Effect of Bovaer inclusion in rations with high proportion of corn silage harvested with different stubble height on production performance and gas emission in dairy cows

This experiment examined how Bovaer (active compound: 3-nitrooxypropanol (3-NOP)) supplementation in feed rations with high proportion of corn silages harvested with different stubble height affected gas emission, dry matter intake (DMI), and milk production in lactating dairy cows. It was also investigated whether the effect of Bovaer supplementation was uniform across cows of different parity and lactation stage. Forty-eight Holstein cows were included in a balanced 4 × 4 Latin square design, with a 2 × 2 factorial arrangement of dietary treatments. The first factor was corn silage harvested with two different stubble heights, low (25 cm) or high (65 cm), respectively, aiming for variation in nutritional quality of the corn silages. The second factor was two levels of Bovaer supplementation (0 or 60 mg 3-NOP/kg of dry matter (DM)). Minor than expected differences were obtained in corn silage nutritional quality (organic matter digestibility and starch-to-fiber ratio) due to difference in stubble height. The DMI and energy corrected milk (ECM) yield were not affected by the stubble height of corn silage, but DMI was reduced by 3.2 kg/d (a 13.2 % reduction) and ECM yield by 1.2 kg/d (a 3.4 % reduction) with Bovaer supplementation. Independent of corn silage stubble height, Bovaer supplementation reduced methane (CH 4 ) production (g/d), yield (g/kg of DMI), and intensity (g/kg of ECM) with 34.6 %, 22.9 %, and 33.0 %, respectively. In conclusion, Bovaer supplementation was effective in reducing CH 4 emission, but negatively affected DMI and ECM yield. Overall, the effect of Bovaer seemed to be uniform across cows of different parity and lactation stage. • Bovaer reduced methane emission in dairy cows fed a diet rich in corn silage. • Feed intake was reduced by 13.3 %, a larger reduction than previously reported. • Energy corrected milk yield was reduced by 3.4 %. • The effect of Bovaer was consistent across parity groups and lactation stages.