The Effects of Grass Silage Additive Type and Barley Grain Preservation Method on Rumen Function, Microbial Ecology, and Energy Metabolism of Dairy Cows

The effects of grass silage and barley grain preservation methods on dairy cows were evaluated using four Nordic Red dairy cows placed in respiration chambers in a 4 x 4 Latin square. Silage was conserved using a formic acid-based product (AS) or a homofermentative lactic acid bacteria inoculant (IS), while grains were dried (DB) or crimped and ensiled (EB). Fermentation profile of silages and the chemical composition of the mixed diets were very similar. The dietary treatments did not affect feed intake, milk production, and rumen fermentation except molar proportion of butyrate, and energy metabolism. Digestibility of dry matter and organic matter were higher (p < 0.05) and that of crude protein was lower (p < 0.05) for AS than IS. Feeding EB compared to DB decreased (p < 0.05) diet organic matter and starch digestibility. The cows receiving AS tended (p = 0.06) to emit more methane per day than those receiving IS, but methane yield and intensity were not different between dietary treatments. Bacteria alpha diversity was higher (p < 0.01) in barley samples than grass silages and was not affected by the diet in rumen samples. All freshly prepared rations were dominated by Lactobacillaceae, Erwiniaceae, and Pseudomonadaceae but rations based on AS than IS remained more stable over 2 days. In conclusion, grass silage and barley grain preservation methods did not affect the measured parameters in dairy cows and the preservation method can be selected based on practical on-farm factors.