Association of glucose metabolism and insulin resistance with feed efficiency and production traits of finishing beef steers.

Increasing nutrient utilization efficiency is an important component of enhancing the sustainability of beef cattle production. The objective of this experiment was to determine the association of glucose metabolism and insulin resistance with dry matter intake (DMI), average daily gain (ADG), gain:feed ratio (G:F), and residual feed intake (RFI). Steers (n = 54; initial body weight = 518 ±â€…27.0 kg) were subjected to an intravenous glucose tolerance test (IVGTT) where glucose was dosed through a jugular catheter and serial blood samples were collected. Three days after the last group's IVGTT, steers began a 63-d DMI and ADG test. Body weight was measured on days 0, 1, 21, 42, 62, and 63, and DMI was measured using an Insentec Roughage Intake Control system (Hokofarm Group, Emmeloord, the Netherlands). To examine relationships between DMI, ADG, G:F, and RFI with IVGTT measurements, Pearson correlations were calculated using Proc Corr of SAS 9.4 (SAS Inst. Inc., Cary, NC). Additionally, cattle were classified based on DMI, ADG, RFI, and G:F, where the medium classification was set as mean ±â€…0.5 SD, the low classification was < 0.5 SD from the mean, and the high classification was > 0.5 SD from the mean. No associations between DMI and IVGTT parameters were observed, and no differences were detected when classifying cattle as having low, medium, or high DMI. Peak insulin concentration in response to the IVGTT tended to be correlated with ADG (r = 0.28; P = 0.07), indicating cattle with greater ADG tend to have a greater insulin release in response to glucose. Glucose nadir concentrations tended to be positively correlated with ADG (r = 0.26; P = 0.10). Additionally, the glucose nadir was greater in high-ADG steers (P = 0.003). The association of greater glucose nadir with high-ADG could indicate that high-ADG steers do not clear glucose as efficiently as low-ADG steers, potentially indicating increased insulin resistance. Further, RFI was not correlated with IVGTT measurements, but low RFI steers had a greater peak glucose concentration (P = 0.040) and tended to have a greater glucose area under the curve (P = 0.09). G:F was correlated with glucose area under the curve (r = 0.33; P = 0.050), glucose nadir (r = 0.35; P = 0.011), and insulin time to peak (r = 0.39; P = 0.010). These results indicate that glucose metabolism and insulin signaling are associated with growth and efficiency, but the molecular mechanisms that drive these effects need to be elucidated.

Feed efficiency is an important component of improving the sustainability of beef production. There is a need to understand how metabolism influences feed efficiency. This experiment aimed to explore the association of glucose metabolism and insulin resistance with feed intake, growth, and efficiency of finishing beef cattle. The results indicate that there is a relationship between insulin resistance and improved efficiency measured as the ratio of growth to feed intake. The findings of this experiment are novel as they show a relationship between insulin resistance and feed efficiency and indicate further research is needed to determine the mechanisms of insulin resistance in ruminants that contribute to improved feed efficiency.

Technical note: Validation of energy dispersive X-ray fluorescence for determination of indigestible markers in ruminant fecal and rumen fluid samples.

Determination of digestibility and passage rate is important for further understanding of nutrient utilization and thereby aids in improving nutrient utilization efficiency. Titanium dioxide and chromium ethylenediaminetetraacetic acid are commonly used as indigestible markers for determining passage rates of diets to aid in determination of digestibility. Analyzing Ti and Cr involves the use of procedures such as acid digestions, inductively coupled plasma spectroscopy, and atomic absorption. These commonly used methodologies involve hazardous chemicals, destruction of samples, and low sample throughput. The objective of this experiment was to develop and validate an accurate and precise method for measuring both Ti and Cr using energy dispersive X-ray fluorescence (ED-XRF). Energy dispersive X-ray fluorescence is an analytical technique used for analyzing elements in various sample types. The samples were added to the ED-XRF machine and irradiated with X-rays. The intensity of the X-rays emitted (termed fluorescent X-rays) was used for calculation of the concentration of the element. The method for Ti was constructed using fecal samples from cattle consuming three different diet types (finishing diet, dairy lactation diet, and grazing native range pasture). The Cr method was developed for rumen fluid analysis. We compared the machine-calculated concentrations of each element to the concentration calculated by a standard curve. For both the Ti and Cr, the standard curve-calculated value had a lower percent difference overall at 4.56% and 12.59%, respectively, compared to the machine percent difference of 8.35% and 16.38% for Ti and Cr, respectively. To determine accuracy and precision of the method, samples were spiked with various amounts of Ti or Cr and measured for their respective compounds with percent recovery and inter- and intra-assay CV-calculated thereafter. The average recovery for Ti across all diet types was 100.3%, and the recovery for Cr in rumen fluid was 95.7%. The average inter- and intra-assay CV for Ti, across all diet types, were 9.70% and 2.16%, respectively. For Cr, the average inter- and intra-assay CV were 5.42% and 8.45%, respectively. The ED-XRF method requires minimal additional chemicals, is cost-effective, and allows for sample preservation as well as a high throughput of samples. Our results indicate utilization of ED-XRF is an accurate and precise method for determination of Ti in feces and Cr in rumen fluid.

