Transcriptional and immunohistochemical signatures of transition dairy cows’ adipose tissue during subclinical ketosis

The objective of this experiment was to determine transcriptional differences in the visceral (VAT) and subcutaneous adipose tissue (SAT) of dairy cows with or without subclinical ketosis. The experiment was conducted from February to March 2022 at a commercial dairy farm located near Friona, TX. Ten multiparous Holstein dairy cows [Days in milk (DIM) 7.6 ± 1.9, parity 3.2 ± 1.4, body condition score (BCS) 3.6 ± 0.3] were enrolled in a nonrandomized trial. Fresh Holstein dairy cows with 5 to 10 DIM were evaluated for BCS and blood BHB. BCS (scale 1 = thin to 5 = obese) was assigned by two experienced individuals, while blood BHB was determined with the Precision Xtra Blood Glucose & Ketone Monitoring System (Abbott Laboratories, Chicago, IL, USA). Cows were then blocked according to parity, BCS, and blood BHB, and assigned into two groups: subclinical ketosis (SCK, n=5, BHB > 1.0 mmol/L) and non-ketotic (NK, n=5, BHB ≤ 1.0 mmol/L). Abdominal SAT and omental VAT samples were obtained through laparotomy (right paralumbar fossa). AT samples were sequenced on an Illumina Novaseq 6000 platform, and 150 bp paired-end reads were generated. Blood was sampled from the coccygeal vein before morning feeding and analyzed for biomarkers related to energy metabolism [i.e., glucose, β-hydroxybutyric acid (BHB), non-esterified fatty acids (NEFA)], muscle mass catabolism [i.e., blood urea nitrogen (BUN)], and liver function (i.e., albumin and cholesterol) by a commercial laboratory.