Fig. 6

Schematic representation of the study design. The screening and grouping of the experimental goats in 2 steps. (i) 96 primiparous dairy goats randomly selected from 2305 Guanzhong dairy goats based on their similarities in expected parturition date, body condition scores (BCS), and no previous medical history formed the experimental group. The blood samples from each goat were removed at -3, -2, -1, 0 (partum), + 1, +2, and + 3 weeks from delivery. The does were blood sampled within 24 h of their kidding. On the same day of blood sampling, BCS was evaluated, always by the same operator, and the milk yield was recorded for each goat. (ii) Next, in the present study, the criterion for subclinical hyperketonemia (SCHK) and subclinical hypocalcemia (SCHC) in dairy goat were blood BHBA level of 0.8–1.7 mmol/L and Ca level of 1.5–2.2 mmol/L at parturition, respectively. Based on the blood analyses, litter size (1 kid) and the gap between the expected and actual kidding dates (≤ 2 days), 10 goats with high BHBA level and 10 goats with low Ca level at parturition were randomly selected to form the SCHK and SCHC groups, respectively. In addition, 10 goats with 2.2–2.9 mmol/L Ca level and < 0.8 mmol/L BHBA level during the trial period and no signs of other diseases were randomly selected to form the healthy (HEAL) group. Finally, plasma biomarkers of oxidative status and metabolites were enumerated