Production performance, nutrient digestibility, and enteric methane emissions of lactating Holstein cows fed triticale silage of different maturities in different dietary forage inclusions

This study evaluated the production performance, milk fatty acid profile, nutrient digestibility, and enteric methane (CH₄) emissions of high-producing dairy cows fed high-forage (HF; 52% forage) or low-forage (LF; 37% forage) diets containing triticale silages harvested at either the boot (BT) or soft-dough (SFT) stage. The BT stage silage contained 16.7% CP, 51.1% NDF, 35.0% ADF, 3.7% ADL, and 2.2% starch, whereas the SFT stage silage contained 8.7% CP, 62.6% NDF, 46.1% ADF, 6.4% ADL, and 4.6% starch. The experiment followed a replicated 4 × 4 Latin square design with 21-d periods using 8 primiparous and 16 multiparous Holstein cows. Treatments followed a 2 × 2 factorial arrangement of forage inclusion level and triticale maturity stage. Forage maturity did not affect DMI in cows fed LF diets, but cows fed the HFBT diet consumed more DM than those fed the HFSFT diet (26.3 vs. 23.4 kg/d). Cows fed BT stage diets produced more milk than those on SFT stage diets (46.9 vs. 43.4 kg/d), whereas cows on LF diets produced more milk than those on HF diets (47.1 vs. 43.2 kg/d). The production of ECM did not differ between maturity stages but was greater for cows consuming LF diets compared with HF diets (49.1 vs. 45.6 kg/d). Cows consuming BT stage diets exhibited greater apparent total-tract digestibility of DM (69.3% vs. 67.3%) and NDF (59.4% vs. 54.5%) than SFT stage diets. Cows consuming HF diets exhibited greater digestibilities of DM (70.2% vs. 66.4%), NDF (60.3% vs. 55.8%), and starch (95.5% vs. 94.8%) than LF diets. Cows fed BT stage diets produced 23 g/d less CH₄ than cows on SFT stage diets (368 vs. 391 g/d), with no difference between HF and LF diets in absolute CH₄ output. However, CH₄ yield was lower in cows consuming BT stage diets compared with SFT stage diets on a DMI basis (13.6 vs. 15.2 g/kg DMI). Cows consuming LF diets exhibited reduced CH₄ yields compared with HF diets (13.2 vs. 15.6 g/kg DMI). In conclusion, dairy production appears relatively resilient to differences in triticale silage maturity. However, harvesting at the boot stage offers a methane mitigation strategy by reducing CH₄ yield. Low-forage diets improved milk yield and reduced CH₄ emissions at the expense of nutrient digestibility.