Localization of chicken parathyroid glands through vital staining

Five, fat-soluble dyes and one, metachromatic tissue dye were administered to White Leghorn hens and broilers to determine how these compounds would color parathyroid tissue for subsequent gland localization. Sudan black, sudan red, canthaxanthin, oil red O, beta-apo-8'-carotenal, and toluidine blue O were administered orally in gelatin capsules once a day for 1, 2, or 3 days before slaughter. The dyes were administered at approximately 100 mg/dose. The carotenoid pigments were given at 200 mg/dose. Two administrations were required to develop sufficient visible staining. All dyes except the toluidine blue O were visibly deposited in the parathyroid glands. Sudan black resulted in the greatest contrast with surrounding adipose tissue. Male broilers 3 wk of age that were given one dose of sudan black showed gland definition comparable to that seen in the hens after two doses. Male broilers 5 wk of age showed less gland definition when given sudan black or sudan red for 1 or 2 days. A histological examination indicated that the fat-soluble dyes were located extracellularly. These results indicate that sudan black can be used to visually identify the parathyroid glands of chickens.