Ground-Based Mobile Measurements to Track Urban Methane Emissions from Natural Gas in 12 Cities across Eight Countries.

To mitigate methane emission from urban natural gas distribution systems, it is crucial to understand local leak rates and occurrence rates. To explore urban methane emissions in cities outside the U.S., where significant emissions were found previously, mobile measurements were performed in 12 cities across eight countries. The surveyed cities range from medium size, like Groningen, NL, to large size, like Toronto, CA, and London, UK. Furthermore, this survey spanned across European regions from Barcelona, ES, to Bucharest, RO. The joint analysis of all data allows us to focus on general emission behavior for cities with different infrastructure and environmental conditions. We find that all cities have a spectrum of small, medium, and large methane sources in their domain. The emission rates found follow a heavy-tailed distribution, and the top 10% of emitters account for 60-80% of total emissions, which implies that strategic repair planning could help reduce emissions quickly. Furthermore, we compare our findings with inventory estimates for urban natural gas-related methane emissions from this sector in Europe. While cities with larger reported emissions were found to generally also have larger observed emissions, we find clear discrepancies between observation-based and inventory-based emission estimates for our 12 cities.

Clinician Perspectives on Caring for Dying Patients During the Pandemic : A Mixed-Methods Study.

BACKGROUND: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has affected the hospital experience for patients, visitors, and staff. OBJECTIVE: To understand clinician perspectives on adaptations to end-of-life care for dying patients and their families during the pandemic. DESIGN: Mixed-methods embedded study. (ClinicalTrials.gov: NCT04602520). SETTING: 3 acute care medical units in a tertiary care hospital from 16 March to 1 July 2020. PARTICIPANTS: 45 dying patients, 45 family members, and 45 clinicians. INTERVENTION: During the pandemic, clinicians continued an existing practice of collating personal information about dying patients and "what matters most," eliciting wishes, and implementing acts of compassion. MEASUREMENTS: Themes from semistructured clinician interviews that were summarized with representative quotations. RESULTS: Many barriers to end-of-life care arose because of infection control practices that mandated visiting restrictions and personal protective equipment, with attendant practical and psychological consequences. During hospitalization, family visits inside or outside the patient's room were possible for 36 patients (80.0%); 13 patients (28.9%) had virtual visits with a relative or friend. At the time of death, 20 patients (44.4%) had a family member at the bedside. Clinicians endeavored to prevent unmarked deaths by adopting advocacy roles to "fill the gap" of absent family and by initiating new and established ways to connect patients and relatives. LIMITATION: Absence of clinician symptom or wellness metrics; a single-center design. CONCLUSION: Clinicians expressed their humanity through several intentional practices to preserve personalized, compassionate end-of-life care for dying hospitalized patients during the SARS-CoV-2 pandemic. PRIMARY FUNDING SOURCE: Canadian Institutes of Health Research and Canadian Critical Care Trials Group Research Coordinator Fund.

Organ Donation at the End of Life: Experiences From the 3 Wishes Project.

PURPOSE: The 3 Wishes Project (3WP) promotes holistic end-of-life care in the intensive care unit (ICU) to honor dying patients, support families, and encourage clinician compassion. Organ donation is a wish that is sometimes made by, or on behalf of, critically ill patients. Our objective was to describe the interface between the 3WP and organ donation as experienced by families, clinicians, and organ donation coordinators. METHODS: In a multicenter evaluation of the 3WP in 4 Canadian ICUs, we conducted a thematic analysis of transcripts from interviews and focus groups with clinicians, organ donation coordinators, and families of dying or died patients for whom donation was considered. RESULTS: We analyzed transcripts from 26 interviews and 2 focus groups with 18 family members, 17 clinicians, and 6 organ donation coordinators. The central theme describes the mutual goals of the 3WP and organ donation-emphasizing personhood and agency across the temporal continuum of care. During family decision-making, conversations encouraged by the 3WP can facilitate preliminary discussions about donation. During preparation for donation, memory-making activities supported by the 3WP redirect focus toward personhood. During postmortem family care, the 3WP supports families, including when donation is unsuccessful, and highlights aspirational pursuits of donation while encouraging reflections on other fulfilled wishes. CONCLUSIONS: Organ donation and the 3WP provide complementary opportunities to engage in value-based conversations during the dying process. The shared values of these programs may help to incorporate organ donation and death into a person's life narrative and incorporate new life into a person's death narrative.

Scale-up and sustainability of a personalized end-of-life care intervention: a longitudinal mixed-methods study.

