Diabetes Stigma and Psychosocial Outcomes in Adolescents and Young Adults: The SEARCH for Diabetes in Youth Study

OBJECTIVE

To examine the association between diabetes stigma, socioeconomic status, psychosocial variables, and substance use in adolescents and young adults (AYAs) with type 1 or type 2 diabetes.

RESEARCH DESIGN AND METHODS

This is a cross-sectional analysis of AYAs from the SEARCH for Diabetes in Youth study who completed a survey on diabetes-related stigma, generating a total diabetes stigma score. Using multivariable modeling, stratified by diabetes type, we examined the relationship of diabetes stigma with variables of interest.

RESULTS

Of the 1,608 AYAs who completed the diabetes-related stigma survey, 78% had type 1 diabetes, and the mean age was 21.7 years. Higher diabetes stigma scores were associated with food insecurity (P = 0.001), disordered eating (P < 0.0001), depressive symptoms (P < 0.0001), and decreased health-related (P < 0.0001) and diabetes-specific quality of life (P < 0.0001).

CONCLUSIONS

Diabetes stigma is associated with food insecurity, disordered eating, and lower psychosocial well-being.

Preconception Counseling in Women With Diabetes: The SEARCH for Diabetes in Youth Study

Preconception counseling is recommended for all women with diabetes starting at puberty to convey the importance of optimal diabetes management for maternal and fetal outcomes. This study included 622 female participants from the SEARCH for Diabetes in Youth study with a mean age of 22.2 years (range 14-35 years). Only 53.7% reported ever receiving preconception counseling, which was significantly lower among women seeing pediatric providers than those seeing adult or all-age providers. Older age and history of prior pregnancy were associated with increased odds of reporting having received preconception counseling. Identification of barriers to delivering preconception counseling to young females with diabetes and strategies to overcome them are needed to reduce the risk for pregnancy complications and adverse offspring health outcomes.

Health Care Transition to Adult Care in Type 1 Diabetes: Associations With Student and Employment Status-The SEARCH for Diabetes in Youth Study

Successful transition from a pediatric to adult diabetes care provider is associated with reduced ambulatory diabetes care visits and increased acute complications. This study aimed to determine whether the degree of independence in diabetes care and the rate of acute complications after transition to adult diabetes care were associated with individuals' student or employment status. Nonstudents were found to be less likely than students to be independent with diabetes care, and employed nonstudents were at lower risk of diabetic ketoacidosis than unemployed nonstudents. Additional support may be needed for young adults who are not students or are unemployed to improve independence and reduce the risk for acute complications.

Chronic ethanol induces a pro-inflammatory switch in interleukin-1β regulation of GABAergic signaling in the medial prefrontal cortex of male mice

Neuroimmune pathways regulate brain function to influence complex behavior and play a role in several neuropsychiatric diseases, including alcohol use disorder (AUD). In particular, the interleukin-1 (IL-1) system has emerged as a key regulator of the brain's response to ethanol (alcohol). Here we investigated the mechanisms underlying ethanol-induced neuroadaptation of IL-1β signaling at GABAergic synapses in the prelimbic region of the medial prefrontal cortex (mPFC), an area responsible for integrating contextual information to mediate conflicting motivational drives. We exposed C57BL/6J male mice to the chronic intermittent ethanol vapor-2 bottle choice paradigm (CIE-2BC) to induce ethanol dependence, and conducted ex vivo electrophysiology and molecular analyses. We found that the IL-1 system regulates basal mPFC function through its actions at inhibitory synapses on prelimbic layer 2/3 pyramidal neurons. IL-1β can selectively recruit either neuroprotective (PI3K/Akt) or pro-inflammatory (MyD88/p38 MAPK) mechanisms to produce opposing synaptic effects. In ethanol naïve conditions, there was a strong PI3K/Akt bias leading to a disinhibition of pyramidal neurons. Ethanol dependence produced opposite IL-1 effects - enhanced local inhibition via a switch in IL-1β signaling to the canonical pro-inflammatory MyD88 pathway. Ethanol dependence also increased cellular IL-1β in the mPFC, while decreasing expression of downstream effectors (Akt, p38 MAPK). Thus, IL-1β may represent a key neural substrate in ethanol-induced cortical dysfunction. As the IL-1 receptor antagonist (kineret) is already FDA-approved for other diseases, this work underscores the high therapeutic potential of IL-1 signaling/neuroimmune-based treatments for AUD.

Diabetes Stigma and Clinical Outcomes in Adolescents and Young Adults: The SEARCH for Diabetes in Youth Study

OBJECTIVE

To examine the association between diabetes stigma and HbA1c, treatment plan and acute and chronic complications in adolescents and young adults (AYAs) with type 1 or type 2 diabetes.

RESEARCH DESIGN AND METHODS

The SEARCH for Diabetes in Youth study is a multicenter cohort study that collected questionnaire, laboratory, and physical examination data about AYAs with diabetes diagnosed in childhood. A five-question survey assessed frequency of perceived diabetes-related stigma, generating a total diabetes stigma score. We used multivariable linear modeling, stratified by diabetes type, to examine the association of diabetes stigma with clinical factors, adjusting for sociodemographic characteristics, clinic site, diabetes duration, health insurance, treatment plan, and HbA1c.

RESULTS

Of 1,608 respondents, 78% had type 1 diabetes, 56% were female, and 48% were non-Hispanic White. The mean (SD) age at study visit was 21.7 (5.1) years (range, 10-24.9). The mean (SD) HbA1c was 9.2% (2.3%; 77 mmol/mol [2.0 mmol/mol]). Higher diabetes stigma scores were associated with female sex and higher HbA1c (P < 0.01) for all participants. No significant association between diabetes stigma score and technology use was observed. In participants with type 2 diabetes, higher diabetes stigma scores were associated with insulin use (P = 0.04). Independent of HbA1c, higher diabetes stigma scores were associated with some acute complications for AYAs with type 1 diabetes and some chronic complications for AYAs with type 1 or type 2 diabetes.

CONCLUSIONS

Diabetes stigma in AYAs is associated with worse diabetes outcomes and is important to address when providing comprehensive diabetes care.

Household Food Insecurity and Fear of Hypoglycemia in Adolescents and Young Adults With Diabetes and Parents of Youth With Diabetes

OBJECTIVE

To evaluate the relation between household food insecurity (HFI) and fear of hypoglycemia among young adults with type 1 and type 2 diabetes and adolescents with type 1 diabetes and their parents.

RESEARCH DESIGN AND METHODS

We analyzed cross-sectional data of 1,676 young adults with youth-onset diabetes (84% type 1, 16% type 2) and 568 adolescents (<18 years old; mean age 15.1 years) with type 1 diabetes from the SEARCH for Diabetes in Youth study. Adult participants and parents of adolescent participants completed the U.S. Household Food Security Survey Module. Adults, adolescents, and parents of adolescents completed the Hypoglycemia Fear Survey, where answers range from 1 to 4. The outcomes were mean score for fear of hypoglycemia and the behavior and worry subscale scores. Linear regression models identified associations between HFI and fear of hypoglycemia scores.

RESULTS

Adults with type 1 diabetes experiencing HFI had higher fear of hypoglycemia scores (0.22 units higher for behavior, 0.55 units for worry, 0.40 units for total; all P < 0.0001) than those without HFI. No differences by HFI status were found for adolescents with type 1 diabetes. Parents of adolescents reporting HFI had a 0.18 unit higher worry score than those not reporting HFI (P < 0.05). Adults with type 2 diabetes experiencing HFI had higher fear of hypoglycemia scores (0.19 units higher for behavior, 0.35 units for worry, 0.28 units for total; all P < 0.05) than those in food secure households.

CONCLUSIONS

Screening for HFI and fear of hypoglycemia among people with diabetes can help providers tailor diabetes education for those who have HFI and therefore fear hypoglycemia.

Genetic architecture of a composite beef cattle population

Composite breeds are widely used in the beef industry. Composites allow producers to combine desirable traits from the progenitor breeds and simplify herd management, without repeated crossbreeding and maintenance of purebreds. In this study, genomic information was used to evaluate the genetic composition and characteristics of a three-breed beef cattle composite. This composite population referred to as Composite Gene Combination (CGC) consisted of 50% Red Angus, 25% Charolais, 25% Tarentaise. A total of 248 animals were used in this study CGC (n=79), Red Angus (n=61), Charolais (n=79) and Tarentaise (n=29). All animals were genotyped with 777k HD panel. Principal component and ADMIXTURE analyses were carried out to evaluate the genetic structure of CGC animals. The ADMIXTURE revealed the proportion of Tarentaise increased to approximately 57% while Charolais decreased to approximately 5%, and Red Angus decreased to 38% across generations. To evaluate these changes in the genomic composition across different breeds and in CGC across generations runs of homozygosity (ROH) were conducted. This analysis showed Red Angus to have the highest total length of ROH segments per animal with a mean of 349.92 Mb and lowest in CGC with a mean of 141.10 Mb. Furthermore, it showed the formation of new haplotypes in CGC around the sixth generation. Selection signatures were evaluated through Fst and HapFlk analyses. Several selection sweeps in CGC were identified especially in chromosomes 5 and 14 which have previously been reported to be associated with coat color and growth traits. The study supports our previous findings that progenitor combinations are not stable over generations and that either direct or natural selection plays a role in modifying the progenitor proportions. Furthermore, the results showed that Tarentaise contributed useful attributes to the composite in a cool semi-arid environment and suggests a re-exploration of this breed's role may be warranted.

Identifying Suicide Risk in Adolescents and Young Adults With Type 1 Diabetes: Are Depression Screeners Sufficient?

