EN
Five heifers and five bulls averaging 11 months of age were used to characterise plasma growth hormone (GH) pattern in Polish Friesian cattle. Animals were fed a diet of corn silage, hay and concentrates twice daily. They gained weight at a mean rate of 0.7 kg/d for heifers and 0.9 kg/d for bulls. Serial blood samples were collected through catheters at 15 min intervals over 4 hours. To estimate the pulse, characteristics of GH the computer program PULSAR was used. The results of the study confirm the pulsatile nature of growth hormone secretion in cattle. The following values for plasma GH parameters were obtained for heifers and bulls respectively: mean concentration, 17.8 and 18.7 ng/ml; smooth value, 9.5 and 9.6 ng/ml; peak amplitude, 15.7 and 20.8 ng/ml; peak frequency, 0.98 and 1.02 h⁻¹. The GH sectretion particularly varied among animals for mean and smooth value. A correlation between basic GH concentration and peak amplitude was found. The obtained results suggest that the peak frequency is a biologically important parameter associated with the growth rate.