Influence of Proportions of Concentrates to Roughage with Various Feed Additives on the Feedlot Performance of Growing and Finishing Steers

In any feeding operation considerable attention should be given to the selection of a proper ration. A ration that will produce the most rapid gain will not necessarily produce the most economical gain. Rate of gain and fattening depend on the intake of digestible energy in excess of maintenance when the ration contains adequate amounts of other essential nutrients. Since many feed additives have become available in recent years, it is important to know their effects with various types of rations. Diethylstillbestrol have been reported to consistently improve gain and feed efficiency. Other feed additives have not been investigated as extensively as diethylstilbestrol, and only limited work has been reported concerning the value of various feed additives when fed with different types of rations. Diethylstillbestrol, diallydiethylstillbestrol, tetra-alkylammonium stearate (dynafac) and an enzyme preparation (Agrozyme) were tested to determine the response to these compunds when feeding rations containing various levels of energy

Improving newborn respiratory outcomes with a sustained inflation: a systematic narrative review of factors regulating outcome in animal and clinical studies

Respiratory support is critically important for survival of newborns who fail to breathe spontaneously at birth. Although there is no internationally accepted definition of a sustained inflation (SI), it has commonly been defined as a positive pressure inflation designed to establish functional residual capacity and applied over a longer time period than normally used in standard respiratory support (SRS). Outcomes vary distinctly between studies and to date there has been no comprehensive investigation of differences in SI approach and study outcome in both pre-clinical and clinical studies. A systematic literature search was performed and, after screening, identified 17 animal studies and 17 clinical studies evaluating use of a SI in newborns compared to SRS during neonatal resuscitation. Study demographics including gestational age, SI parameters (length, repetitions, pressure, method of delivery) and study outcomes were compared. Animal studies provide mechanistic understanding of a SI on the physiology underpinning the cardiorespiratory transition at birth. In clinical studies, there is considerable difference in study quality, delivery of SIs (number, pressure, length) and timing of primary outcome evaluation which limits direct comparison between studies. The largest difference is method of delivery, where the role of a SI has been observed in intubated animals, as the inflation pressure is directly applied to the lung, bypassing the obstructed upper airway in an apnoeic state. This highlights a potential limitation in clinical use of a SI applied non-invasively. Further research is required to identify if a SI may have greater benefits in subpopulations of newborns.Developmen

A YoeB toxin cleaves both RNA and DNA

Type II toxin-antitoxin systems contain a toxin protein, which mediates diverse interactions within the bacterial cell when it is not bound by its cognate antitoxin protein. These toxins provide a rich source of evolutionarily-conserved tertiary folds that mediate diverse catalytic reactions. These properties make toxins of interest in biotechnology applications, and studies of the catalytic mechanisms continue to provide surprises. In the current work, our studies on a YoeB family toxin from Agrobacterium tumefaciens have revealed a conserved ribosome-independent non-specific nuclease activity. We have quantified the RNA and DNA cleavage activity, revealing they have essentially equivalent dose-dependence while differing in requirements for divalent cations and pH sensitivity. The DNA cleavage activity is as a nickase for any topology of double-stranded DNA, as well as cleaving single-stranded DNA. AtYoeB is able to bind to double-stranded DNA with mid-micromolar affinity. Comparison of the ribosome-dependent and -independent reactions demonstrates an approximate tenfold efficiency imparted by the ribosome. This demonstrates YoeB toxins can act as non-specific nucleases, cleaving both RNA and DNA, in the absence of being bound within the ribosome.This work was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health [P20GM103640]. Financial support was provided from the Office of the Vice President for Research and the Office of the Provost, University of Oklahoma. Open Access fees paid for in whole or in part by the University of Oklahoma Libraries.Ye

High vs. Low Initial Oxygen to Improve the Breathing Effort of Preterm Infants at Birth: Study Protocol for a Randomized Controlled Trial

