Validation and application of an immunofluorimetric assay for detection of serum free triiodothyronine and free thyroxine concentrations in buffalo (Bubalus bubalis) under various physiological conditions.

The current study was designed to validate an immunofluorimetric method to measure free triiodothyronine (fT3) and free thyroxine (fT4) concentrations in the serum of buffalo and to develop a better understanding of thyroid metabolism in buffalo (Bubalus bubalis) of different ages and reproductive statuses. Free triiodothyronine and fT4 were determined in sera from 4 groups of 10 animals, each representing 5–10-year-old lactating buffalo, 2–3-year-old first calf heifers, 1–1.5-year-old virgin heifers, and 5–10-year-old dry buffalo. The average sensitivity of the immunofluorimetric assay was 5.9 pmol/l for fT3 and 14.7 pmol/l for fT4. Intra-assay and interassay coefficients of variation were 5.6% and 5.1% for fT3 and 1.5% and 4.3% for fT4, respectively. Virgin heifers had higher average values for fT3 and fT4, while lactating buffalo had the lowest average values. Dry buffalo and first calf heifers had intermediate fT3 and fT4 values. The findings of this study suggested that lactating buffalo were in a state of low thyroid activity, while virgin heifers had increased thyroid activity.