The glucoplastic substance propylene glycol was continuously used as a feed
supplement in six dairy farms. Furthermore it was applied for the first ti
me in one farm with a high rate of ketosis prevalence (28 %). The quantitat
ive milk acetone test served as a suitable mean for controlling the effect
of propylene glycol on the energy metabolism in the dairy cows. Application
of propylene glycol diminishes significantly the number of cows with raise
d milk acetone concentrations (greater than or equal to 0,250 mmol/l) on he
rd basis. It must be particularly emphasised, that the positive metabolic e
ffect of propylene glycol can only be expected, if the feed ration of the c
ows meets the basically demands of ruminants generally and the level of mil
k yield in the herd using propylene glycol. Feeding management must be stab
le without any greater variations. Propylene glycol should be feed from abo
ut three weeks ante partum at the end of the dry period to six to ten weeks
post partum dependant on the special conditions in the herd especially of
the milk yield level. Very important is the homogenous distribution of the
propylene glycol in the whole ration without the possibility of selective e
ating. Relating to the cost benefit ratio, a price of about 0,40 DM per day
and head opposites a lower ketosis prevalence with significant positive ef
fects on milk yield and general health. The presented results support using
propylene glycol as an important and suitable mean in feeding management o
f dairy herds.