Effects of propylene glycol powder on productive performance and blood metabolites of lactating Holstein dairy cows

An experiment was conducted by eight lactating Holstein cows with an average milk production of 32. 75 kg/d and body weight of 643. 6 kg to evaluate the effects of propylene glycol (PG) powder on reproductive performance and blood metabolites. In this experiment a balanced change-over design with four treatment and four periods with 21 days (14 day for adaptation and 7 day for data collection) were employed. Treatments include: 1- Control treatment (without PG)، 2- 250gr PG/cow/day، 3- 500gr PG/cow/day and 4- 750gr PG/cow/day. The cows were fed individually ad libitum and were milked twice per day. Daily milk yield was recorded and milk samples were taken during seven and two last days of each period. The results show that dry matter intake، milk yield، fat corrected milk yield، milk compositions were not affected by different levels of PG (P>0. 05). Supplementing cows with 500gr and 750gr PG/cow/day، significantly increased plasma glucose (P<0. 05)، but other blood metabolites such as blood urea nitrogen، triglyceride and cholesterol were not affected by PG (P>0. 05). In conclusion، plasma glucose was increased by using 500gr and 750gr PG/cow/day (as powder) in the first and mid lactation stage، but different levels of PG did not have any significant effect on dry matter intake، milk yield، milk compositions and other blood metabolites.