Search

Objectives: To assess the feasibility and repeatability of two-dimensional speckle tracking echocardiography for the evaluation of left ventricular function in healthy calves., Animals: 12 Holstein calves, 62 ± 11.6 days old; 75.25 ± 5.4 Kg., Methods: Observational study. Right parasternal short-axis views at papillary muscle level were recorded in standing calves and subsequently analyzed by two-dimensional speckle tracking for global and regional radial and circumferential strains and strain rates and radial displacement. Echocardiographic examinations were performed by 2 observers to evaluate intra- and interobserver repeatability and variability., Results: Two-dimensional speckle tracking was feasible in all calves. Automated tracking was better in systole than in diastole. Repeatability of the technique was good in calves. Systolic radial strain and strain rate peak values showed little variability compared with systolic circumferential strain and strain rate and to all diastolic measurements. Variability of the interobserver measurements was greater than the intraobserver measurements., Conclusions: Two-dimensional speckle tracking is feasible in calves. As in other species, evaluation of systolic radial left ventricular function is more reliable than circumferential and diastolic left ventricular function., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In mammals, thyrotropin, or thyroid-stimulating hormone (TSH), assay is used for the diagnosis of primary hypothyroidism. Hypothyroidism is the most common type of thyroid disorder in cattle. The aim of this study was to develop and validate, under physiologic and pathologic conditions, a radioimmunoassay (RIA) for bovine TSH (bTSH). Double RIA was performed with purified bTSH and specific bovine antiserum. Laboratory validation included research of minimal detection limit, accuracy, and reproducibility. The physiologic validation included a thyrotropin-releasing hormone (TRH) challenge performed on euthyroid cows and a follow-up of bTSH concentration over a 24-hour period. Furthermore, bTSH concentration was assayed in a large population of healthy dairy and beef cows to define reference interval. The pathologic validation was made by assaying bTSH and thyroid hormones on healthy and goitrous newborn calves. The minimum detection limit (MDL) for bTSH assay was 1.3 microU/ml. The recovery was 101% to 106%. The intra- and interassay coefficients of variation (CVs) ranged from 5% to 11% and 11% to 15%, respectively. The RIA covered the whole range of physiologic bTSH values, as shown by bTSH values induced by TRH-challenge. A pulsatile secretion of bTSH was observed, accompanied by a diurnal variation with lower night values than day values. Reference intervals of bTSH ranged from 1.3 to 13.0 microU/ml for beef and dairy breeds. Finally, bTSH easily discriminated goitrous newborn calves from healthy ones, leading to the definition of a cutoff value of 35 microU/ml. The bTSH assay positively reacted to physiologic and pathologic conditions. The accuracy and precision of the RIA were satisfying.

The biochemical composition and biophysical behaviour of pulmonary surfactant samples isolated from healthy Belgian White and Blue (BWB) and Holstein Friesian (HF) calves have been investigated and compared. Interesting differences in composition have been demonstrated. In particular, a higher level of total hydrophobic surfactant-associated proteins (SP) (due to higher levels of SP-B and SP-C) is reported in HF calves compared to BWB calves. Higher levels of phosphatidylcholine (PC) and especially the disaturated form of PC were also found in HF as compared to BWB calves. No immediate effect on the surface tension properties evaluated by the pulsating bubble surfactometer was found between the surfactant samples of the two breeds under physiological conditions. However, since a high content of disaturated PC and the presence of the SP-B and SP-C are thought to be essential for the surface activity, we propose that the reported modifications could contribute to the apparently lower resistance of the BWB calves to respiratory troubles in comparison with HF calves.

Chest wall compliance (CW) was measured in 59 conscious standing calves, aged six to 162 days, which were breathing air spontaneously through a face mask. The airways were occluded at the end of inspiration in order to elicit the Hering-Breuer reflex, the effectiveness of which was ensured by the presence of a plateau on the tracings of airway opening and oesophageal pressure (Pes). CW was measured directly from the inspired volume of the occluded breath and changes in Pes generated by the recoil of the relaxed chest wall. This airway-occlusion technique yielded reproducible CW values similar to those measured by classical invasive methods. The ratio of CW to bodyweight in the growing calves (sCW) ranged from 2.2 to 11.5 ml cmH2O-1 kg-1 and was correlated negatively with age: (log sCW = 0.91-0.003 x age, r = 0.68), the rate of decline corresponding well to the multispecies allometric growth relationship.

