METHANE REDUCTION ▶▶▶


Eucalyptus reduces methane in dairy calves


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.


BY MATTHEW WEDZERAI D Parameter 0


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


9.87


45.62 20.44


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, there- fore, 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. 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.


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


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 8 ▶ ALL ABOUT FEED | Volume 28, No. 7, 2020


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 per- formance 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 Results of the study showed that the leaf extract was able to decrease methane emission by 20.1% and 61.5% when C. citr- iodora was supplemented at 10ml and 20ml, respectively. Ac- cording to the researchers the methane reduction was caused by reduction in rumen protozoa and methanogenic bacteria. The reduction in protozoa count and methanogenic bacteria could be attributed to the inhibitory actions of the terpenes and other plant secondary compounds present in C. citriodo- ra. Ruminal protozoa provide the perfect habitat for meth- anogenic bacteria. In addition, methane production in ruminal fermentation is associated with an increased propi- onate (C3) percentage and a reduced acetate (C2) percentage and C2:C3 ratio; these reductions were also observed in this 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 An increased level of the leaf extract not only caused a meth- ane reduction as well as a reduction in pathogenic bacteria, which are involved in calf diarrhea. The decrease in bacterial counts is attributed to the antimicrobial mechanisms of the secondary metabolites of the leaf extract, which include en- zyme inhibition, cell membrane disruption, substrate depri- vation and prevention of bacterial colonisation. These sec- ondary metabolites are mainly 1,8-cineole, α-pinene, trans-pinocarveol, p-cymene and pinocarvone components. In addition, the researchers found decreases in protozoa counts of 15.6% and 30.6% when C. citriodora was supple- mented at 10ml and 20ml, respectively. Since ruminal proto- zoa provide the perfect habitat for methanogenic bacteria,


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