Enteric methane mitigation in calves fed pyromellitic diimide: a pilot study

Context Evaluating diets to reduce methane production in calves. Aims To determine whether diets with different combinations of pyromellitic diimide (PMDI), monensin, and fumaric acid would reduce methane concentrations and provide a production benefit without adverse outcomes in calves in a pilot study. Methods Individually housed Holstein and Angus × Holstein calves, at a mean of 4.6 months of age, were block-randomised to the following four groups (n = 3 calves/group): (T1) no feed additives (negative control), (T2) monensin (20 mg/kg dry-matter intake, DMI) + fumaric acid (2.5 g/kg DMI) (positive control), (T3) PMDI (90.5 mg/kg DMI), and (T4) PMDI (90.5 mg/kg DMI) + monensin (20 mg/kg DMI) + fumaric acid (2.5 g/kg DMI). Treatments were mixed with dried distillers grain and fed once daily in a total mixed ration. The study included adaptation (8 days), treatment (27 days), and post-treatment (3 days) periods. Methane and carbon dioxide concentrations were measured during feed visitation for each calf for two consecutive days in adaptation and nine treatment days, by using air continuously collected from a semi-confined feeder in 4 of the 12 calf pens. Feed intake and health were recorded daily, and bodyweight (BW) weekly. Key results Final BW and production measures did not differ among groups. The proportion of feed consumed in both the adaptation and treatment periods had treatment by day interactions but did not differ among treatments. Repeated measures of BW and average daily gain were not influenced by treatment. Methane concentration in the treatment period was 75.2% and 72.9% lower in both PMDI-containing treatment groups (T3 and T4 respectively) and 45.8% lower in the positive control (T2), than in the negative control (T1). Mean methane concentration decreased 25.6%, 38.4%, 82.0%, and 78.7%, for T1–T4 respectively, from the adaptation to treatment periods. Conclusions Supplementation with combinations of PMDI, monensin, and fumaric acid all markedly reduced methane concentration during feeding without negative outcomes. Further studies are required to evaluate rumen degradation, long-term methane reduction, rumen fermentation, health, and productivity responses. Implications Supplementation with PMDI has potential as a feed additive to reduce methane in ruminants.