OBJECTIVE

Examine the utility of suicide-risk items embedded within depression screeners for identifying the presence of suicide risk in adolescents and young adults (AYA) with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Sensitivity, specificity, and predictive value of self-report of suicide risk on the Patient Health Questionniaire-9 (PHQ-9) were compared with the pediatric psychologist-administered Columbia-Suicide Severity Rating Scale (C-SSRS) as the reference standard for AYA with type 1 diabetes seen in a multidisciplinary AYA Diabetes Program clinic.

RESULTS

Of 133 participants, 9.8% and 11.3% reported suicide risk on the PHQ-9 and C-SSRS, respectively. Sensitivity of the PHQ-9 risk item was 53.3% (95% CI 27.4%-77.7%), specificity was 95.7% (95% CI 89.9%-98.4%), positive predictive value was 61.5% (95% CI 32.3%-84.9%), and negative predictive value was 94.2% (95% CI 87.9-97.4%).

CONCLUSIONS

Depression screeners appear to under-identify AYA with type 1 diabetes who may otherwise be at risk for suicide.

Mental health comorbidities in adolescents and young adults with type 2 diabetes

BACKGROUND

Screening for mental health comorbidities is recommended in adolescents and young adults (AYAs) with diabetes. There is a paucity of data on mental health comorbidities in AYAs with type 2 diabetes (T2D).

OBJECTIVE

To assess rates of depression, suicidal ideation, and diabetes distress (DD) in AYAs with T2D overall and by sociodemographic and clinical factors.

METHODS

AYAs with T2D ages 13-21 years seen in a pediatric diabetes clinic between March 2018 and June 2019 completed the Patient Health Questionnaire-9 (PHQ-9) for depression screening and the Problem Areas in Diabetes - teen version (PAID-T) survey to assess DD. Chi-square tests were used to assess whether rates of depression and DD were associated with participant characteristics.

RESULTS

The sample consisted of 64 AYAs with T2D (58% female, mean age 15.8 ± 2.0 years, mean HbA1c 8.3% ± 2.6%, mean BMI z-score 2.2 ± 0.6, 59% on insulin). Overall, 31% of participants had high depression and/or DD. Twenty-two percent of participants reported high depressive symptoms and 9% endorsed suicidal ideation on the PHQ-9. There were no differences in rates of depression by sociodemographic factors. Twenty-three percent of participants reported high DD. Rates of DD were higher among those on insulin (p = 0.014) and on public health insurance (p = 0.014).

CONCLUSIONS

Almost 1 in 3 AYAs with T2D endorsed depression and/or DD. Our findings support the importance of mental health screening in AYAs with T2D, as well as the need for strategies to address psychological comorbidities in this population.

Screening for Mental Health Comorbidities in a Pediatric Diabetes Clinic Setting

Quality Improvement Success Stories are published by the American Diabetes Association in collaboration with the American College of Physicians and the National Diabetes Education Program. This series is intended to highlight best practices and strategies from programs and clinics that have successfully improved the quality of care for people with diabetes or related conditions. Each article in the series is reviewed and follows a standard format developed by the editors of Clinical Diabetes. The following article describes an effort to improve mental health screening of patients at a pediatric diabetes clinic in Seattle, WA.

Adapting to telemedicine in the COVID-19 era: Feasibility of dried blood spot testing for hemoglobin A1c

BACKGROUND AND AIMS

The COVID-19 pandemic has led to a rapid growth in the use of telemedicine for delivery of ambulatory diabetes care. This study evaluated the feasibility of remote HbA1c monitoring via dried blood spot (DBS) testing to support assessment of glycemic control for telemedicine visits and examined clinical and demographic characteristics associated with patient completion of DBS testing.

METHODS

Providers could place orders for DBS HbA1c 3 weeks prior to telemedicine visits. Feasibility was assessed by examining DBS completion rates, time to completion, and availability of DBS results prior to telemedicine visits. Chi-square tests and Mann Whitney tests were used to assess whether completion rates were associated with participant characteristics.

RESULTS

Of 303 DBS orders placed for telemedicine visits in June 2020, 162 patients completed the DBS test for a completion rate of (53.4%). Average time from collection at home to result being reported was 6.9 (3.8) days. The DBS result was available in 67.6% of patients who completed successful DBS, before the telemedicine clinic visit. HbA1c was lower in the DBS completion group as compared to the non-completion group (8.2% vs. 8.9%, p = 0.01). No other clinical or demographic characteristics were significantly different between the two groups.

CONCLUSION

Remote HbA1c monitoring via DBS is feasible and offers an avenue to support assessment of glycemic control for patients seen via telemedicine. Future work should focus on improving clinic and laboratory processes to support remote DBS collection.

Association between fear of hypoglycemia and physical activity in youth with type 1 diabetes: The SEARCH for diabetes in youth study

BACKGROUND

Youth with type 1 diabetes (T1D) are encouraged to participate in physical activity (PA). Studies have identified fear of hypoglycemia (FOH) as a barrier to participating in PA.

OBJECTIVES

To examine (a) PA patterns in youth with T1D by age group and (b) the relationship between both parental and youth FOH and youth PA.

METHODS

A cross-sectional analysis from the SEARCH cohort study visit of youth ages 10 to 17 years with T1D (n = 1129) was conducted. Linear regression models estimated the association between self-reported number of days of vigorous PA (VPA) and moderate PA (MPA) and both youth- and parent-reported FOH. Multivariable models were adjusted for age, sex, race, duration of T1D, HbA1c, use of continuous glucose monitoring (CGM), recent severe hypoglycemia, primary insulin regimen, and BMI.

RESULTS

Participants were 52% female, had mean (sd) age 14.4 (4.2) years, diabetes duration 7.5 years (1.8), HbA1c 9.2% (1.7). Older youth were less likely to engage in VPA (P < .01), or sports teams (P < .01), but more likely to engage in MPA (P < .01). Higher youth FOH (behavior subscale) was associated with increased levels of VPA (β (se) 0.30 (0.11), P = .01) but not significantly associated with MPA (P = .06). There was no statistically significant association between parental FOH and youth PA.

CONCLUSIONS

In SEARCH participants with T1D, VPA, and team sports participation declined with age, while MPA increased. We observed that higher scores on the youth FOH behavioral subscale were associated with increased VPA levels, suggesting that FOH may be less of a barrier to PA than previously thought.

Hypoglycaemia avoidance behaviour and exercise levels in active youth with type 1 diabetes

AIMS

The primary goal of this exploratory study was to examine the association between fear of hypoglycaemia (FOH), hypoglycaemia avoidance behaviours and exercise in active youth with type 1 diabetes (T1D).

METHODS

30 youth with T1D who participate in some physical activity (PA), age 15.0 ± 2.4 years, on insulin pump therapy completed the 'Type 1 Diabetes Report of Exercise Practices Survey (T1D-REPS)' and parent and child hypoglycaemia fear surveys (HFS). Twenty-eight participants completed the 3-day PA recall survey. Clinical data and pump downloads were obtained at the time of the survey collection.

RESULTS

Higher child HFS behaviour and total scores were associated with higher PA levels (P = .003, P = .027), and higher parent HFS behaviour score was associated with higher youth PA levels (P = .031), after adjusting for age, sex, duration of diabetes and BMI. Higher child HFS behaviour score was associated with a higher exercise hypoglycaemia avoidance score on T1D-REPS (r = .38, P = .043). Higher child HFS worry and total scores were associated with higher HbA1c (r = .48, P = .008; r = .46, P = .012).

CONCLUSIONS

This study demonstrated that, in a generally active cohort of youth with T1D, increased hypoglycaemia avoidance behaviour was associated with higher PA levels. Higher overall FOH scores were associated with PA level, driven by higher behaviour subscale scores, while worry subscales were not correlated with PA level. Those with more FOH intervene more to specifically avoid exercise-associated hypoglycaemia and appear to have worse overall glycaemic control. Thus, improved education is required to improve glycaemic control around exercise while maintaining avoidance of hypoglycaemia.

Genotype by environment interaction in response to cold stress in a composite beef cattle breed

Extreme weather conditions such as cold stress influence the productivity and survivability of beef cattle raised on pasture. The objective of this study was to identify and evaluate the extent of the impact of genotype by environment interaction due to cold stress on birth weight (BW) and weaning weight (WW) in a composite beef cattle population. The effect of cold stress was modelled as the accumulation of total cold load (TCL) calculated using the Comprehensive Climate Index units, considering three TCL classes defined based on temperature: less than -5°C (TCL5), -15°C (TCL15) and -25°C (TCL25). A total of 4221 and 4217 records for BW and WW, respectively, were used from a composite beef cattle population (50% Red Angus, 25% Charolais and 25% Tarentaise) between 2002 and 2015. For both BW and WW, a univariate model (ignoring cold stress) and a reaction norm model were implemented. As cold load increased, the direct heritability slightly increased in both BW and WW for TCL5 class; however, this heritability remained consistent across the cold load of TCL25 class. In contrast, the maternal heritability of BW was constant with cold load increase in all TCL classes, although a slight increase of maternal heritability was observed for TCL5 and TCL15. The direct and maternal genetic correlation for BW and maternal genetic correlation for WW across different cold loads between all TCL classes were high (r > 0.99), whereas the lowest direct genetic correlations observed for WW were 0.88 for TCL5 and 0.85 for TCL15. The Spearman rank correlation between the estimated breeding value of top bulls (n = 79) using univariate and reaction norm models across TCL classes showed some re-ranking in direct and maternal effects for both BW and WW particularly for TCL5 and TCL15. In general, cold stress did not have a big impact on direct and maternal genetic effects of BW and WW.

Alcohol consumption patterns in young adults with type 1 diabetes: The SEARCH for diabetes in youth study

AIMS

The objective of this study is to describe alcohol consumption behaviors of young adults with T1D and to examine associations between alcohol consumption and diabetes-related clinical markers.

