The effect of clenbuterol on lung function parameters in calves suffering from bronchopneumonia

Pulmonary function testing was performed in calves affected with bronchopneumonia. In these calves respiratory rate, viscous work per litre air and per minute, intrapleural pressure difference, mean inspiratory and expiratory flow rate and ventilation per minute were significantly increased. Total resistance of the lung was just not significantly increased. Dynamic compliance and tidal volume were significantly reduced.The main effect of clenbuterol was a significant increase in dynamic compliance. The reduction in the total resistance of the lung was just not significant. These results indicate that clenbuterol can antagonise, at least partly, the alterations caused by bronchopneumonia.     

The influence of clenbuterol on prostaglandin F2 alpha-induced dyspnoea in calves

Pulmonary function tests were performed in six healthy calves. Prostaglandin F2 alpha causes severe narrowing of both upper and lower airways (total lung resistance increased, dynamic compliance decreased). Clenbuterol administered intravenously fifteen minutes prior to prostaglandin F2 alpha aerosol, and in increasing doses (0, 0.4, 0.8, 1.2 micrograms/kg), on days 1, 2, 4 and 6 of the experiment, effectively but not entirely suppressed these responses. These data indicate that beta-adrenergic receptors are present in the bovine airways and that the use of clenbuterol (0.8 micrograms/kg) may be effective in treating clinical respiratory disease such as bronchopneumonia in calves.     

The effects of clenbuterol hydrochloride on the pulmonary function of calves with subacute and chronic bronchopneumonia

The influence of clenbuterol on some pulmonary function tests in 11 calves with subacute and chronic bronchopneumonia has been investigated. Treatment with clenbuterol caused changes only in calves with subacute bronchopneumonia; in these animals it decreased the total pulmonary resistance, the viscous work per litre and the peak to peak changes in transpulmonary pressure.     

Functional changes induced by necrotic laryngitis in double muscled calves

The effects of necrotic laryngitis on the mechanics of breathing and gas exchange were investigated in five Belgian blue double muscled calves two to three months old. All the animals showed the typical clinical picture of the respiratory syndrome associated with naturally occurring necrotic laryngitis. Highly significant increases in total pulmonary resistance, minute viscous work of breathing and alveolar-arterial oxygen gradient, and highly significant decreases in dynamic lung compliance and arterial oxygen tension were recorded in the infected animals, when compared to reference values for healthy cattle. The ratio of inspiratory to expiratory viscous work of breathing was also significantly increased probably because of a partial collapse of the extrathoracic trachea during inspiration. It was concluded that necrotic laryngitis disturbs pulmonary function to such an extent that it impedes the growing process and predisposes the infected animals to secondary bronchopneumonia and ventilatory failure due to respiratory muscle fatigue.     

Effect of clenbuterol on histamine-induced airway obstruction in ponies

We determined the effect of IV administered beta 2-adrenergic receptor agonist clenbuterol on pulmonary function and on the response to histamine in 12 healthy ponies. Measurements were made at base line and after saline solution or clenbuterol was administered IV at a dosage of 0.2, 0.8, or 1.6 micrograms/kg. The dosage of clenbuterol used in each study was unknown to the investigators until all the data had been analyzed. Intravenous administration of saline solution or clenbuterol did not alter base-line pulmonary function significantly. Aerosol histamine administration significantly decreased arterial oxygen tension and dynamic compliance and increased pulmonary resistance, respiratory frequency, and minute ventilation, but had no effect on arterial carbon dioxide tension and tidal volume. The magnitude of change in these variables was unaffected by previous administration of clenbuterol at any of the dosages tested. We conclude that clenbuterol at the dosages tested is not a bronchodilator in healthy ponies and does not exert a significant protective effect against aerosol histamine-induced airway narrowing.     

Responses of calves to treadmill exercise during beta-adrenergic agonist administration.