Markers are elements supplied to an animal to help determine the digestibility of various feedstuffs. Studying digestibility allows us to improve how nutrients are used by animals and reduce production costs and environmental impact. The method proposed here uses an X-ray fluorescence machine to analyze the markers with no hazardous chemicals, low labor input, and cost. Even though this equipment utilizes radiation, the construction of the equipment eliminates the exposure of operators to radiation. Training and monitoring will differ between institutions. Traditional methods use hazardous chemicals and have higher cost and labor use. We determined that this is a valid method for analyzing titanium in fecal samples and chromium in rumen fluid.

Ergot alkaloids reduce circulating serotonin in the bovine.

Ergot alkaloids can interact with several serotonin (5-hydroxytryptamine [5-HT]) receptors provoking many physiological responses. However, it is unknown whether ergot alkaloid consumption influences 5-HT or its metabolites. Thus, two experiments were performed to evaluate the effect of ergot alkaloid feeding on 5-HT metabolism. In exp. 1, 12 Holstein steers (260 ± 3 kg body weight [BW]) were used in a completely randomized design. The treatments were the dietary concentration of ergovaline: 0, 0.862, and 1.282 mg/kg of diet. The steers were fed ad libitum, kept in light and temperature cycles mimicking the summer, and had blood sampled before and 15 d after receiving the treatments. The consumption of ergot alkaloids provoked a linear decrease (P = 0.004) in serum 5-HT. However, serum 5-hydroxytryptophan and 5-hydroxyindoleacetic acid did not change (P > 0.05) between treatments. In exp. 2, four ruminally cannulated Holstein steers (318 ± 3 kg BW) were used in a 4 × 4 Latin square design to examine the difference between seed sources on 5-HT metabolism. Treatments were: control-tall fescue seeds free of ergovaline, KY 32 seeds (L42-16-2K32); 5Way-endophyte-infected seeds, 5 way (L152-11-1739); KY31-endophyte-infected seeds, KY 31 (M164-16-SOS); and Millennium-endophyte-infected seeds, 3rd Millennium (L108-11-76). The endophyte-infected seed treatments were all adjusted to provide an ergovaline dosage of 15 µg/kg BW. The basal diet provided 1.5-fold the net energy requirement for maintenance. The seed treatments were dosed directly into the rumen before feeding. The experiment lasted 84 d and was divided into four periods. In each period, the steers received seeds for 7 d followed by a 14-d washout. Blood samples were collected on day 0 (baseline) and day 7 for evaluating the treatment response in each period. A 24 h urine collection was performed on day 7. Similar to exp. 1, serum 5-HT decreased (P = 0.008) with the consumption of all endophyte-infected seed treatments. However, there was no difference (P > 0.05) between the infected seeds. The urinary excretion of 5-hydroxyindoleacetic acid in the urine was not affected (P > 0.05) by the presence of ergot alkaloids. In conclusion, the consumption of ergot alkaloids decreases serum 5-HT with no difference between the source of endophyte-infected seeds in the bovine.

Driver crash risk factors and prevalence evaluation using naturalistic driving data.

The accurate evaluation of crash causal factors can provide fundamental information for effective transportation policy, vehicle design, and driver education. Naturalistic driving (ND) data collected with multiple onboard video cameras and sensors provide a unique opportunity to evaluate risk factors during the seconds leading up to a crash. This paper uses a National Academy of Sciences-sponsored ND dataset comprising 905 injurious and property damage crash events, the magnitude of which allows the first direct analysis (to our knowledge) of causal factors using crashes only. The results show that crash causation has shifted dramatically in recent years, with driver-related factors (i.e., error, impairment, fatigue, and distraction) present in almost 90% of crashes. The results also definitively show that distraction is detrimental to driver safety, with handheld electronic devices having high use rates and risk.

