Can Better Fertility Reduce Livestock Greenhouse Gas Emissions?

When the conversation turns to the environmental footprint of cattle, methane usually takes centre stage. Yet one of the most practical ways to reduce livestock greenhouse gas emissions per kilogram of milk or beef starts somewhere else: getting more cows pregnant, sooner, and keeping productive animals in the herd for longer.

For veterinarians and farmers, this changes the way fertility programs should be viewed. They are not only tools for organising breeding or increasing pregnancy rates. By improving the biological efficiency of the whole herd, they can also support profitability, resource efficiency and climate-smart cattle production.

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Why does reproductive efficiency matter for sustainability?

Cattle production generates greenhouse gas (GHG) emissions mainly through enteric fermentation which produces methane, manure management and feed production. Nutritional strategies remain essential, but sustainability cannot be evaluated only by asking how much methane one animal produces. A more useful measure is emission intensity: the kilograms of carbon dioxide equivalent (CO₂-eq) associated with each kilogram of milk or beef produced.

This is where reproduction becomes a powerful lever. Every animal has maintenance requirements, whether or not it is producing milk, raising a calf or contributing to the next generation. When pregnancy rate improves, calving intervals become shorter and replacement needs fall, a greater share of feed, land, labour and energy is converted into saleable product.

The key idea: fertility programs primarily reduce GHG emission intensity by improving whole-herd biological efficiency—not necessarily by reducing methane from each individual animal.

Which reproductive indicators affect cattle greenhouse gas emission intensity?

Several familiar herd indicators have consequences that extend well beyond the breeding chart:

• Pregnancy rate determines how rapidly eligible females become pregnant and how many remain open.
• Calving interval influences the balance between productive and non-productive days in both dairy and beef systems.
• Age at first calving determines how long replacement heifers consume resources before entering production.
• Replacement rate affects the number of young animals that must be reared to maintain herd size.
• Productive longevity spreads the environmental cost of rearing an animal across more lactations or calves.

Modelling studies show that even moderate improvements in these parameters can reduce CO₂-eq per kilogram of product. The logic is straightforward: if each breeding female produces more milk or more weaned calf weight over her lifetime, fewer animals and fewer non-productive days are required to deliver the same output.

How do fertility programs create that improvement?

Modern fertility programs combine tools that were once used separately into a coordinated reproductive strategy. Depending on the herd and production system, this may include synchronization programs, fixed-time artificial insemination (FTAI), resynchronisation, early pregnancy diagnosis, automated estrus detection and embryo production and transfer.

Fixed-time AI: breeding every eligible female

FTAI removes dependence on observed estrus and allows all eligible females to be inseminated at predetermined times. This has been particularly transformative in extensive beef systems, where visual heat detection can be extremely challenging. More females can receive artificial insemination, breeding seasons can become shorter and more compact, and producers can obtain more calves from the same number of breeding cows.

Brazil illustrates the scale of this change: more than 254 million synchronisation protocols have been commercialised since FTAI was introduced. Its widespread adoption reflects the value of combining improved pregnancy outcomes with more predictable herd management.

Resynchronisation and early pregnancy diagnosis: reducing lost time

The first insemination is only one part of a successful program. Resynchronisation protocols allow non-pregnant females to return rapidly to a new breeding opportunity instead of waiting passively for the next observed estrus. Early pregnancy diagnosis, including Doppler ultrasonography where appropriate, can identify non-pregnant animals sooner and support faster decisions.

For the herd, fewer days are lost. For the farmer, the breeding season becomes more controlled. For the veterinarian, reproductive visits can shift from reactive problem-solving towards a systematic cycle of insemination, diagnosis and timely re-insemination.

Embryo technologies: adding genetic potential

Embryo transfer (ET) and in vitro embryo production (IVP) add another dimension. Combined with FTAI, genomic selection and sexed semen, these technologies can multiply genetically superior females and shorten the generation interval. Over time, this accelerates progress in traits such as fertility, feed efficiency, growth, milk yield, disease resistance, carcass quality and longevity.

The sustainability benefit is therefore both immediate and cumulative: better reproductive performance raises present-day output, while faster genetic progress can build a more efficient and resilient future herd.

