Methane
How much methane do livestock produce?
Enteric methane — the stuff a ruminant belches — comes from fermenting feed in the rumen. So it tracks one thing above all others: how much dry matter the animal eats. These pages work it out per stock class, per liveweight and per kilogram of product, from the same engine that runs our feed calculators.
The whole calculation, in two lines
dry matter eaten (kg/day) = energy needed (MJ/day) ÷ feed quality (MJ ME/kg DM)
methane (g/day) = dry matter eaten × yield (g CH₄ per kg DM)
The yields come from the New Zealand national greenhouse-gas inventory — 21.6 g/kg DM for cattle, 20.9 for adult sheep and 16.8 for lambs and hoggets, which belch about a fifth less per kilogram than grown sheep. It is the simplified IPCC 2019 Tier 2 form (Eq 10.21a) the inventory itself uses.
The thing most articles get wrong about feed
In this model the yield per kilogram of dry matter does not change with the feed. A kilogram of silage and a kilogram of grass carry the same methane. So there is no feed you can swap to that lowers methane per mouthful — but there are two things that genuinely move the total, and both of them also make the farm money:
- Better feed quality lowers the kilograms. Denser feed delivers the same energy in less dry matter, and the methane follows the dry matter down. Not because the feed is “low methane” — because there is less of it.
- More production spreads a fixed overhead. Maintenance costs the same feed and the same methane whether an animal produces anything or not. Every extra litre or kilogram divides that overhead further, so methane per unit of product falls even as the daily total rises.
Sheep
Cattle
Dairy cows
A 500 kg dairy cow at typical production belches about 406 g CH₄ a day, from 18.8 kg DM eaten.
Beef cows
A 500 kg beef cow at typical production belches about 180 g CH₄ a day, from 8.3 kg DM eaten.
Growing cattle
A 360 kg beast at typical production belches about 211 g CH₄ a day, from 9.8 kg DM eaten.
Deer
Goats
Dairy goats
A 65 kg dairy goat at typical production belches about 46 g CH₄ a day, from 2.2 kg DM eaten. Provisional yield.
Meat does
A 55 kg meat doe at typical production belches about 31 g CH₄ a day, from 1.5 kg DM eaten. Provisional yield.
Growing meat goats
A 25 kg growing meat goat at typical production belches about 16 g CH₄ a day, from 0.8 kg DM eaten. Provisional yield.
What these figures are, and aren't
- Enteric methane only.Belched methane from the rumen. Not dung or effluent, not nitrous oxide from urine and fertiliser, not fuel or electricity. It is the largest single slice of a pastoral farm's footprint, but it is a slice.
- Modelled, not measured.Every figure is intake × a national average yield. Real animals vary — that variation is exactly what B+LNZ's Cool Beef programme is measuring, on 2,000-plus cattle over four years, to build breeding values for methane and feed intake. Genetics is a lever this model cannot see; feeding and production are the ones it can.
- Methane mass first, CO₂-equivalent second. How biogenic methane should be converted to CO₂e is genuinely contested here. We use GWP100 = 28, New Zealand's official accounting metric, and we say so wherever we show a CO₂e figure — so if you use a different metric you can work from our methane number rather than around it.
- Not an emissions return. For reporting, use whatever your processor, council or scheme requires.
Work it out for your own stock
Every class page has a calculator — your weights, your production, your feed quality, your mob. Or go straight to the feed calculator, which shows the methane alongside the rest of the diet.