Dynamics of Thyroid Hormones in Growth and Development of South Indian Sheep (Bannur)

Abstract

From the data bank of livestock census in India, the total sheep in the country is 65 million numbers in 2012, declined by about 9.09% over census 2007. The total sheep contributes around 12.7% of the total livestock population. Karnataka (South Indian province) contributes second highest in sheep population first is Andra Pradesh. Growth and development are continuous and dynamic processes require integration of numerous physiological functions, they influenced by nutrition, efficiency of metabolism, respiration, hormonal regulation, immune responses, physiological status, and maintenance of homeostasis. The physiological and endocrinological events involved in the onset of puberty and estrus cycle are of primary importance. Appropriate thyroid glands function and activity of thyroid hormones (TH) are considered crucial to sustain the productive performance in domestic animals (growth, milk, hair fiber production) and circulating TH can be considered as indicators of the metabolic and nutritional status of the animals. A total of 24 female Bannur sheep (age from 3.5 month to 11 month) were used in this study. Blood samples were collected from the jugular vein of 24 clinically healthy animals in four groups along with body weight also recorded (GI (>3-5 m), GII (>5-7m), GIII (>7-9m) and GIV (>9-11)). Triidothyroxine and Thyroxine estimation was done using immunoassay test kit method. In the present study, the mean serum Triidothyronine (ng/mL) levels ranged from 1.17 ± 0.01 to 1.80 ± 0.01 ng/mL. Positive correlation was observed between the levels of thyroid hormones (T 3 ) and the age of animal and body weight gain in Bannur ewes. The mean serum thyroxin (μg/dl) levels ranged from 3.98 ± 0.18 to 7.61 ± 0.05 μg/dl. T 4 concentrations elevated at premature phase, where during fattening period growing lambs needed to increase the basal metabolic rate, protein synthesis in their muscles and more of energy to achievements these biological functions, therefore plasma T 4 and glucose concentrations increased in the two last months of fattening period. The age of sheep influenced statically significantly all the investigated parameters. Blood thyroid hormones levels are considered to be good indicators of the nutritional status of an animal.

Seasonal variation of thyroxine concentration in Karagouniko and Chios rams in temperate environmental conditions

“…This hypothesis is strengthened because PHOTO remained practically unchanged for the two experimental periods (in average terms), combined with the statistically different values of AIRT and SUNS between these periods. Also, the negligible fluctuations of the body weight of the experimental rams (Matsoukis et al 2022b) support the hypothesis mentioned above, bearing in mind that a positive relation has been reported between thyroxine concentration and body weight in sheep (Hashem 2014;Veena et al 2018;Aljubouri et al 2021). The thyroxine pattern concerning the direction of day length change in our experiment is in agreement with the results of other researchers for Karagouniko ewes (Kantas et al 2008a;Menegatos et al 1994), Chios ewes (Kantas et al 2008b) as well as Karagouniko × Mytilene ewes (Menegatos et al 2006).…”