Acta Vet. Brno 2007, 76: 525-532

Blood Concentrations of Thyroid Hormones and Lipids and Content of Lipids in the Liver of Dairy Cows in Transitional Period

R. Djoković1, H. Šamanc2, M. Jovanović3, Z. Nikolić2

1Department of Animal Science, Faculty of Agronomy, Čačak, University of Kragujevac,
2Department for Diseases of Ruminants and Pigs,
3Department of Pathology, Faculty of Veterinary Medicine, University of Belgrade, Serbia and Montenegro

Received March 16, 2006
Accepted November 15, 2007

The aim of the present investigation was to determine the correlation in the blood concentrations of thyroid hormones, lipids and glucose as well as the content of lipids in the liver of dairy cows in the transitional period. The animals (n = 40) were divided into four groups: the first group included late pregnant cows (n = 10) from the 10th to 4th day before calving; the second group included late pregnant cows (n = 10) from the 4th to 1st day before calving; the third group included clinically puerperal healthy cows (n = 10), whereas the fourth group included puerperal cows with clinical symptoms of ketosis (n = 10). Samples of liver and blood tissues were taken from all cows. Pathohistological examination of liver samples showed statistically significantly higher (p < 0.01) lipid infiltration in ketotic cows compared to healthy cows in late pregnancy and puerperium. Biochemical examination of blood serum showed significantly higher values (p < 0.01) of free fatty acids in ketotic cows, such as significantly lower blood concentrations of glucose (p < 0.01), triacylglycerols (p < 0.01), total cholesterol (p < 0.05), triiodthyronine (p < 0.05) and thyroxine (p < 0.05), compared to the values obtained in the blood serum in the groups of healthy cows before and after calving. In this study, significantly positive correlations were determined between the content of lipids in the liver and blood concentration of free fatty acids (r = 0.51; p < 0.05) as well as the negative ones between the content of lipids in the liver and blood concentrations of glucose (r = -0.69; p < 0.05), triacylglycerols (r = -0.55; p < 0.05) and total cholesterol (r = -0.50; p < 0.05) in the group of ketotic cows. Our investigations suggested that a hypothyroidal status was established in ketotic cows and that the blood concentrations of free fatty acids, triacylglycerols, total cholesterol and glucose served as major biochemical indicators in determining liver steatosis in the dairy cows in the transitional period.