BACKGROUND: Scaling-up and sustaining healthcare interventions can be challenging. Our objective was to describe how the 3 Wishes Project (3WP), a personalized end-of-life intervention, was scaled-up and sustained in an intensive care unit (ICU). METHODS: In a longitudinal mixed-methods study from January 12,013 - December 31, 2018, dying patients and families were invited to participate if the probability of patient death was > 95% or after a decision to withdraw life support. A research team member or bedside clinician learned more about each of the patients and their family, then elicited and implemented at least 3 personalized wishes for patients and/or family members. We used a qualitative descriptive approach to analyze interviews and focus groups conducted with 25 clinicians who cared for the enrolled patients. We used descriptive statistics to summarize patient, wish, and clinician characteristics, and analyzed outcome data in quarters using Statistical Process Control charts. The primary outcome was enrollment of terminally ill patients and respective families; the secondary outcome was the number of wishes per patient; tertiary outcomes included wish features and stakeholder involvement. RESULTS: Both qualitative and quantitative analyses suggested a three-phase approach to the scale-up of this intervention during which 369 dying patients were enrolled, having 2039 terminal wishes implemented. From a research project to clinical program to an approach to practice, we documented a three-fold increase in enrolment with a five-fold increase in total wishes implemented, without a change in cost. Beginning as a study, the protocol provided structure; starting gradually enabled frontline staff to experience and recognize the value of acts of compassion for patients, families, and clinicians. The transition to a clinical program was marked by handover from the research staff to bedside staff, whereby project catalysts mentored project champions to create staff partnerships, and family engagement became more intentional. The final transition involved empowering staff to integrate the program as an approach to care, expanding it within and beyond the organization. CONCLUSIONS: The 3WP is an end-of-life intervention which was implemented as a study, scaled-up into a clinical program, and sustained by becoming integrated into practice as an approach to care.

Compassionate End-of-Life Care: Mixed-Methods Multisite Evaluation of the 3 Wishes Project.

Background: The 3 Wishes Project (3WP) is an end-of-life program that aims to honor the dignity of dying patients by creating meaningful patient- and family-centered memories while promoting humanistic interprofessional care. Objective: To determine whether this palliative intervention could be successfully implemented-defined as demonstrating value, transferability, affordability, and sustainability-beyond the intensive care unit in which it was created. Design: Mixed-methods formative program evaluation. (ClinicalTrials.gov: NCT04147169). Setting: 4 North American intensive care units. Participants: Dying patients, their families, clinicians, hospital managers, and administrators. Intervention: Wishes from dying patients, family members, and clinicians were elicited and implemented. Measurements: Patient characteristics and processes of care; the number, type, and cost of each wish; and semistructured interviews and focus groups with family members, clinicians, and managers. Results: A total of 730 patients were enrolled, and 3407 wishes were elicited. Qualitative data were gathered from 75 family members, 72 clinicians, and 20 managers or hospital administrators. Value included intentional comforting of families as they honored the lives and legacies of their loved ones while inspiring compassionate clinical care. Factors promoting transferability included family appreciation and a collaborative intensive care unit culture committed to dignity-conserving end-of-life care. Staff participation evolved from passive support to professional agency. Program initiation required minimal investment for reusable materials; thereafter, the mean cost was $5.19 (SD, $17.14) per wish. Sustainability was demonstrated by the continuation of 3WP at each site after study completion. Limitation: This descriptive formative evaluation describes tertiary care center-specific experiences rather than aiming for generalizability to all jurisdictions. Conclusion: The 3WP is a transferrable, affordable, and sustainable program that provides value to dying patients, their families, clinicians, and institutions. Primary Funding Source: Greenwall Foundation.

Principles Guiding Nonpandemic Critical Care Research During a Pandemic.

