Thyroid hormones and their biological variability of Smena 9 cross broilers

The article presents the results of determining the reference limits for thyroid hormones in the blood of Smena 9 cross broilers during the growth period. The object of the study were final hybrid broiler chickens grown in cage conditions; the material for the study was blood, which was taken from the axillary vein in compliance with the principles of asepsis and antisepsis at the age of 14, 23 and 35 days. The total free concentration of thyroid hormones (thyroxine, triiodothyronine) in the blood of chickens was determined by enzyme immunoassay method, using ready-made reagent kits. To assess the possibility of using the analyte reference interval at the population or specific sample level, the analyte individuality index (InIA) and the analyte reference variation (RCV) were calculated. It was found that the level of total and free triiodothyronine, through which the main properties of thyroid hormones are realized in the body of birds, statistically significantly changes during the growing period by 10.00-16.59 and 37.08-58.34%. Biological variability of thyroid hormone level in the blood, determined by the age of Smena 9 cross broilers, forms the following reference limits for the concentration of total and free thyroxine 5.00-6.44 nmol/l and 11.65-14.47 pmol/l; total and free triiodothyronine 11.63- 14.62 nmol/l and 6.72-11.31 pmol/l. This affects the variability of the peripheral hormone conversion index (IPCTH) and the progressive peripheral thyroid hormone conversion index (IPCTH) within the range of 0.39-0.54 and 1.18-1.88 conventional units. The upper and lower reference limits are statistically justified, since the reference change in the analyte (RCV) at a specific age of chickens is no more than 3.93-12.56%, indicating the absence of clinically significant deviations.