Xpert HIV-1 qual point-of-care testing for HIV early infant diagnosis in Tanzania: experiences and perceptions of health care workers in a 2016 study

BACKGROUND

HIV early infant diagnosis (HEID) at the centralized laboratory faces many challenges that impact the cascade of timely HEID. Point of Care (PoC) HEID has shown to reduce test turnaround times, allow for task shifting and has the potential to reduce infant mortality. We aimed at assessing the feasibility of nurse based PoC-HEID in five facilities of Mbeya region.

METHODS

We analysed data from healthcare workers at five obstetric health facilities that participated in the BABY study which enrolled mothers living with HIV and their HIV exposed infants who were followed up until 6 weeks post-delivery. Nurses and laboratory personnel were trained and performed HEID procedures using the Xpert HIV-1 Qual PoC systems. Involved personnel were interviewed on feasibility, knowledge and competency of procedures and overall impression of the use of HIV-1 Qual PoC system in clinical settings.

RESULTS

A total of 28 health care workers (HCWs) who participated in the study between 2014 and 2016 were interviewed, 23 being nurses, 1 clinical officer, 1 lab scientist and 3 lab technicians The median age was 39.5 years. Majority of the nurses (22/24) and all lab staff were confident using Gene Xpert PoC test after being trained. None of them rated Gene Xpert handling as too complicated despite minor challenges. Five HCWs (5/24) reported power cut as the most often occurring problem. As an overall impression, all interviewees agreed on PoC HEID to be used in clinical settings however, about half of them (11/24) indicated that the PoC-HEID procedures add a burden onto their routine workload.

CONCLUSION

Overall, health care workers in our study demonstrated very good perceptions and experiences of using PoC HEID. Efforts should be invested on quality training, targeted task distribution at the clinics, continual supportive supervision and power back up mechanisms to make the wide-scale adoption of nurse based PoC HEID testing a possibility.

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.

Complete Spinal Cord Injury Secondary to Serratia marcescens Spinal Epidural Abscess: A Report of Significant Neurological Improvement After a Delayed Presentation

The exact time at which neurological deficits secondary to a spinal cord injury (SCI) become permanent is unknown. However, urgent decompression within 24 hours of insult is advocated to maximize the return of function. Despite previous literature showing poor neurological recovery with intervention after 24-72 hours, multiple cases have since shown noteworthy clinical improvement following significant delays in presentation. We report the case of a 55-year-old incarcerated male who presented to our hospital with a four-week history of a complete (American Spinal Injury Association (ASIA) A) SCI after a prison altercation. The patient exhibited profound deficits of over one-month duration, and magnetic resonance imaging (MRI) revealed an epidural abscess at T7-T8 with severe cord compression and another epidural abscess at L4-L5. This prompted immediate IV antibiotic therapy. A full neurological examination at hospital admission showed a complete absence of sensation, motor, rectal tone, and rectal function below T8, indicating a grade ASIA A SCI. Blood cultures grew Serratia marcescens. After thorough deliberation, considering over a month of complete neurological deficits, it was decided that surgical intervention would be unlikely to improve the patient's clinical status. Nonetheless, after only 24 hours of IV antibiotic administration, the patient progressed from an ASIA A to B, with a return of 100% accurate, although dull, sensation below T8. Within one week, his abscesses diminished on follow-up MRI, yet T7-T8 remained under significant pressure with no further clinical improvements. Due to his unexpected improvement to an ASIA B, which then plateaued at this level, surgery was again discussed in an attempt to maximize recovery. The patient wished to proceed, even given low chances of a meaningful recovery. He subsequently underwent evacuation and decompression. Two weeks postoperatively, the patient advanced from an ASIA B to C; he remained so until discharge 46 days after presentation and 30 days after surgical decompression. This case is noteworthy within the literature due to two compelling features. Firstly, it represents a significantly delayed presentation of a complete SCI with unexpected, meaningful, and swift improvement after medication and surgical intervention. Secondly, it is one of the few documented cases of Serratia marcescens spinal epidural abscess (SEA).

A dynamic model to measure retention of solid and liquid digesta fractions in chickens fed diets with differing fibre sources

Dietary fibres impact multiple digestive processes, and insights into the effects of various types of fibre on digesta retention time are required to optimise current feed formulation systems. Therefore, the objective of this study was to apply a dynamic modelling approach to generate estimates for the retention time of solid and liquid digesta in broilers fed different fibre sources. A maize-wheat-soybean meal control diet was compared against three diets in which wheat was partially substituted with oat hulls, rice husks, or sugar beet pulp (3% w/w). Non-starch polysaccharide (NSP) digestibility was evaluated in broilers between 23 and 25 days of age (n = 60 birds/treatment) using titanium dioxide (TiO₂, 0.5 g/kg) as a marker, after feeding the experimental diets for 21 days. Digesta mean retention time (MRT) was measured in another 108 birds at 30 days of age by the administration of an oral pulse dose of chromium sesquioxide (Cr₂O₃) as solid marker and Cobalt-EDTA as liquid marker, and subsequent measurement of marker recovery in compartments of the digestive tract (n = 2 or 3 replicate birds/time point/treatment). Marker recovery models to estimate fractional passage rates for solid and liquid digesta in crop, gizzard, small intestine, and caeca compartments of the gastrointestinal tract were developed to predict MRT of solid and liquid digesta for each dietary treatment. The models were composed of a series of first-order differential equations, representing the variation of marker concentration in a compartment over time. Estimated MRT of solid and liquid digesta in the gizzard varied from 20 min for oat hulls and 34 min for rice husks diets to 14 min for sugar beet pulp and 12 min for control diets. In the caeca, liquid MRT was decreased compared to the control diet (989 min) for the sugar beet pulp diet (516 min), while it was increased for both the oat hulls and rice husks diets (≈1 500 min). Overall, these estimates are greater than those previously reported, suggesting that liquid digesta retention in the caeca previously has been underestimated. Digestibility of total NSP was increased by dietary fibre inclusion, regardless of the fibre type, although degradation of constituent sugars of NSP varied among diets. In conclusion, the inclusion of fibre sources at a low level (3% w/w) in the diet of broiler modulated retention time mainly in the gizzard and caeca, and increased digestibility of NSP.