METHODS

Data from 602 SEARCH for Diabetes in Youth Study participants age ≥ 18 yrs. with T1D were collected from 12/2011 to 6/2015 (50% female, mean age 21.3(SD 2.4), 22% race/ethnic minority). Participants were characterized as alcohol non-drinkers (n = 269), drinkers but non-binge drinkers (n = 167), or binge drinkers (n = 166) based on reported consumption in the past 30 days. Analyses were conducted using one-way ANOVAs, chi-square tests, and logistic regression modeling to examine associations between drinking and clinical markers.

RESULTS

Fifty-five percent of participants reported alcohol consumption; 27.6% of participants reported binge drinking. After adjusting for demographic characteristics, neither binge drinking nor non-binge drinking were associated with HbA1c or severe hypoglycemic events relative to non-drinkers. Binge drinking was associated with higher HDL (p = 0.008), lower systolic blood pressure (p = 0.011), and a lower waist:height ratio compared to non-drinkers (p = 0.013).

CONCLUSIONS

Young adults with T1D in the SEARCH cohort reported similar alcohol use but higher rates of binge drinking compared to the general United States population and previously reported rates in adults with T1D.

Efficacy and Safety of Real-Life Usage of MiniMed 670G Automode in Children with Type 1 Diabetes Less than 7 Years Old

The Medtronic MiniMed 670G system with SmartGuard™ (Medtronic, Northridge, CA) is a commercial hybrid closed-loop (HCL) system approved for use in 2018 for children >7 years. Studies of this HCL system in subjects >7 years old show improvement in glycemic control, but no study has described its use in younger children. This is a retrospective analysis of patients with type 1 diabetes (T1D) <7 years of age who used the 670G HCL system at Seattle Children's Hospital for 3 months. We compared 2-week data from Carelink™ while in manual mode (MM) with suspend before low active with those in auto mode (AM). We used two tailed t-test to compare variables related to glycemic control. Sixteen children were reviewed [age of AM start: average 4.3 years (range 2-6); 10 male]. The average time in AM was 6.3 ± 2.9 months (range 3-12). There was a statistically significant change for A1c [MM 7.9% (62.8 mmol/mol), AM 7.4% (57.4 mmol/mol); P-value <0.001], percentage time in range (MM 42.8%, AM 56.2%; P-value <0.001), percentage hypoglycemia (MM 1.3%, AM 2.4%; P-value 0.04), and average sensor glucose [MM 200 mg/dL (11.1 mmol/L), AM 176 mg/dL (9.8 mmol/L); P-value <0.001]. No serious adverse reports noted. This case series showed improvement in glycemic control in very young children using the 670G HCL. We did note more hypoglycemia although no serious adverse events, such as hypoglycemic seizure, were reported. A HCL system can be used in young children with T1D safely and effectively and should be an option for children <7 years.

Feasibility of Routine Assessment of Exercise Knowledge and Safety in Youth With Type 1 Diabetes

PURPOSE

This pilot study assessed the feasibility and satisfaction of an electronic clinical tool to survey management of exercise in youth with type 1 diabetes (T1DM) for use in an outpatient diabetes clinic setting.

METHODS

Fifty youth with T1DM were recruited (ages, 10-18 years; mean ± SD, 14.8 ± 2.4) and 11 diabetes providers. Prior to a clinic visit and with an electronic tablet, participants completed the Type 1 Diabetes Report of Exercise Practices Survey, which included 9 primary exercise management guidelines. Responses were flagged if contrary to guidelines, and automated individualized reports with personalized evidence-based recommendations were produced for providers prior to seeing the patient. Postclinic assessment surveys were completed by patients and providers.

RESULTS

Out of the 9 guidelines, a mean of 4 ± 0.9 responses per patient were flagged as potentially unsafe. Ninety-one percent of providers took <10 minutes to review and discuss the report with their patients. Ninety-one percent of providers rated the tool as highly useful in facilitating patient education regarding exercise guidelines at that clinic visit. Fifty-six percent of youth rated the tool highly when asked whether its use altered their planned behavior around exercise. When participants were asked if such a tool should be used routinely in diabetes clinic, 64% of provider responses and 60% of patient responses were highly positive.

CONCLUSIONS

This electronic tool identified deficits in exercise management in youth with T1DM and improved education in the clinic visit regarding exercise, and a majority felt it feasible and desirable to include in routine outpatient diabetes care.

Effect of low and moderate dose FEIBA to reverse major bleeding in patients on direct oral anticoagulants

OBJECTIVE

Management of acute, major or life threatening bleeding in the presence of direct acting oral anticoagulants (DOAC) is unclear. In the absence of a specific antidote, or in situations where there is a need for adjunctive therapy, the ideal prothrombin complex concentrate and dose is unclear. The goal of our study was to evaluate the outcomes of our reduced dosing strategy with FEIBA in patients experiencing a DOAC-related bleeding event.

DESIGN

Retrospective analysis of patients treated with FEIBA for a DOAC-related bleeding event.

SETTING

Academic medical center PATIENTS: Consecutive patients between May 2011 and April 2017 receiving FEIBA for a DOAC-related bleed INTERVENTIONS: None MEASUREMENTS & MAIN RESULTS: Of the 64 patients included in this analysis, 38 patients received low dose FEIBA (mean 10.0 ± 3.6 units/kg) and 26 received moderate dose (mean 24.3 ± 2.1 units/kg) FEIBA; an additional dose was requested in 6 patients. Six dabigatran patients received idarucizumab. 30 day event rates included 5 thromboembolic events (8%) and 9 (14%) patients expired. Follow-up CT-imaging for ICH, endoscopy/colonoscopy, or interventional radiology exams did not reveal any clinically concerning active bleeding or hematoma expansion except in 2 ICH patients with slight expansion between imaging sessions.

CONCLUSIONS

Low (<20 units/kg) to moderate (20-30 units/kg) doses of FEIBA, with the option for a repeat dose, may be an effective management strategy for obtaining hemostasis in DOAC-related major bleeding events.

A Upf3b-mutant mouse model with behavioral and neurogenesis defects

Nonsense-mediated RNA decay (NMD) is a highly conserved and selective RNA degradation pathway that acts on RNAs terminating their reading frames in specific contexts. NMD is regulated in a tissue-specific and developmentally controlled manner, raising the possibility that it influences developmental events. Indeed, loss or depletion of NMD factors have been shown to disrupt developmental events in organisms spanning the phylogenetic scale. In humans, mutations in the NMD factor gene, UPF3B, cause intellectual disability (ID) and are strongly associated with autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD) and schizophrenia (SCZ). Here, we report the generation and characterization of mice harboring a null Upf3b allele. These Upf3b-null mice exhibit deficits in fear-conditioned learning, but not spatial learning. Upf3b-null mice also have a profound defect in prepulse inhibition (PPI), a measure of sensorimotor gating commonly deficient in individuals with SCZ and other brain disorders. Consistent with both their PPI and learning defects, cortical pyramidal neurons from Upf3b-null mice display deficient dendritic spine maturation in vivo. In addition, neural stem cells from Upf3b-null mice have impaired ability to undergo differentiation and require prolonged culture to give rise to functional neurons with electrical activity. RNA sequencing (RNAseq) analysis of the frontal cortex identified UPF3B-regulated RNAs, including direct NMD target transcripts encoding proteins with known functions in neural differentiation, maturation and disease. We suggest Upf3b-null mice serve as a novel model system to decipher cellular and molecular defects underlying ID and neurodevelopmental disorders.

Barefoot plantar pressure measurement in Chronic Exertional Compartment Syndrome

BACKGROUND

Patients with Chronic Exertional Compartment Syndrome (CECS) have exercise-limiting pain that subsides at rest. Diagnosis is confirmed by intramuscular compartment pressure (IMCP) measurement. Accompanying CECS, subjective changes to gait (foot slap) are frequently reported by patients. This has not previously been investigated. The aim of this study was to investigate differences in barefoot plantar pressure (BFPP) between CECS cases and asymptomatic controls prior to the onset of painful symptoms.

METHODS

40 male military volunteers, 20 with symptoms of CECS and 20 asymptomatic controls were studied. Alternative diagnoses were excluded with rigorous inclusion criteria, magnetic resonance imaging and dynamic IMCP measurement. BFPP was measured during walking and marching. Data were analysed for: Stance Time (ST); foot progression angle (FPA); centre of force; plantarflexion rate after heel strike (IFFC-time); the distribution of pressure under the heel; and, the ratio between inner and outer metatarsal loading. Correlation coefficients of each variable with speed and leg length were calculated followed by ANCOVA or t-test. Receiver operating characteristic (ROC) curves were constructed for IFFC-time.

RESULTS

Caseshad shorter ST and IFFC-times than controls. FPA was inversely related to walking speed (WS) in controls only. The area under the ROC curve for IFFC-time ranged from 0.746 (95%CI: 0.636-0.87) to 0.773 (95%CI: 0.671-0.875) representing 'fair predictive validity'.

CONCLUSION

Patients with CECS have an increased speed of ankle plantarflexion after heel strike that precedes the onset of painful symptoms likely resulting from a mechanical disadvantage of Tibialis Anterior. These findings provide further insight into the pathophysiology of CECS and support further investigation of this non-invasive diagnostic. The predictive value of IFFC-time in the diagnosis of CECS is comparable to post-exercise IMCP but falls short of dynamic IMCP measured during painful symptoms.

