Reference levels of serum thyroid hormones profile in Osmanabadi bucks

Introduction

Thyroid hormones (THs) play a pivotal role in the regulation of metabolic activity throughout all life stages (Behringera et al., 2018) [1] . Appropriate thyroid gland function and activity of thyroid hormones (TH) are considered crucial to sustain the productive performance in domestic animals (growth, milk, hair fibre production) and circulating thyroid hormones can be considered as indicators of the metabolic and nutritional status of the animals (Riis and Madsen, 1985; Todini et al., 2007) [7,9] . Osmanabadi goats are one of the most popular breeds of goat amongst the livestock in Maharashtra, India. The Osmanabadi goats particularly males are being used for meat purposes and also, in industry for raising various antisera production as an experimental animal. There are very few references available for the normal physiological range of thyroid hormones viz. T 3 , T 4 and for fT 4 no reports are available for male goats. Thyroid hormones are affected by various factors, viz. Season, climate, geographical distribution, age, sex, nutritional status and disease conditions (Todini, 2007) [9] . Radioimmunoassay (RIA) is a sensitive in vitro technique for assessing antigens from biological fluids with excellent sensitivity and precision (Goldsmith, 1975) [4] . The purpose of the present study was to establish thyroid hormones reference range in healthy Osmanabadi buck using RIA technique.

Collection and preservation of blood samples

The Advy Chemicals Pvt. Ltd. farm located at Phalegaon, Kalyan, Dist. Thane (India) having more than 500 Osmanabadi buck. Those animals are being maintained on standard managemental conditions. The company replaces the healthy male goat lot periodically and being purchased from farmers in Nasik, Ahmednagar district area of Maharashtra state.

The goats are being used for the raising antisera against various animal and human diseases. To established the normal reference range of these thyroid profile, total 226 blood samples (3-5 ml) were collected from adult Osmanabadi bucks with age range 1-1.5 year and average body weight 28.5 kg from Advy Chemicals Pvt. Ltd. farm located at Phalegaon, Kalyan, Dist. Thane (India). The clear serum was obtained immediately after collection by centrifugation and stored at -20 o C till to be analyzed.

Assay of thyroid hormones

Total 226 Serum samples were analyzed for thyroid hormones viz. total triiodothyronine (T 3 ), thyroxine (T 4 ) and fT 4 . Radioimmunoassay was conducted by implying ready to use kits supplied by Board of Radioisotope Technology (BRIT), Bhaba Atomic Research Centre. The radioimmunoassay was carried out at Radiation Medicine Centre (RMC), BARC, Parel, Mumbai -400 012. All pre-analytical, analytical and post analytical precautions were taken into consideration for ensuring proper quality. All Standard Operating Procedures (SOPs) were followed for sample collection, processing, storage and handling. Internal quality control (QC) was done for each parameter by using lyophilized Quality Control. Intra-assay and interassay coefficient of variance was carried out. The reference ranges were considered only after verification of control ranges. Westgard rules were followed to ensure quality.

Statistical analysis:

The experimental data was tabulated and reference ranges for hormone concentrations were established by the non-parametric method of percentile estimates (25th to 75th percentile) (Snedecor and Cochran, 1994) [8] .

Results & Discussion

As depicted in box plot Fig: 1, the mean value of T 3 of Osmanabadi bucks was 103.15 ± 2.54 ng/dl. 'T bars' represent the range from 19.5 to 201 ng/dl, interquartile range, 25 th to 75th percentile, as 76.6 to 127.1 ng/dl and median 97.68 ng/dl. The mean value of TT 4 of healthy Osmanabadi bucks was recorded as 5.43 ± 0.15 µg/dl (69.9 nmol/L). The box plot (Fig. 2) of TT 4 concentration in goats where 'T bars' represent the range from 1.18 to 11.2 µg/dl, interquartile range, 25th to 75th percentile, as 3.8 to 6.9 µg/dl and median as 4.9 µg/dl. The mean value of fT 4 of healthy Osmanabadi bucks was recorded as 0.99 ± 0.01 ng/dl. The box plot (Fig. 3) of fT 4 concentration in goats where 'T bars' represent the range from 0.46 to 1.58 ng/dl, interquartile range, 25th to 75th percentile, as 0.85 to 1.84 ng/dl and median as 1.0 ng/dl. The reference range for blood serum levels of TT 3 , TT 4 & fT 4 are 76.6 to 127.1 ng/dl, 1.18 to 11.2 µg/dl and 0.85 to 1.84 ng/dl respectively in Osmanabadi bucks. The mean and interquartile reference range of TT 3 levels in our studies are slightly lower than the values reported by Galdhar et al. (2022) [5] in different breeds of adult goats (n = 102) with RIA technique. They reported mean total T 3 levels of 2.42 ± 0.09 nmol/L (157 ng/dl) with reference interval (25th to 75th percentile) 1.69 to 2.98 nmol/L. Mean total T 4 levels of 92.63 ± 3.63 nmol/L (7.2 µg/dl) with reference interval (25th to 75th percentile) was 64.67 to 111.64 nmol/L. In adult sheep more than 99.9% of T 4 and 99.5% of T 3 circulate in blood bound to plasma proteins (Chopra et al., 1975) [2] . Only the free hormone is responsible for the biological activity. Few reports are available for the levels free T 4 in goats. No systematic studies with sizable sample size have been carried out in goat. The levels of fT 4 reference range have been established first time in goat in our study. The levels of fT 4 observed in our study are in close agreement with the reports of I.R. Dias et al., (2010) in Churra -da -Terra-Quente ewes from north east Portugal. They reported mean value of 11.93 ± 1.78 pmol/L (0.92 ± ng/dl). Also, range for total T 3 , T 4 and fT 4 reported by Luigi Liotta et al., (2021) [6] in nonpregnant Nicastrese goats are in close agreement with our findings in our studies in Osmanabadi buck without much difference in the reference range in adult male and female animals.

Summery & Conclusion

Serum total triiodothyronine levels range from 76.6 to 127 ng/dl, total thyroxine concentration range from 3.8 to 6.9 µg/dl and fT 4 concentration in goats range from 0.85 to 1.84 ng/dl Osmanabadi bucks. This physiological serum thyroid hormone profile reference range levels would be valuable information for identifying thyroid dysfunction in Osmanabadi bucks. No systematic studies have been carried out on thyroid hormone levels in goat and the levels of Free T 4 (fT 4 ) established first time in goat, which can be important biomarker with narrow reference range to study the thyroid status in this animal.

Acknowledgement

AcknowledgementsThe authors would like to thank Dr. Santosh Salvi, Manager, M/S Advy Chemicals Pvt. Ltd, Phalegaon, Kalyan, Dist. Thane (India) for providing experimental animals. The authors are also thankful to Associate Dean, Mumbai Veterinary College (MAFSU) for providing facilities and funding and Radiation Medicine Centre (RMC), BARC for providing RIA kits.

References

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