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Abstract
The aim of this study was to investigate the variations in plasma triiodothyronine (T3) and thyroxine (T4) with the advancement of age and to determine their circadian patterns in prepubertal and pubertal Murrah buffaloes. The variations in plasma T3 and T4 with the advancement of age were observed from day 1 to 24 months of age. Significant higher levels of T3 and T4 were observed after birth and a gradual decrease in their concentrations occurred until 15 days of age. The mean plasma T3 and T4 ranged between 1.26–3.79 and 60.7–166 ng/ml, respectively, during 1–30 days of age. During 1–24 months of age, the variations in plasma T3 did not differ (p > 0.05) with the advancement of age, whereas significant (p < 0.0001) changes were observed in plasma T4. The circadian patterns of T3 and T4 were evaluated in prepubertal Murrah buffaloes (n = 8) aged between 14 and 16 months. The mean plasma T3 and T4 ranged between 1.04–1.85 and 43.0–76.1 ng/ml, respectively. Significant (p > 0.0001) changes in the secretory pattern of T3 were observed, whereas the secretory pattern of T4 did not differ significantly (p > 0.05). In addition, the circadian patterns of T3 and T4 in pubertal buffaloes (n = 4) aged between 28 and 30 months were observed and compared to that of prepubertal group (n = 4). The prepubertal group showed significant (p < 0.001) higher plasma T3 concentrations over 24 h than the pubertal group.
Acknowledgements
Financial support provided by the Director, NDRI, Karnal, India is greatly acknowledged.