Genomic prediction of continuous and binary fertility traits of females in a composite beef cattle breed

Reproduction efficiency is a major factor in the profitability of the beef cattle industry. Genomic selection (GS) is a promising tool that may improve the predictive accuracy and genetic gain of fertility traits. There is a wide range of traits used to measure fertility in dairy and beef cattle including continuous (days open), discrete (pregnancy status), and count (number of inseminations) responses. In this study, a joint analysis of age of puberty (AOP), age at first calving (AOC), and the heifer pregnancy status (HPS) was performed. Data used in this study consisted of records from 1,365 Composite Gene Combination (CGC; 50% Red Angus, 25% Charolais, 25% Tarentaise) first parity females born between 2002 and 2011. The pedigree file included 5,374 animals. A total of 3,902 animals were genotyped with different density SNP chips (3K to 50K SNP). Animals genotyped with low-density arrays were imputed to higher density (BovineSNP50 BeadChip) using FImpute. Data were analyzed using univariate and multivariate classical quantitative models (pedigree based) and univariate genomic approaches. For the latter, 3 different Bayesian methods (BayesA, BayesB, and BayesCπ) were implemented and compared. Estimates of heritabilities using univariate and multivariate analyses based on pedigree relationships ranged between 0.03 (for AOC) to 0.2 (AOP). Heritability of pregnancy status was 0.15 and 0.09 using the univariate and multivariate analyses, respectively. Genetic correlation between pregnancy status and the other 2 traits was low being 0.08 with age at puberty and -0.10 with age at first calving. Heritability estimates were slightly higher using genomic rather than average additive relationships. The accuracy of genomic prediction was similar across the 3 Bayesian methods with higher accuracies for age of puberty than the age at first calving likely due to the higher heritability of the former. The prediction of the binary pregnancy status measured using the area under the curve increased by 27% to 29% compared to a random classifier. Due to the small size of the data, all estimates have large posterior standard deviations and results should be interpreted with caution.

Developmental and reproductive characteristics of beef heifers classified by pubertal status at time of first breeding

Data collected for 10 or more years at the West Central Research and Extension Center, North Platte, NE ( = 1,104); the Gudmundsen Sandhills Laboratory, Whitman, NE ( = 1,333); and the USDA, ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City, MT ( = 1,176) were retrospectively analyzed to evaluate growth and reproductive performance of beef heifers classified by pubertal status before first breeding. Concentrations of progesterone in serum from 2 blood samples collected 9 to 11 d apart before the breeding season classified heifers as pubertal (progesterone ≥ 1.0 ng/mL in 1 or both samples) or nonpubertal (progesterone < 1.0 ng/mL in both samples). Average date of birth was earlier ( < 0.06) and proportion born in the first 21 d of the calving season was 10 to 20 percentage points greater for heifers that were pubertal at the start of breeding compared with heifers not pubertal by the start of breeding. Heifers that were pubertal by the start of breeding were 7 to 10 kg heavier ( < 0.01) and 1 cm taller ( < 0.01) at weaning than heifers not pubertal by the start of breeding. Differences in BW persisted through the start of breeding to pregnancy diagnosis. Heifers that achieved puberty by the start of breeding had greater ( < 0.05) feed intake and G:F during postweaning development and had greater ( < 0.01) LM area and fat thickness over the LM at approximately 1 yr of age compared with heifers not pubertal by the start of breeding. Heifers that achieved puberty before the start of breeding had greater ( < 0.01) ADG from birth to weaning but slower ( < 0.10) rates of gain from the start of breeding through pregnancy diagnosis. Pregnancy rate was greater ( < 0.01) for heifers that were pubertal at the start of breeding. In heifers that became pregnant, those that were pubertal before the start of breeding calved earlier ( < 0.01), with a greater ( < 0.01) percentage calving in the first 21 d of calving than heifers not pubertal at the start of breeding. Calves from heifers that achieved puberty before the start of breeding were heavier at weaning ( < 0.01) than calves from heifers that had not achieved puberty by the start of breeding. In summary, heifers that failed to achieve puberty by the start of breeding were less desirable for several traits evaluated. Based on these results, implementing feeding strategies to increase the proportion of heifers that achieve puberty before first breeding could result in propagation of undesirable characteristics.

Effects of anterior compartment fasciotomy on intramuscular compartment pressure in patients with chronic exertional compartment syndrome

Background

Patients with chronic exertional compartment syndrome (CECS) have pain during exercise that usually subsides at rest. Diagnosis is usually confirmed by measurement of intramuscular compartment pressure (IMCP) following exclusion of other possible causes. Management usually requires fasciotomy but reported outcomes vary widely. There is little evidence of the effectiveness of fasciotomy on IMCP. Testing is rarely repeated postoperatively and reported follow-up is poor. Improved diagnostic criteria based on preselection and IMCP levels during dynamic exercise testing have recently been reported.

Objectives

(1) To compare IMCP in three groups, one with classical symptoms and no treatment and the other with symptoms of CECS who have been treated with fasciotomy and an asymptomatic control group. (2) Establish if differences in IMCP in these groups as a result of fasciotomy relate to functional and symptomatic improvement.

Methods

Twenty subjects with symptoms of CECS of the anterior compartment, 20 asymptomatic controls and 20 patients who had undergone fasciotomy for CECS were compared. All other possible diagnoses were excluded using rigorous inclusion criteria and MRI. Dynamic IMCP was measured using an electronic catheter wire before, during and after participants exercised on a treadmill during a standardised 15 min exercise challenge. Statistical analysis included t-tests and analysis of variance.

Results

Fasciotomy results in reduced IMCP at all time points during a standardised exercise protocol compared with preoperative cases. In subjects responding to fasciotomy, there is a significant reduction in IMCP below that of preoperative groups (P<0.001). Postoperative responders to fasciotomy have no significant differences in IMCP from asymptomatic controls (P=0.182).

Conclusion

Fasciotomy reduces IMCP in all patients. Larger studies are required to confirm that the reduction in IMCP accounts for differences in functional outcomes and pain reductions seen in postoperative patients with CECS.

Do youth with type 1 diabetes exercise safely? A focus on patient practices and glycemic outcomes

OBJECTIVE

Insulin adjustments have been shown to reduce glycemic excursions during and after exercise, but little is known about their use in youth with type 1 diabetes (T1D). We aimed to assess practices in youth with T1D around exercise, assess factors that influence practices, and examine associations between key behaviors and glycemic outcomes.

RESEARCH DESIGN AND METHODS

We developed the 'Type 1 Diabetes Report of Exercise Practices Survey (T1D-REPS)' and piloted this tool in 100 youth with T1D on an insulin pump. Participants completed a 3-day physical activity recall and 30 days of pump/glucose data were collected. Chart review was conducted for key clinical measures.

RESULTS

Eighty-four percent of participants modified their insulin regimen around exercise; only 40% reported adjusting prandial insulin immediately before exercise while 68% reported some modification (suspension or decrease) of basal insulin during exercise. Following exercise, only 10% reported reducing overnight basal insulin. Those who performed ≥ 5 glucose checks/day adjusted basal insulin during exercise more frequently than those with fewer daily glucose checks (33% vs. 13%, p = 0.05, chi-squared = 3.7), and were more likely to report decreasing insulin dose for the bedtime snack following exercise (50% vs. 17%, p = 0.004, chi-squared = 8.2).

CONCLUSIONS

Despite several studies showing the frequency of hypoglycemia during and after exercise, many youth are not adjusting insulin for exercise. A tool designed to capture patient practices and provide clinicians with a framework for patient education may lead to improved safety around exercise in youth with T1D.

Water temperature impacts water consumption by range cattle in winter

Water consumption and DMI have been found to be positively correlated, and both may interact with ingestion of cold water or grazed frozen forage due to transitory reductions in the temperature of ruminal contents. The hypothesis underpinning the study explores the potential that cows provided warm drinking water would have increased in situ NDF and OM disappearances and a more stable rumen temperature, drink more water, and lose less BW during the winter. This hypothesis was tested in 3 experiments. In Exp. 1, ruminal extrusa (93.1% DM, 90.2% OM, 81.1% NDF [DM], and 4.9% CP [DM]) were randomly allocated to 1 of 5 in vitro incubation temperatures. In 2 independent trials, temperatures evaluated were 39, 37, or 35°C (trial 1) and 39, 33, or 31°C (trial 2). In Exp. 2, 4 pregnant rumen cannulated cows grazing in January were fitted with Kahne (KB1000) temperature continuous recording boluses for 22 d. Two grazed in a paddock provided cold water (8.2°C) and 2 in a paddock provided warm water (31.1°C). Two in situ trials were conducted placing 6 in situ bags containing 2 g of winter range ruminal extrusa in each of the 4 ruminally cannulated cows and incubating bags for 72 h for measurement of NDF disappearance. In Exp. 3, 6 paddocks ( = 3/water treatment) were grazed by 10 to 13 pregnant crossbred Angus cows from December through February across 3 yr from 2009 to 2012. Water intake per paddock was measured daily and ambient temperature was recorded. Motion-activated cameras were used to determine the time of day water was consumed and the number of cow appearances at water. In Exp. 1, rate and total gas production ( < 0.05) and NDF disappearance ( < 0.001) at 48 h was reduced by each incubation temperature below 39°C. In Exp. 2, ruminal temperature for cows supplied with warm water dropped below 38°C 1.5% of the time whereas ruminal temperature for cows provided cold water dropped below 38°C 9.4% of the time ( < 0.01). Drinking water temperature did not alter in situ OM or NDF disappearance. In Exp. 3, cows with access to warm water consumed 30% ( < 0.05) more water than cows provided cold water. In this study, there were energetic costs to range cows proportional to consumption of water at temperatures less than body temperature. The magnitude of these costs were found to be less than the heat increment because no improvement to BW gain, BCS change, or calf birth weight were found for cows consuming warmed water.

BEEF SPECIES SYMPOSIUM: Can we build the cowherd by increasing longevity of females?

