Microbiome-Metabolomics Insights into the Milk of Lactating Dairy Cows to Reveal the Health-Promoting Effects of Dietary Citrus Peel Extracts on the Mammary Metabolism

Abstract

The effects of dietary supplementation with citrus peel extract (CPE) on milk biochemical parameters, milk bacterial community, and milk metabolites were evaluated. Eight lactating cows were allocated to a replicated 4 × 4 Latin square. Experimental treatments included the control diet (CON), and CON supplemented with CPE at 50 g/d (CPE50), 100 g/d (CPE100), and 150 g/d (CPE150). Supplementing with CPE linearly decreased milk interleukin-6 and malondialdehyde concentrations and linearly increased lysozyme activity and 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity. Compared with CON, the milk of CPE150 cows had fewer abundances of several opportunistic pathogens and psychrotrophic bacteria, such as Escherichia-Shigella, Sphingobacterium, Alcaligenes, Stenotrophomonas, and Ochrobactrum. Supplementing with CPE significantly altered the metabolic profiling in the milk. The metabolites of flavonoids were enriched in the milk of cows fed CPE150, while some proinflammation compounds were decreased compared with CON. Correlation analysis showed that the change in the bacterial community might partly contribute to the alteration in the expression of milk cytokines. In conclusion, CPE exerts health-promoting effects (e.g., antioxidant, anti-microbial, and anti-inflammatory) in the mammary metabolism of cows due to its flavonoid compounds, which also provide additional value in terms of milk quality improvement.

Dietary Supplementation with Naringin Improves Systemic Metabolic Status and Alleviates Oxidative Stress in Transition Cows via Modulating Adipose Tissue Function: A Lipid Perspective

“…As one of the primary constituents of citrus flavonoids, naringin has garnered widespread attention in recent years. Studies have revealed the health-promoting effect of naringin-rich citrus peel extract (naringin > 19%) as a feed supplement in mid-lactation cows [ 13 , 14 , 15 , 16 ]. In particular, citrus peel extract supplementation improved ruminal fermentation [ 16 ], improved milk yield and milk lactose content, decreased milk somatic cell count (SCC), and improved milk lipid composition and antioxidant capacity in cows [ 13 , 14 ].…”

“…Studies have revealed the health-promoting effect of naringin-rich citrus peel extract (naringin > 19%) as a feed supplement in mid-lactation cows [ 13 , 14 , 15 , 16 ]. In particular, citrus peel extract supplementation improved ruminal fermentation [ 16 ], improved milk yield and milk lactose content, decreased milk somatic cell count (SCC), and improved milk lipid composition and antioxidant capacity in cows [ 13 , 14 ]. In a study by Zhao et al [ 15 ], cows fed a high-starch diet with 100 g/d of citrus peel extract rich in naringin showed an improved hindgut microbiome and host metabolic homeostasis through regulating sphingolipid metabolism.…”