OBJECTIVES: To describe the importance of critical care clinical research that is not pandemic-focused during pandemic times; outline principles to assist in the prioritization of nonpandemic research during pandemic times; and propose a guiding framework for decisions about whether, when and how to continue nonpandemic research while still honoring the moral and scientific imperative to launch research that is pandemic-focused. DESIGN/DATA SOURCES: Using in-person, email, and videoconference exchanges, we convened an interprofessional clinical research group, conducted a literature review of empirical studies, ethics documents and expert commentaries (2010 to present), and viewed traditional and social media posts (March 2020 to May 2020). Stakeholder consultation involved scientific, ethics, clinical, and administrative leaders. SETTING: Clinical research in the ICU. PATIENTS: Patients with and without coronavirus disease 2019. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: While clinical research should be prioritized to advantage patients with coronavirus disease 2019 in order to care for affected patients, it ideally would not unduly disadvantage patients without coronavirus disease 2019. Thus, timely, rigorous, relevant, and ethical clinical research is needed to improve the care and optimize outcomes for both patients with and without coronavirus disease 2019, acknowledging how many studies that are not exclusively focused on coronavirus disease 2019 remain relevant to patients with coronavirus disease 2019. Considerations to continue nonpandemic-focused research include the status of the pandemic, local jurisdictional guidance, capacity and safety of bedside and research personnel, disposition of patients already enrolled in nonpandemic studies, analyzing characteristics of each nonpandemic-focused study, research oversight, and final reporting requirements. CONCLUSIONS: Deliberation about continuing nonpandemic research should use objective, transparent criteria considering several aspects of the research process such as bedside and research staff safety, infection control, the informed consent model, protocol complexity, data collection, and implementation integrity. Decisions to pause or pursue nonpandemic research should be proportionate, transparent, and revisited as the pandemic abates.

Building organizational compassion among teams delivering end-of-life care in the intensive care unit: The 3 Wishes Project.

BACKGROUND: The 3 Wishes Project is a semistructured program that improves the quality of care for patients dying in the intensive care unit by eliciting and implementing wishes. This simple intervention honors the legacy of patients and eases family grief, forging human connections between family members and clinicians. AIM: To examine how the 3 Wishes Project enables collective patterns of compassion between patients, families, clinicians, and managerial leaders in the intensive care unit. DESIGN: Using a qualitative descriptive approach, interviews and focus groups were used to collect data from family members of dying patients, clinicians, and institutional leaders. Unconstrained directed qualitative content analysis was performed using Organizational Compassion as the analytic framework. SETTING/PARTICIPANTS: Four North American intensive care units, participants were 74 family members of dying patients, 72 frontline clinicians, and 20 managerial leaders. RESULTS: The policies and processes of the 3 Wishes Project exemplify organizational compassion by supporting individuals in the intensive care unit to collectively notice, feel, and respond to suffering. As an intervention that enables and empowers clinicians to engage in acts of kindness to enhance end-of-life care, the 3 Wishes Project is particularly well situated to encourage collective responses to suffering and promote compassion between patients, family members, and clinicians. CONCLUSIONS: Examining the 3 Wishes Project through the lens of organizational compassion reveals the potential of this program to cultivate the capacity for people to collectively notice, feel, and respond to suffering. Our data document multidirectional demonstrations of compassion between clinicians and family members, forging the type of human connections that may foster resilience.

Expanding the 3 Wishes Project for compassionate end-of-life care: a qualitative evaluation of local adaptations.

BACKGROUND: The 3 Wishes Project (3WP) is an end-of-life program that honors the dignity of dying patients by fostering meaningful connections among patients, families, and clinicians. Since 2013, it has become embedded in the culture of end-of-life care in over 20 ICUs across North America. The purpose of the current study is to describe the variation in implementation of 3WP across sites, in order to ascertain which factors facilitated multicenter implementation, which factors remain consistent across sites, and which may be adapted to suit local needs. METHODS: Using the methodology of qualitative description, we collected interview and focus group data from 85 clinicians who participated in the successful initiation and sustainment of 3WP in 9 ICUs. We describe the transition between different models of 3WP implementation, from core clinical program to the incorporation of various research activities. We describe various sources of financial and in-kind resources accessed to support the program. RESULTS: Beyond sharing a common goal of improving end-of-life care, sites varied considerably in organizational context, staff complement, and resources. Despite these differences, the program was successfully implemented at each site and eventually evolved from a clinical or research intervention to a general approach to end-of-life care. Key to this success was flexibility and the empowerment of frontline staff to tailor the program to address identified needs with available resources. This adaptability was fueled by cross-pollination of ideas within and outside of each site, resulting in the establishment of a network of like-minded individuals with a shared purpose. CONCLUSIONS: The successful initiation and sustainment of 3WP relied on local adaptations to suit organizational needs and resources. The semi-structured nature of the program facilitated these adaptations, encouraged creative and important ways of relating within local clinical cultures, and reinforced the main tenet of the program: meaningful human connection at the end of life. Local adaptations also encouraged a team approach to care, supplementing the typical patient-clinician dyad by explicitly empowering the healthcare team to collectively recognize and respond to the needs of dying patients, families, and each other. TRIAL REGISTRATION: NCT04147169 , retrospectively registered with clinicaltrials.gov on October 31, 2019.

