Amino acid balancing and microalgal proteins (Spirulina) improve production performance and milk quality in dairy cows under low-protein diets.

Microalgal protein (MP, Spirulina) is a highly promising novel sustainable protein resource, yet the mechanisms by which it regulates the production performance and milk quality of lactating dairy cows remain unclear. This study elucidates the regulatory mechanisms by which amino acid balancing and MP supplementation modulate production performance and milk quality in mid-lactation dairy cows fed low-protein diet (LPD). Results demonstrated that dietary interventions significantly altered milk composition. To elucidate the underlying molecular mechanisms, proteomic and metabolomic analyses were employed, leading to the identification of 1186 differentially expressed proteins (DEPs) and 1167 differentially expressed metabolites (DEMs). Key signaling molecules, such as GNB1, GNG5, GNG10, and GRB2, interacted with metabolic hubs like α-ketoglutaric acid/Glutamic acid within a regulatory network, enhancing amino acid sensing and signal transduction. The observed coordinated changes in key signaling molecules and metabolic hubs suggest that amino acid sensing and signal transduction pathways may be activated, potentially promoting energy metabolism and nitrogen conversion efficiency. The identified key molecular markers of milk quality lay a scientific basis for the production of high-quality dairy raw materials and the development of value-added dairy products.