Br. vet. J. (1992) . 148, 33
PULMONARY FUNCTION CHANGES AND CLINICAL FINDINGS ASSOCIATED WITH CHRONIC RESPIRATORY DISEASE IN CALVES
D . D . S . COLLIE Department of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, Veterinary Field Station, Easter Bush, Roslin, Midlothian EH25 9RG
SUMMARY Thirteen field cases of chronic respiratory disease in crossbred calves aged between 1 and 8 months were subjected to a standardized examination in which clinical criteria were scored and weighted to allow quantification . Predicted values for pulmonary function variables were generated using regression equations previously established in normal calves which related measured pulmonary function variables to thoracic perimeter . Subsequent pulmonary function testing of each calf was undertaken and values obtained compared with predicted values and correlated with clinical scores . Diagnosis was confirmed at post-mortem examination . Calves with chronic respiratory disease had significantly reduced inspiratory and expiratory times, tidal volume, dynamic compliance and Pao 2 , significantly increased respiratory frequency, airway resistance and Paco 2 and more negative transpulmonary pressure values when compared to predicted pulmonary function values for the same calves . Pao2 and Paco2 were the only variables correlated with clinical scores, suggesting their value in the assessment of severe cases of calf respiratory disease .
INTRODUCTION The value of pulmonary function testing as a means of assessing the mechanics of ventilation in conscious cattle with respiratory disease has been increasingly recognized in recent years . However, interest has generally focused on its potential as a research tool and, although several workers have used this technique to monitor changes in experimentally induced disease (Kiorpes et al., 1978 ; Lekeux et al., 1985a, b, c, 1986 ; Nuytten et al., 1986a), relatively few reports are available describing changes associated with naturally occurring disease (Lekeux et al., 1985d ; Nuytten et al., 1986b ; Hajer, 1988) . It is recognized that chronic respiratory disease is a frequent sequel to outbreaks of acute respiratory disease within groups of intensively managed calves . Such calves, which may have severe and often irreversible lung pathology, are generally unresponsive to treatment (Gibbs, 1986), tend to be uneconomical
34
BRITISH VETERINARY JOURNAL, 148, 1
(Thomas et al., 1978), and in addition may act as a permanent source of infection to other calves (Marschang et al., 1979 ; Allan et al., 1985) . However, it is often difficult to determine the severity of lung damage by clinical examination alone and to decide whether treatment or culling is indicated (Vestweber et al., 1977) . Further, once the decision to treat is made, assessment of the response to treatment of these chronic cases on clinical grounds may be very subjective . In view of the frequency with which this condition is recognized and treated in general practice it was considered appropriate to examine field cases of chronic respiratory disease in calves using the technique of pulmonary function testing such that objective data relating to the mechanics of ventilation of these animals could be examined in relation to clinical findings . MATERIALS AND METHODS Thirteen cross-bred calves aged between 1 and 8 months were used . They were admitted as referred cases to the large animal medicine hospital . During the period of study the calves were penned individually and fed on a daily diet of proprietary concentrates and hay ad libitum . Calves were accepted as suffering from chronic respiratory disease on the basis of clinical examination and a history of prior treatment with at least two courses of antibiotics followed by an unsatisfactory response . Clinical examination of the calves was performed in a standardized manner using clinical worksheets (Fig . 1) . These worksheets identified the clinical criteria adjudged to be of importance in the objective assessment of respiratory disease . Scores were assigned according to the presence or absence of certain clinical criteria and arbitrary weightings applied to these such that total clinical scores could be derived for each calf (Fig . 1) . The criteria used in the scoring system and the weightings applied to these criteria were modelled on a previous study (Thomas et al., 1977) . The scoring system was designed such that a clinically normal animal would have a clinical score equal to its respiratory rate . Pulmonary function testing on the unsedated, unanaesthetized calves was performed as previously described (Collie, 1992) . Prior to this procedure arterial blood was sampled from the brachial artery using the method described by Fisher et al. (1980) . Samples were analysed as previously described (Collie, 1992) . Mean pulmonary function values recorded for these calves were compared with predicted values for calves of similar age and breed (Collie, 1992) using Student's unpaired t-test. Predicted values were generated using regression equations relating pulmonary function variables to thoracic perimeter . Clinical scores were correlated with individual pulmonary function parameters . Each calf examined was subsequently killed and subjected to a post-mortem examination . Although gross and histopathological features were recorded, no attempt was made to grade or classify the lesions observed . RESULTS The most frequently identified clinical abnormalities of the diseased calves were, in order
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PULMONARY FUNCTION CHANGES AND CLINICAL FINDINGS ASSOCIATED WITH CHRONIC RESPIRATORY DISEASE IN CALVES
D . D . S . COLLIE Department of Veterinary Clinical Studies, Royal (Dick) School of Veterinary Studies, Veterinary Field Station, Easter Bush, Roslin, Midlothian EH25 9RG
SUMMARY Thirteen field cases of chronic respiratory disease in crossbred calves aged between 1 and 8 months were subjected to a standardized examination in which clinical criteria were scored and weighted to allow quantification . Predicted values for pulmonary function variables were generated using regression equations previously established in normal calves which related measured pulmonary function variables to thoracic perimeter . Subsequent pulmonary function testing of each calf was undertaken and values obtained compared with predicted values and correlated with clinical scores . Diagnosis was confirmed at post-mortem examination . Calves with chronic respiratory disease had significantly reduced inspiratory and expiratory times, tidal volume, dynamic compliance and Pao 2 , significantly increased respiratory frequency, airway resistance and Paco 2 and more negative transpulmonary pressure values when compared to predicted pulmonary function values for the same calves . Pao2 and Paco2 were the only variables correlated with clinical scores, suggesting their value in the assessment of severe cases of calf respiratory disease .