Antimethanogenic effects of nitrate supplementation in cattle: A meta-analysis.

Supplementing a diet with nitrate is regarded as an effective and promising methane (CH4) mitigation strategy by competing with methanogens for available hydrogen through its reduction of ammonia in the rumen. Studies have shown major reductions in CH4 emissions with nitrate supplementation, but with large variation in response. The objective of this study was to quantitatively investigate the effect of dietary nitrate on enteric CH4 production and yield and evaluate the variables with high potential to explain the heterogeneity of between-study variability using meta-analytical models. A data set containing 56 treatments from 24 studies was developed to conduct a meta-analysis. Dry matter (DM) intake, nitrate dose (g/kg of DM), animal body weight, roughage proportion of diet, dietary crude protein and neutral detergent fiber content, CH4 measurement technique, and type of cattle (beef or dairy) were considered as explanatory variables. Average DM intake and CH4 production for dairy cows (16.2 ± 2.93 kg/d; 311 ± 58.8 g/d) were much higher than for beef cattle (8.1 ± 1.57 kg/d; 146 ± 50.9 g/d). Therefore, a relative mean difference was calculated and used to conduct random-effect and mixed-effect model analysis to eliminate the large variations between types of animal due to intake. The final mixed-effect model for CH4 production (g of CH4/d) had 3 explanatory variables and included nitrate dose, type of cattle, and DM intake. The final mixed-effect model for CH4 yield (g of CH4/kg of DM intake) had 2 explanatory variables and included nitrate dose and type of cattle. Nitrate effect sizes on CH4 production (dairy: -20.4 ± 1.89%; beef: -10.1 ± 1.52%) and yield (dairy: -15.5 ± 1.15%; beef: -8.95 ± 1.764%) were significantly different between the 2 types of cattle. When data from slow-release nitrate sources were removed from the analysis, there was no significant difference in type of cattle anymore for CH4 production and yield. Nitrate dose enhanced the mitigating effect of nitrate on CH4 production and yield by 0.911 ± 0.1407% and 0.728 ± 0.2034%, respectively, for every 1 g/kg of DM increase from its mean dietary inclusion (16.7 g/kg of DM). An increase of 1 kg of DM/d in DM intake from its mean dietary intake (11.1 kg of DM/d) decreased the effect of nitrate on CH4 production by 0.691 ± 0.2944%. Overall, this meta-analysis demonstrated that nitrate supplementation reduces CH4 production and yield in a dose-dependent manner, and that elevated DM intake decreases the effect of nitrate supplementation on CH4 production. Furthermore, the stronger antimethanogenic effect on CH4 production and yield in dairy cows than in beef steers could be related to use of slow-release nitrate in beef cattle.

Acute and chronic toxicity of neonicotinoid and butenolide insecticides to the freshwater amphipod, Hyalella azteca.

Neonicotinoids are the most widely used insecticides in the world. They are preferentially toxic to insects while displaying a low toxicity toward vertebrates, and this selective toxicity has resulted in the rapid and ubiquitous use of these compounds. However, neonicotinoids have been detected in agricultural surface waters and are known to cause adverse effects in non-target aquatic organisms. A wide range of toxicity has been reported for aquatic crustaceans, but most of the studies focus on the acute effects of imidacloprid, and few data are available regarding chronic effects of other neonicotinoids or neonicotinoid replacements (e.g., butenolides). The objective of this study was to assess the acute and chronic toxicity of six neonicotinoids (imidacloprid, thiamethoxam, acetamiprid, clothianidin, thiacloprid, and dinotefuran) and one butenolide (flupyradifurone) to the freshwater amphipod Hyalella azteca. Chronic (28-d), water-only, static-renewal tests were conducted. Survival was assessed weekly, and growth was measured at the end of the exposure. Effects of neonicotinoids varied depending on the compound. Acute (7-d) LC50s were 4.0, 4.7, 60, 68, 230, and 290 µg/L for clothianidin, acetamiprid, dinotefuran, thiacloprid, imidacloprid, and thiamethoxam, respectively. Chronic (28-d) survival and growth were reduced at similar concentrations to acute (7-d) survival for thiamethoxam, acetamiprid, clothianidin, and dinotefuran. However, chronic survival and growth of amphipods exposed to imidacloprid and thiacloprid were reduced at lower concentrations than acute survival, with respective 28-d LC50s of 90 and 44 µg/L, and EC50s of 4 and 3 µg/L. Flupyradifurone was intermediate in toxicity compared to the neonicotinoids: 7-d LC50, 28-d LC50, and 28-d EC50 were 26, 20, and 16 µg/L, respectively. The concentrations of imidacloprid and clothianidin reported for North American surface waters fall within the effect ranges observed in this study, indicating the potential for these compounds to cause adverse effects to indigenous populations of H. azteca.

