Influence of a lower content of energy in the ration on blood biochemical profile and selected hormones concentration in bulls Wplyw obnizonej zawartosci energii w dawce pokarmowej buhajkw na profil biochemiczny krwi i stezenie wybranych hormonw

The purpose of the study was to examine the blood biochemical profile and selected hormones content in Black-and-White Polish Holstein-Fresian bulls (PHF) and crossbreds obtained from PHF dams sired by Limousine (PHFxLM), on different date during the experiment. Animals in group: I (PHF) and III (PHFxLM) over 63 days prior to slaughter were provided with the ration energy limited to 80% of the maintenance requirement. Until slaughter the bulls in group II (PHF) and IV (PHFxLM) were receiving a balanced ration. Blood from all the animals was collected three times. The date of blood collection during the experiment did not have a significant effect on the content of total protein, albumin, triglyceride and alanine aminotransferase activity (ALT) as well as the insulin and triiodothyronine (T3) content. Significant increase in the level of glucose in group II and IV, HDL and urea in III and activity of AST in all groups in 14th (B) and 70th (C) day of experiment occurred. Significant decrease of thyroxine (T4) was found in all animals. The analyses of total blood plasma cholesterol initially showed decrease and then significant increase.