Multi-omics analysis of soy isoflavone-induced responses in rumen fermentation, endocrine status and milk production in cows with varying milk yields
摘要
Improving milk yield and feed efficiency is pivotal for climate-smart dairy systems, as rumen mediated fermentation governs energy and nitrogen utilization and thereby greenhouse-gas emission intensity. Soybean isoflavones (SIF) may modulate rumen fermentation, yet their effects on rumen function, microbiome features, host endocrine/metabolic responses, and lactation performance-particularly across cows with divergent milk-yield phenotypes-remain unclear.
ResultsFifty‑six lactating Holstein cows (28 high‑yield cows, HY; 28 low‑yield cows, LY) were divided into two categories by milk yield. Within each yield category, cows were randomly assigned to one of two dietary treatments: a basal diet (Control) or the basal diet supplemented with SIF at 0.01% of dry matter. This yielded a 2 × 2 factorial design with four experimental groups (n = 14 per group): high‑yield control (HCON), high‑yield SIF (HSIF), low‑yield control (LCON), and low‑yield SIF (LSIF). SIF increased milk yield by 8.75% and improved fat-corrected milk (+ 7.20%), dry matter intake (+ 3.20%), and feed efficiency (+ 3.26%), with larger gains in HY cows (milk yield + 8.89%; feed efficiency + 4.55%). Rumen fermentation shifted toward a more energetically favorable profile, with lower acetate (– 2.70%), higher propionate (+ 4.55%), and a reduced acetate-to-propionate ratio (– 7.02%), accompanied by increased microbial crude protein (+ 21.53%) without changes in pH or NH3-N. SIF altered endocrine status irrespective of phenotype, increasing estradiol and progesterone while decreasing prolactin and growth hormone, and reduced blood ALP, lactate, and triglycerides. Metagenomics indicated phenotype-dependent microbial and functional responses to SIF: HY cows showed enrichment of taxa (e.g., Caudoviricetes sp., Eubacterium sp., and Butyrivibrio sp.) associated with amino-acid, cofactor metabolism and propionate pathways, whereas LY cows exhibited enrichment of Prevotella sp. and Bacteroides sp. with functions favoring carbohydrate degradation. The HCON group exhibited greater abundances of Prevotella sp. and Hallella spp. with enhanced carbohydrate degradation functions, whereas the LCON group was enriched in Ruminococcus sp. and Methanobrevibacter sp., associated with methane metabolism.
ConclusionsIn conclusion, this study highlights the potential of SIF supplementation to improve lactation efficiency, modulate rumen microecology and endocrine function in dairy cows. These findings establish a theoretical framework for achieving efficient and precise feeding management on large-scale dairy farms.