Postpartum Body Condition Loss and Muscle Proteolysis in Dairy Cows

A recent study published in Scientific Reports examined the relationship between postpartum body condition score (BCS) loss and skeletal muscle proteolysis in high-yielding multiparous Holstein cows. The research focused on cows producing 30 kg or more of milk per day and assessed the expression of genes involved in protein metabolism.

The study grouped 200 cows based on BCS loss between calving and 42 days in milk (DIM), with categories of 0.00, -0.25, -0.50, and -0.75 units. Muscle biopsies were collected on days 21 and 42 postpartum to quantify mRNA abundance of genes in the ubiquitin-proteasome pathway, including UBE2G1, UBE2G2, UBA1, MuRF1, and Atrogin-1. Additionally, mTOR signaling genes such as mTOR, EIF3K, and 4EBP1 were analyzed.

Results indicated that cows experiencing a BCS loss of -0.50 or -0.75 units had significantly higher expression of the ubiquitin-proteasome pathway genes and lower expression of 4EBP1 compared to cows with no or mild BCS loss (P < 0.05). The expression of mTOR and EIF3K remained unaffected across the groups.

Furthermore, cows with greater BCS loss (0.50 and 0.75 units) exhibited significantly higher plasma concentrations of creatinine and 3-methylhistidine, which correlated with the extent of BCS loss. The highest concentrations were observed in the group with a 0.75-unit loss.

These findings highlight the association between moderate to severe BCS loss and the activation of proteolytic pathways, as well as the suppression of key protein synthesis regulators in skeletal muscle. The study underscores the importance of maintaining optimal BCS during the transition period to preserve muscle integrity and metabolic health in dairy cows.