Abstract #84

# 84
Milk yield and CH4 emission in Jersey cows grazing forage canola.
L. H. P. Silva*1, Y. Zang1, M. Ghelickhan1, Y. C. Geng2, E. M. Meyer1, A. F. Brito1, 1University of New Hampshire, Durham, NH, 2Chinese Academy of Agricultural Sciences, Beijing, China.

Forage canola is an annual crop that can be used to extend the fall grazing season. Along with high mass yield, canola also has high DM digestibility and recent in vitro research showed decreased in CH4 production. We aimed to evaluate the effect of canola as a grazing resource on milk yield and enteric CH4 emissions in dairy cows. Twelve multiparous and 6 primiparous mid-lactating organic-certified Jersey cows were blocked by parity and, within block, assigned to 1 of 2 treatments (control = CTRL or canola = CAN) in a randomized complete block design. Cows in the CTRL group were fed indoors and had no access to pasture, while CAN cows stayed in the barn during the day and grazed at night (from 1800 to 0500 h). The experiment last 6 wk with sample collection done during wk 3 and 5 and wk 0 used as covariate. Diets were formulated to yield a 60:40 forage-to-concentrate ratio with half of the baleage replaced by canola in cows assigned to CAN. Data were analyzed using SAS with repeated measures over time. Daily herbage allowance was set at 7.5 kg of DM/cow. Canola averaged 4,000 kg of DM/ha, 24.8% CP, and 15.5% NDF. Cows in the CTRL group consumed 21 kg/d of DMI. Estimated herbage DMI (pre- minus post-grazing mass) averaged 3.2 kg/d and mean baleage plus concentrate DMI was 15.5 kg/d in CAN cows. Milk yield was lower in CAN than CTRL diet (20.8 vs 22.3 kg/d; P < 0.01) due to decreased DMI and increased energy expenditure for grazing. However, yields of FCM and ECM and concentration and yield of milk fat did not differ between treatments. While milk protein concentration increased in CAN cows (P < 0.001), milk protein yield did not change. Cows grazing canola had elevated MUN compared with those in the CTRL diet (13.5 vs. 11.1 mg/dL; P < 0.001) possibly because of greater concentration of soluble protein in canola (mean = 55%) vs. baleage (mean = 38.3%). Enteric CH4 production (415 vs. 469 g/d; P < 0.01) and intensity (15.0 vs 16.4 g/kg of ECM) were lower in cows fed CAN vs. the CTRL diet, which may be associated with decreased DMI and presence of glucosinolates in canola. Overall, forage canola has potential to be used for grazing during the fall season.

Key Words: CH4 emission, brassica, grazing