INFLUENCE OF SALINOMYCIN AND AVOPARCIN ON THE PLASMA-CONCENTRATION OFINSULIN-LIKE GROWTH-FACTOR OF BEEF-CATTLE

The influence of antibiotics on IGF-I concentration was measured in th ree feeding experiments within beef cattle. Salinomycin and avoparcin increased significantly the plasma concentration of IGF-I in consequen ce of improved nutrient supply for animals. The IGF-I level was closer correlated with the body weight than with the daily weight gain of bu lls. IGF-I increased significantly in heavier animals. Enhanced produc tion of sexual steroids of older bulls may stimulate the growth hormon e release. There existed significant differences between various breed s in IGF-I concentration, probably caused by a genetic fixed GH-secret ion. The diet depending IGF-I production in the peripheral tissues (es p. liver) represents a link between growth hormone axis (genetic possi ble growth) and the realizable growth depending on nutrient supply.