How does better fertility reduce emission intensity in dairy and beef herds?

In dairy systems, improved reproductive performance can reduce days open, support a more efficient calving pattern and increase lifetime milk output. Nutrients and maintenance inputs are consequently distributed across more energy-corrected milk, lowering emission intensity.

In beef systems, the key outcome is more calves weaned per female exposed and more kilograms of beef produced per hectare. Higher pregnancy rates and a concentrated calving season increase output without requiring proportional increases in land, feed resources or breeding females.

In practical terms: the sustainability gain comes from producing more with the herd and resources already in place.

Which reproductive management practices should veterinarians and farmers prioritise?

A fertility program is not a single injection or a scheduled calendar copied from another farm. Its value depends on disciplined implementation and on fitting the strategy to the herd. The strongest programs connect reproductive physiology with practical execution.

• Start with herd data: pregnancy rate, submission rate, conception rate, calving interval, age at first calving and reproductive culling.
• Identify the main bottleneck: poor estrus detection, postpartum anestrus, delayed reinsemination, pregnancy loss or inconsistent protocol compliance.
• Choose the right combination of FTAI, estrus detection and resynchronisation for the production system.
• Use early, accurate pregnancy diagnosis to shorten the interval to the next decision.
• Protect protocol compliance: correct animals, products, doses and timing are essential.
• Review outcomes with both economic and environmental efficiency in mind—not pregnancy rate alone.

This is a natural area for veterinarian–farmer collaboration. Veterinarians bring knowledge of physiology and implementation understanding, protocol design and diagnostic discipline; farmers and farm teams provide the consistency of execution that determines whether the program works in practice.

Where is reproductive management heading next?

The next generation of fertility programs will increasingly integrate precision livestock farming, artificial intelligence, wearable sensors, automated estrus detection, genomic prediction and precision nutrition. These tools can provide real-time information and help target interventions more accurately.

Technology, however, will not replace sound reproductive management. Its greatest value will come from connecting better data with timely action: identifying the right animal, making the right decision and executing it at the right moment.

Take-home messages

• Reproductive efficiency is a key driver of both biological and environmental efficiency.
• Fertility programs lower GHG emission intensity mainly by reducing non-productive animals and days, and by increasing lifetime output.
• FTAI, resynchronisation and early pregnancy diagnosis can make breeding more timely and predictable.
• ET, IVP, genomics and sexed semen can accelerate long-term genetic progress towards more efficient cattle.
• The best results come from farm-specific programs, reliable compliance and continuous measurement.

Better reproduction will not solve every sustainability challenge in cattle production. But it is one of the rare interventions capable of delivering an immediate operational return while also improving how efficiently the herd uses feed, land, labour and time. That makes fertility management more than a reproductive strategy—it is a practical route towards sustainable intensification.

Want to learn more? Download our WBC 2026 Booklet of Abstracts to discover how reproductive management can help reduce greenhouse gas emissions and support more sustainable livestock production.

References

1. Abreu LA, Rezende VT, Gameiro AH, Baruselli PS. Effect of reduced age at first calving and an increased weaning rate on CO₂-equivalent emissions in a cow-calf system. Revista Engenharia na Agricultura. 2022.
2. Abreu LA, Paula VR, Carvalho BC, Souza AH, Rebeis LM, Mori FK, Gricio E, Baruselli PS. Influence of calving interval on the carbon footprint of lactating dairy cows under the life cycle assessment metric. Animal Science Proceedings. 2023.
3. Abreu LA, Paula VR, Carvalho BC, Benhami VML, Mori FK, Gricio EA, Albertini A, Rebeis LM, Souza AH, Baruselli PS. Contrast of low and high reproductive performance on herd composition, productivity, and carbon footprint in dairy production system. Animal Science Proceedings. 2024.
4. Baruselli PS, de Abreu LÂ, de Paula VR, Carvalho B, Gricio EA, Mori FK. Applying assisted reproductive technology and reproductive management to reduce CO₂-equivalent emissions in dairy and beef cattle: a review. Animal Reproduction. 2023.
5. de Paula VR. Life cycle assessment of milk production: a case study in Minas Gerais and Paraná. Master's dissertation, Federal University of Juiz de Fora. 2022.