Abstract #W163

# W163
Dose-response effect of the macroalga Asparagopsis taxiformis on enteric methane emission in lactating dairy cows.
H. Stefenoni*1, S. Räisänen1, A. Melgar1, C. Lage2, M. Young1, A. Hristov1, 1The Pennsylvania State University, University Park, PA, 2Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.

An in vitro and an in vivo study were conducted to determine the antimethanogenic activity of the macroalga Asparagopsis taxiformis (AT) in lactating dairy cows. In vitro, 9 treatments were tested in 24-h incubations with ruminal inoculum collected from 2 lactating Holstein cows. Treatments were: control (no additives), AT at 0.25, 0.5, 0.75, 1.0 and 1.5% of feed dry matter (DM), and bromoform (CHBr3), the active compound in AT, equivalent to CHBr3 found in AT dosed at 0.25, 1.0, and 1.5%. The in vivo study was conducted with 6 multiparous Holstein cows [68 ± 4.2 d in milk, 46 ± 2.5 kg/d milk yield (MY)]. All cows received the same AT inclusion rates of 0, [background (BG) period], 0.25, 0.5, and 0.75% of feed DM. Each phase consisted of 7-d diet adaptation and 3-d sampling, followed by a 7-d washout period. Enteric methane (CH4) emission was measured 8 times over 3 d using the GreenFeed system. The last 4 d of each phase were used for statistical analysis of MY and DM intake (DMI). Data were analyzed using the REG (in vitro) and MIXED (in vivo; the model included treatment) procedures of SAS using contrasts. In the in vitro experiment, AT decreased CH4 yield linearly [P < 0.001; 27.3, 35.4, 29.4, 15.0, 1.42, and 0.26 mL CH4/g feed DM (SEM = 3.68) for control, 0.25, 0.5, 0.75, 1.0, and 1.5% AT, respectively]. CHBr3 had no effect (P ≥ 0.59) on CH4 production. In the in vivo experiment, DMI was decreased by the highest (0.75%) level of AT [P = 0.03; 22.7, 27.6, 25.4, and 17.7 kg/d (SEM = 1.7) for BG, 0.25, 0.5, and 0.75% AT, respectively]. MY was also decreased by 0.75% AT (P = 0.05; 46.2, 47.5, 46.0, and 39.2 kg/d respectively; SEM = 3.4). Daily CH4 emission decreased linearly (P < 0.001) with AT inclusion rate: 392, 367, 84, and 83 g/d, (SEM = 20) respectively. CH4 yield was decreased quadratically (P = 0.02; from 17.5 to 5.7 g/kg DMI; SEM = 1.3) and CH4 intensity was decreased linearly (P < 0.001; from 8.4 to 2.4 g/kg milk; SEM = 3.2) by AT. In the short term in vivo experiment, inclusion of AT at 0.50% of DMI decreased CH4 emission in lactating dairy cows by 80% and had no effect on DMI or MY.

Key Words: methane, Asparagopsis taxiformis, dairy cattle