Spinal deformity surgery is accompanied by serious complications: report from the Morbidity and Mortality Database of the Scoliosis Research Society from 2013 to 2020

PURPOSE

The Morbidity and Mortality (M&M) report of the Scoliosis Research Society (SRS) has been collected since 1965 and since 1968 submission of complications has been required of all members. Since 2009, the SRS has collected information on death, blindness, and neurological deficit, with acute infection being added in 2012 and unintentional return to the operating room (OR) being added in 2017. In this report, we use the most recent data submitted to the SRS M&M database to determine the rate of neurological deficit, blindness, acute infection, unintentional return to the OR, and death, while also comparing this information to previous reports.

METHODS

The SRS M&M database was queried for all cases from 2013 to 2020. The rates of death, vision loss, neurological deficit, acute infection, and unintentional return to the OR were then calculated and analyzed. The rates were compared to previously published data if available. Differences in complication rates between years were analyzed with Poisson regression with significance set at α = 0.05.

RESULTS

The total number of cases submitted per year varied with a maximum of 49,615 in 2018 and a minimum of 40,464 in 2020. The overall reported complication rate from 2013 to 2020 was 2.86%. The overall mortality rate ranged from 0.09% in 2018 to 0.14% in 2015. The number of patients with visual impairment ranged from 4 to 13 between 2013 and 2015 (no data on visual impairment were collected after 2015). The overall infection rate varied from 0.95 in 2020 to 1.30% in 2015. When the infection rate was analyzed based on spinal deformity group, the neuromuscular scoliosis group consistently had the highest infection rate ranging from 3.24 to 3.94%. The overall neurological deficit rate ranged from 0.74 to 0.94%, with the congenital kyphosis and dysplastic spondylolisthesis groups having the highest rates. The rates of unintentional return to the OR ranged from 1.60 to 1.79%. Multiple groups showed a statistically significant decreasing trend for infection, return to the operating room, neurologic deficit, and death.

CONCLUSIONS

Neuromuscular scoliosis had the highest infection rate among all spinal deformity groups. Congenital kyphosis and dysplastic spondylolisthesis had the highest rate of neurological deficit postoperatively. This is similar to previously published data. Contrary to previous reports, neuromuscular scoliosis did not have the highest annual death rate. Multiple groups showed a statistically significant decreasing trend in complication rates during the reporting period, with only mortality in degenerative spondylolisthesis significantly trending upwards.

LEVEL OF EVIDENCE

Level III.

Unaffected ex vivo clotting cascade by experimental hemostatic nanoparticles when introduced in the presence of recombinant tissue plasminogen activator

CONTEXT

Hemostatic nanoparticles (hNPs) have shown efficacy in decreasing intracerebral hemorrhage (ICH) in animal models and are suggested to be of use to counter tissue plasminogen activator (tPA)-induced acute ICH.

AIMS

The objective of this study was to test the ability of an hNP preparation to alter the clotting properties of blood exposed to tPA ex vivo.

MATERIALS AND METHODS

Fresh blood samples were obtained from normal male Sprague-Dawley rats (~300 g; n = 6) and prepared for coagulation assays by thromboelastography (TEG) methods. Samples were untreated, exposed to tPA, or exposed to tPA and then to hNP. TEG parameters included reaction time (R, time in minutes elapsed from test initiation to initial fibrin formation), coagulation time (K, time in minutes from R until initial clot formation), angle (α, a measure in degrees of the rate of clot formation), maximum amplitude (MA, the point when the clot reaches its MA in mm), lysis at 30 min after MA (LY30, %), and clot strength (G, dynes/cm2), an index of clot strength.

STATISTICAL ANALYSIS USED

Kruskal-Wallis test was employed to compare TEG parameters measured for untreated control samples versus those exposed to tPA and to compare tPA-exposed samples to samples treated with tPA + hNPs. Significances were inferred at P ≤ 0.05.

RESULTS

Compared to untreated samples, tPA-treated samples showed a trend toward decreased angle and G suggesting potentially clot formation rate and clot strength. The addition of hNP did not affect any of these or other measured indices.