Calves perorally administered the beta-adrenergic agonist (beta-A) clenbuterol for 28 d were studied before, during, and after a 12-min treadmill exercise. During exercise on d 1 of clenbuterol administration, respiratory rate, respiratory minute volume, and heart rate and blood glucose, lactate, and insulin concentrations increased more in beta-A-treated calves than in controls. Oxygen extraction rate and growth hormone concentrations were lower in clenbuterol-treated calves, whereas oxygen consumption, carbon dioxide production, and blood cortisol concentration increased similarly in the absence and presence of the beta-A. After 2 wk of daily clenbuterol administration, respiratory rate and respiratory minute volume during exercise were still higher and oxygen extraction was still lower, whereas all other measures were similar to those in controls. The increased heart rate in response to isoproterenol after 3 wk of clenbuterol administration was reduced markedly in resting but only slightly in exercising animals, whereas heart rate reduction by propranolol during exercise was similar to that in controls. Seven days after withdrawal of clenbuterol, newly administered clenbuterol evoked the same effects as on d 1. In conclusion, there were marked reactions to the first clenbuterol treatment that were in part enhanced during treadmill exercise. After 2 wk of beta-A administration, animals responded much less to the beta-A and changes were not different from those in controls. Resensitization to the beta-A was observed 7 d after its withdrawal.     

Oscillatory measurements,blood gas analysis and clinical observations after intravenous clenbuterol administration in healthy and acutely pneumonic calves

The effects of clenbuterol (Ventipulmin, Boehringer Ingelheim) on respiratory functions were investigated in 6 calves aged 4–6 weeks prior to and after experimental infection withPasteurella haemolytica A1. On days 1–3 (prior to infection) and on days 7–9 (after infection), blood gas analysis, monofrequency forced oscillation techniques and clinical examinations (heart rate, respiratory rate) were conducted for 135 min after the intravenous administration of clenbuterol (0.8 µg/kg body weight). In healthy calves prior toPasteurella infection, intravenous administration of clenbuterol induced a mild tachycardia and a reduction in the mean oscillatory respiratory resistance. Using the same dose of clenbuterol in diseased calves after infection, the statistically significant reduction in oscillatory respiratory resistance was more impressive and it was accompanied by a significant increase in the oxygen pressure of the arterialized blood. Heart rate and respiratory rate did not change significantly after the administration of clenbuterol in infected calves.Abbreviations HR heart rate - IV intravenous - MFOT monofrequency forced oscillation technique - PaO₂ arterial oxygen pressure - R_os oscillatory resistance - RR respiratory rate     

Physiological effects of experimental verminous bronchitis in Friesian calves.

Pulmonary function values were measured in five Friesian calves of five months of age during the patent phase of an experimental moderate lungworm infection and were compared with the pulmonary function values recorded in four control animals. All the nine calves were free of any previous challenge with Dictyocaulus viviparus and were submitted to the same standardized conditions of body conformation, housing, feeding and procedures for pulmonary function testing. A significant increase of respiratory rate, minute ventilation, total pulmonary resistance and power of breathing and a significant decrease of tidal volume, dynamic lung compliance and PaO2 were observed in the infested animals. The absolute intrapleural pressure values were also significantly more negative. The conclusions of the statistical analysis were almost identical when predicted instead of measured pulmonary function values were used in the control group. The clinical, functional and pathological findings in the infested animals were all consistent with the picture of a lower airway obstructive disease.     

Effect of intravenous and aerosol administration of 5-hydroxytryptamine on pulmonary function values in healthy calves.

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 effect of a β-agonist (clenbuterol) on the heart rate,nitrogen balance and some carcass characteristics of veal calves

Friesian bull calves were used to determine whether rapidly growing calves could be used to study the action of a β-adrenergic agonist (clenbuterol). At seventeen days of age calves were allocated to treatment (4 in initial slaughter group; 8 controls and two groups each of 5 calves given 0.1 or 1.0 mg clenbuterol kg⁻¹ milk replacer DM). Three digestibility/nitrogen balance trials were performed and calves were slaughtered between 150 and 170 kg live weight. Treatment with clenbuterol doubled heart rate for approximately 24 and 72 h in calves treated with 0.1 and 1.0 mg kg⁻¹ clenbuterol, respectively, thereafter heart rate was normal. N retention as a proportion of N intake was increased by treatment with clenbuterol, but differences were only significant in calves weighing 110 kg. At the same mean slaughter weight (160 kg) carcasses from clenbuterol-treated calves were heavier (96.3 and 100.1 kg for 0.1 and 1.0 mg kg⁻¹ clenbuterol-treated calves, respectively) compared with controls (92.2 kg). Results suggest that the proportion of muscle was higher and fat lower in the carcasses of treated compared with untreated calves.     

