The colostrum and milk samples were thawed and kept in a water bath at 40 °C for 20 min before analysis of the microchemical composition including fat, protein, lactose and total solids (TS). The 3-folded dilution of colostrum with distilled water was performed before analysis. The approximately 30 mL of samples were sucked into the machine and analysed with infrared spectroscopy (MilkoScan FT2 instrument, Foss Milkoscan, Hillerød, Denmark).

After the sample were thawed, they were pretreated with acid extraction according to the manufacturer’s instructions. The concentrations of IGF-1 in both colostrum and milk were analysed using solid-phase enzyme-labelled chemiluminescent immunometric assay (Immulite 2000 IGF-1, Siemens-Healthcare GmbH, Erlangen, Germany). The concentrations of IgG in both the colostrum and milk samples were determined by a goat specific goat IgG ELISA kit (Cat. no. K3231053P, Koma Biotech Inc., Seoul, Korea).

The Vit A in colostrum was measured using high-performance liquid chromatography (HPLC) with a UV detector as described previously [13]. In brief, after the samples were thawed, the fat was saponified with alcoholic potassium hydroxide solution. The Vit A was extracted from unsaponifiable portions with n-hexane and evaporated under nitrogen. The residue was dissolved in methanol and injected into the reverse phase C18 µ-Bondapak (3.9 × 300 mm) column (Water Corp., Milford, MA, USA). The mobile phase consisted of methanol (RCI Labscan Ltd., Bangkok, Thailand) set at the flow rate of 1 mm/min and Vit A was detected at 340 nm using the HPLC system (HPLC-Shimadzu, Kyoto, Japan). The recovery of the added standard at the level 5–20 ppm was 99.5% and a standard deviation of 3.78.

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