Abstract

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.

The results of this experiment on dairy cows showed that there were not significant changes in dry matter intake of lactating dairy cows with or without a supplement of exogenous fibrolytic enzymes at early lactation. Exogenous fibrolytic enzymes supplementd to lactating dairy cows improved (P<0.003) milk yield (41.0 vs. 39.5 kg/cow/d) compared to untreated dairy cows. Also, the fat corrected milk was increased (P<0.025) as a response to exogenous fibrolytic enzymes supplementation to lactating dairy cows compared to un-supplemented dairy cows. In addition, the supplementation of exogenous fibrolytic enzymes enhanced (P<0.006) the energy corrected milk (40.6 vs. 39.4 kg) and feed efficiency in early lactating dairy cows compared to the control group. The results revealed that supplementation of exogenous fibrolytic enzymes had no significant effect on milk fat, protein lactose and solid not fat (SNF) percentage compared to the control group of dairy cows. While, the quantities of milk protein (1.36 vs. 1.30kg), lactose (2.0 vs. 1.92kg) and SNF (3.47 vs. 3.31kg) in supplemented-dairy cows were improved significantly compared to the control group except quantity of milk fat (P<0.096). Serum glucose, albumin, urea and triglycerides were not affected (P>0.05) but total protein, globulin and cholesterol were declined (P<0.05) due to fibrozyme inclusion compared to control group of dairy cows. The supplementation of exogenous fibrolytic enzymes to early lactating dairy cows achieved higher net profit by 0.93 US$ per cow than control group. It is concluded that exogenous fibrolytic enzymes supplementation to early lactating dairy cows improved significantly milk production, SNF and energy corrected milk.

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