The physiological peculiarities of the oxygen transport chain in double-muscled Blue Belgian cattle are described. The investigations performed at several levels of the oxygen transport chain suggest that the increased susceptibility of these cattle to stress, resulting mainly in respiratory diseases, is due to an insufficient functional reserve capacity mainly involving the pulmonary and cardiovascular systems. The resulting lack of 'functional hardiness' of the oxygen transport chain is seen in those double-muscled cattle which do not react in an appropriate or predictable way when submitted to a hostile environment.

Although healthy and diseased bovine respiratory tracts have been intensively studied during the last years, to the authors' knowledge, there have been no attempts to objectively examine the inspiratory drive from the brain to the nerves and muscles and its transformation in pressure. Such technique would be useful in assessing the possibility of altered ventilatory drive or inspiratory muscle fatigue in the context of an animal with ventilatory failure. The relation among ventilation, airway opening occlusion pressure generated 100 milliseconds after onset of inspiration (Pawo100ms) and 6 indexes describing diaphragmatic electromyographic activity (EMGdi) recorded via implanted fishhooks was evaluated during free and impeded CO2 rebreathing in 6 young bulls. The best significant linear correlations (r > 0.8) with inspiratory center afferent stimulation, as judged by end-tidal CO2 concentration in expired air, were found for Pawo100ms, peak moving time average or variance EMGdi, and mean integrated EMGdi, whatever had been the respiratory impedance. However, with an inspiratory load, Pawo100ms responses systematically had greater increase for a given change in the driving EMGdi, implying dependence of the former not only on neural input, but also on configurational factors that determine inspiratory muscle excitation-pressure generation couplings. The reproducibility of EMGdi absolute values and changes was satisfactory up to 10 hours, but could not be repeated from one day to the other. It was concluded that, provided the constancy of the electrical coupling of the recording system to the tissue being studied is ensured, specific EMGdi and Pawo100ms values correlate reliably with amount of CO2 during free and loaded breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

During growth, central venous, right ventricular, pulmonary arterial, pulmonary capillary wedge, and systemic arterial pressures, heart rate, and cardiac output were repeatedly measured in 41 Friesian calves, considered as having conventional muscular conformation, and in 19 Belgian White and Blue double-muscled calves. A total of 123 and 70 recordings were collected in conventional and double-muscled calves, respectively. These circulatory indices were calculated: stroke volume, cardiac and stroke indices, pulmonary and systemic pulse pressures, pulmonary and systemic vascular resistance indices, and right and left ventricular work indices. Results indicated that systemic arterial and pulse pressures, as well as cardiac output, stroke volume, cardiac and stroke indices, and right and left ventricular work indices were significantly (P < or = 0.05 to 0.001) lower but, in contrast, pulmonary and systemic vascular resistance indices were significantly (P < or = 0.001) higher in double-muscled than in conventional calves. Right-sided vascular pressures and heart rate were similar in the 2 groups. These results indicated that global cardiac performance may be considerably poorer in double-muscled calves. Diminished cardiac performance of double-muscled calves appears to be related neither to relative bradycardia nor to reduced ventricular preload. The potential role of increased ventricular afterload or of reduced myocardial contractility in double-muscled cattle should be determined by direct measurements.

The purpose of this work was to study electrocardiographic features of double-muscled beef cattle. Electrocardiograms were recorded on one to six occasions from each of a group of 18 conventional calves of the Friesian breed and 29 double-muscled calves of the Belgian White and Blue breed. Ages of the calves at the times of examination ranged from eight to 348 days. The Holmes semi-orthogonal lead system was used. The waves and interval durations and the tridimensional P, QRS, and T modal vector orientation and amplitude were calculated. The magnitude of the cardiac vectors was significantly lower and the ventricular waves and QT interval duration significantly shorter in the double-muscled than in the conventional calves. The P modal vector pointed significantly less downwards and the QRS modal vector pointed significantly more forwards and less up- and rightwards in the Belgian White and Blue, than in the Friesian group. Most of the observed differences might be a consequence of the bodily, and more specifically the thoracic, conformation of the former calves. However, the lower cardiac vector magnitude and shorter wave and interval durations might also reflect lower cardiac mass in the double-muscled subjects.