Background: Although most preterm infants breathe at birth, their respiratory drive is weak and supplemental oxygen is often needed to overcome hypoxia. This could in turn lead to hyperoxia. To reduce the risk of hyperoxia, currently an initial low oxygen concentration (21–30%) is recommended during stabilization at birth, accepting the risk of a hypoxic period. However, hypoxia inhibits respiratory drive in preterm infants. Starting with a higher level of oxygen could lead to a shorter duration of hypoxia by stimulating breathing effort of preterm infants, and combined with subsequent titration based on oxygen saturation, prolonged hyperoxia might be prevented.Study design: This multi-center randomized controlled trial will include 50 infants with a gestational age between 24 and 30 weeks. Eligible infants will be randomized to stabilization with an initial FiO2 of either 1.0 or 0.3 at birth. Hereafter, FiO2 will be titrated based on the oxygen saturation target range. In both groups, all other interventions during stabilization and thereafter will be similar. The primary outcome is respiratory effort in the first 5 min after birth expressed as average minute volume/kg. Secondary outcomes include inspired tidal volumes/kg, rate of rise to maximum tidal volume/kg, percentage of recruitment breaths with tidal volumes above 8 mL/kg, duration of hypoxia and hyperoxia and plasma levels of markers of oxidative stress (8-iso-prostaglandin F2α).Discussion: Current resuscitation guidelines recommend oxygen titration if infants fail to achieve the 25th percentile of the SpO2 reference ranges. It has become clear that, using this approach, most preterm infants are at risk for hypoxia in the first 5 min after birth, which could suppress the breathing effort. In addition, for compromised preterm infants who need respiratory support at birth, higher SpO2 reference ranges in the first minutes after birth might be needed to prevent prolonged hypoxia. Enhancing breathing effort by achieving an adequate level of oxygenation could potentially lead to a lower incidence of intubation and mechanical ventilation in the delivery room, contributing to a lower risk on lung injury in high-risk preterm infants. Measuring 8-iso-prostaglandin F2α could lead to a reflection of the true amount of oxygen exposure in both study groups

Increasing Respiratory Effort With 100% Oxygen During Resuscitation of Preterm Rabbits at Birth

Background: Spontaneous breathing is essential for successful non-invasive respiratory support delivered by a facemask at birth. As hypoxia is a potent inhibitor of spontaneous breathing, initiating respiratory support with a high fraction of inspired O2 may reduce the risk of hypoxia and increase respiratory effort at birth. Methods: Preterm rabbit kittens (29 days gestation, term ~32 days) were delivered and randomized to receive continuous positive airway pressure with either 21% (n = 12) or 100% O2 (n = 8) via a facemask. If apnea occurred, intermittent positive pressure ventilation (iPPV) was applied with either 21% or 100% O2 in kittens who started in 21% O2, and remained at 100% O2 for kittens who started the experiment in 100% O2. Respiratory rate (breaths per minute, bpm) and variability in inter-breath interval (%) were measured from esophageal pressure recordings and functional residual capacity (FRC) was measured from synchrotron phase-contrast X-ray images. Results: Initially, kittens receiving 21% O2 had a significantly lower respiratory rate and higher variability in inter-breath interval, indicating a less stable breathing pattern than kittens starting in 100% O2 [median (IQR) respiratory rate: 16 (4–28) vs. 38 (29–46) bpm, p = 0.001; variability in inter-breath interval: 33.3% (17.2–50.1%) vs. 27.5% (18.6–36.3%), p = 0.009]. Apnea that required iPPV, was more frequently observed in kittens in whom resuscitation was started with 21% compared to 100% O2 (11/12 vs. 1/8, p = 0.001). After recovering from apnea, respiratory rate was significantly lower and variability in inter-breath interval was significantly higher in kittens who received iPPV with 21% compared to 100% O2. FRC was not different between study groups at both timepoints. Conclusion: Initiating resuscitation with 100% O2 resulted in increased respiratory activity and stability, thereby reducing the risk of apnea and need for iPPV after birth. Further studies in human preterm infants are mandatory to confirm the benefit of this approach in terms of oxygenation. In addition, the ability to avoid hyperoxia after initiation of resuscitation with 100% oxygen, using a titration protocol based on oxygen saturation, needs to be clarified

Physiologic-Based Cord Clamping Maintains Core Temperature vs. Immediate Cord Clamping in Near-Term Lambs

Background: Physiologic-based cord clamping (PBCC) involves deferring umbilical cord clamping until after lung aeration. It is unclear if infant is at risk of becoming hypothermic during PBCC. Objectives: To test if PBCC would maintain core temperature more effectively than immediate cord clamping (ICC). Design: At 0.93 gestation, fetal lambs were surgically exteriorized and instrumented from pregnant ewes under general anesthesia. Prior to the start of the experiment, lambs were thoroughly dried, placed on hot water bottles, and core temperature was continuously monitored using a rectal thermometer. PBCC lambs (n = 21), received intermittent positive pressure ventilation (iPPV) for ≥5 min prior to umbilical cord clamping. In ICC lambs (n = 23), iPPV commenced within 60 s after umbilical cord clamping. iPPV was provided with heated/humidified gas. Lambs were moved under a radiant warmer after umbilical cord clamping. Additional warmth was provided using a plastic overlay, hairdryer, and extra water bottles, as needed. Two-way mixed and repeated measures one-way ANOVAs were used to compare temperature changes between and within a single group, respectively, over time. Results: Basal fetal parameters including core temperature were similar between groups. ICC lambs had a significant reduction in temperature compared to PBCC lambs (p < 0.001), evident by 1 min (p = 0.002). ICC lambs decreased temperature by 0.51◦C (± 0.42) and 0.79◦C (± 0.55) at 5 and 10 min respectively (p <

Assessing lung aeration using ultrasound after birth in near-term lambs at risk of respiratory distress