Increasing longevity of beef cows by decreasing the proportion culled due to reproductive failure provides an efficient process to rebuild a cow herd and can reduce number of replacements needed to sustain a constant herd size. Rate of reproductive failure varies due to cow age, where failure in cows 2 to 4 yr of age is often greater than in cows 5 to 7 yr of age. In addition, BW of cow and calf at weaning increase as cows advance from 2 to 5 yr of age. The cumulative effect of increasing retention of young cows is improved production efficiency through decreased replacement rate and changing age structure of the herd resulting in a greater proportion of cows at maximal production potential for calf BW at weaning and cow BW at time of culling. Calculations from cow age-specific culling and BW data from commercial and research herds indicated that reducing replacement rate from 18% to 14% resulted in a 23% increase in calf BW weaned and a 2% increase in cull cow BW per pregnant replacement heifer going into the herd. Although improving longevity increases production efficiency, genetic advancement in sustained reproductive function is challenging, as it is the sequential culmination of the annual repetition of numerous discrete physiological processes, each ending in a qualitative response. Successful completion of one process is prerequisite to evaluating subsequent processes. These physiological processes are subject to nutritional threshold requirements that may vary due to genetic potential for other production traits such as milk, growth, and mature size resulting in genetic-by-nutrition interactions. This is in contrast to most traits for which EPD exist, where genetic-by-environment interactions are not considered to be significant. Extensive research concerning impact of limited nutrition on reproduction has led to recommendations that heifers and cows be fed to a threshold BW or BCS to ensure reproductive success; a process that masks nutritional interactions that might otherwise result in reproductive failure. This management approach minimizes selection for animals capable of sustained reproductive function under limited nutritional environments. Rearing and managing cows under nutritionally limited environments may lead to adaptations that result in relatively high levels of reproductive success under lower input levels. Such adaptation may improve chances for longer retention in their offspring in nutrient-limited environments.

Evaluation of TLR4 Inhibitor, T5342126, in Modulation of Ethanol-Drinking Behavior in Alcohol-Dependent Mice

AIMS

Several lines of evidence support a critical role of TLR4 in the neuroimmune responses associated with alcohol disorders and propose inhibitors of TLR4 signaling as potential treatments for alcoholism. In this work, we investigated the effect of T5342126 compound, a selective TLR4 inhibitor, on excessive drinking and microglial activation associated with ethanol dependence.

METHODS

We used 2BC-CIE (two-bottle choice-chronic ethanol intermittent vapor exposure) paradigm to induce ethanol dependence in mice. After induction of the ethanol dependence, we injected T5342126 (i.p., 57 mg/kg) for 14 days while monitoring ethanol intake by 2BC (limited access to ethanol) method.

RESULTS

T5342126 decreased ethanol drinking in both ethanol-dependent and non-dependent mice but T5342126 showed also dose-dependent non-specific effects represented by decreased animal locomotor activity, saccharine intake, and body core temperature. Six days after the last ethanol-drinking session, we examined the immunohistochemical staining of Iba-1 (ionized calcium-binding adapter molecule 1), a microglial activation marker, in the central nucleus of the amygdala (CeA) and dentate gyrus (DG) of the hippocampus. Notably, T5342126 reduced Iba-1 density in the CeA of both ethanol-dependent and non-dependent mice injected with T5342126. There were no significant differences in the DG Iba-1 density among the treatment groups.

CONCLUSIONS

Collectively, our data suggest that T5342126, via blocking TLR4 activation, contributes to the reduction of ethanol drinking and ethanol-induced neuroimmune responses. However, the non-specific effects of T5342126 may play a significant role in the T5342126 effects on ethanol drinking and thus, may limit its therapeutic potential for treatment of alcohol dependence.

SHORT SUMMARY

T5342126, an experimental TLR4 inhibitor, is effective in reducing ethanol drinking and inhibiting the activation and proliferation of microglia in both ethanol-dependent and non-dependent mice. However, T5342126's use as a potential candidate for the treatment of alcohol addiction may be limited due to its non-specific effects.

Sources of variability in livestock water quality over 5 years in the Northern Great Plains

Concentrated dissolved minerals in naturally occurring water accessible to livestock grazing semiarid landscapes can negatively influence animal productivity and well-being. Twelve indicators of water quality (Ca, Cl, Fe, F, Mg, Mn, Na, nitrate N, pH, SO4, total dissolved solids [TDS], and temperature) were measured at 45 livestock water sites over 5 yr from 2009 through 2013 at the 22,257-ha USDA-ARS Fort Keogh Livestock and Range Research Laboratory (Miles City, MT) to estimate variation. Water was sampled from 4 sources: 1) flowing surface water, 2) groundwater, 3) reservoirs, and 4) springs. The sampled area was classified by 3 cardinal compass bearings (locations): 1) north, 2) southeast, and 3) southwest of the Yellowstone River. Samples were collected twice yearly in 2 seasons, May (wet) and September (dry). Year, location, source, and season and their interactions were analyzed as a 5 × 3 × 4 × 2 factorial arrangement of treatments. A location × year interaction (P < 0.04) was found for Mg, Na, SO4, and TDS. The southwest location had the greatest concentrations in 2012 of Na, SO4, and TDS. A source × year interaction (P < 0.02) was found for Ca, Fe, F, Mg, Mn, Na, SO4, TDS, and temperature. Iron, Mg, and Mn had the greatest concentrations in flowing surface water in 2012. Greater and then lower precipitation in 2011 followed by below-average precipitation in 2012 was associated with elevated mineral concentrations in sources in the southwest location and flowing surface water sources demonstrating sources of water quality variability within time and space at the study site. Average concentrations of Ca, Cl, Mg, and nitrate N and pH levels across sources and locations did not exceed the upper maximum intake level for beef cattle. In contrast, concentrations of F, Fe, Na, SO4, and TDS at times exceeded the upper maximum level for beef cattle, indicating these minerals may negatively impact range beef cattle performance.

Exercise in Youth with Type 1 Diabetes

Exercise is important in the management of type 1 diabetes mellitus (T1DM). Modern diabetes care includes the goal that all youth meet guidelines for regular physical activity. Evidence suggests regular physical activity improves cardiovascular health, lipid profiles, psychosocial wellbeing and, possibly, glycemic control in youth with T1DM. However, exercise is especially problematic for children and adolescents because wide glycemic excursions commonly occur during and after exercise and may increase the risk of severe hypoglycemia. In addition, youth with T1DM have abnormal counterregulatory hormone responses, further increasing the risk of exercise-associated hypoglycemia. Recent studies have demonstrated that this risk is present during, and many hours after exercise, and have tested strategies to prevent exercise-induced hypoglycemia in youth. Despite these recent studies, the fear of hypoglycemia remains a major impediment to achieving target glycemic control in youth, targets that have recently been tightened. Equally, data suggests fear of hypoglycemia is the major impediment to participation in regular daily exercise in T1DM. Recent advances in insulin delivery systems and in real time continuous glucose monitoring have improved care for youth with T1DM, allowing safer participation in exercise programs. The impending development and approval of "closed loop" insulin delivery systems (the artificial pancreas) holds great promise for the safe participation in exercise for all youth with T1DM.

Aspen shaving versus chip bedding: effects on breeding and behavior

The choice of laboratory cage bedding material is often based on both practical and husbandry issues, whereas behavioral outcomes rarely appear to be considered. It has been noted that a breeding success difference appears to be associated with the differential use of aspen chip and aspen shaving bedding in our facility; therefore, we sought to analyze breeding records maintained over a 20-month period. In fact, in all four mouse strains analyzed, shaving bedding was associated with a significant increase in average weanlings per litter relative to chip bedding. To determine whether these bedding types also resulted in differences in behaviors associated with wellbeing, we examined nest building, anxiety-like, depressive-like (or helpless-like), and social behavior in mice housed on chip versus shaving bedding. We found differences in the nests built, but no overall effect of bedding type on the other behaviors examined. Therefore, we argue that breeding success, perhaps especially in more challenging strains, is improved on shaving bedding and this is likely due to improved nest-building potential. For standard laboratory practices, however, these bedding types appear equivalent.

The formation of a large summertime Saharan dust plume: Convective and synoptic-scale analysis

Haboobs are dust storms produced by the spreading of evaporatively cooled air from thunderstorms over dusty surfaces and are a major dust uplift process in the Sahara. In this study observations, reanalysis, and a high-resolution simulation using the Weather Research and Forecasting model are used to analyze the multiscale dynamics which produced a long-lived (over 2 days) Saharan mesoscale convective system (MCS) and an unusually large haboob in June 2010. An upper level trough and wave on the subtropical jet 5 days prior to MCS initiation produce a precipitating tropical cloud plume associated with a disruption of the Saharan heat low and moistening of the central Sahara. The restrengthening Saharan heat low and a Mediterranean cold surge produce a convergent region over the Hoggar and Aïr Mountains, where small convective systems help further increase boundary layer moisture. Emerging from this region the MCS has intermittent triggering of new cells, but later favorable deep layer shear produces a mesoscale convective complex. The unusually large size of the resulting dust plume (over 1000 km long) is linked to the longevity and vigor of the MCS, an enhanced pressure gradient due to lee cyclogenesis near the Atlas Mountains, and shallow precipitating clouds along the northern edge of the cold pool. Dust uplift processes identified are (1) strong winds near the cold pool front, (2) enhanced nocturnal low-level jet within the aged cold pool, and (3) a bore formed by the cold pool front on the nocturnal boundary layer.

