Biomedical subjects

P Lekeux

Publications and source records attributed to P Lekeux.

At least 19 recordsLinked to original sources

PubMed1992

Cardiovascular response to acute hypoxia in double-muscled calves.

Hypoxic-induced pulmonary hypertension is known to be intensive in the bovine species and sometimes leads to pathological cardiac repercussions. On the other hand, doubled-muscled cattle are predisposed to develop hypoxaemia during exercise and with respiratory diseases. Therefore the purpose of this study was to investigate the cardiovascular response to acute hypoxia in double-muscled calves compared with calves of standard conformation. Pulmonary arterial pressure, electrocardiogram and blood temperature were simultaneously recorded, arterial blood was sampled for blood gas analysis and cardiac output was determined in six Friesian calves and six double-muscled calves of the Belgian White and Blue breed(BWB) when breathing air (fractional inspiratory oxygen concentration [FIO2]: 21 per cent) and when breathing a hypoxic gas mixture (FIO2: 10 per cent). All the absolute values of the measured parameters were significantly (P less than or equal to 0.001) different between the two breeds, except heart rate and arterial blood gas values. The pattern of hypoxic-induced decrease in arterial PO2 was similar in the two breeds of calves, suggesting that the pulmonary exchange capacities during hypoxia are no less efficient in double-muscled calves than in calves of standard conformation. Similarly, the percentage of variation of the mean pulmonary arterial pressure from its normoxic to its hypoxic value was the same in the two breeds of calves, suggesting that double-muscled calves are not predisposed to develop a more precocious or more intense pulmonary hypertension for a given level of hypoxaemia. The significantly smaller normoxic and hypoxic cardiac index and stroke index found in BWB compared with Friesian calves was interpreted as a less efficient cardiac function in double-muscled subjects.

Acute Disease↗

PubMed1992

Transdiaphragmatic pressure measurement in cattle: technical data.

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.

Abdomen↗

PubMed1992

Validation of the monofrequency forced oscillation technique for pulmonary function investigation in calves: an in vitro and in vivo study.

This study was to investigate whether the monofrequency forced oscillation (MFO) technique could be accurately used for pulmonary function testing in calves. The airflow resistance measured by this technique was compared to the resistance measured by the classical reference method by an in vitro study, using an artificial lung model, and by an in vivo study, using 11 healthy calves. The effect of the reference impedance of this oscillation equipment was also investigated. The results show linear relationships (r2 > 0.924, P < 0.001) in the resistance ranges 0 to 0.7 kPa litre-1 s and 0 to 1.0 kPa litre-1 s with a reference impedance of 1.0 kPa litre-1 s and 2.0 kPa litre-1 s, respectively. The MFO resistance values lower and higher than 0.4 kPa litre-1 s are slightly overestimated and underestimated, respectively. It was shown that, if some technical requirements are met, the MFO technique is a simple, reproducible, fast and accurate method which allows measurement of airflow resistance even in field conditions.

Airway Resistance↗

PubMed1992

Bovine vectocardiography: a comparative study relative to the validity of four tridimensional lead systems.

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.

Animals↗

PubMed1992

Echocardiographic evaluation of cardiac morphologic and functional variables in double-muscled calves.

We studied, by means of echocardiography in vivo, the cardiac consequences of the double-muscled character selection in beef cattle. Morphologic and functional echocardiographic variables were regularly estimated in 17 Friesian and 8 Belgian White and Blue calves during their growth. A total of 50 and 44 sets of data were collected in each group, respectively. Recordings were obtained, using 2-dimensional and M-mode echocardiography, and included measurements in long- and short-axis views of the heart. Most of the diastolic measurements of the left ventricle were not significantly different between breeds when normalized for body weight. To the contrary, systolic measurements of left ventricular wall thickness and dimensions were significantly (P less than or equal to 0.001) lower and greater, respectively, in Belgian White and Blue calves than in Friesian calves. This was interpreted as a result of significantly (P less than or equal to 0.001) lower left ventricular systolic functional indices in Belgian White and Blue than in Friesian calves. Echocardiographic evidence that the double-muscled selection in cattle induces alteration in morphologic variables of left ventricle was not found. However, results indicate that indices of left ventricular systolic function are lower in double-muscled calves than in calves with standard conformation.

