SUMARRY

The effects of zeolite tipe "Mikozel" as the forage additive in the concentrations of 0,2% , 0,3% and 0,5% on the activities of enzymes AP (alkaline phosphatase) , AST (aspartate aminotransferaze) and ALT (alanine aminotransferaze) in blood serum of trained horses. American tratter and English thoronghbred hoerse, were studied in this paper.

It was established that the used additive, depending on the applied quantity, cansed certain changes of the examined ferments values, but these values-are within their physiological limits and recordes exceptions are unrealistic and insignificant.

Key words: zeolite, AP, AST, ALT, English thorongh — bred horse, American trottek