Beef Species Symposium: an assessment of the 1996 Beef NRC: metabolizable protein supply and demand and effectiveness of model performance prediction of beef females within extensive grazing systems

Interannual variation of forage quantity and quality driven by precipitation events influence beef livestock production systems within the Southern and Northern Plains and Pacific West, which combined represent 60% (approximately 17.5 million) of the total beef cows in the United States. The beef cattle requirements published by the NRC are an important tool and excellent resource for both professionals and producers to use when implementing feeding practices and nutritional programs within the various production systems. The objectives of this paper include evaluation of the 1996 Beef NRC model in terms of effectiveness in predicting extensive range beef cow performance within arid and semiarid environments using available data sets, identifying model inefficiencies that could be refined to improve the precision of predicting protein supply and demand for range beef cows, and last, providing recommendations for future areas of research. An important addition to the current Beef NRC model would be to allow users to provide region-specific forage characteristics and the ability to describe supplement composition, amount, and delivery frequency. Beef NRC models would then need to be modified to account for the N recycling that occurs throughout a supplementation interval and the impact that this would have on microbial efficiency and microbial protein supply. The Beef NRC should also consider the role of ruminal and postruminal supply and demand of specific limiting AA. Additional considerations should include the partitioning effects of nitrogenous compounds under different physiological production stages (e.g., lactation, pregnancy, and periods of BW loss). The intent of information provided is to aid revision of the Beef NRC by providing supporting material for changes and identifying gaps in existing scientific literature where future research is needed to enhance the predictive precision and application of the Beef NRC models.

Does β-hydroxybutyrate concentration influence conception date in young postpartum range beef cows?

Cows in negative energy balance after calving often have reduced reproductive performance, which is mediated by metabolic signals. The objective of these studies was to determine the association of serum metabolites, days to first postpartum ovulation, milk production, cow BW change, BCS, and calf performance with conception date in spring-calving 2- and 3-yr-old beef cows grazing native range. In Exp. 1, cows were classified by conception date in a 60-d breeding season as early (EARLY; conceived in first 15 d of breeding) or late conception (LATE; conceived during the last 45 d of breeding). Beginning on d 35 postpartum, blood samples were collected twice per week for serum metabolite analysis and progesterone analysis to estimate days to resumption of estrous cycles. As a chute-side measure of nutrient status and glucose sufficiency, whole-blood β-hydroxybutyrate (BHB) concentrations were measured 14 ± 2 d before breeding. In Exp. 2, cows were classified by subsequent calving date resulting from a 55 ± 2 d breeding season as conceiving either early (EARLY; conceived in first 15 d of breeding) or late (LATE; conceived during the remaining breeding season). Blood samples were collected in 2 periods, 30 ± 4 d before calving and 14 ± 3 d before the initiation of breeding, to determine circulating concentrations of IGF-I and BHB. In Exp. 1, BHB and serum glucose concentrations were less (P ≤ 0.04) in EARLY cows than LATE cows. Serum insulin concentrations were greater (P = 0.03) in EARLY cows relative to LATE cows. Milk production and composition did not differ (P ≥ 0.24) by conception date groups. In Exp. 2, cow age × sample period × conception date interaction (P < 0.01) occurred for serum BHB concentrations. Serum BHB concentrations were similar (P > 0.10) for 2-yr-old cows (in greater nutritional plane compared with Exp. 1) regardless of their conception date classification and sampling period. However, precalving serum BHB concentrations were greater (P < 0.01) for LATE than EARLY in 3-yr-old cows with no difference (P = 0.86) at prebreeding. Serum IGF-1 concentrations were greater (P < 0.01) for EARLY cows relative to LATE cows at precalving and prebreeding. This study indicates that blood BHB concentrations during times of metabolic dysfunctions may provide a more sensitive indicator of energy status than body condition, predicting rebreeding competence in young beef cows as measured by interval from calving to conception.

Joint Alpharma-Beef Species Symposium: implications of beef heifer development systems and lifetime productivity

Research emphasis has been placed on heifer development strategies in recent years, comparing traditional, more intensive systems to more extensive systems using less feed and relying on compensatory gain to reach a target BW. Recent research has indicated that developing heifers to a lighter target BW at breeding (i.e., 50 to 57% of mature BW compared with 60 to 65% BW) reduced development costs and did not impair reproductive performance. Research published through the late 1980s demonstrated greater negative effects of limited postweaning growth on age at puberty and pregnancy rates whereas more recent studies demonstrate less of a negative impact of delayed puberty on pregnancy rate. A limitation of most research concerning influences of nutrition on heifer development and cow reproductive performance is little or limited consideration of long-term implications. Longevity has relatively low heritability; therefore, heifer development and other management strategies have a greater potential to impact cow retention. Establishing the impact of heifer development protocols on longevity is complex, requiring consideration of nutritional factors after the start of breeding and through subsequent calvings. Lower-input heifer development, where all heifers are managed together after the postweaning period, did not impair rebreeding, but continued subsequent restriction in the form of marginal winter supplementation resulted in decreased retention in the breeding herd. Therefore, the compensatory BW gain period for restricted-growth heifers may be important to longevity and lifetime productivity. Adequate growth and development to ensure minimal calving difficulty can be of critical importance for longevity; however, providing additional supplemental feed during postweaning development to accomplish this may be less efficient than later in development. Restricting gain during postweaning development by limiting DMI or developing heifers on dormant winter forage resulted in increased economic advantages compared with developing heifers at greater rates of ADG to achieve a greater target BW. Implications of heifer development system on cow longevity must be considered when evaluating economics of a heifer enterprise; however, studies evaluating the effects of heifer development systems on cow longevity are extremely limited.

Physiology and Endocrinology Symposium: Nutritional aspects of developing replacement heifers

Studies in numerous species provide evidence that diet during development can mediate physiological changes necessary for puberty. In cattle, several studies have reported inverse correlations between postweaning growth rate and age at puberty and heifer pregnancy rates. Thus, postweaning growth rate was determined to be an important factor affecting age of puberty, which in turn influences pregnancy rates. This and other research conducted during the late 1960s through the early 1980s indicated puberty occurs at a genetically predetermined size, and only when heifers reach their target BW can increased pregnancy rates be obtained. Guidelines were established indicating replacement heifers should achieve 60 to 65% of their expected mature BW by breeding. Traditional approaches for postweaning development of replacement heifers used during the last several decades have primarily focused on feeding heifers to achieve or exceed an appropriate target BW and thereby maximize heifer pregnancy rates. Intensive heifer development systems may maximize pregnancy rates, but not necessarily optimize profit or sustainability. Since inception of target BW guidelines, subsequent research demonstrated that the growth pattern heifers experience before achieving a critical target BW could be varied. Altering rate and timing of BW gain can result in compensatory growth periods, providing an opportunity to decrease feed costs. Recent research has demonstrated that feeding replacement heifers to traditional target BW increased development costs without improving reproduction or subsequent calf production relative to development systems in which heifers were developed to lighter target BW ranging from 50 to 57% of mature BW.

Differential gene expression in anterior pituitary glands from anestrous and cycling postpartum beef cows

Oligonucleotide microarrays (GeneChip Bovine Genome Arrays, Affymetrix Inc., Santa Clara, CA) were used to evaluate gene expression profiles in anterior pituitary glands collected from 4 anestrous and 4 cycling postpartum primiparous beef cows to provide insight into genes associated with transition from an anestrous to a cycling status. Tissues were collected 40 to 61 d after calving from anestrous cows and from cyclic cows between d 7 and 13 of the estrous cycle (luteal phase) from d 54 to 77 after calving. Hybridization signals were normalized across arrays, and genes with mean differences in expression that were at least 1.5-fold apart and with a minimum difference in mean signal intensity of 10 were compared. Based on these criteria, 47 transcripts were increased (P < 0.025) and 31 transcripts were decreased (P < 0.025) in pituitary gland tissue from cycling compared with anestrous cows. Few transcripts identified in this analysis were associated previously with reproductive function. To provide greater detail on the influence that stage of the estrous cycle (i.e., collection during the luteal phase) might have on the differences detected in gene expression, quantitative real-time PCR was used to compare gene expression in anterior pituitaries of anestrous cows with an additional independent set of anterior pituitary glands collected at 4 different stages of the estrous cycle: 0.5 to 2 d (n = 9), 5 to 6.5 d (n = 5), 11.4 to 13.7 d (n = 5), and 17.9 to 19 d (n = 6) after the onset of estrus. Gastrin-releasing peptide, the gene that exhibited the largest fold increase in expression in the microarray experiment, and IGFBP3 mRNA were expressed at greater (P < 0.004) amounts in samples from the different stages of the estrous cycle than in samples from anestrous cows. In addition, expression of IGFBP3 mRNA was proportional to serum progesterone concentrations throughout the estrous cycle (P < 0.05). Expression of versican mRNA was decreased (P = 0.03) in samples from the different stages of the estrous cycle compared with anestrous cow samples. Results identified numerous genes that may be involved in the transition from anestrous to cycling status, providing novel insight into mechanisms regulating reproductive function.