INTRODUCTION The value of pulmonary function testing as a means of assessing the mechanics of ventilation in conscious cattle with respiratory disease has been increasingly recognized in recent years . However, interest has generally focused on its potential as a research tool and, although several workers have used this technique to monitor changes in experimentally induced disease (Kiorpes et al., 1978 ; Lekeux et al., 1985a, b, c, 1986 ; Nuytten et al., 1986a), relatively few reports are available describing changes associated with naturally occurring disease (Lekeux et al., 1985d ; Nuytten et al., 1986b ; Hajer, 1988) . It is recognized that chronic respiratory disease is a frequent sequel to outbreaks of acute respiratory disease within groups of intensively managed calves . Such calves, which may have severe and often irreversible lung pathology, are generally unresponsive to treatment (Gibbs, 1986), tend to be uneconomical
34
BRITISH VETERINARY JOURNAL, 148, 1
(Thomas et al., 1978), and in addition may act as a permanent source of infection to other calves (Marschang et al., 1979 ; Allan et al., 1985) . However, it is often difficult to determine the severity of lung damage by clinical examination alone and to decide whether treatment or culling is indicated (Vestweber et al., 1977) . Further, once the decision to treat is made, assessment of the response to treatment of these chronic cases on clinical grounds may be very subjective . In view of the frequency with which this condition is recognized and treated in general practice it was considered appropriate to examine field cases of chronic respiratory disease in calves using the technique of pulmonary function testing such that objective data relating to the mechanics of ventilation of these animals could be examined in relation to clinical findings . MATERIALS AND METHODS Thirteen cross-bred calves aged between 1 and 8 months were used . They were admitted as referred cases to the large animal medicine hospital . During the period of study the calves were penned individually and fed on a daily diet of proprietary concentrates and hay ad libitum . Calves were accepted as suffering from chronic respiratory disease on the basis of clinical examination and a history of prior treatment with at least two courses of antibiotics followed by an unsatisfactory response . Clinical examination of the calves was performed in a standardized manner using clinical worksheets (Fig . 1) . These worksheets identified the clinical criteria adjudged to be of importance in the objective assessment of respiratory disease . Scores were assigned according to the presence or absence of certain clinical criteria and arbitrary weightings applied to these such that total clinical scores could be derived for each calf (Fig . 1) . The criteria used in the scoring system and the weightings applied to these criteria were modelled on a previous study (Thomas et al., 1977) . The scoring system was designed such that a clinically normal animal would have a clinical score equal to its respiratory rate . Pulmonary function testing on the unsedated, unanaesthetized calves was performed as previously described (Collie, 1992) . Prior to this procedure arterial blood was sampled from the brachial artery using the method described by Fisher et al. (1980) . Samples were analysed as previously described (Collie, 1992) . Mean pulmonary function values recorded for these calves were compared with predicted values for calves of similar age and breed (Collie, 1992) using Student's unpaired t-test. Predicted values were generated using regression equations relating pulmonary function variables to thoracic perimeter . Clinical scores were correlated with individual pulmonary function parameters . Each calf examined was subsequently killed and subjected to a post-mortem examination . Although gross and histopathological features were recorded, no attempt was made to grade or classify the lesions observed . RESULTS The most frequently identified clinical abnormalities of the diseased calves were, in order
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