Effect of Bovaer inclusion in diets with a high proportion of grass-clover silage of different nutritional quality on gas emissions and production performance in dairy cows

This experiment examined how supplementation of Bovaer in dietary rations with a high proportion of grass-clover silage affected DMI, milk production, and gas emissions in lactating dairy cows, and whether the effect was uniform across parity and stage of lactation. Forty-eight Holstein cows (equally balanced between primiparous and multiparous cows, and between early and mid-late lactation) were included in a balanced 4 × 4 Latin square design, with a 2 × 2 factorial arrangement of dietary treatments. The first factor was 2 different sources of grass-clover silage, a spring growth or a first regrowth, which differed in nutritional quality. The second factor was 2 levels of Bovaer supplementation (0 or 60 mg 3-nitrooxypropanol/kg of DM). The DMI was not affected by the source of grass-clover silage but was reduced by 1.1 kg/d (5% reduction) with Bovaer supplementation. Energy-corrected milk yield decreased by 0.8 kg/d (2.2% reduction), and there was a tendency for this reduction to be larger in early lactation than in mid-late lactation (-1.1 vs. -0.3 kg/d). Independent of the source of grass-clover silage, Bovaer supplementation reduced CH₄ production (g/d), yield (g/kg of DMI), and intensity (g/kg of ECM) by 33.0%, 28.1%, and 31.3%, respectively. In conclusion, Bovaer was effective in reducing CH₄ production but with negative associated effects on DMI and ECM yield. The experiment indicated that the reduction in milk production due to Bovaer supplementation may be larger for cows in early lactation than for cows in mid-late lactation.