Reproductive performance of heifers offered ad libitum or restricted access to feed for a one hundred forty-day period after weaning

Reproductive performance was evaluated in composite heifers born over a 3-yr period that were randomly assigned to control (fed to appetite; n = 205) or restricted (fed at 80% of that consumed by controls adjusted to a common BW basis; n = 192) feeding for a 140-d period, beginning about 2 mo after weaning at 6 mo of age and ending at about 12.5 mo of age. Heifers were fed a diet of 67% corn silage, 18% alfalfa, and 9% of a protein-mineral supplement (DM basis). Restricted heifers consumed 27% less feed over the 140 d and had less ADG (0.53 +/- 0.01 vs. 0.65 +/- 0.01 kg/d; P < 0.001) than control heifers. After 140 d, all heifers were placed in common pens and subjected to an estrous synchronization protocol to facilitate AI at about 14 mo of age. Heifers were then exposed to bulls for the remainder of a 51-d breeding season. Average BW of heifers diverged within 28-d after initiation of feed restriction, and differences (P < 0.001) persisted through the prebreeding period (309 +/- 1 vs. 326 +/- 1 kg at approximately 13.5 mo of age) and subsequent grazing season (410 +/- 2 vs. 418 +/- 2 kg at about 19.5 mo of age). From the end of the 140-d restriction at about 12.5 to 19.5 mo of age, ADG was greater (P < 0.001) in restricted heifers than control heifers (0.51 +/- 0.01 vs. 0.47 +/- 0.01 kg/d). Proportion of heifers attaining puberty by 14 mo of age tended to be less (P = 0.1) in restricted (60 +/- 3%) than control-fed heifers (68 +/- 3%). Mean BW at puberty was less (P < 0.01) in restricted (309 kg) than control (327 kg) heifers. Pregnancy rate from AI tended to be less (P = 0.08) in restricted (48 +/- 4%) than control heifers (57 +/- 3%). Proportion of animals that were pubertal at breeding and pregnant from AI were positively associated (P < 0.1) with heifer age and ADG from birth to beginning of study. Final pregnancy rates were 87 and 91% for restricted and control heifers, respectively (P = 0.27). Day of breeding season that conception occurred was negatively associated with ADG from birth to weaning (P = 0.005), but was not associated with ADG within treatment (P = 0.60). Economic analysis revealed a $33 reduction in cost to produce a pregnant heifer under the restricted protocol when accounting for pregnancy rates and differences in BW and market prices between selection at weaning and marketing as open heifers at l.5 yr of age. A potential economic advantage exists for rearing replacement heifers on a restricted level of feeding during the postweaning period.

Physiological and functional impact of an unsupervised but supported exercise programme for claudicants

OBJECTIVES

To evaluate an unsupervised home-based exercise programme for physiological, functional, and quality of life impact in patients with symptomatic peripheral arterial disease.

DESIGN

Prospective cohort with exercise intervention.

MATERIALS

Human performance laboratory with non-invasive haemodynamic assessment facilities.

METHODS

Forty-seven patients with symptomatic peripheral arterial disease (mean age 67.6+/-7 years, 33 males) participated in an unsupervised home-based exercise programme. Heart rate (HR), ankle brachial blood pressure index (ABPI), leg blood flow (BF), and blood lactate were measured before and after a graded treadmill walk at baseline and after the 12-week exercise programme. Maximum walking distance (MWD) during the treadmill walk was measured at baseline and 12 weeks. Exercise compliance, functional parameters, and quality of life (VascuQoL) were assessed by questionnaire.

RESULTS

MWD, leg BF, and VascuQoL scores increased significantly, while resting HR, exercise HR, and end of walk rate-pressure-product (RPP) decreased significantly after 12 weeks. Exercise compliance was significantly correlated with increase in MWD (r=0.89, p<0.001) and QOL score improvement (r=0.61, p<0.001).

CONCLUSIONS

This supported but unsupervised exercise programme generated improvements in walking distance and leg blood flow without detectable increases in cardiorespiratory work. Exercise compliance is related to MWD and VascuQoL score in a dose-response manner.

Large variation in steroid concentrations and insulin-like growth factor binding proteins exists among individual small antral follicles collected from within cows at random stages of the estrous cycle

Variation in the biochemical status of individual small (< or = 5 mm diameter) antral follicles within the ovaries of a cow at any given time likely influences the capacity for undergoing recruitment, selection, and establishing dominance. The objectives of this study were to provide insight into the magnitude of variation in follicular fluid concentrations of steroids and activities of IGFBP that exists among individual small antral follicles within and between cows, and to determine the relationships between follicular fluid IGFBP and steroid concentrations in these follicles. A total of 108 small antral follicles were collected from 6 cows at random stages of the estrous cycle, with 10 to 26 follicles/cow. Concentrations of steroids (ng/mL of follicular fluid) in the overall population of follicles ranged from 0.1 (lowest detectable limit) to 51 for estradiol (E2), 4 to 1,149 for progesterone (P4), and 5 to 504 for androstenedione (A4). Concentrations of E2 and A4 were associated positively (r = 0.2; P < 0.02), but E2 (r = -0.4) and A4 (r = -0.4) were associated negatively, with P4. The proportion of variation in steroid concentrations accounted for by differences among animals (P < 0.05) was small for E2 (12%), moderate for P4 (43%), and greatest for A4 (74%). Least differences between minimum and maximum concentrations of steroids observed in follicles from within a cow were 21-, 5.5-, and 3.5-fold for E2, P4, and A4, respectively, whereas the greatest differences between minimum and maximum concentrations were 505-, 108-, and 26-fold for E2, P4, and A4, respectively. Ranges of IGFBP concentrations (arbitrary densitometer units) detected in fluid from a sub-sample of 43 follicles were 1.18 to 4.50 for IGFBP-3, 0.54 to 4.68 for IGFBP-2, 0.07 to 2.56 for IGFBP-4, and 0.01 to 6.71 for IGFBP-5. Concentrations of E2 were correlated negatively with each IGFBP (r = -0.4 to -0.8; P < 0.05) except IGFBP-3. In contrast, concentrations of A4 were correlated positively with IGFBP-3 (r = 0.4; P < 0.05) but were not correlated with other IGFBP. Concentrations of P4 were correlated positively (r > 0.4; P < 0.05) with IGFBP-4 and -5. The results indicate that steroid concentrations and IGFBP activities vary substantially among small antral follicles collected from within and among individual animals and that increasing production of E2, the hallmark of a developing follicle, was associated with reduced activity of all IGFBP except IGFBP-3, thereby implicating these IGFBP in the regulation of follicular recruitment.

Utilization of soybeans or corn milling by-products in beef heifer development diets

Whole raw soybeans (SB), wet corn gluten feed (WCGF), and corn dried distillers grains (DDG) are sources of protein in heifer development rations. The objectives of this study were to compare puberty status before synchronization of estrus, response to synchronization, and AI and final pregnancy rates in heifers developed on diets containing SB, WCGF, or DDG that were formulated to be similar in energy and CP. These ingredients vary substantially in fat content, which may affect reproductive performance. Rate of gain during the feeding period and post-AI performance were also compared. In a preliminary experiment, 104 crossbred heifers were fed diets containing either 1.25 kg of SB/d or 2.0 kg of WCGF/d for 110 d (DM basis), beginning at 10 mo of age. In Exp. 1, 100 crossbred heifers received either 1.25 kg of SB/d or 2.5 kg of WCGF/d from approximately 7 to 10 mo of age (91 d; 4 pens/diet), and then were fed 1.25 kg of SB/d for an additional 114 d (4 pens/diet). In Exp. 2, 1.25 kg of SB/d or 1.25 kg of DDG/d was fed to 100 crossbred heifers for 226 d, beginning at 6 mo of age (4 pens/diet). At approximately 13 mo of age, heifers were fed melengestrol acetate (0.5 mg/d) for 14 d, followed by an i.m. injection of PGF(2 alpha) (25 mg) 19 d later to synchronize estrus. Heifers (14 mo of age) received AI for 5 d after PGF(2 alpha), at which time the dietary treatments were ended. Heifers were commingled while grazing on native pasture and were exposed to bulls for approximately 60 d beginning 10 d after the last day of AI. Pregnancy to AI was determined by ultrasound 45 d after the last day of AI. Heifers fed SB in the preliminary experiment had a lower (P < 0.05) synchronization rate (81 vs. 96%) and longer interval (P = 0.05) from PGF(2 alpha) to estrus (76.6 vs. 69.2 h) compared with heifers fed WCGF. In Exp. 1, the age at which the heifers were begun on SB diets did not alter (P > 0.10) the synchronization rate (79%) or timing of estrus after PGF(2 alpha) (77.8 h). In Exp. 2, the synchronization rate (86%) and timing of estrus after PGF(2 alpha) (69.3 h) did not differ (P > 0.10) because of diet. No differences (P > 0.10) were due to diet for AI conception rates (overall mean for each experiment: 76.5, 60, and 68.5%), percentage of all heifers becoming pregnant to AI (67, 46, and 59%), or final pregnancy rates (92, 90, and 90%) in the preliminary experiment, Exp. 1, or Exp. 2, respectively. In summary, SB, DDG, and WCGF can be used as sources of protein in heifer development diets at the inclusion rates used in these studies.

Milk yield of primiparous beef cows from three calving systems and varied weaning ages

Primiparous beef cows produced in 3 calving systems were used in a 2-yr study with a completely random design to measure milk yield throughout a 190-d lactation (2002, n = 20; 2003, n = 24 per calving system). Calving occurred in late winter (average calving date = February 4 +/- 2 d), early spring (average calving date = March 30 +/- 2 d), and late spring (average calving date = May 26 +/- 1 d). Additionally, cows used in this study had been weaned at varied ages as calves, creating 6 dam treatments. Dam age at weaning was 140 (late spring), 190 (late winter, early spring, late spring), or 240 (late winter, early spring) d of age. Milk production was measured by using the weigh-suckle-weigh technique at an average of 20, 38, 55, 88, 125, 163, and 190 d in milk. Milk yield for the 190-d lactation period was calculated as area under the curve by trapezoidal summation. Data were analyzed with a model containing treatment, year, and their interaction. Orthogonal contrasts were used to separate effects when treatment was significant (P < 0.10). Total milk yield did not differ (P = 0.42) between cows in the late winter and early spring systems, but cows in the late spring system tended to differ (P = 0.09) from the average of the other 2 systems. Cows in the late spring calving system had increased milk yield in 2002 and lesser milk yield in 2003 compared with the other calving systems (treatment x year interaction, P < 0.001). Cows born in late spring that had been weaned at 140 d of age produced more (P = 0.05) total milk than those weaned at 190 d of age. Peak milk yield was affected (P < 0.001) by treatment and showed a treatment x year interaction (P = 0.006). Day of peak lactation differed among treatments (P = 0.002), with cows in the late winter system peaking later (P = 0.007) than early spring cows, and late spring cows peaking earlier (P = 0.004) than the average of late winter and early spring cows. The average date of peak lactation was May 4 for the late winter system, May 31 for the early spring system, and July 19 for the late spring system. Calf ADG differed (P < 0.001) for the late spring system compared with the average of the late winter and early spring systems, but the relationship interacted with year (P < 0.001). Cow BW and BW change differed among treatments (P < 0.004), with much of the difference associated with the amount of milk produced or the timing of peak lactation. Season of calving affects milk yield of primiparous cows grazing Northern Great Plains rangelands and ADG of their calves.

