The height of the follicular epithelium of the bovine thyroid gland was tested as a sorting method for antithyroid drug residues detection in 53 bovine thyroids. Five glands with residues, tested for high performance thin layer chromatography (HPTLC), were collected from five steers treated with oral suspension of methylthiouracil (MTU) for 20 days (5g/animal/day), interrupted five days before slaughter. The other glands without residues were collected from six experimental control animals and from 42 animals slaughtered in an industrial slagthterhouses of Minas Gerais (n=25) and Goiás States (n=17), Brazil. All positive glands were severely hyperplastic and the follicular epithelium height was statistically greater as compared with negative glands, although 42 negative thyroids showed also moderate hyperplasia. The typical individual responses of 47 hyperplasic glands and six normal glands determined a follicular epithelium height limit of 16 micrometers above which all glands should be considered suspect of containing residues and should be submitted to chemical analysis. The correlation between follicular epithelium height and other indirect traits used for residues detection was made. The follicular epithelium height was considered a good sorting method for the official control of antithyroid drug residues in meat.
Bovine; thyroid; methylthiouracil; antithyroid; drug; sorting method
