Diets supplementation with Bacillus subtilis and Macleaya cordata extract improve production performance and the metabolism of energy and nitrogen, while reduce enteric methane emissions in dairy cows

The objective of this experiment was to evaluate the effectiveness of Bacillus subtilis and Macleaya cordata extract on production performance, enteric methane emissions, nutrient digestion and utilization of dairy cows. Sixty healthy lactating Holstein dairy cows averaged (mean ± SD) 145 ± 12.5 of days in milk, 38.3 ± 3.3 kg/d of milk production, and 2.5 ± 0.9 in parity were used in the experiment. Cows were assigned to 1 of 3 treatments: (1) control diet (CON), (2) control diet plus Bacillus subtilis (BS) dosed at 50 g/head/d, (3) control diet plus Macleaya cordata extract (MCE) dosed at 450 mg/head/d. The entire experimental was 75 d in length, using GreenFeed system (C-Lock Inc.) measured enteric methane (CH4) and carbon dioxide (CO2) emissions for individual cows. Six cows from each treatment were randomly selected to measure nutrient digestion and utilization. Compared with CON, BS and MCE diets increased dry matter intake (DMI) by 14 % and 11 %, as well as milk yield (6.9 % and 4.7 %), milk fat yield, milk protein yield, and milk lactose yield (P ≤ 0.05). Furthermore, BS and MCE diets reduced (P ≤ 0.05) CH4 yield (g/kg·DMI) by 10 % and 9 % compared with CON, respectively. Based on fat-corrected milk (FCM) or energy-corrected milk (ECM) yield, CH4 intensity was also reduced (P ≤ 0.05) by 6.8 % and 5.3 % (g/kg·FCM), or 6.8 % and 5.3 % (g/kg·ECM), respectively. BS diet had greater (P ≤ 0.05) neutral detergent fiber (NDF) and acid detergent fiber (ADF) digestibility than CON and MCE diets. Compared with CON, BS and MCE diets both increased (P ≤ 0.05) digestible energy, metabolizable energy, digestible nitrogen (N), and retained N, whereas it reduced (P ≤ 0.05) CH4 energy as a percent of gross energy. Cows offered the BS had greater (P ≤ 0.05) energy and N digestibility, as well as retained N and it as a percent of N intake or digestible N, compared with CON and MCE. Results suggested that implementation of these dietary interventions had potential to improve animal productivity led to a decrease in enteric CH4 yield or intensity.