Effects of sustained reduction of enteric methane emissions with dietary supplementation of 3-nitrooxypropanol on growth performance of growing and finishing beef cattle.

The study objective was to evaluate the effects of sustained reduction of enteric methane (CH) emissions with dietary supplementation of the inhibitor 3-nitrooxypropanol (NOP) on growth rate and feed conversion efficiency of growing and finishing beef cattle. Eighty-four crossbred steers were used in a 238-d feeding study and fed a backgrounding diet for the first 105 d (backgrounding phase) and transition diets for 28 d followed by a finishing diet for 105 d (finishing phase) with 3 doses of NOP (0, 100, and 200 mg/kg DM). The experiment was a completely randomized design using 21 pens (4 cattle/pen) with 7 pens per treatment. When cattle were fed the backgrounding diet, pen DMI was reduced ( < 0.01) whereas G:F tended to improve ( = 0.06) with increasing dose of NOP supplementation. During the finishing phase, DMI ( = 0.06) and ADG ( = 0.07) tended to decrease with increasing dose of NOP supplementation. Although both levels of NOP were effective in reducing CH emissions from the backgrounding diet ( < 0.01), only NOP supplemented at the highest dose was effective in reducing total CH emissions from the finishing diet ( < 0.01). Methane yield (g/kg DMI) was reduced whereas hydrogen emissions were increased at the highest dose of NOP supplementation with both backgrounding and finishing diets ( < 0.01). Overall, these results demonstrate efficacy of NOP in reducing enteric CH emissions from cattle fed backgrounding and finishing diets, and these effects were negated once NOP supplementation was discontinued.