Materials and Methods
Forty-four Holstein cows were used in this experiment. This experiment began 14 days prior to expected calving date and continued until 100 DIM. Cows were placed into 15 blocks according to parity, expected calving date, and previous lactation milk yield (multiparous cows) and assigned to one of three treatments randomly within a block. Treatments consisted of a control (n = 15), 10 mg of biotin (n = 14), and 20 mg of biotin (n = 15) supplemented daily. Prior to calving, multiparous and primiparous cows were housed in the same free stall pen. Biotin was dosed orally once daily via gelatin capsules prior to calving. Cows were housed in tie stalls following parturition and received biotin in a concentrate mix. The dry cow ration consisted primarily of grass silage and grass hay (Table 1). The lactating cow ration had a forage to concentrate ratio of 50:50 (Table 1). Cows were milked twice daily and fed once daily. Milk production and dry matter intake were measured daily. Body weights (BW) and body condition scores (BCS) were taken at 14 days prepartum, calving, and 30, 60, and 100 DIM. Weekly milk samples were taken during milking for determination of milk fat and protein percentages using near infrared absorbance spectrophotometry (DHI Cooperative, Inc., Powell, OH).
| Dry cows | Lactating cows | |
| Ingredient | ||
| Grass silage | 50.8 | . . . |
| Grass hay | 30.1 | . . . |
| Alfalfa silage | . . . | 23.7 |
| Alfalfa hay | . . . | 3.6 |
| Corn silage | . . . | 22.4 |
| Corn grain, ground | 16.2 | 28.9 |
| Soybean meal, 44% CP | . . . | 9.9 |
| Roasted soybeans | . . . | 6.0 |
| Fish meal | . . . | 0.6 |
| Fat (animal/veg blend) | 0.6 | |
| Sodium bicarbonate | . . . | 0.7 |
| Vitamins and minerals | 2.9 | 3.6 |
| Nutrients | ||
| Crude protein | 12.6 | 17.2 |
| Neutral detergent fiber | 57.4 | 32.1 |
| 1During the dry period biotin was supplemented via gelatin capsules. During lactation a biotin premix replaced a small portion of the soybean meal. | ||
Blood was sampled at 14 days prepartum, day of calving, and 30, 60, and 100 DIM via the coccygeal vein. Blood samples were processed to obtain plasma and analyzed for biotin, glucose, and non-esterified fatty acids (NEFA). Samples of first milking colostrum and milk samples were taken at 30, 60, and 100 DIM for biotin analysis. Blood and milk biotin concentrations were determined using RIDASCREEN Biotin kit (Art. No: R 2201, R-Biopharm GMBH, Germany). Glucose and NEFA concentrations were determined using commercial kits (glucose: Glucose Trinder Reagent, Sigma Diagnostics; NEFA; Wako NEFA C kit, Wako Chemicals Inc., Richmond, VA).