Evaluation of 3-nitrooxypropanol to decrease enteric methane emissions in beef cattle

  • Author / Creator
    Romero, Atmir
  • The main objective of this research was to evaluate the potential of 3-nitrooxypropanol (NOP) to lower enteric methane (CH4) production by ruminants. Methane is an undesirable byproduct of enteric fermentation that represents a loss of energy to the animal. Additionally, CH4 is a greenhouse gas that contributes to global warming. 3-Nitrooxypropanol is a novel compound that inhibits methyl-CoM reductase, a key enzyme of methanogenesis. Four experiments were conducted using either beef cattle or the rumen simulation technique (Rusitec). The first study evaluated the addition of increasing levels of NOP [0, 0.75, 2.25 and 4.50 mg/kg of body weight (BW)] to a beef cattle diet. Enteric CH4 production was linearly decreased with increasing NOP dose with 33% less CH4 at the highest level of supplementation. There was a shift in rumen fermentation towards more propionate and less acetate concentration in the rumen with NOP addition. However, NOP did not affect BW gain, feed digestibility or the numbers of of rumen bacteria, protozoa or methanogens, but slightly decreased dry matter intake (DMI). In the second experiment, the long-term (112 d) addition of NOP (2 g/d) to a beef cattle diet resulted in 60% less enteric CH4 production compared to the control with no signs of microbial adaptation. Total numbers of methanogens and the proportion of acetate in the rumen were lowered, while the proportion of propionate was increased. This study included a recovery period (16 d) in which NOP addition was discontinued. During this period the residual effects of NOP on the variables studied were either nonexistent or minimal. The third study evaluated different NOP doses (0, 5, 10 and 20 mg/d) using Rusitec fermenters. Methane was linearly and quadratically decreased on average by 82% compared with NOP addition with no effect on feed digestibility; however, CH4 reduction was accompanied with hydrogen gas accumulation. In this study, total methanogens associated with the solid phase (feed residuals) were decreased with NOP addition; but, methanogens associated with the liquid phase were not affected. The fourth study evaluated the effects of NOP (2 mg/d), monensin (MON; 2 mg/d) and the combination of NOP (2 mg) and MON (2 mg) using the Rusitec system. Addition of NOP decreased CH4 production by 71.5% and MON by 11.8% when compared to the control treatment with no additive reduction in CH4 when the two compounds were combined. This study included a recovery period at the end of the experiment in which treatments were discontinued. During this period a gradual increse in CH4 production was observed for NOP or NOP plus MON treatments, which approached control levels 3 d after treatment withdrawal. In conclusion, NOP is an effective means of mitigating enteric CH4 emissions from beef cattle during prolonged feeding periods with no evidence of microbial adaptation. The reduction of CH4 production observed in the in vivo experiments together with increased propionate proportion, a small reduction in DMI and no effect on BW are encouraging and open the possibility to further evaluate NOP with larger number of animals under farm conditions.

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  • Degree
    Doctor of Philosophy
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