Observations were carried out on volatile fatty acid (VFA) concentrations, enzyme activities and the microflora of the rumen contents in heifers during transition from winter to pasture feeding and in the subsequent gazing cycles. After turn‐out to pasture, total VFA concentrations in the rumen contents of heifers significantly decreased from 107.7 to 88.7 mmol.l−1(P < 0.01). After subsequent increase the total VFA concentrations reached their highest value (117.0 mmol.l−1) in the 8th week of grazing. The proportion of the molar acetic acid concentration in the rumen content increased insignificantly whereas that of propionic acid decreased insignificantly. In the molar proportion of butyric acid no significant differences could be stated. In the subsequent weeks the molar proportions of acetic acid were rather balanced and ranged within 66.2 and 68.0 mol%; the molar proportion of propionic acid insignificantly increased in the 4th week (18.7 mol%). Molar proportions of butyric acid on pasture insignificantly increased in week 3 (15.2 mol%) and appeared as balanced, later acquiring values between 14.0 and 14.8 mol%. The energetic yield of VFA production in the rumen of heifers decreased insignificantly from 73.6 to 72.15; the acetate: propionate ratio revealed an insignigicant increase from 3.66 to 4.18.