Effects of replacing natural pasture hay with Napier grass on lactation performance and estimated methane emissions in dairy cows

This experiment was conducted to evaluate the effects of replacing natural pasture hay (NPH) with Napier grass hay (NGH) on feed intake, milk yield and composition, feed efficiency, and estimated enteric methane (CH₄) emission intensity of lactating crossbred dairy cows supplemented with a concentrate mixture. Five cows were assigned to treatments in a 5 × 5 Latin square design. The treatments were 100% NPH, 75% NPH + 25% NGH, 50% NPH + 50% NGH, 25% NPH + 75% NGH, and 100% NGH, with concentrate supplementation at 0.5 kg dry matter (DM) per liter of milk. Increasing the level of NGH in the diet increased dietary crude protein (CP) content and improved dry matter (DM) and nutrient intakes (P < 0.001). Milk yield increased significantly (P < 0.001) from 11.4 to 16.1 L/day between cows fed 100% NPH and 100% NGH, respectively, accompanied by higher milk protein yield and improved feed efficiency. Estimated enteric CH₄ emission and intensity decreased (P < 0.001) from 26.9 to 20.6 g/kg milk yield with increasing NGH inclusion. These results demonstrate that replacing NPH with NGH enhances lactation performance, while reducing estimated enteric CH₄ emission intensity, providing a practical climate-smart feeding strategy for smallholder dairy systems in Ethiopia.