Influence of the concentrate inclusion level in a grass silage-based diet on hepatic transcriptomic profiles in Holstein-Friesian dairy cows in early lactation

Excessive negative energy balance in early lactation is linked to an increased disease risk but may be mitigated by appropriate nutrition. The liver plays central roles in both metabolism and immunity. Hepatic transcriptomic profiles were compared between 3 dietary groups in each of 40 multiparous and 18 primiparous Holstein-Friesian cows offered isonitrogenous grass silage-based diets with different proportions of 50% concentrate + 50% grass silage), or (3) high cond in milk for RNA sequencing, and blood metabolites were measured. The sequencing data were analyzed separately for primiparous and multiparous cows using CLC Genomics Workbench V21 (Qiagen Digital Insights), focusing on comparisons between HC , LC groups. More differentially expressed genes (DEG) were seen between the primiparous cows receiving HC ver-sus LC diets than for multiparous cows (597 vs. 497), with only 73 in common, indicating differential dietary responses. Multiparous cows receiving the HC diet had significantly higher circulating glucose and insulin-like growth factor-1 and lower urea than those receiving the LC diet. In response to HC, only the multiparous cows produced more milk. In these animals, bioinfor-matic analysis indicated expression changes in genes regulating fatty acid metabolism and biosynthesis (e.g., ACACA, ELOVL6, FADS2), increased cholesterol biosynthesis (e.g., CYP7A1, FDPS, HMGCR), down -regulation in hepatic AA synthesis (e.g., GPT, GCLC, PSPH, SHMT2) , decreased expression of acute phase proteins (e.g., HP, LBP, SAA2). The primiparous cows on the HC diet also downregulated genes control-ling AA metabolism and synthesis (e.g., CTH, GCLC, GOT1, ODC1, SHMT2) but showed higher expression of genes indicative of inflammation (e.g., CCDC80, IL1B, S100A8) and fibrosis (e.g., LOX, LUM, PLOD2). This potentially adverse response to a HC diet in physi-cally immature animals warrants further investigation.

Automated summary

Excessive negative energy balance in early lactation is associated with increased disease risk, but nutrition can help mitigate this. The liver plays important roles in metabolism and immunity. This study compared the liver transcriptomic profiles of Holstein-Friesian cows on different diets and found different responses between primiparous and multiparous cows. Multiparous cows on a high concentrate diet had higher glucose and insulin-like growth factor-1 levels and lower urea. They also produced more milk and showed changes in gene expression related to fatty acid metabolism, cholesterol biosynthesis, and acute phase proteins. Primiparous cows on the same diet had similar gene expression changes but also showed increased expression of genes indicative of inflammation and fibrosis.