Leptin hormone is produced by fat cells and is believed to coordinate the control of body weight. This study was conducted to determine the levels of leptin, triglyceride, cholesterol, VLDL, LDL, HDL and glucose in serum apart from the body weight of animals, and to find out the correlations between them. Four breeds of sheep (Karakul; semi-fat tailed breed, Morkaraman and Norduz; fat tailed breeds, Tahirova; thin tailed breed) were used as research material under the same feeding conditions. Fifteen sheep of each group -for a total of 60- were selected as research material. ELISA tests were used to determine serum leptin levels; auto analyzer was used for the estimation of triglyceride, cholesterol, VLDL, LDL, HDL and glucose levels. Body weights were measured by a weighing scale.  Leptin levels, along with triglyceride, cholesterol, VLDL, LDL, HDL levels and body weight, were higher in Tahirova sheep breed, and the difference was found statistically significant (P<0.05). There was no statistically significant difference between the HDL levels of sheep breeds. Glucose levels were high in Karakul breed and statistically significant difference was determined between Karakul, Norduz and Tahirova breeds (P<0.05). In conclusion, thin tailed sheep breeds were found to have a high leptin level, which shows that leptin levels are independent of the tail fat ratios. Leptin has been studied in detail in human medicine, but researches on animals were scarce. Apparently, further studies are needed to elucidate the factors of production of leptin in animals.

Key words: Body weight, Glucose, Leptin, Lipids, Sheep