Tropical cattle methane emissions: the role of natural statins supplementation

Abstract

A natural food-based supplementation in the basal diet (BD) of cattle for lowering methane emissions was conducted over a 2.5-month period in 2013 at Lansdown Research Station, in north Queensland, Australia. Using eight rumen-cannulated Belmont Red Composite steers [436 ± 18.2 kg liveweight (LW); least squares means ± s.e.m.] fed a diet mixture of 0.85 CSIRO’s Ridley beef finisher pellets and 0.15 Rhodes grass (Chloris gayana); Experiment 1 compared for 7 weeks dose-dependent effects of the fermented-Monascus purpureus red rice powder (FRR) on dry matter intake (DMI), feed efficiency and tolerability. Consistent with the developed feeding methodology, the second experiment used four (461 ± 18.2 kg LW) fistulated Belmont Red Composite steers to assess rumen fermentation parameters and methane emissions measured in an open-circuit respiratory chamber system over ~4 weeks. Overall, LW increased throughout the study. In Experiment 1, the supplementation of FRR containing a natural lovastatin (monakolin K) reached 120 g/day (i.e. 2.88 ± 0.057 mg monakolin K/kg LW) fed in two approximately equal portions at 0900 hours and 1600 hours. However, once the diet was equal to or higher than 110 g/day of FRR, adverse effects were evident in terms of DMI (P < 0.05) and animal physiology. Compared with the BD, dietary intake of 40 g of FRR/day (i.e. 0.92 ± 0.034 mg monakolin K/kg LW) was associated (P < 0.05) with increased DMI and reduced methane yield (g/kg DMI) emissions. However, the effect was transient and not observed as FRR increased to 100 g/day. It was concluded that the adverse effects of FRR on animal health precludes further investigation with high doses of supplementation, and the transient reduction in methane yield was probably due to rumen adaptation.