Modelling cumulative egg production in laying hens and parent stocks of broiler chickens using classical growth functions.

1. The objective of the present study is to introduce fresh insight into modelling of egg production by applying classical growth functions to egg production records reported by Aviagen Management Guide to laying hens and the parent stock of broiler chickens. 2. The functions (monomolecular, logistic, Gompertz, Richards and Morgan) were fitted using nonlinear regression procedures of SAS software, and their performance was assessed using goodness-of-fit statistics (coefficient of determination, residual mean squares, Akaike information criterion and Bayesian information criterion). 3. Overall, except for the logistic and Gompertz, the growth functions evaluated gave an acceptable fit to the cumulative egg production curves, with the Morgan equation ranking first followed by the Richards equation. The Morgan and Richards equations provided satisfactory predictions of weekly egg yield at different egg production stages, from early to late production, whereas the least accurate estimates were obtained with the logistic equation. 4. In conclusion, classical growth functions proved feasible alternatives to fit cumulative egg production curves of laying hens and parent stock of broiler chickens, resulting in suitable statistical performance and accurate estimates of production.

An isotope dilution model for partitioning of phenylalanine and tyrosine uptake by the liver of lactating dairy cows.

An isotope dilution model to describe the partitioning of phenylalanine and tyrosine in the bovine liver was developed. The model comprises four intracellular and six extracellular pools and various flows connecting these pools and external blood. Conservation of mass principles were applied to generate the fundamental equations describing the behaviour of the system in the steady state. The model was applied to datasets from multi-catheterised dairy cattle during a constant infusion of [1-13C]phenylalanine and [2,3,5,6-2H]tyrosine tracers. Model solutions described the extraction of phenylalanine and tyrosine from the liver via the portal vein and hepatic artery. In addition, the exchange of free phenylalanine and tyrosine between extracellular and intracellular pools was explained and the hydroxylation of phenylalanine to tyrosine was estimated. The model was effective in providing information about the fates of phenylalanine and tyrosine in the liver and could be used as part of a more complex system describing amino acid metabolism in the whole animal.

Short communication: Antimethanogenic effects of 3-nitrooxypropanol depend on supplementation dose, dietary fiber content, and cattle type.

3-Nitrooxypropanol (NOP) is a promising methane (CH4) inhibitor. Recent studies have shown major reductions in CH4 emissions from beef and dairy cattle when using NOP but with large variation in response. The objective of this study was to quantitatively evaluate the factors that explain heterogeneity in response to NOP using meta-analytical approaches. Data from 11 experiments and 38 treatment means were used. Factors considered were cattle type (dairy or beef), measurement technique (GreenFeed technique, C-Lock Inc., Rapid City, SD; sulfur hexafluoride tracer technique; and respiration chamber technique), dry matter (DM) intake, body weight, NOP dose, roughage proportion, dietary crude protein content, and dietary neutral detergent fiber (NDF) content. The mean difference (MD) in CH4 production (g/d) and CH4 yield (g/kg of DM intake) was calculated by subtracting the mean of CH4 emission for the control group from that of the NOP-supplemented group. Forest plots of standardized MD indicated variable effect sizes of NOP across studies. Compared with beef cattle, dairy cattle had a much larger feed intake (22.3 ± 4.13 vs. 7.3 ± 0.97 kg of DM/d; mean ± standard deviation) and CH4 production (351 ± 94.1 vs. 124 ± 44.8 g/d). Therefore, in further analyses across dairy and beef cattle studies, MD was expressed as a proportion (%) of observed control mean. The final mixed-effect model for relative MD in CH4 production included cattle type, NOP dose, and NDF content. When adjusted for NOP dose and NDF content, the CH4-mitigating effect of NOP was less in beef cattle (-22.2 ± 3.33%) than in dairy cattle (-39.0 ± 5.40%). An increase of 10 mg/kg of DM in NOP dose from its mean (123 mg/kg of DM) enhanced the NOP effect on CH4 production decline by 2.56 ± 0.550%. However, a greater dietary NDF content impaired the NOP effect on CH4 production by 1.64 ± 0.330% per 10 g/kg DM increase in NDF content from its mean (331 g of NDF/kg of DM). The factors included in the final mixed-effect model for CH4 yield were -17.1 ± 4.23% (beef cattle) and -38.8 ± 5.49% (dairy cattle), -2.48 ± 0.734% per 10 mg/kg DM increase in NOP dose from its mean, and 1.52 ± 0.406% per 10 g/kg DM increase in NDF content from its mean. In conclusion, the present meta-analysis indicates that a greater NOP dose enhances the NOP effect on CH4 emission, whereas an increased dietary fiber content decreases its effect. 3-Nitrooxypropanol has stronger antimethanogenic effects in dairy cattle than in beef cattle.

