peer reviewed

peer reviewed

International audience

International audience

peer reviewed

peer reviewed | 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. | Le but de cette étude était d'etudier les spécificités électrocardiographiques des bovins de boucherie de conformation hypermusclée. Des enregistrements électrocardiographiques ont été réalises de une a six reprises chez chacun des 18 veaux conventionnels de la race Frisonne et des 29 veaux hypermusclés de la race Blanc Bleu Belge investigués et repartis en deux groupes. L'âge des veaux au moment des investigations était compris entre huit et 348 jours. Le système de dérivation semiorthogonal de Holmes a été applique. La durée des ondes et des intervalles électro-cardiographiques ainsi que l'orientation et l'amplitude des vecteurs cardiaques tridimensionnels P, QRS et T ont été calculées. L'amplitude des vecteurs cardiaques était significativement plus petite et la durée des ondes ventriculaires et de l'intervalle QT significativement plus courte chez les veaux hypermusclés que chez les veaux conventionnels. Le vecteur P était oriente dans une direction significativement moins ventrale et le vecteur QRS dans une direction significativement plus craniale et moins dextro-dorsale chez les veaux hyper musclés que chez les veaux conventionnels. La plupart des différences observées pourraient être attribuées a une conformation corporelle, et particulièrement thoracique, spécifique chez les veaux hyper musclés. Cependant, la plus faible amplitude des vecteurs cardiaques et la durée plus courte des ondes et intervalles électro-cardiographiques pourraient également constituer le signe d'une réduction de la masse myocardique chez ces derniers.

peer reviewed | Oral immunization of foxes against rabies, by distributing vaccine-baits in the field, has been in progress since 1993 in the whole of the infected area of Belgium (10,000 km2). A vaccinia-rabies recombinant virus (VR-G) was used as vaccine because of its efficacy, safety and heat-stability. The successive campaigns of fox vaccination have induced a drastic decrease in rabies incidence and in 1993 there were no cases of rabies detected in the fox population. A marked decrease of human post-exposure treatments and the elimination of the disease in domestic animals have been the consequence of fox rabies control.

peer reviewed | 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.

We investigated the influence of parasympathetic tone on the arrhythmogenic dose of dobutamine in horses premedicated with xylazine, anesthetized with guaifenesin and thiamylal, and maintained on halothane in oxygen. Six horses were used in 12 randomized trials. In each trial, after end-tidal halothane concentration was stabilized at 1.1% (1.25 times minimum alveolar concentration [MAC]) in oxygen, either saline solution (0.02 ml/kg of body weight) or atropine (0.04 mg/kg) was administered IV. Five minutes later, dobutamine infusion was started at dosage of 2.5 micrograms/kg/min, IV. The dobutamine infusion was continued for 10 minutes, or until 4 or more premature ventricular complexes occurred within 15 seconds, or sustained narrow-complex tachyarrhythmia clearly not sinus in nature occurred. If the criteria for termination were not met, dobutamine infusion was increased by 2.5 micrograms/kg/min, after the hemodynamic variables had returned to baseline. The horses were allowed to recover, and were rested for at least 1 week before the second trial. The arrhythmogenic dose of dobutamine was calculated by multiplying the infusion rate by the elapsed time into infusion when arrhythmia occurred. There was significant difference between the arrhythmogenic dose of dobutamine (ADD) in saline-treated horses (mean +/- SEM, ADD 105.6 +/- 16.3 micrograms/kg) and atropinized horses (ADD 36.2 +/- 8.7 micrograms/kg). There were no differences in the prearrhythmia or immediate postarrhythmia ventricular heart rate (HR) or systolic (SAP), diastolic (DAP), or mean (MAP) arterial pressures between treated and control groups. The change in hemodynamic variables from prearrhythmia to immediate postarrhythmia formation was not different between the 2 groups. Ventricular beats were clearly evident in 8 of the 12 arrhythmias meeting the criteria for establishing the ADD. These results indicate that atropine may lower the arrhythmogenic threshold for dobutamine in halothane-anesthetized horses.