Animals↗

PubMed1991

Effects of growth on functional and morphological echocardiographic variables in Friesian calves.

For echocardiography to become a reliable tool for the diagnosis, monitoring and prognosis of cardiac diseases in cattle, it is necessary to determine normal values of echocardiographic variables and their changes during the growth of healthy animals. In this study, 53 echocardiographic protocols were collected from 17 healthy Friesian calves during their period of growth. The protocol consisted of the measurement or calculation of 10 dimensional and six functional variables from M-mode long axis views of the heart. The relationships between these variables and age, body-weight and body surface area were analysed. Most of the dimensional parameters increased significantly with body size and were best predicted by an allometric regression. However, the functional indices did not change with growth, and the normal values obtained in this study may be applied to calves of any body weight.

Animals↗

PubMed1991

Quantitative M-mode and two-dimensional echocardiography in calves.

A standardised echocardiographic protocol was applied to 18 healthy calves for the estimation of 51 anatomical and functional cardiac variables. These variables were measured in a long axis and a short axis view of the heart, and both two-dimensional and cursor-directed time-motion (M-) modes were used. The repeatability of each of the measurements was estimated by comparing values obtained twice within 24 hours, and most of the 51 variables showed a high degree of repeatability. Statistical analysis revealed a close correlation between cardiac measurements taken post mortem and by in vivo echocardiography, and between the echocardiographic values obtained in different scanning planes of the heart or ultrasonic modes, indicating that quantitative echocardiography is a reliable technique in calves.

Animals↗

PubMed1991

The effect of shape, age and extension on the compliance of equine tracheal segments.

The influence of the age and weight of the animal as well as that of the extension and the shape of the trachea on the mechanical properties of the cervical trachea was studied in 33 isolated tracheal segments obtained from freshly slaughtered horses. The relationship between intraluminal pressure and volume was determined in the cervical tracheal segments positioned firstly under normal longitudinal tension and secondly in hyperextension. At the same time, changes in the area of the cross-section of the lumen (X-SA) at the midpoint of the segment were measured using photographs obtained by slit-lamp transillumination and endoscopy. The sagittal (DS) and transverse (DT) diameters were determined for each segment and the DT/DS ratio was calculated to give an estimate of the shape of the X-SA. The results showed that (i) neither the age nor the weight of the horses had any influence on the mechanical properties of the trachea; (ii) extension decreases the compressibility of the tracheal segment in vitro; (iii) there is a wide variation in the extrathoracic tracheal X-SA shape in horses; and (iv) the shape of the X-SA has a major influence on the mechanical properties of the trachea. It was concluded that (i) hyperextension of the neck will partly facilitate respiration at high levels of ventilation by elongating the trachea and by decreasing its collapsibility; and (ii) the tracheal collapse which may occur during high levels of ventilation will be more or less important depending on the individual X-SA shape.

Aging↗

PubMed1991

Mechanical properties of the isolated equine trachea.

In order to study the in vitro mechanical properties of the equine trachea submitted to the compressive pressures observed in vivo, the pressure-volume relationship was determined in intra- and extra-thoracic tracheal segments taken post mortem from 29 healthy horses (one to 15 years old; 352 to 651 kg). At the same time, the cross-sectional lumen area (X-SA) at the mid-point of the segment was measured using a slit-lamp transillumination and photographic measurement by endoscopy. The tracheal specific compliance (Cs) as well as the relative changes in X-SA and in the sagittal and transverse diameters, for intraluminal pressures from 5 to - 5 kPa, were calculated. The extrathoracic tracheal Cs was 0.060 +/- 0.002 kPa-1 and, at an intraluminal pressure of - 5 kPa, X-SA was reduced to about 73 per cent of its resting value. The intrathoracic segments were more compliant and, at similar compressive pressure, their X-SA was more reduced. These data show that the equine tracheal compliance is high and suggest that the increase in pulmonary resistance observed during strenuous exercise may be partly explained by a partial tracheal collapse.

Animals↗

PubMed1991

Quantitative buffy coat analysis related to adrenocortical function in horses during a three-day event competition.

