by Gordon Refshauge (Jan 2024)

Why Methane Matters in Sheep Production

Methane emissions from sheep are becoming an increasingly important issue for the livestock industry, driven by pressure from consumers, markets, and government. Most of the methane produced on a sheep farm comes from adult breeding ewes, which means that anything improving the productivity of these ewes has a major impact on reducing emissions per kilogram of wool or meat produced. This measure, known as emissions intensity, is more important than total emissions, because it reflects how efficiently a farm converts feed into saleable product.

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Reproductive efficiency: The Biggest Opportunity

A key problem for emissions intensity is reproductive waste. Ewes that fail to get pregnant still consume feed and produce methane, but they generate no lambs and no income. Improving reproduction therefore becomes one of the most powerful tools available to farmers. Increasing pregnancy rates, lifting litter size, improving lamb survival, and reducing ewe mortality all contribute to higher weaning rates, which in turn lower emissions intensity. Even though total methane may rise slightly when more lambs are born and reared, the emissions per kilogram of product fall significantly.

Wool vs Prime Lamb

While the core principles for reducing emissions intensity are the same across all sheep enterprises, the practical emphasis differs between wool and prime lamb systems.

Wool systems

• Lower natural fecundity
• Higher lamb mortality
• Biggest gains come from:
  • lifting scanning %
  • improving lamb survival
  • increasing lifetime productivity of breeding ewes
• Higher fleece weight + higher weaning rate = strong emissions reductions

Prime lamb systems:

• Naturally higher fecundity
• Focus on managing twins and triplets
• Faster growth rates reduce days to slaughter
• Terminal sires with high growth/muscling improve efficiency

In short:

• Wool systems benefit most from improving reproductive efficiency and ewe longevity.
• Prime lamb systems gain the most from managing high‑fecundity ewes and accelerating lamb growth.

What the Modelling Shows

Across many modelling studies, the message is consistent: improving reproduction is one of the most effective ways to reduce emissions intensity.

Key findings include:

• Increasing fecundity can reduce emissions intensity by 7–8%.
• Joining ewe lambs can reduce emissions intensity by 10–12%, with good management.
• No modelling has directly examined lamb survival, even though it likely has one of the biggest impacts.
• Adjusting stocking rate to match higher fecundity can reduce total emissions by up to 20%.

Genetics: A Long‑Term, Permanent Solution

Genetics offers long‑term opportunities to reduce emissions intensity. Selecting animals that naturally produce less methane, are more feed‑efficient, or have higher reproductive performance can gradually reduce emissions over time.

Useful genetic traits include:

• CON ASBV (conception rate)
• LS ASBV (litter size)
• Feed efficiency
• Muscling and body fatness
• Lower methane yield

Larger, well‑grown ewes tend to be more efficient producers, and their lambs grow faster, shortening the time to sale and reducing emissions per kilogram of product.

Combining Strategies Gives the Biggest Reductions

The biggest reductions in emissions intensity occur when several strategies are combined. Studies show that:

• High fleece weight + low methane genetics + feed efficiency → 13–15% reduction
• Lower joining age + higher weaning rate + feed efficiency → up to 17% reduction

No single strategy is enough on its own; the best outcomes come from a whole‑farm approach.

Understanding the Trade‑offs

Farmers need to be aware of potential trade‑offs:

• Higher fecundity increases lamb and ewe mortality if nutrition isn’t adjusted.
• Joining ewe lambs works well but requires skill and good nutrition.
• Faster lamb growth reduces emissions intensity but may encourage higher stocking rates.

These trade‑offs mean improvements must be matched with appropriate management changes.

Practical On‑Farm Actions

Improving the performance of the breeding ewe flock is the most practical way to reduce emissions intensity.

Ram preparation

• Check rams at least 6 weeks before joining
• Assess testes, feet, teeth, body condition, prepuce
• Supplement with lupins or maize pre‑joining

Boosting pregnancy rate

• Meet age, weight, and condition targets
• Use teasers
• Spike feed with high protein/energy
• Consider melatonin (Regulin®) or Ovastim®

Managing litter size

• Pregnancy scan for litter size
• Manage singles and twins separately
• Provide high‑quality feed pre‑joining

Improving lamb survival

• Use training programs (LTEM, Bred Well Fed Well, T90)
• Ensure nutrition matches litter size
• Focus on twin‑bearing ewes

Conclusion

Most farms can realistically reduce emissions intensity by around 15% through improved reproduction and flock management. The most powerful lever is increasing weaning rate, supported by higher pregnancy rates, higher fecundity, better lamb survival, and lower ewe mortality. For farmers who cannot or do not wish to increase weaning rates, improving lamb growth rates to shorten the time to sale is another effective pathway. Ultimately, improving reproductive efficiency is not only good for emissions, it is also good for productivity and profitability.