This study investigated the pattern of growth-induced haemodynamic changes in normal calves during their first year of life. The central venous pressure (CVP), the right ventricular pressure (RVP), the pulmonary arterial pressure (PAP), the pulmonary capillary wedge pressure (PW), the systemic arterial pressure (SAP) and the cardiac output (CO) were measured in 41 healthy Friesian calves. The heart rate (HR), the stroke volume (SV), the cardiac and stroke indices (CI and SI, respectively), the pulmonary and systemic vascular resistance (PVR and SVR, respectively), the right ventricular and left ventricular work (RVW and LVW, respectively) and their corresponding indices (PVRI, SVRI, RVWI and LVWI, respectively) were also measured or calculated. The cardiac output, SV, SAP, PVRI, SVRI, RVW and LVW increased significantly while the HR, CI, PVR, SVR, RVWI and LVWI decreased significantly with somatic growth. The right-sided vascular pressures did not change significantly. The significant increase in systemic arterial pressure may be due to the simultaneous increase in CO. The high CI observed in the first few weeks of life was attributed to a high metabolic rate and might induce a reduced cardiac pumping reserve in young calves. In consequence, a therapeutic inotropic intervention may have little potential benefit at this age.

This study derives normal values for electro- and vectorcardiographic parameters, as generated by the Holmes semi-orthogonal lead system, in healthy growing calves. Sixty-four electrocardiograms were recorded from healthy Friesian calves aged from one week to one year. Waveform and duration were analysed and compared in the X-, Y- and Z-leads. The modal P, QRS and T tridimensional vectors were graphically constructed and their magnitude and orientation were calculated. The duration of waves and intervals were similar to data previously reported in the bovine species. Differences from data reported in other species were attributed to heart rate. The duration of waves and QT and ST intervals significantly lengthened with the decrease in heart rate which occurred during growth. PR interval significantly lengthened with physical maturation, and this change was independent of the decrease in heart rate. The magnitude and the orientation of the spatial modal vectors were approximately similar to the few data previously reported in cattle and in other ungulates and were not affected by somatic growth.

The purpose of this study was to investigate the mechanism by which 5-hydroxytryptamine (5-HT) modifies respiratory function, specifically, hyperventilation, diffuse bronchoconstriction, and pulmonary arterial hypertension in cattle. We determined whether the IV response to 5-HT in calves was attributable to stimulation of 5-HT2 receptors. Six healthy unsedated young bull calves of the Friesian (n = 4) and of the Belgian White and Blue (n = 2) breeds were used. A specific 5-HT2 antagonist (metrenperone, 0.05 mg/kg of body weight) was administered IM 30 minutes before the cattle were given a 5-minute IV 5-HT infusion. Pulmonary function values were registered before, during, and after the 5-HT challenge infusion. Minute volume increased significantly, because of an increase in respiratory rate. Conversely, lung dynamic compliance, total pulmonary resistance, and pulmonary arterial pressure were not changed. We concluded that in cattle, 5-HT-induced ventilatory response is not mediated through activation of 5-HT2 receptors. However, the 5-HT2 receptors are involved in 5-HT-induced broncho- and pulmonary vasoconstriction.

Techniques and methods required for accurate and reproducible measurements of transdiaphragmatic pressure (Pdi), were studied in seven-week and five-month-old calves. Since reliable pleural pressure measurement in cattle has already been described, separate experiments were conducted to compare retrodiaphragmatic pressures measured (i) with balloon-catheters and needle catheters, (ii) before and after eructation and (iii) in the ruminal and in the peritoneal cavities. Whereas respiratory-induced pressure changes were equally transmitted throughout the rumen content, a marked anteroposterior damping was observed as the recording site in the abdominal cavity was moved away from the diaphragm (P < 0.0001). It was concluded that the most appropriate and accurate way to measure Pdi changes in polygastric animals is to measure the pressure changes existing in the mid-thoracic portion of the oesophagus and in the liquid content of the rumen with balloon-tubing units. Neither growth- and diet-related rumen enlargement nor eructation, which are two typical characteristics of ruminants, altered the reliability of retrodiaphragmatic pressure measurements in the two age groups studied.