This study was carried out to investigate stress induced in a cross-country by measuring plasma cortisol and to compare the changes in cortisol level with the leucocytic changes measured with the quantitative buffy coat (QBC) analysis, which is a new method applicable in field conditions for the evaluation of haematological parameters in horses. Seven healthy horses competing in a national three-day event were investigated. Venous blood was sampled under resting condition, 2 min and 180 min after the completion of the cross-country and analysed for haematological parameters, plasma cortisol, protein and lactate levels. Immediately after the event, there was a significant increase in all values except in the granulocytes (Gr) to lymphocytes-monocytes (LM) ratio. 180 min after the event, all the parameters returned to their resting levels while white blood cells (WBC), Gr and Gr/LM ratio were significantly higher with respect to their resting values. A high correlation (r = 0.82) was found between the relative increase in plasma cortisol levels 2 min after exercise and the relative increase in Gr/LM 180 min after exercise. Therefore it was concluded that the Gr/LM ratio measured 180 min after exercise with the QBC analysis is a reliable index to estimate the plasma cortisol levels measured 2 min after exercise. This new technique could consequently be used in order to evaluate, in field conditions, the exercise-induced stress.

Adrenal Cortex↗

PubMed1991

Validation of the thermodilution technique for the estimation of the cardiac output in the unsedated calf.

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.

Animals↗

PubMed1991

Economic and production consequences of liver fluke disease in double-muscled fattening cattle.

The frequency of liver fluke disease in fattening units was determined by the analysis of random faeces samples issued from 1,513 Belgian White Blue bulls aged from 5 to 7 months and weighing from 200 to 300 kg. 12.5% of the investigated bulls were positive for liver fluke disease. These bulls were spread over 56.5% of the investigated fattening units. Furthermore the infestation rate varied from 0 to 33.3% inside the fattening units. In order to assess the economic consequences of bovine fascioliasis in double-muscled cattle and the beneficial effects of a treatment against such a disease, a trial including 30 Belgian White Blue bulls, weighing 365 +/- 9 kg and aged from 10 to 12 months, was conducted in a selected fattening unit. On the basis of faecal examinations, the 30 animals were subdivided in negative (group A; n = 10) and positive animals (n = 20) for fascioliasis, the latter being either treated with nitroxinil (group B; n = 10) or not (group C; n = 10) on day 0 of this trial which was conducted during 75 days. The daily body gains in group C (1.661 +/- 0.140 kg) were significantly lower than those in group A (1.975 +/- 0.120 kg). On the other hand there was no significant difference between the daily body gains registered in group B (1.960 +/- 0.085 kg) and A. The estimated financial loss, due to flukes and accounted on a 75 day-period, averaged 2,748 Belgian Francs per bull in group C.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Economic and production repercussions of deworming by pulse release device and oral suspension in grazing double-muscled fattening cattle.

In this field trial, the repercussions of 2 administration forms of oxfendazole, namely a single administration of a front-loaded device (group 1; n = 18) and a repeated administration of a 90.6 per cent oral suspension (group 2; n = 18), were compared in first season-grazing double-muscled fattening bulls. The comparison was based on the production performances, the mean worm egg counts and the product- and labour-costs. The daily body gains determined on the whole trial period, i.e. 1.312 +/- 0.055 kg and 1.270 +/- 0.056 kg for groups 1 and 2 respectively, and mean worm egg counts per gram (on days 0 and 130:200.0 +/- 44.3 and 94.4 +/- 27.4 for group 1; 366.7 +/- 98.4 and 100.0 +/- 33.6 for group 2) did not differ significantly between the two groups. However, the total costs were lower with a front-loaded device (1,021 Belgian Francs) than with oral suspension (1,248 Belgian Francs per bull).

Administration, Oral↗

PubMed1991

[Effect of an oral sedative on the behavior and the zootechnologic performance of fattening bulls of the white-blue Belgian breed].