The Impact of Family Rules on Children's Eating Habits, Sedentary Behaviors, and Weight Status.

BACKGROUND: Family rules may be influential in helping children to modify their dietary and sedentary behaviors, which are important modifiable risk factors for childhood obesity. However, data examining family rules in relation to children's health behaviors and weight status are limited. METHODS: This cross-sectional study examined differences in family rules by demographic characteristics of students enrolled in the HEROES (Healthy, Energetic, Ready, Outstanding, Enthusiastic Schools) Initiative, a school-based childhood obesity prevention program. It also investigated the relationship between eating and screen time family rules and six eating and screen time behaviors: fast food consumption; soft drink consumption; fruit and vegetable intake; television viewing; computer use; and video game use, in addition to the association between family rules and children's weight status. Measures included self-reported behavioral data and anthropometric data from students in fourth to eighth grade at 16 schools (N=2819) in a tri-state area of the United States in spring 2012. RESULTS: Approximately one-third of students had each of the family rules examined. Whereas the profile of students who had specific rules varied, in general, younger, female, white, and low socioeconomic status students were more likely to have rules than their counterparts. Family rules were associated with healthier outcomes for each of the six behaviors examined (p<0.001), even after controlling for demographics (p<0.001). However, family rules were not associated with children's weight status. CONCLUSIONS: This study demonstrates that family rules are an underutilized strategy to promote healthier eating habits and reduce children's screen time hours and may serve as an intermediary mechanism to curb childhood obesity.

The relationship between school-level characteristics and implementation fidelity of a coordinated school health childhood obesity prevention intervention.

BACKGROUND: Curtailing childhood obesity is a public health imperative. Although multicomponent school-based programs reduce obesity among children, less is known about the implementation fidelity of these interventions. This study examines process evaluation findings for the Healthy, Energetic Ready, Outstanding, Enthusiastic, Schools (HEROES) Initiative, a tri-state school-based childhood obesity prevention intervention based on the coordinated school health (CSH) model. METHODS: Site visits were conducted that included key stakeholder interviews, observation, and document review. Scores were given for 8 domains, and a total implementation score was calculated. Two-way analyses of variance were conducted to examine the relationship of 4 school-level characteristics: elementary vs. middle/high schools, public vs. private schools, district vs. building level implementation, and socioeconomic status on each implementation area. RESULTS: Overall, schools had high fidelity scores, although some domains were implemented more successfully than others. Three school-level characteristics were associated with 1 or more domains, with elementary schools and schools implementing at the building level consistently having higher implementation scores than their counterparts. CONCLUSIONS: Process evaluation findings provide insight into successes and challenges schools implementing the CSH approach may encounter. Although preliminary, these findings on school-level characteristics establish a new area of research related to school-based childhood obesity prevention programs' implementation fidelity.

Predictors for Persistent Overweight, Deteriorated Weight Status, and Improved Weight Status During 18 Months in a School-Based Longitudinal Cohort.

PURPOSE: To examine predictors for persistent overweight/obesity, deteriorated weight status, and improved weight status among students who participated in a school-based obesity prevention intervention from fall 2009 to spring 2011. DESIGN: Longitudinal assessment of a school-based cohort was conducted to determine the characteristics of students who remained overweight/obese, improved their weight status, or showed deteriorated weight status during an 18-month period. SETTING: Eleven schools in southern Indiana, northwestern Kentucky, and southeastern Illinois. SUBJECTS: N = 5309 students in 4th through 12th grade. MEASURES: Weight, height, and self-reported physical activity and nutrition behaviors of students were measured at baseline and 6, 12, and 18 months. ANALYSIS: SAS 9.3 was employed to examine predictors for the three different weight categories using logistic regression. RESULTS: Low socioeconomic status (SES) (adjusted odds ratio [AOR] = 1.56 and p < .001, AOR = 1.35 and p = .0069, respectively) and higher soda intake (AOR = 1.07 and p = .0016, AOR = 1.08 and p = .0278, respectively) increased the odds of belonging to persistent overweight/obesity (30.6%) and deteriorated weight status (6.9%), compared to the persistent nonoverweight status group. CONCLUSION: While SES is an important determinant of weight category change, students' screen time and soda consumption may be important factors. Schools and families may be able to successfully focus on these modifiable risk factors, decreasing the burden of childhood obesity.