Effects of restricted feeding of beef heifers during the postweaning period on growth, efficiency, and ultrasound carcass characteristics1

Traits used for identification of replacement beef heifers and feeding levels provided during postweaning development may have major financial implications due to effects on maintenance requirements and level of lifetime production. The current study evaluated the effects of 2 levels of feeding during the postweaning period on growth, G:F, and ultrasound carcass measurements of heifers, and the associations among these traits. Heifers (1/2 Red Angus, 1/4 Charolais, and 1/4 Tarentaise) born in 3 yr were randomly assigned to a control (fed to appetite; n = 205) or restricted (fed at 80% of that consumed by controls adjusted to a common BW basis; n = 192) feeding during a 140-d postweaning period. Heifers were individually fed a diet of 68% corn silage, 18% alfalfa, and protein-mineral supplement (DM basis) in pens equipped with Calan gates. Ultrasound measurements of LM area, intramuscular fat, and subcutaneous fat thickness over the LM were made on d 140 (382 +/- 0.8 d of age). Average daily DMI was 4.1 and 5.6 kg/d for restricted and control heifers, respectively (P < 0.001). Feed restriction decreased (P < 0.001) BW (292 vs. 314 kg), ADG (0.52 vs. 0.65 kg/d), LM area (55 vs. 59 cm2), intramuscular fat (3.2 vs. 3.5%), and subcutaneous fat thickness over the LM (3.2 vs. 3.9 mm), but increased G:F (0.12 vs. 0.11) when compared with control at the end of the 140-d study. The magnitude of the associations of DMI with ADG (r = 0.32 vs. 0.21), 140-d BW (r = 0.78 vs. 0.36), hip height (r = 0.57 vs. 0.17), LMA (r = 0.30 vs. 0.18), and BCS (r = 0.17 vs. 0.11) was greater in restricted- than control-fed heifers. Variance of residual feed intake, calculated within each treatment, was greater (P < 0.01) in control (0.088) than restricted (0.004) heifers, and magnitude of association between residual feed intake and average DMI was greater in control (r = 0.88) than restricted (r = 0.41) heifers. Pregnancy rate tended (P = 0.11) to be reduced in heifers that had been developed on restricted feeding (86.3 +/- 2.3 vs. 91.5 +/- 2.3%). However, ADG was greater (P < 0.001) in restricted than control heifers (0.51 vs. 0.46 kg/d) while grazing native range in the 7 mo after restriction. In summary, restricted heifers consumed 22% less feed on a per-pregnant-heifer basis during the development period and had a greater magnitude of association between DMI and several growth-related traits at the end of the 140-d postweaning feeding period, which is indicative of improved efficiency.

Influence of seasonal forage quality on glucose kinetics of young beef cows1

Extensive range livestock production systems in the western United States rely heavily on rangeland forages to meet the nutritional needs of grazing livestock throughout the year. Interannual variation in the quantity and quality of rangeland forage in the Northern Great Plains, as well as throughout much of the western United States, may play a pivotal role in how well grazing ruminants sequester nutrients in their tissues. This variation in forage quality may influence the ability of a beef cow to utilize dietary nutrients via changes in tissue responsiveness to insulin. Identifying specific periods and production states in which this phenomenon is manifested will provide insight into the development and implementation of strategic and targeted supplementation practices that improve nutrient utilization during times of nutritional imbalance and may improve the lifetime productivity of grazing range beef cows. A 2-yr study was conducted to monitor serum metabolites, glucose kinetics during glucose tolerance tests, and forage chemical composition every 90 d in young cows (2 to 4 yr of age; n = 28). In yr 1 and 2, cows were managed on 4 pastures varying in size from 36 to 76 ha in yr 1 and 49 to 78 ha in yr 2. Regardless of year, cow age, or cow physiological status, the main factor influencing glucose half-life was season of the year (P = 0.02). Effects of season on glucose half-life closely followed assessments describing forage quality, with glucose half-lives of 46, 39, 43, and 51 +/- 3.9 min for May, August, December, and March, respectively. Elevated glucose half-life during seasons in which forage quality is of lower nutritive value indicated that tissue responsiveness to the actions of insulin followed seasonal changes in forage quality. Glucose half-life tended (P = 0.09) to decrease between May and August, increased (P = 0.04) between December and March, and showed a tendency (P = 0.10) to decrease in seasons of greater nutrient density (May and August) compared with seasons of lower nutrient density (December and March). Seasonal changes in serum metabolites were also observed and corresponded with changes in forage quality. The results support our hypothesis that as the season progresses and forage quality declines, maternal tissues become less responsive to insulin, indicating that targeted supplementation with glucogenic precursors during these seasons of nutritional stress may improve cow performance.

Caries Prevalence Four Years after the End of a Randomised Controlled Trial

This study measured dental caries in children after cessation of a 30-month randomised clinical trial in which the intervention group received supervised toothbrushing once a day at school with 1,000 ppm fluoride toothpaste and a home support package encouraging twice-daily toothbrushing. The non-intervention group did not brush at school or receive the home support package. Children were aged 5 years at baseline and were examined every 6 months during the trial, then at 6, 18, 30 and 54 months after the end of the trial. Significantly less caries developed in first permanent molars of intervention children at the end of the trial. Of the 428 children who were examined at the end of the trial 329 (77%) were examined 54 months later when the children were aged 12 years on average. The intervention group still had less caries (D3FS caries increment 1.62) than the non-intervention children (D3FS caries increment 2.65, p < 0.05). Prolonged benefits have been found for intervention children principally in less caries in first permanent molars. Further follow-up at an age when the second molars and premolars have all erupted will help determine whether this benefit is due to a long-term behavioural change or a prolonged biological effect.

Relationship between size of the ovulatory follicle and pregnancy success in beef heifers1

Previous research indicated that the size of the ovulatory follicle at the time of insemination significantly influenced pregnancy rates and embryonic/fetal mortality after fixed-timed AI in postpartum cows, but no effect on pregnancy rates was detected when cows ovulated spontaneously. Our objective was to evaluate relationships of fertility and embryonic/fetal mortality with preovulatory follicle size and circulating concentrations of estradiol after induced or spontaneous ovulation in beef heifers. Heifers were inseminated in 1 of 2 breeding groups: (1) timed insemination after an estrous synchronization and induced ovulation protocol (TAI n = 98); or (2) AI approximately 12 h after detection in standing estrus by electronic mount detectors during a 23-d breeding season (spontaneous ovulation; n = 110). Ovulatory follicle size at time of AI and pregnancy status 27, 41, 55, and 68 d after timed AI (d 0) were determined by transrectal ultrasonography. Only 6 heifers experienced late embryonic or early fetal mortality. Interactions between breeding groups and follicle size did not affect pregnancy rate (P = 0.13). Pooled across breeding groups, logistic regression of pregnancy rate on follicle size was curvilinear (P < 0.01) and indicated a predicted maximum pregnancy rate of 68.0 +/- 4.9% at a follicle size of 12.8 mm. Ovulation of follicles < 10.7 mm or > 15.7 mm was less likely (P < 0.05) to support pregnancy than follicles that were 12.8 mm. Ovulatory follicles < 10.7 mm were more prevalent (28% of heifers) than ovulatory follicles > 15.7 mm (4%). Heifers exhibiting standing estrus within 24 h of timed AI had greater (P < 0.01) follicle diameter (12.2 +/- 0.2 mm vs. 11.1 +/- 0.3 mm) and concentrations of estradiol (9.9 +/- 0.6 vs. 6.6 +/- 0.7) and pregnancy rates (63% vs. 20%) than contemporaries that did not exhibit behavioral estrus. However, when differences in ovulatory follicle size were accounted for, pregnancy rates were independent of expression of behavioral estrus or circulating concentration of estradiol. Therefore, the effects of serum concentrations of estradiol and behavioral estrus on pregnancy rate appear to be mediated through ovulatory follicle size, and management practices that optimize ovulatory follicle size may improve fertility.

Aged APP23 mice show a delay in switching to the use of a strategy in the Barnes maze

Spatial learning and memory deficits in the APP23 transgenic mice have mainly been studied using the Morris water maze (MWM). However learning in the MWM relies on swimming abilities and may be confounded by the stressful nature of this test. We have therefore assessed spatial learning and memory in 12-month-old APP23 using a dry-land maze test developed by Barnes. Mice were given daily learning trials for a total of 41 successive days. After a 12-day interval the mice were re-tested for 4 additional days in order to examine the spatial memory retention. Immediately following this phase, reversal learning was examined for 13 additional days by moving the escape tunnel to the opposite position. During the initial learning phase, APP23 mice showed a significantly longer latency to find the escape tunnel as well as an increased number of errors compared to non-transgenic littermates. These deficits appeared to be due to a delay in switching from a "no strategy" to a spatial strategy. Indeed, this same delay in the use of spatial strategy was observed in the reversal phase of the study. Our results suggest that impairments in APP23 mice in learning and memory maze tests may be due to a specific deficit in the use of spatial strategy.