Combined effects of 3-nitrooxypropanol and canola oil supplementation on methane emissions, rumen fermentation and biohydrogenation, and total tract digestibility in beef cattle

Citation

Zhang, X.M., Smith, M.L., Gruninger, R.J., Kung, L., Vyas, D., McGinn, S.M., Kindermann, M., Wang, M., Tan, Z.L., Beauchemin, K.A. (2021). Combined effects of 3-nitrooxypropanol and canola oil supplementation on methane emissions, rumen fermentation and biohydrogenation, and total tract digestibility in beef cattle, 99(4), http://dx.doi.org/10.1093/jas/skab081

Plain language summary

Enteric methane emissions account for 3.2% of total greenhouse gases in Canada, and therefore we are studying ways to reduce methane production. In this study, the individual and combined effects of two enteric methane mitigation strategies were investigated in beef cattle fed a high forage diet. The strategies were: the inhibitor 3-nitrooxypropanol (3-NOP) and canola oil (OIL) supplementation. We found no major interactions between the two feed supplements, and thus we concluded that their methane mitigating effects were incremental. Therefore, supplementing ruminant diets with a combination of 3-NOP and OIL may help substantially mitigate enteric methane emissions (> 50% reduction). With 3-NOP there were no negative effects on diet digestibility; however OIL decreased fiber digestibility which could decrease animal performance. The effects need to be evaluated in further studies that measure animal performance.

Abstract

© Her Majesty the Queen in Right of Canada, as represented by the Minister of Agriculture and Agri-Food Canada, 2021.The individual and combined effects of 3-nitrooxypropanol (3-NOP) and canola oil (OIL) supplementation on enteric methane (CH4) and hydrogen (H2) emissions, rumen fermentation and biohydrogenation, and total tract nutrient digestibility were investigated in beef cattle. Eight beef heifers (mean body weight ± SD, 732 ± 43 kg) with ruminal fistulas were used in a replicated 4 × 4 Latin square with a 2 (with and without 3-NOP) × 2 (with and without OIL) arrangement of treatments and 28-d periods (13 d adaption and 15 d measurements). The four treatments were: control (no 3-NOP, no OIL), 3-NOP (200 mg/kg dry matter [DM]), OIL (50 g/kg DM), and 3-NOP (200 mg/kg DM) plus OIL (50 g/kg DM). Animals were fed restrictively (7.6 kg DM/d) a basal diet of 900 g/kg DM barley silage and 100 g/kg DM supplement. 3-NOP and OIL decreased (P < 0.01) CH4 yield (g/kg DM intake) by 31.6% and 27.4%, respectively, with no 3-NOP × OIL interaction (P = 0.85). Feeding 3-NOP plus OIL decreased CH4 yield by 51% compared with control. There was a 3-NOP × OIL interaction (P = 0.02) for H2 yield (g/kg DM intake); the increase in H2 yield (P < 0.01) due to 3-NOP was less when it was combined with OIL. There were 3-NOP × OIL interactions for molar percentages of acetate and propionate (P < 0.01); individually, 3-NOP and OIL decreased acetate and increased propionate percentages with no further effect when supplemented together. 3-NOP slightly increased crude protein (P = 0.02) and starch (P = 0.01) digestibilities, while OIL decreased the digestibilities of DM (P < 0.01) and neutral detergent fiber (P < 0.01) with no interactions (P = 0.15 and 0.10, respectively). 3-NOP and OIL increased (P = 0.04 and P < 0.01, respectively) saturated fatty acid concentration in rumen fluid, with no interaction effect. Interactions for ruminal trans-monounsaturated fatty acids (t-MUFA) concentration and percentage were observed (P = 0.02 and P < 0.01); 3-NOP had no effect on t-MUFA concentration and percentage, while OIL increased the concentration (P < 0.01) and percentage (P < 0.01) of t-MUFA but to a lesser extent when combined with 3-NOP. In conclusion, the CH4-mitigating effects of 3-NOP and OIL were independent and incremental. Supplementing ruminant diets with a combination of 3-NOP and OIL may help mitigate CH4 emissions, but the decrease in total tract digestibility due to OIL may decrease animal performance and needs further investigation.