Sample collecting and analysis

The vein blood and umbilical cord blood samples were collected with normal vacuum blood collection tubes from jugular vein and umbilical cord before slaughter, respectively. All blood samples were allowed to stand for 2 h, centrifuged at 3,000 g/min for 15 min at 4 °C, and separated into 1.5 ml centrifugation tubes, stored at −80 °C refrigerator until further analysis. After slaughtered, the left femur and left humerus of the young and maternal goats were collected entirely and peeled off the associated soft tissue completely. The bone samples were washed with normal saline, dried with filter paper, and recorded the bone weights. The length and diameter of the middle spine of bone were measured with a Vernier Caliper and recorded all the parameters.

We used ELISA kits to determine the dynamic profiles of some skeleton ossification-associated parameters in the serum, like parathyroid hormone (PTH), bone alkaline phosphatase (BALP), osteocalcin (also known as bone gamma-carboxyglutamic acid containing protein, BGLAP), tartrate-resistant phosphatase (TRAP), type I collagen amino terminal peptide (INTP), and type I collagen carboxy terminal peptide (CTX-I) with the specific ELISA kits. Among, the PTH kit (catalog: CSB-E13082G; lot: C0351620332), BALP kit (catalog: CSB-E13080G; lot: G13035060), BGLAP kit (catalog: CSB-EL002682GO; lot: F30035061) were purchased from CUSABIO Biotech. Co., Ltd. The TRAP kit (catalog: MBS014917; lot: #0812015), INTP kit (catalog: MBS028250; lot: #0812015), and CTX-I kit (catalog: MBS267426; lot: #36271309) were made in USA, and purchased from Well Biological Science Co., Ltd.