| The experiment was conducted to study the effects of biotin on the performance, metabolic parameters and the optimal dose of Holstein cows during early lactatation period.Eight Primiparous healthly Holstein cows in early lactatation with similar milk yieldand parturition date were selected in a replicated 4×4 Latin square design, and wereassigned randomly into 4 groups each with 2 replicates. The cows in control group werefed the basic diet and that in treatment groups were fed the basic diet plus biotin (20mg/d,30mg/d or 40mg/d, separately). The results showed that: (1)Dry matter intakes (DMI) andfeed efficiencies were not affected by dietary biotin supplement and were similar amongthe treatment groups (P>0.05); (2)The apparent digestibility of crude protein, NDF tendedto be higher with biotin supplement, but no significant difference was found among thetreatment groups (P>0.05); The apparent digestibilities of crude fat and ADF was notinfluenced(P>0.05); (3)The milk yields (biotin supplement at 20mg/d, 30mg/d or 40mg/d,separately) were respectively higher 1.69kg/d(P <0.05), 2.19 kg/d (P <0.05), 1.56 kg/d(P<0.05) than that of the control group, but no significant difference appeared among thetreatment groups(P>0.05); (4)Biotin supplement had no effects on milk fat percentage(P>0.05), but milk fat yield of the treatment groups was significantly increased comparedwith the control group (P<0.05); Biotin supplement tended to increase the milk proteinpercentage and milk protein yield. The milk protein percentage with biotin supplement at20mg/d, 30mg/d or 40mg/d was 2.96%, 2.89% or 2.86%, separately. Especially, biotinsupplement at the level of 30mg/d had the significant effect (P<0.05). The milk proteinyield (biotin, 20mg/d, 30mg/d or 40mg/d )were 0.87kg/d,0.87kg/d or 0.84kg/d, wereseparately higher 0.10kg/d (P<0.05) ,0.1 kg/d (P<0.05) or 0.07kg/d(P>0.05) than that ofthe control group (P<0.05) . Biotin supplement in diet of dairy cow had no effects on thepercentages of lactose and non-fat solid of milk (P>0.05); (5)Biotin supplement tended todecrease the milk somatic cell count (P>0.05). The SCC in treatment groups (biotinsupplemented at 20mg/d, 30mg/d or 40mg/d) were 4.25×10~4/ml, 23.63×10~4/ml or22.50×10~4/ml, seperately decreased about 8.79mg/dL, 11.27 mg/dL or 15.51 mg/dL comparing with control group (26.66×10~4/mL).(6)Dietary biotin supplement significantly increased serum glucose concentration (P<0.05) and decreased serum non-etherified fatty acid (NEFA) concentration (P<0.05), Compared to the control group, the serum glucose concentration were separately increased 5.83% (P<0.05 ) ,11.98% (P<0.05 ) and 16.71%(P<0.01)with dietary biotin supplement at 20mg/d, 30mg/d and 40mg/d. Blood urea nitrogen (BUN) concentration tended to be lower in the treatment groups (P>0.05); The concentrations of serum total protein, albumin and triglyceride were not influenced by dietary biotin supplement(P>0.05); (7)Comparing with the control group without additional biotin supplement, the income of feeding a cow were separately increased 2.85 RMB/d, 3.22RMB/d and 2.91RMB/d with biotin supplement at the dose of 20mg/d, 30mg/d and 40mg/d.In summary, dietary biotin supplement was advantage to Chinese Holstein cows during early lactation period. The supplement of dietary biotin could improve performance and economic profit of feeding. Dietary biotin level in this region might be critical deficient in the diet of lactation cows and the optimal dose of biotin supplement was 30mg/d.
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