CONCLUSIONS

The data demonstrated no hemostatic effects when the hNP was used in the presence of tPA. The lack of change in any of the TEG parameters measured in the present study may indicate limitations of the hNPs to reverse the thrombolytic cascade initiated by tPA.

Uncertain in the face of change: Lack of contingency shift awareness during extinction is associated with higher fear-potentiated startle and PTSD symptoms in children

Intolerance of uncertainty is a transdiagnostic risk factor for fear-related disorders and is associated with higher levels of anxiety in children and adolescents. It is unclear how uncertainty relates to development of psychopathology in children who have experienced trauma in early life. The present study used a fear-potentiated startle paradigm in children to examine associations between uncertainty (assessed as unawareness of a change in reinforcement during fear extinction) and symptoms of anxiety and posttraumatic stress disorder (PTSD), as well as startle potentiation to threat and safety cues. Results showed that unaware children had strong positive associations between trauma exposure and PTSD symptoms, whereas aware children did not. Uncertainty interacted with anxiety in that children who were both unaware and had higher anxiety displayed higher fear-potentiated startle to safety cues and did not show discrimination between threat and safety during fear conditioning. These results suggest that anxious children who persist in associating a threat cue with an aversive event during extinction, after repeated presentations of the no longer reinforced conditioned stimulus, may express psychophysiological phenotypes related to PTSD.

HPV Type Distribution in HIV Positive and Negative Women With or Without Cervical Dysplasia or Cancer in East Africa

Background

Women living with HIV in sub-Saharan Africa are at increased risk to develop cervical cancer (CC), which is caused by persistent infection with 13 oncogenic human papilloma viruses (HR-HPVs). It is important to accurately identify and target HIV-positive women at highest risk to develop CC for early therapeutic intervention.

Methods

A total of 2,134 HIV+ and HIV− women from South-West Tanzania were prospectively screened for cervical cancer and precancerous lesions. Women with cervical cancer (n=236), high- and low-grade squamous intraepithelial lesions (HSIL: n=68, LSIL: n=74), and without lesion (n=426) underwent high-resolution HPV genotyping.

Results

Eighty percent of women who were diagnosed with HSIL or LSIL were living with HIV. Any lesion, young age, HIV status, and depleted CD4 T cell counts were independent risk factors for HPV infections, which were predominantly caused by HR-HPV types. While multiple HR-HPV type infections were predominant in HIV+ women with HSIL, single-type infections predominated in HIV+ CC cases (p=0.0006). HPV16, 18, and 45 accounted for 85% (68/80) and 75% (82/110) of HIV+ and HIV− CC cases, respectively. Of note, HPV35, the most frequent HPV type in HSIL-positive women living with HIV, was rarely detected as a single-type infection in HSIL and cancer cases.

Conclusion

HPV16, 18, and 45 should receive special attention for molecular diagnostic algorithms during CC prevention programs for HIV+ women from sub-Saharan Africa. HPV35 may have a high potential to induce HSIL in women living with HIV, but less potential to cause cervical cancer in single-type infections.

Effects of oral anticoagulation for atrial fibrillation after spontaneous intracranial haemorrhage in the UK: a randomised, open-label, assessor-masked, pilot-phase, non-inferiority trial

BACKGROUND

Oral anticoagulation reduces the rate of systemic embolism for patients with atrial fibrillation by two-thirds, but its benefits for patients with previous intracranial haemorrhage are uncertain. In the Start or STop Anticoagulants Randomised Trial (SoSTART), we aimed to establish whether starting is non-inferior to avoiding oral anticoagulation for survivors of intracranial haemorrhage who have atrial fibrillation.

METHODS

SoSTART was a prospective, randomised, open-label, assessor-masked, parallel-group, pilot phase trial done at 67 hospitals in the UK. We recruited adults (aged ≥18 years) who had survived at least 24 h after symptomatic spontaneous intracranial haemorrhage, had atrial fibrillation, and had a CHA2DS2-VASc score of at least 2. Web-based computerised randomisation incorporating a minimisation algorithm allocated participants (1:1) to start or avoid long-term (≥1 year) full treatment dose open-label oral anticoagulation. The participants assigned to start oral anticoagulation received either a direct oral anticoagulant or vitamin K antagonist, and the group assigned to avoid oral anticoagulation received standard clinical practice (antiplatelet agent or no antithrombotic agent). The primary outcome was recurrent symptomatic spontaneous intracranial haemorrhage, and was adjudicated by an individual masked to treatment allocation. All outcomes were ascertained for at least 1 year after randomisation and assessed in the intention-to-treat population of all randomly assigned participants, using Cox proportional hazards regression adjusted for minimisation covariates. We planned a sample size of 190 participants (one-sided p=0·025, power 90%, allowing for non-adherence) based on a non-inferiority margin of 12% (or adjusted hazard ratio [HR] of 3·2). This trial is registered with ClinicalTrials.gov (NCT03153150) and is complete.

