Abstract
Twenty month feeding studies with tylosin using Wister strain rats were carried out to estimate the toxicity and the safety of this antibiotics as a food additive. A total of 160 albino rats, weighing 80∼115g was used. Five groups of 16 each, equally divided as to sex, were fed diets containing 0.1, 0.01, 0.1, 1.0 and 10.0% of tylosin, repectively, for a 20-month period. The results obtained were following. Macroscopically, during the course of experiments, no difinite signes of toxic effects for the animals were observed in each drug levels; such as food cosumption, appearance of skin, hair and state of motility.
From an analysis of growth curves, no significant differences were shown between the groups fed tylosin and control in body weight gain, even at the high level of 10% drug diet. After a feeding period of 20-month, 75, 43, 31 and 30% of the rats survived at the drug level of 10, 1.0, 0.1, 0.01% respectively, while only 26% of the control animals survived. Postmortem examination in experimental animals did not show any pathological changes in liver, kidney and other main organs. Haematological testes were also shown normal limits.
Microsckopic studies on the main organs of the rats sacrificed at 12-month and 20-month were made in detail. Degenrative changes, atorophy, hydropic degeneration, pyknosis and fatty metamorphosis of hepatic cell were not demonstrated in all cases. Any cirrhotic changes in liver were not observed. There was nothing of the neoplastic changes in hepatic cells of all the rats tested. Remarkable toxic effect in the kidney, spleen, heart and testes was also not observed.
