to 1 of the 3 forage conservation treatments. Cows were trained to Calan feeding gates and were offered a common partial mixed ration in a 10-d covariate period followed by a 42-d treatment feeding period. Forage dry matter losses were highest for OSH, but were similar between BSH and baleage. Conservation method had little effect on poststorage crude protein levels, but acid detergent fiber and neutral detergent fiber concentrations were higher in OSH than in either BSH or BAL, which resulted in a 12.8% depression in net energy for OSH compared with the other treatments. Dry matter intake (20.5 vs. 22.1 kg/d) and milk yield (28.2 vs. 30.2 kg/d) tended to be lower for OSH than for BSH. Lactation performance was similar between BSH and BAL: 29.6 versus 28.7 kg/d of fat-corrected milk, respectively. No differences in milk composition, feed efficiency, body weight, or body condition score change related to conservation system were observed. In this study, dry matter losses and lactation performance from bahiagrass conserved as baleage were similar to that of similar forage stored indoors as hay, whereas hay stored outside resulted in less satisfactory forage quality.

Precision Design of Antimicrobial Surfaces.

The overall expectation from an antimicrobial surface has been high considering the need for efficiency in preventing the attachment and growth of pathogenic microbes, durability, safety to both humans and environment as well as cost-effectiveness. To date, antimicrobial surface design has been mostly conducted liberally, without rigorous consideration of establishing robust structure-activity relationships for each design strategy or of the use intended for a specific antimicrobial material. However, the variability among the domain bacteria, which is the most diverse of all, alongside the highly dynamic nature of the bacteria-surface interface have taught us that the likelihood of finding universal antimicrobial surfaces is low. In this perspective we discuss some of the current hurdles faced by research in this promising field, emphasizing the relevance and complexity of probing the bacteria-surface interface, and explain why we feel it would greatly benefit from a more streamlined ad-hoc approach.

Influence of calcium and phosphorus feeding on markers of bone metabolism in transition cows.

A study was carried out to verify the effect of Ca and P levels on production, digestibility, and serum bone metabolism biomarkers in dairy cows. Fifty-two nonlactating multiparous cows (>or=3 lactations) were confined in a free-stall barn approximately 20 d before calving. A standard close-up diet was fed to cows once daily until d 2 postpartum. Cows were randomly assigned to 1 of 4 dietary treatments arranged in a 2 x 2 factorial approach averaging 0.64% Ca for high Ca (HCa), 0.46% Ca for low Ca (LCa), 0.47% P for high P (HP), and 0.38% P for low P (LP) on a dry matter basis. Experimental diets were fed twice daily from 3 d in milk (DIM) until 31 DIM. Intake and milk yield were recorded daily. Milk samples were collected on d 28, 29, and 30 postpartum for components analyses. Blood samples were drawn 10 d before expected calving, at calving, and at 15 and 30 DIM for serum analyses of osteocalcin, a biomarker of bone accretion, and pyridinoline, a biomarker of bone resorption. Total fecal collection was conducted when cows in a block averaged 20 DIM. Intake and production traits were not significantly affected by any of the dietary treatments. Cows averaged nearly 21 kg/d dry matter intake and 44 kg/d milk yield from 6 to 31 DIM. There were no significant differences across treatments in body weight or body condition score loss. Phosphorus intake, P fecal output, P digestibility, and P apparent absorption were affected by dietary P content. Calcium intake was higher with HCa, but Ca fecal output, digestibility, and apparent absorption showed an interaction between dietary Ca and dietary P. Calcium fecal output was 100.6 g/d for cows fed HCaHP, intermediate for cows on the HCaLP diet (89 g/d), and similar among cows fed the 2 LCa diets (70 g/d with LCaHP and 75 with LCaLP). There was no significant effect of Ca or P on osteocalcin measurements. Pyridinoline concentrations were affected by dietary Ca levels and tended to have a significant dietary Ca x dietary P interaction. Phosphorus apparent digestibility occurred independently of dietary Ca levels. Results of this study suggest that more bone was mobilized in cows fed LCa diets, but excess dietary P caused greater and prolonged bone mobilization regardless of dietary Ca content.

Influence of contact configuration and lubricating conditions on the microtriboactivity of the zirconia-Ti6Al4V pair used in dental applications.

