This study was conducted to investigate the impacts of exogenous fibrolytic enzymes (Fibrozyme, Alltech inc
company, USA) supplementation for 12 weeks on milk production and composition as well as blood metabolites
in early lactating dairy cows. Total of 120 multiparous Holstein dairy cows at early lactation (57±4.2 days in
milk) were randomly assigned into two groups according to lactation period "stage of lactation" and lactation
season. The first group (control, n=60) were fed total mixed ration (TMR) without a supplement of exogenous
fibrolytic enzymes. The second group (treatment, n=60) were fed TMR supplemented with a commercial
exogenous fibrolytic enzymes at the rate of 15 g/cow/d for 12 weeks. Each group was placed in a shaded pen
equipped with free stalls. An exogenous fibrolytic enzymes was added to the TMR at the time of feeding once
per day at 10 am. Cows were fed as a group open feed, with free access to water