Reducing enteric methane emissions from dairy cattle: Two ways to supplement 3-nitrooxypropanol

The aim of this work was to determine the effect of 3-nitrooxypropanol (3-NOP) on the enteric methane (CH₄) emissions and performance of lactating dairy cows when mixed in with roughage or incorporated into a concentrate pellet. After 2 pretreatment weeks without 3-NOP supplementation, 30 Holstein Friesian cows were divided into 3 homogeneous treatment groups: no additive, 3-NOP mixed in with the basal diet (roughage; NOP_bas), and 3-NOP incorporated into a concentrate pellet (NOP_conc). The pretreatment period was followed by a 10-wk treatment period in which the NOP_bas and NOP_conc cows were fed 1.6 g of 3-NOP/cow per day. After the treatment period, a 2-wk washout period followed without 3-NOP supplementation. The CH₄ emissions were measured using a GreenFeed unit (C-Lock Inc., Rapid City, SD) installed in a freestall with cubicles during the entire experimental period. On average for the total treatment period and compared with the no-additive group, CH₄ production (g/d) was 28 and 23% lower for NOP_bas and NOP_conc, respectively. Methane yield (g/kg of dry matter intake) and methane intensity (g/kg of milk) were 23 and 24% lower for NOP_bas, respectively, and 21 and 22% lower for NOP_conc, respectively. No differences were found between NOP_bas and NOP_conc. Moreover, supplying 3-NOP did not affect total dry matter intake, milk production, or milk composition. The results of this experiment show that 3-NOP can reduce enteric CH₄ emissions of dairy cattle when incorporated into a concentrate pellet and that this reduction is not different from the effect of mixing in 3-NOP with the basal diet (roughage). This broadens the possibilities for using 3-NOP in the dairy sector worldwide, as it is not always feasible to provide an additive mixed in with the basal diet.