Long-term predictors of blood pressure among adolescents during an 18-month school-based obesity prevention intervention.

PURPOSE: To evaluate the effectiveness of the HEROES (Healthy, Energetic, Ready, Outstanding, Enthusiastic Schools) initiative, a multicomponent school-based obesity prevention intervention based on the Centers for Disease Control and Prevention's coordinated school health approach, on the improvement of blood pressure (BP) and to determine long-term predictors of systolic and diastolic BP changes among high school students who were exposed to the intervention. METHODS: Biometric and behavioral data from high school students were analyzed at baseline, 6, 12, and 18 months (N = 847, three schools). The attrition rate at 18 months was 26.1%. Sequential generalized estimating equation models were fit to the data using SAS 9.3, taking into account clustering effects within the same school and correlations within repeated measures. RESULTS: A significant downward trend was observed in systolic BP (p = .0006) and diastolic BP (p < .0001) among the students who were exposed to the HEROES initiative. The prevalence of hypertension decreased from 17.1% at baseline to 12.8% at 6 months (p < .0001), 12.0% at 12 months (p < .0001), and 15.0% (p = .0024) at 18 months. Baseline body mass index, increases in body mass index percentiles, and increases of television-viewing hours were associated with BP increases. Increases in frequencies of eating french fries or chips, skipping breakfast, and consuming supersize meals when eating fast food were predictive of systolic BP changes, not of diastolic BP changes. CONCLUSIONS: An 18-month multicomponent school-based obesity intervention program may be effectively used to decrease rates of high BP among adolescents.

Implementation and evaluation of the HEROES initiative: a tri-state coordinated school health program to reduce childhood obesity.

This article describes the design, implementation, and evaluative findings of the HEROES (Healthy, Energetic, Ready, Outstanding, Enthusiastic, Schools) Initiative, a school-based multilevel childhood obesity prevention intervention. Based on the Centers for Disease Control and Prevention's recommended coordinated school health approach, the HEROES Initiative works to alleviate the burden of childhood obesity in Southern Indiana, Northwestern Kentucky, and Southeastern Illinois in the United States. Process evaluation was conducted with the 17 participating schools in spring 2012 based on interviews with school personnel and observation of the school environment. Findings showed that despite some variability, schools were generally able to implement the intervention with fidelity. School-level outcome evaluation was also based on observation of the school environment, and revealed that schools had implemented a number of new practices to encourage physical activity and healthy eating. Assessment of student-level outcomes was based on professionally collected physiological measurements and self-reported behavioral data collected over an 18-month period of time, last collected in spring 2012. Findings demonstrated that the HEROES Initiative has been successful in reducing the percentage of overweight children in participating schools and healthfully modifying their dietary, physical activity, and sedentary behaviors. Strategies that have facilitated success and challenges related to the intervention are discussed.

Predictors for moderate- and vigorous-intensity physical activity during an 18-month coordinated school health intervention.

OBJECTIVE: To evaluate if the HEROES Initiative, a school-based childhood obesity prevention program based on the U. S. Centers for Disease Control and Prevention (CDC)'s coordinated school health approach was able to effectively increase physical activity among elementary and middle school students who were exposed to the program for 18 months and to determine student and school-level predictors of success. METHOD: Students who participated in physiological data collection were invited to participate in a survey at baseline, 6 months, and 18 months (N=1091, 8 schools). The dropout rate at 18 months was 39.1% when graduates were counted. Data was analyzed using generalized estimating equations. RESULTS: A significant increase (p=.0067) was observed in vigorous-intensity physical activity (VPA) but a non-significant increase (p=.1753) was observed in moderate-intensity physical activity (MPA). Each school's implementation fidelity score was also only associated with VPA increases. Students' screen time and vegetable/fruit intake were independently associated with both VPA and MPA increases. Body mass index of students was not predictive of VPA or MPA changes. CONCLUSION: An 18-month school-based intervention that employs the CDC's coordinated school health approach appears to be effective in increasing physical activity among elementary and middle school children.