For spatial vectocardiography to become applicable for cardiac investigation in cattle, it was necessary to develop a reliable standardized electrocardiographic lead system in this species. In this study, four tridimensional lead systems, initially developed in horses, were compared when applied in calves. Fifty seven electrocardiograms were collected. The between-subject variability of the magnitude and angles of the tridimensional P, QRS and T modal vectors obtained by use of each lead system was compared. Reproducibility of vectrocardiographic measurements was analyzed by comparing results obtained in 10 calves within a one day interval. The Holmes semi-orthogonal lead system, giving the lowest between-subject variability and the highest between-day reproducibility, appeared to be the most reliable lead system in order to apply vectocardiography in the bovine species.

Effects of IV and aerosol administration of 5-hydroxytryptamine (5-HT) on ventilation, pulmonary mechanics values, pulmonary arterial pressure, and heart rate were investigated in healthy unsedated Friesian calves. Minute volume increased significantly, mainly because of an increase in respiratory rate. Except for total pulmonary resistance after bolus injection, continuous administration of 5-HT given by either route caused significant alterations of lung dynamic compliance and total pulmonary resistance, the former decreasing to one-fifth of its baseline value and the latter increasing twofold. Pulmonary arterial pressure increased significantly, whatever the speed or route of administration. Administration of a bolus did not affect heart rate, whereas continuous IV administration of 5-HT as well by perfusion or by aerosol resulted in sustained tachycardia. It was concluded that 5-HT induces reversible bronchoconstriction and pulmonary vasoconstriction in healthy unsedated calves, 5-HT-induced functional alterations depend on the speed of administration, and excess of 5-HT production or depression in uptake by the lungs during bovine respiratory tract diseases could contribute to pulmonary dysfunction.

The purpose of this study was (1) to evaluate the technical and methodological problems associated with invasive haemodynamic measurements in unsedated cattle; (2) to assess the reproducibility of such measurements both within and between days; and (3) to compare the values with those previously reported. Twenty-one healthy calves, aged from 5.5 to 12 months, were studied. The central venous, the right ventricular, the pulmonary arterial, the pulmonary capillary wedge and the systemic arterial pressures were obtained by means of fluid-filled catheters, and the cardiac output was measured by the thermodilution technique. The heart rate, the stroke volume, the pulmonary and systemic vascular resistances and the pulmonary and systemic ventricular workloads were calculated. An adverse reaction, consisting of severe pulmonary hypertension, tachycardia, tachypnoea and transient weakness, occurred in 7 calves during the catheterization procedures. Such a reaction might be due to a local reflex induced by stimulation of mechano-receptors by the catheter tip. It should be avoided by reducing the manipulation of the catheter as much as possible and by inflating the tip of the balloon when moving it forwards. A comparison of the vascular pressures with those previously reported was difficult because of methodological or technical limitations, such as, for instance, a lack of standardization of the baseline. The reproducibility of the haemodynamic measurements obtained was satisfactory, in contrast to previous studies performed in conscious animals. This was attributed to our animals being better trained to the experimental conditions and emphasizes the importance of reducing mental stress in obtaining reliable haemodynamic measurements in unsedated and potentially uncooperative animals.

The purpose of this study was to establish a standardized protocol in order to obtain accurate and reproducible cardiac output (CO) measurements by the thermodilution technique in the unsedated calf. In 5 healthy calves, the effect of various temperatures, volumes, rates, means and sites of injection of the thermal indicator were tested for their effect on accuracy and reproducibility of CO measurement by the thermodilution technique, the Fick method being used as the standard technique. Five milliliters of an iced 5% dextrose solution per 100 kg body weight constituted the correct amount of thermal indicator. Manual injection of the indicator bolus and/or injection of this bolus through the proximal lumen of a thermodilution Swan-Ganz catheter gave poor results of CO measurements by the thermodilution technique. On the other hand, results of CO measurements were highly reliable when the bolus injection was performed by an ECG-synchronized injection pump and/or through a right atrial catheter with a larger diameter and a shorter length than the classical Swan-Ganz catheter. It was concluded that an iced 5% solution of dextrose (5 ml/100 kg body weight) injected through a right atrial catheter by an ECG-synchronized pump gives the most accurate and reproducible CO measurements by the thermodilution technique in unsedated calves.

