INTERRELATIONS BETWEEN DISEASES AND EFFECTS OF TREATMENT PROCEDURES ON SOME PRODUCTION PARAMETERS AT DANISH PIG-BREEDING TEST STATIONS

The epidemiologies of the most common diseases diagnosed in pigs at the Danish pig-breeding test stations were studied. The population under study comprised 9 084 test pigs housed at nine test stations from September 1983 to September 1984. At some stations the animals were treated for respiratory disease at an early stage, while at others the animals were treated late in the testing period. Great differences among stations were found in the intensity of treatment expressed as average number of treatments per test pig (total incidence), average number of treatment periods per treated pig (repeated treatments) and average number of treated pigs per treated group (prophylactic treatment of pen mates). The time at which the treatment started and the intensity of treatment both had significant effects on the culling rate and on the average growth rate at the station level. Associations between clinical respiratory disease, diarrhoea and other diseases were positive in the specific-pathogen-free (SPF) system, but differed from station to station in the conventional health system. Higher prevalences of pleuritic and pneumonic lesions were found at routine meat inspection in pigs treated for respiratory disease than in non-treated pigs. The time between last treatment for respiratory disease and slaughter influenced the meat inspection findings (suggesting that pneumonic lesions, in particular, were resolved with time).