FINDINGS

Between March 29, 2018, and Feb 27, 2020, consent was obtained at 61 sites for 218 participants, of whom 203 were randomly assigned at a median of 115 days (IQR 49-265) after intracranial haemorrhage onset. 101 were assigned to start and 102 to avoid oral anticoagulation. Participants were followed up for median of 1·2 years (IQR 0·97-1·95; completeness 97·2%). Starting oral anticoagulation was not non-inferior to avoiding oral anticoagulation: eight (8%) of 101 in the start group versus four (4%) of 102 in the avoid group had intracranial haemorrhage recurrences (adjusted HR 2·42 [95% CI 0·72-8·09]; p=0·152). Serious adverse events occurred in 17 (17%) participants in the start group and 15 (15%) in the avoid group. 22 (22%) patients in the start group and 11 (11%) patients in the avoid group died during the study.

INTERPRETATION

Whether starting oral anticoagulation was non-inferior to avoiding it for people with atrial fibrillation after intracranial haemorrhage was inconclusive, although rates of recurrent intracranial haemorrhage were lower than expected. In view of weak evidence from analyses of three composite secondary outcomes, the possibility that oral anticoagulation might be superior for preventing symptomatic major vascular events should be investigated in adequately powered randomised trials.

FUNDING

British Heart Foundation, Medical Research Council, Chest Heart & Stroke Scotland.

Prehospital Tibial Intraosseous Drug Administration is Associated with Reduced Survival Following Out of Hospital Cardiac Arrest: A study for the CARES Surveillance Group

BACKGROUND

Recent reports have questioned the efficacy of intraosseous (IO) drug administration for out-of-hospital cardiac arrest (OHCA) resuscitation. Our aim was to determine whether prehospital administration of resuscitative medications via the IO route was associated with lower rates of return of spontaneous circulation (ROSC) and survival to hospital discharge than peripheral intravenous (IV) infusion in the setting of OHCA.

METHODS

We obtained data on all OHCA patients receiving prehospital IV or IO drug administration from the three most populous counties in Michigan over three years. Data was from the Michigan Cardiac Arrest Registry to Enhance Survival (CARES) database. The association between route of drug administration and outcomes was tested using a matched propensity score analysis.

RESULTS

From a total of 10,626 OHCA patients, 6869 received parenteral drugs during their prehospital resuscitation (37.8% by IO) and were included in analysis. Unadjusted outcomes were lower in patients with IO vs. IV access: 18.3% vs. 23.8% for ROSC (p < 0.001), 3.2% vs. 7.6% for survival to hospital discharge (p < 0.001), and 2.0% vs. 5.8% for favorable neurological function (p < 0.001). After adjustment, IO route remained associated with lower odds of sustained ROSC (OR 0.72, 95% CI 0.63-0.81, p < 0.001), hospital survival (OR 0.48, 95% CI 0.37-0.62, p < 0.001), and favorable neurological outcomes (OR 0.42, 95% CI 0.30-0.57, p < 0.001).

CONCLUSION

In this cohort of OHCA patients, the use of prehospital IO drug administration was associated with unfavorable clinical outcomes.

A Pilot Trial of Topical Capsaicin Cream for Treatment of Cannabinoid Hyperemesis Syndrome

OBJECTIVES

Patients with cannabinoid hyperemesis syndrome (CHS) present frequently to the emergency department. Previous case studies suggest dramatic symptomatic improvement with topical capsaicin treatment. This exploratory study examined the potential effectiveness of topical capsaicin in patients with nausea and vomiting due to a suspected CHS exacerbation.

METHODS

This was a double-blind, randomized placebo-controlled pilot trial. Adults who presented with vomiting suspected to be from CHS were eligible for enrollment. We excluded pregnant women and those with resolution of symptoms. Following randomization, topical 0.1% capsaicin or placebo cream was applied to the anterior abdomen in a uniform manner. The primary outcome was the severity of nausea on a visual analog scale (VAS) of 0 to 10 cm assessed at 30 minutes. Secondary outcomes were adverse events, occurrence of posttreatment vomiting, nausea by VAS at 60 minutes, and hospital admission.

RESULTS

This pilot trial enrolled 30 patients, 17 in the capsaicin arm and 13 in the placebo arm. One patient in the capsaicin arm did not tolerate treatment due to skin irritation. Mean ± SD nausea severity at 30 minutes was 4.1 ± 2.3 cm in the capsaicin arm and 6.1 ± 3.3 cm in the placebo arm (difference = -2.0 cm, 95% confidence interval [CI] = 0.2 to -4.2 cm). At 60 minutes, mean ± SD nausea severity was 3.2 ± 3.2 cm versus 6.4 ± 2.8 cm (difference = -3.2 cm, 95% CI = -0.9 to -5.4 cm). The percent reduction in nausea at 60 minutes from baseline was 46.0% in the capsaicin arm and 24.9% in the placebo arm (difference = 21.1%, 95% CI = -5.6% to 47.9%). A higher proportion of capsaicin group patients (29.4% vs. 0%) had complete resolution of nausea (relative risk = 3.4, 95% CI = 1.6 to 7.1).

CONCLUSION

In this pilot trial, the application of topical capsaicin cream was associated with a significant reduction in nausea at 60 minutes but not at 30 minutes and provided more complete relief of nausea.

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.

Accuracy and Operational Characteristics of Xpert Human Immunodeficiency Virus Point-of-Care Testing at Birth and Until Week 6 in Human Immunodeficiency Virus-exposed Neonates in Tanzania

Background

Point-of-care (PoC) systems for early infant diagnosis (EID) may improve timely infant human immunodeficiency virus (HIV) management. Experiences within African public health settings are limited.

