Abstract
Season may be considered as a factor that affects the equine endocrine profile. Hence, from January to November 2015, 27 clinically healthy adult Darehshori racehorses were selected. Thirteen of them were stallions and the others were mares. Ten of them were more than 10 years old and 17 horses were under the age of 10 years. None of them were pregnant or lactating during the study. Body condition scores of 12 horses were below and the others were above 5. Blood samplings and body condition score evaluations were performed every 45 days during a year. Serum levels of cortisol, IGF-1, T3, T4, and TSH were assayed in all specimens. T3 and TSH were significantly decreased following the warming up of the climate in different ages, sexes, and body condition scores, but there were no significant changing patterns in T4. There were various trend changes of both cortisol and IGF-1 in different ages, sexes, and body condition scores during the seasons of the study period. Based on the results, circulating levels of cortisol, IGF-1, and thyroid hormones of Darehshori horses are dependent on many factors such as breed, sex, age, body condition, season, geographical location, and individual characteristics.
Highlights
There are several concepts about physiological alterations in the body in various seasons and several theories have explained these mechanisms, but the mechanisms are not clear in various seasons
Considering the importance of cortisol, insulinlike growth factor-1 (IGF-1), and thyroid hormones in the growth and immune system of the horse’s body, as well as many other functions that are proposed for these hormones, the aim of this study was investigation of the serum levels of these hormones in different sexes, ages, and body conditions among Darehshori horses in various seasons during a year
3.1.Thyroid hormone alterations The lowest T3 in the young horses was detected in June and its lowest levels in aged horses were seen in the August
Summary
There are several concepts about physiological alterations in the body in various seasons and several theories have explained these mechanisms, but the mechanisms are not clear in various seasons. There is no information on changes in cortisol, insulinlike growth factor-1 (IGF-1), and thyroid hormones in Darehshori horses in different seasons. The present study investigated the seasonal changes in the mentioned hormones in both sexes of Darehshori horses [1,2]. Cortisol secretion occurs in the body’s reaction to stress, and because it is responsible for several stress-related changes in the body, it is called stress hormone. This hormone has several effects on inflammatory reactions, blood glucose metabolism, release of insulin hormone to maintain the proper level of blood
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