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We evaluated the relationship, in cynomolgus macaques (Macacafascicularis), between rank for order of blood collection with serum concentrations of 3,5,3'-triiodothyronine (T3), thyroxine (T4), free thyroxine (FT4), and serum cortisol. These relationships were determined for males and females that were housed in two room arrangements. For both room arrangements, males and females were housed separately. For room arrangement 1, macaques were housed on both sides of the animal holding room. The sides of the animal holding room were designated as side A or side B. Blood was initially collected from animals on side A, then from animals on side B. Animals on side B were able to visually observe macaques on side A being physically restrained and sedated for blood collection. In room arrangement 2, the macaques were housed on only one side of the animal holding room and could not directly observe other animals being physically restrained and sedated for blood collection. The relationship for serum FT4 concentration with blood sample collection sequence was different for each room arrangement. For room arrangement 1, we observed an inverse relationship between serum FT4 concentration and the rank for order of blood collection. This finding was observed for males and females and was consistent with the lower serum Ff4 value observed for animals housed on room side B. We also observed a trend for higher serum T4 concentration on room side A, but the reverse was true for serum cortisol concentration. In contrast, a macaque's rank for blood collection sequence in room arrangement 2 was not predictive of the rank for serum thyroid hormone (T3, T4, FT4) or serum cortisol concentration. These results suggest that the arrangement of cages in a nonhuman primate holding room contributes to the variability for serum FT4 concentrations.


open access article