Methods

We evaluated the accuracy and operational feasibility of the Xpert HIV-1 Qual for PoC-EID testing, using fresh blood and dried blood spots (DBS) samples at obstetric health facilities in Tanzania at birth and at postpartum weeks 1, 2, 3, and 6 in HIV-exposed infants. Test results were confirmed using TaqMan DBS HIV-deoxyribonucleic acid and/or plasma HIV-ribonucleic acid (RNA) testing.

Results

At week 6, 15 (2.5%) out of 614 infants were diagnosed with HIV; 10 (66.7%) of them at birth (median HIV-RNA 4570 copies/mL). At birth, the Xpert-PoC and Xpert-DBS were 100% sensitive (95% confidence intervals: PoC, 69.2–100%; DBS, 66.4–100%) and 100% specific (PoC, 92.1–100%; DBS, 88.4–100%). By week 3, 5 infants with intra/postpartum HIV-infection (median HIV-RNA 1 160 000 copies/mL) were all correctly diagnosed by Xpert. In 2 cases, Xpert-PoC testing correctly identified HIV-infection when DBS tests (Xpert and TaqMan) were negative, suggesting a greater sensitivity. In 2 infants with confirmed HIV at birth, all tests were negative at week 6, possibly because of viral suppression under nevirapine prophylaxis. Problems were reported in 183/2736 (6.7%) of Xpert-PoC tests, mostly related to power cuts (57.9%).

Conclusions

We demonstrated excellent Xpert HIV-1 Qual performance and good operational feasibility for PoC-EID testing at obstetric health facilities. Week 6 sensitivity issues were possibly related to nevirapine prophylaxis, supporting additional birth PoC-EID testing to avoid underdiagnosis.

Clinical Trials Registration

NCT02545296

Potential of Mobile Health Technology to Reduce Health Disparities in Underserved Communities

Introduction

Mobile health (mHealth) has the potential to change how patients make healthcare decisions. We sought to determine the readiness to use mHealth technology in underserved communities.

Methods

We conducted a cross-sectional survey of patients presenting with low-acuity complaints to an urban emergency department (ED) with an underserved population. Patients over the age of two who presented with low-acuity complaints were included. We conducted structured interview with each patient or parent (for minors) about willingness to use mHealth tools for guidance. Analysis included descriptive statistics and univariate analysis based on age and gender.

Results

Of 560 patients included in the survey, 80% were adults, 64% female, and 90% Black. The mean age was 28 ± 9 years for adults and 9 ± 5 years for children. One-third of patients reported no primary care physician, and 55% reported no access to a nurse or clinician for medical advice. Adults were less likely to have access to phone consultation than parents of children (odds ratio [OR] 0.49, 95% confidence interval [CI], 0.32 – 0.74), as were males compared to females (OR 0.52, 95% CI, 0.37–0.74). Most patients (96%) reported cellular internet access. Two-thirds of patients reported using online references. When asked how they would behave if an mHealth tool advised them that their current health problem was low risk, 69% of patients responded that they would seek care in an outpatient clinic instead of the ED (30%), stay home and not seek urgent medical care (28%), or use telehealth (11%).

Conclusion

In this urban community we found a large capacity and willingness to use mHealth technology in medical triage.

Application of adaptive neuro-fuzzy inference systems to estimate digestible critical amino acid requirements in young broiler chicks

This study aimed to find the digestible lysine (d.Lys), digestible sulfur amino acids (d.SAA), and digestible threonine (d.Thr) requirements to optimize body weight gain (BWG) and feed conversion ratio (FCR) via adaptive neuro-fuzzy inference systems (ANFIS) using either the Genetic algorithm (ANFIS-GA) or Particle Swarm Optimization algorithm (ANFIS-PSO) in Cobb-500 chicks from 1 to 10 d of age. The range of amino acids was 90 to 115% of the recommendations for male Cobb-500 chicks. The estimated dietary d.Lys, d.SAA, and d.Thr requirements by ANFIS-GA and ANFIS-PSO to optimize BWG were the same and were 12.10, 8.98, and 7.89 g/kg, respectively. The optimum BWG predicted by ANFIS-GA and ANFIS-PSO were 270 and 266 g, respectively for the 1 to 10 d period. The estimated dietary requirements of d.Lys, d.SAA, and d.Thr to minimize FCR at 0.995 by ANFIS-GA were 12.10, 8.98, and 7.89 g/kg, respectively. Although the estimated d.Lys and d.SAA requirements by ANFIS-PSO and ANFIS-GA were identical, the predicted d.Thr requirement by ANFIS-PSO was 0.01 g/kg higher than by ANFIS-GA to minimize FCR at 0.963. Comparison of goodness of fit in term of root mean square error revealed that the ANFIS-GA prediction was more accurate than ANFIS-PSO. This study demonstrates that the hybrid methodology of ANFIS-GA is as an effective and accurate approach to modeling and optimizing nutrient requirements.

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.