BackgroundOptimizing respiratory support after birth requires real-time feedback on lung aeration. We hypothesized that lung ultrasound (LUS) can accurately monitor the extent and progression of lung aeration after birth and is closely associated with oxygenation.MethodsNear-term (140 days gestation, term ∼147 days), spontaneously breathing lambs with normal (controls; n = 10) or elevated lung liquid levels (EL; n= 9) were delivered by Caesarean section and monitored for four hours after birth. LUS (Phillips CX50, L3–12 transducer) images and arterial blood gases were taken every 5–20 min. LUS images were analyzed both qualitatively (grading) and quantitatively (using the coefficient of variation of pixel intensity (CoV) to estimate the degree of lung aeration), which was correlated with the oxygen exchange capacity of the lungs (Alveolar-arterial difference in oxygen; AaDO2).ResultsLung aeration, measured using LUS, and the AaDO2 improved over the first 4 h after birth. The increase in lung aeration measured using CoV of pixel intensity, but not LUS grade, was significantly reduced in EL lambs compared to controls (p = 0.02). The gradual decrease in AaDO2 after birth was significantly correlated with increased lung aeration in both control (grade, r2 = 0.60, p &lt; 0.0001; CoV, r2 = 0.54, p &lt; 0.0001) and EL lambs (grade, r2 = 0.51, p &lt; 0.0001; CoV, r2 = 0.44, p &lt; 0.0001).ConclusionsLUS can monitor lung aeration and liquid clearance after birth in spontaneously breathing near-term lambs. Image analysis techniques (CoV) may be able detect small to moderate differences in lung aeration in conditions with lung liquid retention which are not readily identified using qualitative LUS grading

Effect of maternal oxytocin on umbilical venous and arterial blood flows during physiological-based cord clamping in preterm lambs

Background Delayed umbilical cord clamping (UCC) after birth is thought to cause placental to infant blood transfusion, but the mechanisms are unknown. It has been suggested that uterine contractions force blood out of the placenta and into the infant during delayed cord clamping. We have investigated the effect of uterine contractions, induced by maternal oxytocin administration, on umbilical artery (UA) and venous (UV) blood flows before and after ventilation onset to determine whether uterine contractions cause placental transfusion in preterm lambs.Methods and findingsAt similar to 128 days of gestation, UA and UV blood flows, pulmonary arterial blood flow (PBF) and carotid arterial (CA) pressures and blood flows were measured in three groups of fetal sheep during delayed UCC; maternal oxytocin following mifepristone, mifepristone alone, and saline controls. Each successive uterine contraction significantly (pDevelopmen

Increased end-expiratory pressures improve lung function in near-term newborn rabbits with elevated airway liquid volume at birth

Approximately 53% of near-term newborns admitted to intensive care experience respiratory distress. These newborns are commonly delivered by cesarean section and have elevated airway liquid volumes at birth, which can cause respiratory morbidity. We investigated the effect of providing respiratory support with a positive end-expiratory pressure (PEEP) of 8 cmH(2)O on lung function in newborn rabbit kittens with elevated airway liquid volumes at birth. Near-term rabbits (30 days; term = 32 days) with airway liquid volumes that corresponded to vaginal delivery (similar to 7 mL/kg, control, n = 11) or cesarean section (similar to 37 mL/kg; elevated liquid (EL), n = 11] were mechanically ventilated (tidal volume= 8 mL/kg). The PEEP was changed after lung aeration from 0 to 8 to 0 cmH(2)O (control, n = 6; EL, n = 6), and in a separate group of kittens, PEEP was changed after lung aeration from 8 to 0 to 8 cmH(2)O (control, n = 5; EL, n = 5). Lung function (ventilator parameters, compliance, lung gas volumes, and distribution of gas within the lung) was evaluated using plethysmography and synchrotron-based phase-contrast X-ray imaging. EL kittens initially receiving 0 cmH(2)O PEEP had reduced functional residual capacities and lung compliance, requiring higher inflation pressures to aerate the lung compared with control kittens. Commencing ventilation with 8 cmH(2)O PEEP mitigated the adverse effects of EL, increasing lung compliance, functional residual capacity, and the uniformity and distribution of lung aeration, but did not normalize aeration of the distal airways. Respiratory support with PEEP supports lung function in near-term newborn rabbits with elevated airway liquid volumes at birth who are at a greater risk of suffering respiratory distress.NEW & NOTEWORTHY Term babies born by cesarean section have elevated airway liquid volumes, which predisposes them to respiratory distress. Treatments targeting molecular mechanisms to clear lung liquid are ineffective for term newborn respiratory distress. We showed that respiratory support with an end-expiratory pressure supports lung function in near-term rabbits with elevated airway liquid volumes at birth. This study provides further physiological understanding of lung function in newborns with elevated airway liquid volumes at risk of respiratory distress.Developmen