Loosening and fracture of implanted dental crowns is a consequence of relative micromovements between the zirconia abutment and the titanium alloy of the implant, in a biochemical aggressive environment. Thus, it is important to establish the in vitro tribological testing conditions that better mimics such environment. The present work aims to evaluate the effect of ball-on-plate tests configuration on the tribological behavior of ZrO2/Ti6Al4V pair in dry and lubricated conditions, using different lubricants: water, artificial saliva solution and human saliva. Ceramic balls sliding on metallic plates (TiPlate) and metallic balls sliding on ceramic plates (TiBall) were tested and the coefficient of friction (CoF) and wear response was monitored trough nanotribological tests. Open circuit potential was also measured during the tests carried out in saline solution (artificial saliva) to access the tribochemical response. The wear mechanisms were evaluated by scanning electron microscopy and atomic force microscopy analysis. Relevant differences were found between the two configurations, with and without the presence of human saliva: TiPlate presented always a higher CoF than TiBall, which may have resulted from differences in the degradation and regeneration processes of the titanium passive film during sliding. TiBall demonstrated to be the best choice to reproduce the in vivo conditions, since the metallic surface contacts permanently with zirconia, impairing the titanium repassivation. Regarding the effect of the lubricants, it was observed that human saliva had a protective action of the surfaces, leading to the lowest CoF among the lubricants used (0.19 ±â€¯0.05 for TiBall and 0.35 ±â€¯0.08 for TiPlate) and neglectable wear.

CYP17 inhibitors for prostate cancer treatment--an update.

It is almost 70 years since the discovery by Huggins et al. that androgens are essential for prostate cancer (PC) growth and progression, and there has been about 30 years experience using ketoconazole for PC therapy. Since then we have come a long way in learning about the disease and developing new strategies to approach it, among which is cytochrome 17alpha-hydroxylase-C(17,20)-lyase (CYP17) inhibition. This review focuses on the efforts to find prospective CYP17 inhibitors, both steroidal and nonsteroidal, in the absence of a 3D structure of the enzyme. It covers almost 4 decades of literature with highlights on the most significant achievements in this area, providing insight into PC pathophysiology, management and treatment options.

[Recurrent acute liver toxicity from intravenous methylprednisolone]. / Toxicidad hepática recurrente secundaria a metilprednisolona intravenosa.

Adverse drug reactions (hepatotoxicity) are a frequent cause of acute liver injury with a wide clinical and histological spectrum. An early recognition of drug-related liver disease has been considered essential in clinical practice due to potential risks. In most cases exposure discontinuation improves the clinical picture.Steroids are used in a variety of clinical settings. However, intravenous steroids have rarely been associated with hepatotoxicity. We report the case of a middle-aged woman with multiple sclerosis who received a bolus of methylprednisolone on three occasions for the management of relapsing disease, with the development of repeated episodes of elevated liver enzymes after corticoid administration. In the third episode a liver biopsy was performed, which showed acute hepatitis with bridging necrosis; such histological picture has not been described before in patients treated with intravenous steroids.

[Hepatic encephalopathy secondary to porto-systemic shunt satisfactorily treated with interventionist radiology]. / Encefalopatía hepática secundaria a la existencia de un shunt portosistémico tratada satisfactoriamente mediante radiología intervencionista.

Hepatic encephalopathy is a reversible state of altered cognition that may occur in patients with acute or chronic liver disease or porto-systemic shunt, and in which known neurological or psychiatric signs may develop. Nitrogenated substances from intestinal digestion reach the brain without being cleared by their passage through the liver due to the presence of porto-systemic shunt. We report two cases of patients with porto-systemic shunt diagnosed with recurrent chronic hepatic encephalopathy refractory to conventional medical treatment. They were satisfactorily treated with shunt embolization using interventionist radiology techniques.

Effect of scraping frequency in a freestall barn on volatile nitrogen loss from dairy manure.

The objective of this investigation was to evaluate the effect of scraping frequency (2x vs. 6x daily) on N volatilization from manure on the floor of a dairy free-stall barn. Three trials (crossover design) were conducted in the summers of 2001 and 2002, and in the winter of 2003. Nitrogen volatilization was estimated from the change in the N:P ratio in excreta at the time of excretion to the time when manure was scraped from the barn. Total N loss was considered a maximum estimate of NH3-N loss, because small amounts of nonammonia N may be volatilized. Nitrogen was determined after manure subsamples were lyophilized; P content was measured by direct current emission spectroscopy of ashed subsamples of manure. Lactating dairy cows were fed high-protein (18.5 to 19.3% crude protein), alfalfa-based diets. Average milk yield was 31.9 (SD = 7.4) kg/d. Scraping frequency had no effect on N loss in summer 2001. An average of 41% of excreted N, or 238 +/- 19.0 g of N/d per cow, was volatilized. For the trial in summer 2002, nitrogen volatilization was reduced from 50% of the excreted N with 2x to 46.7% with 6x, equivalent to 265 and 248 g of N lost/d per cow, respectively. Scraping had no effect on N volatilization during the winter trial. An average of 17.7% of excreted N was volatilized during the winter, equivalent to 109 +/- 11.0 g of N lost/d per cow. Scraping frequency of manure had little or no effect on N loss from manure in a freestall barn. Nitrogen loss during the winter was less than half of the loss during the summer.