Replacing up to 50% of Corn Silage with Triticale Silage Alters the Fecal Microbiome but Not Milk Yield or Composition in Mid-Lactation Holstein Cows

Diversifying forage sources may improve the sustainability and flexibility of dairy production. In a 60 d feeding trial, 72 mid-lactation Holstein cows were assigned to three treatments (24 cows/group) and fed a total mixed ration in which corn silage represented 41.16% of dietary dry matter in the control diet; 25% or 50% of this corn silage fraction was replaced with triticale silage (TS) on a dry matter basis. The study evaluated whether partial TS substitution could maintain lactational performance while affecting fecal fermentation and microbiota. Replacing corn silage with TS did not affect milk yield, 4% fat-corrected milk, major milk components, or metabolic indicators. However, 50% replacement increased fecal bacterial richness and diversity, as reflected by ACE, Chao1, and Shannon indices, and altered the overall microbial community structure. This treatment also changed fecal volatile fatty acid profiles, including increasing the proportions of branched-chain volatile fatty acids. Overall, TS can replace up to 50% of the corn silage fraction in the ration of mid-lactation cows without compromising milk production or composition, while modifying hindgut microbial ecology and fermentation patterns, thereby offering greater ration flexibility when corn silage availability is limited or costly.