Sinusoidal function to describe the growth curve of dairy heifers

The objective of the present study is to introduce a sinusoidal function into dairy research and production by applying it to bodyweight records (from 1 to 24 months) from six dairy cow breeds reported by the Dairy Heifer Evaluation Project of Penn State Extension (USA) from 1991 to 1992. The function was evaluated with regard to its ability to describe the relationship between bodyweight and age in dairy heifers, and then compared with seven standard growth functions, namely monomolecular, logistic, Gompertz, von Bertalanffy, Richards, Schumacher and Morgan. The models were fitted to monthly bodyweight records of dairy heifers using non-linear regression to derive estimates of the parameters of each function. The models were tested for goodness of fit by using adjusted coefficient of determination, root mean square error, Akaike’s information criterion and Bayesian information criterion. Values of adjusted coefficient of determination were generally high for all models, suggesting the generally appropriate fit of the models to the data. The sinusoidal function provided the best fit of the growth curves for Brown Swiss, Guernsey and Milking Shorthorn breeds due to the lowest values of root mean square error, Akaike’s information criterion and Bayesian information criterion. According to the chosen statistical criteria, the Richards function provided the best fit for Ayrshire heifers, and the monomolecular the best for Holstein and Jersey. The least accurate estimates were obtained with the logistic. In conclusion, the sinusoidal function introduced here can be considered as an appropriate alternative to standard growth functions when modelling growth patterns in dairy heifers.

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.

A sinusoidal function and the Nelder-Mead simplex algorithm applied to growth data from broiler chickens

There has been much recent interest in mathematical developments for the analysis of growth in poultry. In this paper, we present a sinusoidal function to describe the evolution of growth as a function of time based on real life experiments. The function was evaluated with regard to its ability to describe the relationship between body weight and age in broilers and was compared to 4 standard growth functions: Gompertz, logistic, Lopez, and Richards. In order to estimate the model parameters, we adopted a global optimization method based on a direct search method instead of using gradient-based techniques. The results of this study show that both the sinusoidal function and the direct search method precisely describe the growth dynamics of broiler chickens. Fitting the growth functions to different data profiles nearly always led to the same or less maximized log-likelihood values for the sinusoidal equation, which is an indication of its superiority in describing growth data from broiler chickens.

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.

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 BW^0.75/h) and either DMI or MEI (g or MJ/d or g or MJ/kg of BW^0.75/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.

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.

Survival and Clinical Outcomes in Surgically Treated Patients With Metastatic Epidural Spinal Cord Compression: Results of the Prospective Multicenter AOSpine Study

PURPOSE

Although surgery is used increasingly as a strategy to complement treatment with radiation and chemotherapy in patients with metastatic epidural spinal cord compression (MESCC), the impact of surgery on health-related quality of life (HRQoL) is not well established. We aimed to prospectively evaluate survival, neurologic, functional, and HRQoL outcomes in patients with MESCC who underwent surgical management.

PATIENTS AND METHODS

One hundred forty-two patients with a single symptomatic MESCC lesion who were treated surgically were enrolled onto a prospective North American multicenter study and were observed at least up to 12 months. Clinical data, including Brief Pain Inventory, ASIA (American Spinal Injury Association) impairment scale, SF-36 Short Form Health Survey, Oswestry Disability Index, and EuroQol 5 dimensions (EQ-5D) scores, were obtained preoperatively, and at 6 weeks and 3, 6, 9, and 12 months postoperatively.

RESULTS

Median survival time was 7.7 months. The 30-day and 12-month mortality rates were 9% and 62%, respectively. There was improvement at 6 months postoperatively for ambulatory status (McNemar test, P < .001), lower extremity and total motor scores (Wilcoxon signed rank test, P < .001), and at 6 weeks and 3, 6, and 12 months for Oswestry Disability Index, EQ-5D, and pain interference (paired t test, P < .013). Moreover, at 3 months after surgery, the ASIA impairment scale grade was improved (Stuart-Maxwell test P = .004). SF-36 scores improved postoperatively in six of eight scales. The incidence of wound complications was 10% and 2 patients required a second surgery (screw malposition and epidural hematoma).

CONCLUSION

Surgical intervention, as an adjunct to radiation and chemotherapy, provides immediate and sustained improvement in pain, neurologic, functional, and HRQoL outcomes, with acceptable risks in patients with a focal symptomatic MESCC lesion who have at least a 3 month survival prognosis.

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.

Some novel growth functions and their application with reference to growth in ostrich