Acute Metabolic Effects of Clenbuterol in Calves

The acute metabolic effects of clenbuterol were studied in calves. Clenbuterol was given intravenously at a dose of 1 µg/kg body weight. Glucagon was used to increase insulin secretion. Pretreatment with clenbuterol did not change the glucagon-induced hyperglycaemia, but the serum levels of insulin were significantly higher. Clenbuterol showed a significant lipolytic effect. The post prandial increases in glucose and insulin were significantly higher in clenbuterol treated calves. The findings are in accordance with results from earlier studies where clenbuterol was given orally in much higher doses.     

The influence of clenbuterol on prostaglandin F2α-induced dyspnoea in calves

Pulmonary function tests were performed in six healthy calves. Prostaglandin F₂ causes severe narrowing of both upper and lower airways (total lung resistance increased, dynamic compliance decreased). Clenbuterol administered intravenously fifteen minutes prior to prostaglandin F₂ aerosol, and in increasing doses (0, 0.4, 0.8, 1.2 g/kg), on days 1, 2, 4 and 6 of the experiment, effectively but not entirely suppressed these responses.These data indicate that -adrenergic receptors are present in the bovine airways and that the use of clenbuterol (0.8 g/kg) may be effective in treating clinical respiratory disease such as bronchopneumonia in calves.     

Longitudinal study of the effects of lungworm infection on bovine pulmonary function

Clinical and physiologic investigations were done weekly in 5 nonsedated Friesian calves before, during, and after an induced infection with Dictyocaulus viviparus infective larvae. Clinical, hematologic, serologic, and parasitologic findings were all compatible with the classic picture of moderate subacute verminous bronchitis. Most pulmonary function values revealed significant (P less than or equal to 0.05) changes in the 2nd or 3rd week after inoculation and maximal changes at 5 weeks after inoculation. Most marked changes included a decrease in tidal volume, dynamic lung compliance, and arterial oxygen tension, and an increase in minute ventilation, minute viscous work of breathing, and alveolar-arterial oxygen difference. Minute ventilation, dynamic lung compliance, minute viscous work of breathing, and PaO2 revealed the most homogeneous change. Conversely, maximal change of intrapleural pressure, total pulmonary resistance, and viscous work of breathing had higher variability from week to week.     

Partitioning of pulmonary resistance in Friesian calves

Eight right cranial lobes of healthy Friesian calves were suspended in an airtight box. They were inflated at a constant transpulmonary pressure (Ptp) and ventilated from the outside by modifying pressures in the box with a quasi-sinusoidal pump at a frequency of 30 counts per minute. Peak-to-peak changes were 0.5 kPa. Lobar resistance (Rl) was partitioned into three components: central airway resistance (Rc), small airway resistance (Rp) and tissue resistance (Rt). Partitioning of R1 was realised at six different lung volumes. Minimal R1 was observed for a value of Ptp between 0.5 and 0.7 kPa. At a Ptp of 0.5 kPa, Rc, Rp, Rt represent 30, 15 and 55 per cent of R1, respectively. Lobar resistance increases at high and low lung volumes. Small airway resistance is small and independent of the level of lung inflation, except at low lung volumes where a marked increase is observed. Tissue resistance is relatively high and responsible for the increase of R1 at high lung volumes. Central airway resistance does not change significantly with lung volumes.     

Pulmonary function changes induced by experimental dichlorvos toxicosis in calves

Clinical and pulmonary function changes induced by intravenous dichlorvos (2,2-dichlorvinyldimethyl phosphate) (DDVP) toxicosis, and reversibility of these changes after atropine treatment were investigated in six Friesian calves one to three months old. From one minute after dosage, all animals showed severe respiratory distress, excitation, weakness, muscle fasciculation and cholinesterase inhibition. Decrease in dynamic lung compliance and arterial oxygen tension and increase in total pulmonary resistance, viscous work of breathing and alveolar arterial oxygen gradient were highly significant (P less than 0.01). On the other hand, body secretions, heart rate, respiratory rate, tidal volume and arterial carbon dioxide tension were not significantly affected by DDVP injection. Atropine promptly and completely reversed these changes, except for muscle fasciculations, central depression and cholinesterase inhibition which disappeared progressively within 24 hours.     

