Context: An Indian Council of Agricultural Research (ICAR) institute has developed an anti-methanogenic feed supplement ‘Harit Dhara’.

• The supplement not only cuts down their methane emissions by 17-20%, but also results in higher milk production and body weight gain.
• In other words, win-win for both the environment and livestock farmers.

Background

• Belching cattle, buffaloes, sheep and goats in India emit an estimated 9.25 million tonnes (mt) to 14.2 mt of methane annually, out of a global total of 90 mt-plus from livestock.
• Methane’s global warming potential – 25 times of carbon dioxide (CO2) over 100 years, making it a more potent greenhouse gas – that’s cause for concern.
• An average lactating cow or buffalo in India emits around 200 litres of methane per day, while it is 85-95 litres for young growing heifers and 20-25 litres for adult sheep.
• Feeding Harit Dhara can reduce these by a fifth.

How Methane is produced?

• Methane is produced by animals having rumen, the first of their four stomachs where the plant material they eat – cellulose, fibre, starch and sugars – gets fermented or broken down by microorganisms prior to further digestion and nutrient absorption.
• Carbohydrate fermentation leads to production of CO2 and hydrogen. These are used as substrate by archaea – microbes in the rumen with structure similar to bacteria – to produce methane, which the animals then expel through burping.

How ‘Harit Dhara’ reacts?

• Harit Dhara acts by decreasing the population of protozoa microbes in the rumen, responsible for hydrogen production and making it available to the archaea for reduction of CO2 to methane.
• Tropical plants containing tannins – bitter and astringent chemical compounds – are known to suppress or remove protozoa from the rumen.
• Harit Dhara has been prepared using condensed and hydrolysable tannin-rich plant-based sources abundantly available in the country.
• It roughly costs Rs 6/kg and it is to be fed only to animals aged above three months having fully functional rumen.

Other benefits

• As the fermentation continues as before, there is more production of propionic acid now in proportion to acetic and butyric acid.
• Since propionic acid provides much of the energy for lactose (milk sugar) production and body weight gain, there is economic benefit, too, from feeding of Harit Dhara.
• The biological energy loss from methane emission can be rechannelled and utilised by the animal for milk production and growth.
• Feeding 500 g Harit Dhara to lactating cattle and buffaloes would increase milk output by 300-400 ml/animal/day.
• The additional weight gain will be 20-25 g/day from 150 g for growing bovines and about 7 g/day from 50 g for adult sheep.