Dietary mannoheptulose does not alter glucose or lipid metabolism in adult Labrador Retrievers.

Mannoheptulose (MH), a glycolytic inhibitor, has been preliminarily investigated as a novel functional food ingredient for dogs. This study aimed to determine the effects of dietary MH, delivered as an extract of un-ripened avocados, on fatty acid and glucose kinetics in healthy adult Labrador Retriever dogs (n = 12 dogs). The study was a double-blindcrossover with each dog receiving both dietary treatments, control (CON) and MH (400 mg/kg of diet), in random order. Glucose and glycerol plasma turnover (Ra) and oxidation (Ox) were measured in fasting and in response to repeated meal feeding ("fed") with stable isotope tracers (U-13 C-glucose, 1,1,2,3,3-D5 -glycerol) and indirect calorimetry. Palmitate Ra and Ox were examined during repeated meal feeding only using an oral bolus of U-13 C-K2 -palmitate and indirect calorimetry. MH had no discernible effect on fasting glucose Ra (677, 722 SEM 36 µmol/min, CON, MH) or Ox (107, 109 µmol/min, CON, MH SEM 10 µmol/min) or fed glucose Ra (2913, 3626 SEM 644 µmol/min, CON, MH) or Ox (951, 936 SEM 174 µmol/min, CON, MH). Glycerol Ra, an index of the rate of lipolysis, was not different between dietary treatments (Fast 162, 113 SEM 35 µmol/min CON, MH; Fed 172, 135 SEM 21 µmol/min, CON, MH). Similarly, palmitate oxidation was not impacted by MH feeding (1966, 2276 SEM 79 µmol/min, CON, MH). Together, these findings do not support MH as a novel functional food ingredient at least at the dietary dose tested.

A mechanistic model of small intestinal starch digestion and glucose uptake in the cow.

The high contribution of postruminal starch digestion (up to 50%) to total-tract starch digestion on energy-dense, starch-rich diets demands that limitations to small intestinal starch digestion be identified. A mechanistic model of the small intestine was described and evaluated with regard to its ability to simulate observations from abomasal carbohydrate infusions in the dairy cow. The 7 state variables represent starch, oligosaccharide, glucose, and pancreatic amylase in the intestinal lumen, oligosaccharide and glucose in the unstirred water layer at the intestinal wall, and intracellular glucose of the enterocyte. Enzymatic hydrolysis of starch was modeled as a 2-stage process involving the activity of pancreatic amylase in the lumen and of oligosaccharidase at the brush border of the enterocyte confined within the unstirred water layer. The Na+-dependent glucose transport into the enterocyte was represented along with a facilitative glucose transporter 2 transport system on the basolateral membrane. The small intestine is subdivided into 3 main sections, representing the duodenum, jejunum, and ileum for parameterization. Further subsections are defined between which continual digesta flow is represented. The model predicted nonstructural carbohydrate disappearance in the small intestine for cattle unadapted to duodenal infusion with a coefficient of determination of 0.92 and a root mean square prediction error of 25.4%. Simulation of glucose disappearance for mature Holstein heifers adapted to various levels of duodenal glucose infusion yielded a coefficient of determination of 0.81 and a root mean square prediction error of 38.6%. Analysis of model behavior identified limitations to the efficiency of small intestinal starch digestion with high levels of duodenal starch flow. Limitations to individual processes, particularly starch digestion in the proximal section of the intestine, can create asynchrony between starch hydrolysis and glucose uptake capacity.

Technical note: Bayesian calibration of dynamic ruminant nutrition models.

