Background: Lipid mobilization increases significantly in cows around the time of calving and a correlation between excessive blood NEFA concentrations, oxidative stress, and impaired health status in transition dairy cattle was observed. Aims: The relationship between serum thyroxin (T4) values with energy indices and lipid profile in all cows, non-fat cow (NFC), fat cow (FC), healthy and diseased animals were estimated in the present study. Methods: Blood samples were obtained from fifty multiparous cows on -14, +10, +20, and +30 days relative to parturition. They had similar diets and were kept under the same management conditions. Results: NEFA and BHBA values increased significantly on the 10th day of calving. Inversely, glucose, T4, triglyceride, LDL-C, and VLDL-C decreased significantly ten days after calving. There has been a significant negative correlation between serum T4 with NEFA for all cows and FCs. Serum T4 and BHBA values had a significant negative correlation in NFC, FC, healthy, and diseased cows. In addition, serum T4 and fructosamine had a significant negative relationship in FCs and a significant positive correlation in diseased cows. The serum T4 values had a significant negative correlation with cholesterol, HDL-C, and a positive correlation with triglyceride and VLDL-C for all cows, NFC, FC, and healthy cows. Conclusions: The data emphasized the effects of negative energy balance during the transition period on serum lipids profile and thyroid function. In addition, the correlation between T4 and energy and lipids indices may indicate a possible effect of health and body condition status on thyroid responses.

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