Figure 1. Effect of daily biotin supplementation (0, 10, or 20 mg/day) on milk production.
Results and Discussion
Supplementing Holstein cows in early lactation with biotin (10 and 20 mg/day) linearly increased milk yield but did not affect DMI (Table 2). Percent fat and protein and fat yield were not different across treatments, but protein yield increased linearly with biotin supplementation. The milk yield response to biotin was immediate and was sustained throughout the experiment (Figure 1).
Figure 1. Effect of daily biotin supplementation (0, 10, or 20
mg/day) on milk production.
Possible reasons for the increase in milk production with biotin supplementation include improvements in DMI, hoof horn quality, energy balance, glucose production or utilization, or cellulose digestion. When cows eat more they will be likely to produce more milk. In this study, DMI was not different across treatments (20 kg/day) and therefore was not responsible for the increase in milk production. A link between biotin supplementation and improved hoof health has previously been shown (Midla et al., 1998; Bergsten et al., 1999). Hoof quality was not measured in this study, but improved hoof health is unlikely to be the cause of increased milk production with biotin supplementation. Information pertaining to hoof horn development (Peterse, 1985) would support that the increase in milk production immediately at the start of lactation likely did not occur due to improved hoof health. Body fat mobilization could have been responsible for increasing milk production. Body weight, BCS, and plasma NEFA concentrations (data not shown) followed a pattern that suggests that body fat mobilization was not responsible for increasing milk production. Body weight, BCS, and plasma NEFA concentrations were not significantly different across treatments. Biotin is known to be involved with the metabolism and production of glucose. Biotin supplementation could have stimulated glucose production and ultimately increased milk production. However, plasma glucose concentrations were not significantly altered by biotin supplementation. Plasma glucose concentrations averaged 66.2, 67.4, and 65.4 ng/ml for 0, 10, and 20 mg/day of supplemental biotin, respectively, during the first 100 DIM. The amount of glucose available to the mammary gland for milk synthesis was not determined and could have possibly been altered with biotin supplementation. In future studies, the amount of glucose used by the mammary gland for milk synthesis should be determined to better understand the relationship between biotin supplementation and glucose production and utilization. In vitro cellulose digestion has increased when biotin was included in the media. The effect of biotin supplementation on cellulose digestion was not determined in the current study.
| Supplemental Biotin | |||
| 0 mg/day | 10 mg/day | 20 mg/day | |
| Dry matter intake, kg/day | 19.4 | 19.8 | 19.9 |
| Milk a, kg/day | 36.9 | 37.8 | 39.7 |
| Energy-corrected milk, kg/day | 37.0 | 36.8 | 38.6 |
| Milk fat, % | 3.63 | 3.50 | 3.45 |
| Milk fat, kg/day | 1.31 | 1.26 | 1.32 |
| Milk protein, % | 3.03 | 3.05 | 3.01 |
| Milk proteina, kg/day | 1.11 | 1.13 | 1.18 |
| Body weight, kg | 581 | 591 | 590 |
| Body condition score (1=thin, 5=fat) | 3.3 | 3.3 | 3.3 |
| aLinear effect (P < 0.05) of biotin. | |||
Supplemental biotin linearly increased (P < 0.01) plasma biotin concentrations at all time points (Figure 2). Supplemental biotin (10 and 20 mg/day) substantially increased plasma biotin concentrations at calving when compared to the control. At the calving time point, plasma biotin concentrations were 0.65, 2.30, and 4.53 ng/ml for cows supplemented with 0, 10, and 20 mg/day of supplemental biotin, respectively. Increased plasma biotin concentrations at parturition for cows supplemented with biotin is an indication that biotin metabolism is altered at parturition when biotin supplementation occurs. During lactation (excluding the calving time point), plasma biotin concentrations averaged 0.67, 0.83, 1.22 ng/ml for cows supplemented with 0, 10, and 20 mg/day of supplemental biotin, respectively.
Figure 2. Effect of daily biotin
supplementation (0, 10, or 20 mg/day) on plasma biotin concentrations.
Colostrum and milk biotin concentrations followed a similar pattern to plasma biotin concentrations with biotin supplementation. Biotin concentrations in colostrum were 15.2, 109.6, and 305.6 ng/ml (linear effect, P < 0.01) for the control, 10, and 20 mg/day of supplemental biotin. Milk biotin concentrations averaged over time were 22.6, 31.3, and 69.8 ng/ml for the control, 10, and 20 mg/day treatments, respectively (quadratic effect, P < 0.01). The mode of transport of biotin into the mammary gland is not known. Active transport of biotin into the mammary gland is likely because of the large plasma: milk biotin concentration gradient.