The mechanics of breathing was investigated in six healthy calves breathing either air or a mixture of 79% helium and 21% oxygen (He-O2). Intrapleural pressure (Ppl) was measured with an esophageal balloon catheter and transpulmonary pressure was obtained by subtracting the mouth pressure (Pm) from Ppl. Respiratory airflow (V) was measured using a Fleisch pneumotachograph N degrees 3 and tidal volume (Vt) was electronically derived by integrating V with respect to time. Respiratory airflow, Vt, Ppl and Pm were simultaneously recorded while the calves breathed first air (1 min), secondly He-O2 (1 min) and finally air again (1 min). The pulmonary function values were calculated on the tracings and the He-O2 values were compared to the corresponding "air" values. The ventilatory response to resistance unloading was characterized by a significant increase in minute volume exclusively due to an increase in respiratory frequency, while Vt remained unchanged. A decrease of 32% in the total pulmonary resistance (RL) and 16% in the work per litre of ventilation (Wrm/l) were observed when calves breathed He-O2. The effect of the He-O2 on RL and on Wrm/l suggests that, in the bovine species, airflow turbulances in the upper part of the respiratory tract play a significant role in the total airways resistance.

The purpose of this study was to investigate the variability of the peak systolic (PAPs) and the end diastolic (PAPd) pulmonary arterial pressures induced by intrapleural pressure changes in cattle. The pleural pressure (Ppl), the electrocardiogram and the pulmonary arterial pressure (PAP) were simultaneously recorded in five healthy calves under three different conditions, i.e. normoxia (N), normoxia with an added airflow resistance (R) and hypoxia (H). PAPs, PAPd and their corresponding transmural pressures were measured and averaged over 10 successive regular cardiac cycles. The maximum Ppl changes (max delta Ppl) were measured on the same tracings. The variance and coefficients of variation were calculated for each set of vascular measurements. Max delta Ppl was significantly increased with regard to N values during R and H conditions. This increase in max delta Ppl induced a simultaneous rise in the variability of PAP measurements, while in each condition, this variability was greatly lowered by use of the corresponding transmural pressure. It was concluded that, in calves with high max delta Ppl, the influence of respiration on PAP becomes considerable. In such cases, the use of transmural pressures rather than luminal pressures can greatly reduce the variability of these pulmonary pressure measurements and therefore increase their sensitivity.

Background: Reports of doxycycline-induced toxicity are limited despite common use of this antibiotic to treat infectious respiratory disorders in calves. Objective: To describe previously unreported kidney lesions and diagnostic test results in doxycycline-overdosed calves and to compare these results with other findings reported previously. Animals: Thirty-two calves that presented with adverse effects after receiving high doses of doxycycline as a treatment for mild respiratory disorders. Method: Retrospective review of medical records. Results: Clinical examination identified mainly lethargy, dyspnea, cough, tongue paresia or paralysis associated with dysphagia and sialorrhea, tachycardia, tachypnea, and signs of myopathy. Blood analysis indicated increases in creatine kinase, lactate dehydrogenase, aspartate aminotransferase, and sorbitol dehydrogenase activities and increased serum creatinine and urea concentrations. ECG recordings and Doppler echocardiography examination identified ventricular premature beats and a decrease in left ventricular global and systolic function, respectively. Necropsy and histopathology disclosed necrosis of the myocardium, tongue, and some striated muscles, acute renal tubular necrosis, and fatty degeneration or congestion of the liver. Conclusions: Most of these findings corroborate previous observations made in doxycycline-overdosed calves, and further suggest myocardial and striated muscular toxicity as well as renal toxicity in doxycycline-overdosed calves. [ABSTRACT FROM AUTHOR]

An abstract of the article "Investigation of colostrum quality in beef cattle by radial immunodiffusion and brix refractometry," by S. Vandeputte, J. Detilleux, and F. Rollin is presented.