Clinical signs and performance of pigs during the administration of different levels of carbadox and after withdrawal.

An experiment was designed to study the clinical effects of carbadox in pigs. Five different carbadox levels were tested namely 25, 50, 100, 150, and 200 ppm. They were compared with a control group fed on a diet without medication. After 10 weeks all pigs received a diet without carbadox till the end of the experiment, 21 weeks after the start. After two weeks of carbadox treatment the first clinical signs were observed in the 200 ppm group. The most obvious effects seen were production of dry faeces and drinking of urine from the floor or from pen-mates. Other signs were a decreased abdominal volume, a pale skin with long withered hair, perverted eating and a restless behaviour. The haematocrit values in pigs receiving 100 ppm and upwards were increased. There was a negative correlation between the dose of carbadox and the time after which the response occurred. Weight gain was significantly lowered and feed conversion essentially poorer in the 200 ppm, 150 ppm and 100 ppm groups during the treatment as compared to the controls. No growth promoting effect was seen in the 25 and 50 ppm groups. After withdrawal of carbadox, clinical signs persisted in the 150 and 200 ppm groups. The 100 ppm group produced normal faeces 5 weeks after withdrawal, whereas drinking of urine persisted. From this study it appears that only an oral dosage of 25 ppm or lower can be given to pigs without risks of toxic effects. The widely claimed growth promoting effect of carbadox could not be confirmed in this study. This might be due to the small number of animals per group.