Four novel growth functions, namely, Pareto, extreme value distribution (EVD), Lomolino, and cumulative β-P distribution (CBP), are derived, and their ability to describe ostrich growth curves is evaluated. The functions were compared with standard growth equations, namely, the monomolecular, Michaelis-Menten (MM), Gompertz, Richards, and generalized MM (gMM). For this purpose, 2 separate comparisons were conducted. In the first, all the functions were fitted to 40 individual growth curves (5 males and 35 females) of ostriches using nonlinear regression. In the second, performance of the functions was assessed when data from 71 individuals were composited (570 data points). This comparison was undertaken using nonlinear mixed models and considering 3 approaches: 1) models with no random effect, 2) random effect incorporated as the intercept, and 3) random effect incorporated into the asymptotic weight parameter (Wf). The results from the first comparison showed that the functions generally gave acceptable values of R2 and residual variance. On the basis of the Akaike information criterion (AIC), CBP gave the best fit, whereas the Gompertz and Lomolino equations were the preferred functions on the basis of corrected AIC (AICc). Bias, accuracy factor, the Durbin-Watson statistic, and the number of runs of sign were used to analyze the residuals. CBP gave the best distribution of residuals but also produced more residual autocorrelation (significant Durbin-Watson statistic). The functions were applied to sample data for a more conventional farm species (2 breeds of cattle) to verify the results of the comparison of fit among functions and their applicability across species. In the second comparison, analysis of mixed models showed that incorporation of a random effect into Wf gave the best fit, resulting in smaller AIC and AIC values compared with those in the other 2 approaches. On the basis of AICc, best fit was achieved with CBP, followed by gMM, Lomolino, and Richards functions, respectively. The exponential, MM, Pareto, and EVD equations produced negative values for initial weight (W0) if left unconstrained. The Gompertz equation, in spite of having a fixed inflection point and therefore being less flexible, gave accurate estimates of both W0 and Wf and an acceptable goodness of fit favored by having fewer parameters than the other sigmoidal functions. Nevertheless, all the sigmoidal functions appeared appropriate in describing the growth trajectory of male and female ostriches to a reasonable level of accuracy.

On the analysis of Canadian Holstein dairy cow lactation curves using standard growth functions

Six classical growth functions (monomolecular, Schumacher, Gompertz, logistic, Richards, and Morgan) were fitted to individual and average (by parity) cumulative milk production curves of Canadian Holstein dairy cows. The data analyzed consisted of approximately 91,000 daily milk yield records corresponding to 122 first, 99 second, and 92 third parity individual lactation curves. The functions were fitted using nonlinear regression procedures, and their performance was assessed using goodness-of-fit statistics (coefficient of determination, residual mean squares, Akaike information criterion, and the correlation and concordance coefficients between observed and adjusted milk yields at several days in milk). Overall, all the growth functions evaluated showed an acceptable fit to the cumulative milk production curves, with the Richards equation ranking first (smallest Akaike information criterion) followed by the Morgan equation. Differences among the functions in their goodness-of-fit were enlarged when fitted to average curves by parity, where the sigmoidal functions with a variable point of inflection (Richards and Morgan) outperformed the other 4 equations. All the functions provided satisfactory predictions of milk yield (calculated from the first derivative of the functions) at different lactation stages, from early to late lactation. The Richards and Morgan equations provided the most accurate estimates of peak yield and total milk production per 305-d lactation, whereas the least accurate estimates were obtained with the logistic equation. In conclusion, classical growth functions (especially sigmoidal functions with a variable point of inflection) proved to be feasible alternatives to fit cumulative milk production curves of dairy cows, resulting in suitable statistical performance and accurate estimates of lactation traits.

Integrated animal and cropping systems in single and multi-objective frameworks for enhancing the livelihood security of farmers and agricultural sustainability in Northern India

Fast degrading and declining land, water availability, biodiversity, environment and other natural resources, together with shrinking farm returns and reduced crop productivity caused by continuous and intensive cultivation of rice-wheat systems, necessitate diversification of farming in Northern India. Integrated farming systems (IFS) involving animals (livestock, fish, etc.) and cropping (cereals, trees, etc.) are recognised as an alternative for preserving ecosystems and enhancing livelihood security. A study was therefore undertaken under Northern Indian conditions to develop IFS models for various sizes of farm and to compare these models with the existing rice-wheat system for sustainability and profitability. The IFS models were developed in single objective (using linear programming) and multi-objective (using compromise programming) frameworks. Multi-objective analysis provides deeper insight into the problem as it caters directly for the multi-faceted needs of the farmers. These parallel methodologies offer a novel approach to modelling IFS to draw different farming scenarios for comparison. The IFS strategies developed show the potential to generate a greater farm income than with existing rice-wheat cropping for all sizes of farm. The study revealed that IFS offer more perspectives for an economically viable and sustainable agriculture for typical farms in Northern India.

Quantifying body water kinetics and fecal and urinary water output from lactating Holstein dairy cows

Reliable estimates of fresh manure water output from dairy cows help to improve storage design, enhance efficiency of land application, quantify the water footprint, and predict nutrient transformations during manure storage. The objective of the study was to construct a mechanistic, dynamic, and deterministic mathematical model to quantify urinary and fecal water outputs (kg/d) from individual lactating dairy cows. The model contained 4 body water pools: reticulorumen (QRR), post-reticulorumen (QPR), extracellular (QEC), and intracellular (QIC). Dry matter (DM) intake, dietary forage, DM, crude protein, acid detergent fiber and ash contents, milk yield, and milk fat and protein contents, days in milk, and body weight were input variables to the model. A set of linear equations was constructed to determine drinking, feed, and saliva water inputs to QRR and fractional water passage from QRR to QPR. Water transfer via the rumen wall was subjected to changes in QEC and total water input to QRR. Post-reticulorumen water passage was adjusted for DM intake. Metabolic water production and respiratory cutaneous water losses were estimated with functions of heat production in the model. Water loss in urine was driven by absorbed N left after being removed via milk. Model parameters were estimated simultaneously using observed fecal and urinary water output data from lactating Holstein cows (n=670). The model was evaluated with data that were not used for model development and optimization (n=377). The observations in both data sets were related to thermoneutral conditions. The model predicted drinking water intake, fecal, urinary, and total fresh manure water output with root mean square prediction errors as a percentage of average values of 18.1, 15.6, 30.6, and 14.6%, respectively. In all cases, >97% of the prediction error was due to random variability of data. The model can also be used to determine saliva production, heat and metabolic water production, respiratory cutaneous water losses, and size of major body water pools in lactating Holstein cows under thermoneutral conditions.

