circulating metabolic hormones in different metabolic states of high producing holstein dairy cows

background: information regarding the metabolic hormones in different metabolic states of high producing dairy cows can aid high producing herds to manage and resolve the metabolic and production problems. furthermore, it can be considered as a tool to evaluate metabolic status of dairy cows. herd managers can also evaluate the energy input-output relationships by assessing the metabolic profile to prevent and control  negative energy balance, metabolic disorders and nutritional insufficiencies. objectives: the present study was performed to clarify the metabolic hormone profile in each metabolic state of high producing holstein dairy cows. the results of this research can reveal the normal metabolic state of these animals. methods: 25 multiparous holstein dairy cows were divided to 5 equal groups containing early, mid and late lactations, far-off and close-up dry periods. blood samples were collected from all cows and sera were analyzed for concentrations of triiodothyronine (t3), thyroxine (t4), free t3 (ft3), free t4 (ft4), cortisol and insulin like growth factor-1 (igf-1). results: serum t3 concentration in early lactation group was significantly higher than other ones (p