Mechanistic models of ruminant digestion and metabolism have advanced our understanding of the processes underlying ruminant animal physiology. Deterministic modeling practices ignore the inherent variation within and among individual animals and thus have no way to assess how sources of error influence model outputs. We introduce Bayesian calibration of mathematical models to address the need for robust mechanistic modeling tools that can accommodate error analysis by remaining within the bounds of data-based parameter estimation. For the purpose of prediction, the Bayesian approach generates a posterior predictive distribution that represents the current estimate of the value of the response variable, taking into account both the uncertainty about the parameters and model residual variability. Predictions are expressed as probability distributions, thereby conveying significantly more information than point estimates in regard to uncertainty. Our study illustrates some of the technical advantages of Bayesian calibration and discusses the future perspectives in the context of animal nutrition modeling.

A model of milk production in lactating dairy cows in relation to energy and nitrogen dynamics.

A generic daily time-step model of a dairy cow, designed to be included in whole-system pasture simulation models, is described that includes growth, milk production, and lactation in relation to energy and nitrogen dynamics. It is a development of a previously described animal growth and metabolism model that describes animal body composition in terms of protein, water, and fat, and energy dynamics in relation to growth requirements, resynthesis of degraded protein, and animal activity. This is further developed to include lactation and fetal growth. Intake is calculated in relation to stage of lactation, pasture availability, supplementary feed, and feed quality. Energy costs associated with urine N excretion and methane fermentation are accounted for. Milk production and fetal growth are then calculated in relation to the overall energy and nitrogen dynamics. The general behavior of the model is consistent with expected characteristics. Simulations using the model as part of a whole-system pasture simulation model (DairyMod) are compared with experimental data where good agreement between pasture, concentrate and forage intake, as well as milk production over 3 consecutive lactation cycles, is observed. The model is shown to be well suited for inclusion in large-scale system simulation models.

Utilization of macrominerals and trace elements in pregnant heifers with distinct feed efficiencies.

The objective of the study was to evaluate utilization of dietary minerals and trace elements in pregnant heifers with distinct residual feed intakes (RFI). Feed intake, body weight (BW), and body composition traits were recorded in 36 crossbred heifers over a period of 37 wk, starting shortly after weaning at 8.3 (0.10; standard deviation) mo of age with an average BW of 276 (7.8) kg. Both BW and body composition were monitored regularly throughout the study, whereas individual feed intake was assessed during the last 84 d of the trial. Data recorded were used to calculate RFI for each heifer. Heifers were ranked based on RFI and assigned to high (n=14) or low (n=10) RFI groups. After the RFI study, 24 selected heifers [age 18.2 (0.14) mo; 87.5 (4.74) d in gestation; 497 (8.5) kg of BW] were used in an indirect digestibility trial (lignin as internal marker). Heifers were fed a ration containing corn silage, haylage, and a mineral premix in which Ca, P, K, Na, Mg, S, Cu, Fe, Mn, Mo, Se, Zn, and Co were provided in the diet according to National Research Council requirements of pregnant replacement heifers. The digestibility trial lasted 1 wk, during which samples of feces were gathered twice daily, and blood and liver biopsy samples were collected on the last day. We noted no significant differences between low- and high-RFI heifers in dry matter digestibility. Apparent absorption of Cu, Zn, and Mn was increased in heifers with low RFI, and apparent absorption of Co tended to be greater for these animals. Concentrations of macrominerals and trace elements in serum of pregnant heifers were similar for both groups except for Se, which was increased in the serum of low-RFI heifers. Liver concentrations of Cu, Fe, Mn, Mo, Se, and Zn did not differ between low- and high-RFI heifers. In conclusion, whereas improved absorption of some trace elements (Cu, Zn, Mn, and Co) and increased Se serum concentration appear to be associated with superior feed efficiency in pregnant heifers, further studies are needed to investigate the causality of such relationships.

Prediction of portal and hepatic blood flow from intake level data in cattle.