A meta-analysis of the effects of dietary copper, molybdenum, and sulfur on plasma and liver copper, weight gain, and feed conversion in growing-finishing cattle

The minerals Cu, Mo, and S are essential for metabolic functions related to cattle health and performance. The interaction between Cu, Mo, and S can determine the utilization of each mineral, in particular Cu, by ruminants. A meta-analysis was performed to evaluate the effects of dietary Cu, Mo, and S and their interactions on plasma and liver Cu, ADG, and G:F in growing-finishing cattle. Data were collated from 12 published studies. The model with the best fit to data indicated plasma Cu was positively affected by dietary Cu (P < 0.01) and negatively affected by both dietary Mo (P < 0.01) and S (P < 0.01). Another model also indicated that plasma Cu concentration is positively related to Cu:Mo ratio in the diet (P < 0.01). Dietary Cu had a positive effect on liver Cu (P < 0.01), whereas Mo showed a negative effect (P < 0.05), and no effect of dietary S on liver Cu was observed (P > 0.05). Average daily gain was negatively affected by dietary Mo (P < 0.05) and S (P < 0.01) and positively affected by Cu:Mo ratio (P < 0.01), likely because an increased Cu:Mo ratio minimizes the antagonistic effect of Mo on Cu. The feed conversion ratio was negatively affected by Mo (P < 0.05) and S (P < 0.01), whereas effects of the Cu:Mo ratio and dietary Cu were not significant (P > 0.05). The interaction between S and Mo affected (P < 0.01) G:F, which was likely related to a positive response with the proper balance between these minerals. In conclusion, dietary Cu, Mo, and S and the Cu:Mo ratio caused changes in plasma Cu. Only dietary Mo and S led to a negative response in the performance of growing-finishing cattle, whereas the diet Cu:Mo ratio has a linear and quadratic effect on ADG. Nutritionists and producers need to consider with caution the supplementation of growing-finishing cattle diets with Mo and S because of their potentially adverse effects on animal performance. An appropriate Cu:Mo ratio is desirable to minimize the effects of an impaired supply of Mo on Cu metabolism and ADG.

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

An isotope dilution model for partitioning phenylalanine and tyrosine uptake by the mammary gland of the lactating dairy cow is constructed and solved in the steady state. The model contains four intracellular and four extracellular pools and conservation of mass principles are applied to generate the fundamental equations describing the behaviour of the system. The experimental measurements required for model solution are milk secretion and plasma flow rate across the gland in combination with phenylalanine and tyrosine concentrations and plateau isotopic enrichments in arterial and venous plasma and free and protein bound milk during a constant infusion of [1-(13)C]phenylalanine and [2,3,5,6-(2)H]tyrosine tracer. If assumptions are made, model solution enables determination of steady state flows for phenylalanine and tyrosine inflow to the gland, outflow from it and bypass, and flows representing the synthesis and degradation of constitutive protein and phenylalanine hydroxylation. The model is effective in providing information about the fates of phenylalanine and tyrosine in the mammary gland and could be used as part of a more complex system describing amino acid metabolism in the whole ruminant.

Alternative growth functions for predicting body, carcass, and breast weight in ducks: Lomolino equation and extreme value function

In this study, 2 alternative growth functions, the Lomolino and the extreme value function (EVF), are introduced and their ability to predict body, carcass, and breast weight in ducks evaluated. A comparative study was carried out of these equations with standard growth functions: Gompertz, exponential, Richards, and generalized Michaelis-Menten. Goodness of fit of the functions was evaluated using R(2), mean square error, Akaike information criterion, and Bayesian information criterion, whereas bias factor, accuracy factor, Durbin-Watson statistic, and number of runs of sign were the criteria used for analysis of residuals. Results showed that predictive performance of all functions was acceptable, though the Richards and exponential equations failed to converge in a few cases for both male and female ducks. Based on goodness-of-fit statistics, the Richards, Gompertz, and EVF were the best equations whereas the worst fits to the data were obtained with the exponential. Analysis of residuals indicated that, for the different traits investigated, the least biased and the most accurate equations were the Gompertz, EVF, Richards, and generalized Michaelis-Menten, whereas the exponential was the most biased and least accurate. Based on the Durbin-Watson statistic, all models generally behaved well and only the exponential showed evidence of autocorrelation for all 3 traits investigated. Results showed that with all functions, estimated final weights of males were higher than females for the body, carcass, and breast weight profiles. The alternative functions introduced here have desirable advantages including flexibility and a low number of parameters. However, because this is probably the first study to apply these functions to predict growth patterns in poultry or other animals, further analysis of these new models is suggested.