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Eucalyptus reduces methane in dairy calves


BY MATTHEW WEDZERAI D


uring microbial degradation of feed in the rumen, considerable amounts of energy and nitrogen are lost in the form of methane. Methane is a green- house gas with significant potential for increasing


global warming. Ameliorating rumen-methane emission, therefore, could result in economic and environmental benefits.


According to a recent study from the Animal Production Research Institute, feeding calves the leaf extract from Co- rymbia citriodora (Eucalyptus) significantly reduces the production of methane and improves their health status.


Properties of the leaf extract The researchers stated that the potential of the leaf extract to modify the rumen fermentation and mitigate methane emis- sion in ruminants lies in its secondary metabolites that con- sist of 1,8-cineole, α-pinene, trans-pinocarveol, p-cymene and pinocarvone. In addition, the extracts of C. citriodora possess antimicrobial (antibacterial and antiprotozoal) and antioxi- dant properties that are also vital to modulate methane production and improve health.


The study Thirty crossbred male (Baladi×Holstein Friesian) calves of av- erage body weight (BW) 37.3 ± 0.02kg and aged 4 or 5 days were selected to evaluate the effect of milk supplemented with different doses of aqueous extract of C. citriodora (CC) on methane production, nutrient digestibility, growth perfor- mance and health status. Treatments were implemented by mixing CC with milk at levels of 0ml, 10ml and 20ml per calf per day throughout the experimental period of 15 weeks.


Methane reduction The researchers found that the leaf extract was able to de- crease methane emission by 20.1% and 61.5% when C. citri- odora was supplemented at 10ml and 20ml, respectively. They cited the reduction in rumen protozoa and methano- genic bacteria as the main causes of the reduced methane production. The reduction in protozoa count and methano- genic bacteria could be attributed to the inhibitory actions of the terpenes and other plant secondary compounds present


Mitigating methane production is still a major concern in dairy production. Researchers are turning to sustainable and environmentally friendly strategies. The leaf extract of Corymbia citriodora (Eucalyptus) has emerged to be of high efficacy in reducing methane production in dairy calves.


in C. citriodora. Ruminal protozoa provide the perfect habitat for methanogenic bacteria. In addition, methane production in ruminal fermentation is associated with an increased pro- pionate (C3) percentage and a reduced acetate (C2) percent- age and C2:C3 ratio; these reductions were observed in their study (Table 1). The decrease of acetate may be due to a de- crease in protozoa population, since acetate is a product of protozoa metabolism.


Antibacterial and antiprotozoal activities The researchers considered a reduction in common patho- genic bacteria (Escherichia coli, Enterococcus and Clostridia) involved in calf diarrhoea as an index of health status in their study. These bacteria decreased with an increase in the level of the leaf extract. The decrease in bacterial counts is attribut- ed to the antimicrobial mechanisms of the secondary metab- olites of the leaf extract, which include enzyme inhibition, cell membrane disruption, substrate deprivation and preven- tion of bacterial colonisation. These secondary metabolites are mainly 1,8-cineole, α-pinene, trans-pinocarveol, p-cymene and pinocarvone components. The researchers also found decreases in protozoa counts of


Table 1 – Rumen fermentation parameters of calves fed varying levels of C. citriodora leaf extract.


Parameter 0


Methane (ml/g DM) Acetic acid (mmol/L) Propionic acid (mmol/L)


9.87


45.62 20.44


ml CC/calf/day 10


7.89


44.63 21.26


20 5.02


44.33 22.70


Acetate:propionate 2.23 2.10 1.96 ▶DAIRY GLOBAL | Volume 7, No. 2, 2020 25


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