This trial was conducted with 22 Belgian White and Blue double-muscled cattle (body weight: 241.5 +/- 6.2 kg; age: 7 months). Two similar groups were constituted: a group of bulls which were treated with potassium bromide (BT; n = 11) and another one which remained untreated (UT; n = 11). The treatment (736 mg potassium bromide/kg feed dry matter) was stopped 60 days before the slaughtering day. The treatment with potassium bromide induced a significant reduction in the rear engagements during the whole trial period (221 days), in direct attacks during the period A (from day 0 to day 53) and in side-on attacks during the period B (from day 54 to day 167). The daily weight gains, calculated for the whole trial period, were not significantly different between the two groups. Feed utilization was lower in treated bulls. During the period C (from day 168 to day 221), the sedative potency of potassium bromide seemed to be weaker than during the periods A and B. This might be due to the habituation to potassium bromide. On the basis of these results, we can conclude that the frequency of rear engagements and, during a restricted period of fattening, the frequencies of side and direct attacks are significantly reduced when potassium bromide (736 mg/kg feed dry matter) is used. The time spent for hay intake, the frequency of water intake (even if the time consumed at the drinking trough was the same) was reduced and the time during which the bulls were standing was prolonged by bromide.

Animals↗

PubMed1991

Lobeline-induced hyperpnea in equids. Comparison with rebreathing bag and exercise.

In order to facilitate lung auscultation, a transitory hyperpnea may be obtained by lobeline administration, use of a rebreathing bag or exercise. The effect of these three methods on the pulmonary function were studied and compared in 5 healthy ponies. Respiratory airflow and tidal volume were measured with a pneumotachograph Nr. 5 and pleural pressure with the esophageal balloon catheter technique. Pulmonary function values were measured before, during and after the hyperpnea induced by (i) lobeline, (ii) rebreathing and (iii) exercise. Lobeline administration induced an hyperpnea due to both an increase in tidal volume and respiratory rate; this increase in ventilation lasted for about 90 s and was accompanied by a sharp rise in the respiratory peak airflows, especially the expiratory ones. The rebreathing method induced a less hyperpnea which lasted only 30 s. Lastly the hyperpnea after a light treadmill exercise was the longer in duration and intermediate between the preceding methods in intensity.

Animals↗

PubMed1990

Growth-related changes in the pulmonary function of goats.

Growth-related changes in pulmonary function values were investigated in 20 healthy French Alpine goats, aged between 20 and 550 days, weighing 7-55 kg. Pulmonary ventilation, mechanics of breathing and arterial oxygen tension were measured using standardized techniques and methods adapted for goats of different body sizes. The Ppl values and the tI/tTOT ratio showed no significant changes with age and body size. The ventilation values (Vt, Ve, mVI and mVE) increased linearly with growth. There was a significant correlation of age and body weight with dynamic lung compliance (Cdyn), total pulmonary resistance (RL), viscous work of breathing (Wvis tot) and minute viscous work (Wvis min) throughout the age range studied. Cdyn, Wvis tot and Wvis min increased and RL decreased with age and body weight. Arterial blood gases (PaO2 and PaCO2) did not show significant changes over the age range studied. Regression equations for each pulmonary function parameter are given with body weight as the independent variable. Data for the mechanics of breathing were compared with those elsewhere for cattle, horses, man and dogs.

Age Factors↗

PubMed1990

Respiratory-induced variability of pulmonary arterial pressure measurements in cattle.

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.

Airway Resistance↗

PubMed1990

Mechanics of breathing during strenuous exercise in Thoroughbred horses.

The changes induced by exercise on the mechanics of breathing, as well as the simultaneous changes occurring in arterial blood gas tensions and in respiratory gas exchange were investigated in 6 healthy thoroughbred horses, performing a treadmill exercise of increasing intensity. Respiratory airflow and tidal volume (VT) were measured with ultrasonic flowmeters. Pleural pressure changes were measured by an oesophageal balloon catheter. Gas concentration of the expired air was analysed with a mass spectrometer; the oxygen consumption (VO2) and the carbon dioxide output (VCO2) were computed breath-by-breath. Arterial blood gas values were obtained by sampling from the carotid artery. Between rest and fast gallop VT, respiratory frequency, expired minute ventilation (VE), VO2, VCO2, total pulmonary resistance (RL), mechanical work of breathing (Wrm) and PaCO2 increased significantly while PaO2 decreased significantly. The Wrm.VO2(-1) ratio in galloping horses increased exponentially with VE. This, together with the relationship between the changes in PaO2 and in PaCO2 and the increase in the ventilatory mechanics parameters, suggests that the mechanics of breathing may be one of the factors constraining further increase in ventilation in exercising healthy horses.

Animals↗