Integrated multiomics reveals that replacing corn silage with triticale silage improves milk quality via rumen microbiome-metabolome crosstalk in dairy cows

The objective of this study was to evaluate the effects of replacing corn silage with triticale ( × Triticosecale Wittmack) silage on lactation performance, milk fatty acid profile, and rumen microbiome-metabolome interactions in dairy cows.In this study, 27 mid-lactation dairy cows were used in replicated 3 × 3 Latin squares with 3 28-d periods and 3 treatments, in which 0, 25, or 50% of the corn silage (DM basis) was replaced with triticale silage.Replacing 25% of corn silage maintained DMI and milk yield, whereas 50% replacement reduced both variables.Diets containing triticale silage lowered SCC and increased the proportion of oleic acid in milk fat.The 50% replacement further increased the proportions of linoleic acid (LA), α-linolenic acid (ALA), and milk protein concentration.In the rumen, the 50% replacement increased pH and NH 3 -N concentration, and triticale diets increased the proportions of ALA and several C18:1 and C18:2 biohydrogenation intermediates, resulting in a greater UFA proportion and a lower SFA: UFA ratio in rumen fluid.Metataxonomic analysis revealed higher relative abundances of Butyrivibrio_A, Ruminococcus_E, and Prevotella in triticale diets, whereas metabolomic profiling indicated enrichment of pathways related to LA, ALA, and amino acid metabolism.Correlation analysis associated Butyrivibrio_A and Ruminococcus_E with LA oxidation products and amino acid derivatives, indicating the involvement of rumen microbiome-metabolome interactions in shaping the milk UFA responses.Overall, partial replacement of corn silage with triticale silage improved the milk fatty acid profile and udder health indicators without compromising performance at 25% inclusion, indicating that winter triticale is a promising component of forage systems.