Comparison of pathophysiologic changes in the lungs of calves challenge exposed with Escherichia coli-derived endotoxin and Pasteurella haemolytica, alone or in combination

Pulmonary responses to intratracheal challenge exposure with Pasteurella haemolytica, with or without Escherichia coli-derived endotoxin, E coli endotoxin alone, or saline solution were compared in anesthetized, mechanically ventilated neonatal calves. Baseline values for dynamic compliance, total pulmonary resistance, functional residual capacity, arterial blood gas tensions, hemogram, leukogram, and systemic and pulmonary arterial pressures were recorded for each calf. After baseline data were obtained, calves were challenge exposed with logarithmic-growth phase P haemolytica organisms with or without E coli endotoxin, E coli endotoxin alone, or saline solution (0.9% NaCl). Physiologic data were obtained immediately after challenge exposure and at various intervals over the next 6 hours. Calves challenge exposed with P haemolytica alone developed sever hypoxemia, had increased alveolar-arterial oxygen difference and threefold increases in total pulmonary resistance, became hypercarbic, had decreased functional residual capacity, and developed systemic hypotension without change in pulmonary arterial pressure. At necropsy, these calves had extensive multifocal areas of necrohemorrhagic and purulent pneumonia. Ratio of extravascular lung water to lung dry weight was not significantly increased in lung specimens obtained from calves challenge exposed with P haemolytica, but ratio of lung wet weight to dry weight was increased, indicating that increased lung wet weight was attributable largely to increased solids and not to fluid alone. (Extravascular lung water measurement excludes fluid from the vascular compartment.) Intratracheal challenge exposure with endotoxin failed to alter lung function and caused minor changes in lung structure consisting of focal areas of hemorrhage and edema.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ascorbic acid levels in the bronchopneumonia of calves]

The level of ascorbic acid in the blood plasma of 59 calves was determined. The age of the calves ranged between two and three months and the samples of blood were collected in January. The first group of calves included 30 animals displaying no clinical symptoms of disease: the average ascorbic acid level was 0.50 +/- 0.18 mg per 100 ml. In the second group, consisting of 19 calves, the blood of the animals was collected three weeks after the termination of the acute stage of bronchopneumonia; the average value of ascorbic acid was 0.30 +/- 0.14 mg per 100 ml. The lowest average value of ascorbic acid was obtained in the calves at an acute stage of bronchopneumonia, reaching 0.18 +/- 0.11 mg per 100 ml. The differences of results between groups I and II and between groups I and III were found to be statistically significant. A conspicuous drop of ascorbic acid level was ascertained in calves suffering from bronchopneumonia-this problem needs deeper scrutiny, owing to the fact that bronchopneumonia is responsible for considerable economic losses in large-capacity calf houses.     

Effect of clenbuterol on the incidence of abomasal ulcers in veal calves

The effect of clenbuterol on the incidence of abomasal lesions in veal calves was studied in two fattening units. Some of the calves in each unit were treated with 1.6 micrograms clenbuterol/kg bodyweight/day from the seventh until the 23rd week of the fattening period. In one unit the calves were fed milk replacer only and 176 of the 236 calves were treated with clenbuterol. In the other unit the calves were fed roughage pellets in addition to milk replacer and 92 of the 194 calves were treated with clenbuterol. Only in the second unit did the calves treated with clenbuterol have significantly fewer abomasal lesions.     

Influence of beta-adrenergic antagonism on the response of bovine neonatal lungs to intravenous histamine

The effects of IV histamine infusion and beta-adrenergic blockade on pulmonary function were studied in neonatal Holstein calves, beta-Adrenergic blockade with IV propranolol increased total pulmonary resistance, but was without effect on lung compliance, lung volumes, and gas exchange. beta-Adrenergic blockade enhanced the histamine-induced increase in total pulmonary resistance and the decrease in dynamic and quasistatic compliance, lung volumes, and arterial oxygen tension. These data indicate that beta-adrenergic receptors may be present in the large and small airways of cattle and they modulate the effects of bronchoconstrictor agents as in other species.     

Clenbuterol hydrochloride in calves with a natural bovine respiratory syncytial virus infection

The effect of clenbuterol hydrochloride on the course of disease in calves with a natural bovine respiratory syncytial virus infection was examined. Six calves (three to nine months of age) originating from four herds with respiratory tract disease and serological evidence of a bovine respiratory syncytial virus infection were used in this study. The calves were injected intravenously with clenbuterol hydrochloride. The effect of clenbuterol on the course of disease was measured using the PO2 in blood taken from an indwelling canula inserted in the caudal auricular artery and by clinical signs. Clenbuterol did not improve clinical signs. After clenbuterol administration arterial PO2 values decreased significantly in five out of six patients. Six to eight hours after medication the mean arterial PO2 values were higher than initial values. The moderate positive effect of clenbuterol after six to eight hours may be caused by enhancing ciliary activity and by the secretolytic activity of clenbuterol.