Interest is growing in developing integrated postabsorptive metabolism models for dairy cattle. An integral part of linking a multi-organ postabsorptive model is the prediction of nutrient fluxes between organs, and thus blood flow. The purpose of this paper was to use a multivariate meta-analysis approach to model portal blood flow (PORBF) and hepatic venous blood flow (HEPBF) simultaneously, with evaluation of hepatic arterial blood flow (ARTBF; ARTBF=HEPBF - PORBF) and PORBF/HEPBF (%) as calculated values. The database used to develop equations consisted of 296 individual animal observations (lactating and dry dairy cows and beef cattle) and 55 treatments from 17 studies, and a separate evaluation database consisted of 34 treatment means (lactating dairy cows and beef cattle) from 9 studies obtained from the literature. Both databases had information on dry matter intake (DMI), metabolizable energy intake (MEI), body weight, and a basic description of the diet including crude protein intake and forage proportion of the diet (FP; %). Blood flow (L/h or L/kg of BW0.75/h) and either DMI or MEI (g or MJ/d or g or MJ/kg of BW0.75/d) were examined with linear and quadratic fits. Equations were developed using cow within experiment and experiment as random effects, and blood flow location as a repeated effect. Upon evaluation with the evaluation database, equations based on DMI typically resulted in lower root mean square prediction errors, expressed as a % of the observed mean (rMSPE%) and higher concordance correlation coefficient (CCC) values than equations based on MEI. Quadratic equation terms were frequently nonsignificant, and the quadratic equations did not outperform their linear counterparts. The best performing blood flow equations were PORBF (L/h)=202 (±45.6) + 83.6 (±3.11) × DMI (kg/d) and HEPBF (L/h)=186 (±45.4) + 103.8 (±3.10) × DMI (kg/d), with rMSPE% values of 17.5 and 16.6 and CCC values of 0.93 and 0.94, respectively. The residuals (predicted - observed) for PORBF/HEPBF were significantly related to the forage % of the diet, and thus equations for PORBF and HEPBF based on forage and concentrate DMI were developed: PORBF (L/h)=210 (±51.0) + 82.9 (±6.43) × forage (kg of DM/d) + 82.9 (±6.04) × concentrate (kg of DM/d), and HEPBF (L/h)=184 (±50.6) + 92.6 (±6.28) × forage (kg of DM/d) + 114.2 (±5.88) × concentrate (kg of DM/d), where rMSPE% values were 17.5 and 17.6 and CCC values were 0.93 and 0.94, respectively. Division of DMI into forage and concentrate fractions improved the joint Bayesian information criterion value for PORBF and HEPBF (Bayesian information criterion=6,512 vs. 7,303), as well as slightly improved the rMSPE and CCC for ARTBF and PORBF/HEPBF. This was despite minimal changes in PORBF and HEPBF predictions. Developed equations predicted blood flow well and can easily be used within a postabsorptive model of nutrient metabolism. Results also suggest different sensitivity of PORBF and HEPBF to the composition of DMI, and accounting for this difference resulted in improved ARTBF predictions.

Broiler responses to digestible threonine at different ages: a neural networks approach.

Three experiments were conducted with broiler chickens to evaluate the effects of digestible threonine (DThr) and crude protein (CP) on their performance at three different phases of age: 1-14, 15-28 and 29-42 days. The measured traits included the following: average daily gain (ADG), feed intake (FI), feed conversion ratio (FCR), carcass crude protein (CCP), body lipid (BL), feather weight gain (FWG), protein deposited in feather (FCP), carcass plus feather protein (CFCP), carcass Thr deposition (CDThr) and nitrogen excretion (NE). A dilution technique was used to create seven diets (with eight replicates) increasing the DThr content from 1.5 to 10 g/kg of diet for phase 1, 1.3-8.9 g/kg of diet for phase 2, and 1.2-8.2 g/kg of diet for phase 3. Data measured were imported into neural networks (NNs) to: (i) predict the measured traits in response to DThr and CP, (ii) rank the importance of DThr and CP on these traits through sensitivity analysis and (iii) find the optimal levels of DThr and CP that lead to the desired (maximum or minimum) responses. For each trait investigated, 50 different random groups of data were generated using a bootstrapping method. These 50 data groups were then used to develop 50 separate NNs which were subsequently combined to construct the final ensemble NN model. In general, accuracy of the models constructed was acceptable, although models of high (ADG, FCR, CFCP, BL, DThr and NE; 0.64 ≤ R(2)  ≤ 0.99) and low (CCP, FWG and FCP; 0.26 ≤ R(2)  ≤ 0.79) accuracy were obtained. All models developed showed the greatest sensitivity to DThr. This may be explained by the dilution technique diet preparation used in these experiments. Optimization results showed decreases in optimal values of DThr and CP with increasing age for all traits. The highest level of DThr was suggested for minimum BL, followed by minimum FCR, maximum ADG, maximum CFCP, minimum NE and maximum CCP respectively. Results showed that the optimal values of DThr for minimum FCR in phases 1-3 were 8.5, 7.4 and 6.4 g/kg of diet, while these values for maximum ADG were 8.2, 7.2 and 6.4 g/kg of diet respectively.