Selective Breeding
System: Dairy Cattle
Mainly applicable for: Farming systems with access to a breeding program, where the feed can be adapted to the production of the animals. Largest progress can be made in animals with poor genetic merit for production and feed efficiency.
Not applicable or effective for: Breeds and countries without breeding programs. Currently breeding values for methane exist only for a few countries, but in future will become available to countries world-wide and different breeds.
Description
Multiple traits are included in breeding schemes, with individual traits being weighted differently in breeding indexes. Selective breeding of animals can contribute to reduction of GHG emissions per unit of product and/or absolute emissions. Many traits contribute to reduction of emissions per unit of product, such as milk yield, fat and protein, longevity, feed efficiency, fertility and animal health. To reduce absolute absolute emissions (per animal), however, only particular traits such as feed efficiency, longevity and fertility contribute to lower emissions. In addition, international breeding organizations are now introducing methane breeding values for bulls, allowing siring of cows by bulls with lower methane profiles.
Besides selective breeding, changing breed or cross-breeding may contribute to reduced emissions, but this highly depends on the specific breeds and farming system. Note that genetically improved animals will require an adjusted diet and higher feed intake, to accommodate increased nutritional requirements (energy, protein, minerals and vitamins).
Mechanism of effect
Selective breeding can increase milk yield, protein yield and fat yield per cow, which will reduce emissions per kg fat-and protein-corrected milk by diluting emissions related to maintenance and young stock. Net effects depend on accompanied changes in the footprint of animal diets and other changes in farm management. Also, absolute emissions per cow may increase with a higher milk yield because cows require more feed intake, which results increased emissions from enteric fermentation, manure, and forage and feed production.
Breeding for other traits, such as longevity, feed efficiency or fertility, can reduce both absolute emissions and emissions per kg milk, mainly through fewer replacements and lower feed requirements. For example increasing longevity results in a lower replacement rate, reducing emissions related to young stock, while improving feed efficiency reduces emissions for feed and forage production. As reduction of emissions due to genetic change involves a certain rate per year, the achieved reduction potential depends on the period of time considered.
Reference situation
Average farm
Legend
| ● – Small effect (<5%) | o – No effect |
| ●● – Medium effect (5-20%) | ● – Unfavourable effect |
| ●●● – Large effect (>20%) | ● – ● – Variable effect (depending on farm characteristics or way/level of implementation) |
Effect on total greenhouse gas (GHG) emissions
| Mean effect and range in kg CO2-equivalents | per kg product | per farm | |||
| Mean | Min-Max | Mean | Min-Max | Level of evidence | |
| Selective breeding for improved performance (multiple traits) | ●● | ● – ●● | N/A | ●●–●● | Medium |
| Selective breeding for higher milk yield and solids | ●● | ● – ●● | ●● | ●–●● | Low |
| Including methane in the breeding goal | ●● | ● – ●● | ●● | ●–●● | Low |
| Change from low to high yielding breed | N/A | ●● – ●● | ●● | ●–●● | Medium |
Effect per emission source
| Mean effect on emission from | Manure | Animal | Feed and forage production | Barn & farm inputs | |||
| CH4 | N2O | CH4 | CO2 | N2O | LUC | CO2 | |
| Selective breeding for improved performance (multiple traits) | N/A | N/A | N/A* | N/A | N/A | N/A | N/A |
| Selective breeding for higher milk yield and solids | ●● | ●● | ●● | ●● | ●● | ●● | ●● |
| Including methane in the breeding goal | o | o | ●● | o | o | o | o |
| Change from low to high yielding breed | ●● | N/A | ●● | ●● | ●● | N/A | o |
*risk of an adverse effect (see ’cause of variable or unfavourable effect’)
Explanation of variable effect
Selective breeding for improved performance (multiple traits)
Effects depends on the weights of traits in selection indexes, as these account for the impact genetic change in traits will have on greenhouse gas emissions. In case more weight is placed on milk yield and milk components (protein and fat), this can reduce emissions per kg product, but may counteract reduction of absolute emissions. For reduction of absolute emissions, more weight on – for example – feed efficiency, longevity and fertility will have more beneficial effects.
Selective breeding for higher milk yield and solids
A high-productive cow has a higher feed intake, causing higher emissions from enteric fermentation and manure. She also requires more and better feed than a low-productive cow to reach its potential production, increasing emissions related to feed and forage production. Effects will mainly depend on the extend of increase in productivity, and changes in feed efficiency and the footprint of the feed ration. The increase in total emissions at the farm level can be avoided by combining the increase in productivity (and emissions per animal) with a reduction in herd size.
Including methane in the breeding goal
The size of effect depends on the rate of implementation, and any other changes in the management (e.g. footprint of the feed ration fed). As reduction of emissions due to genetic change involves a certain rate per year, the achieved reduction potential depends on the period of time considered.
Change from low to high yielding breed
Effects of changing to a high yielding breed on emissions highly depend on the specific breeds in the old and new situation. For example, although Holstein-Frisian cows show higher milk yields than Jerseys, emissions per kg of product are often equal or higher than from Jersey cows. Absolute emissions generally increase as a high-productive cow has a higher feed intake and requires more and better feed than a low-productive cow, increasing absolute emissions from enteric fermentation and manure, and feed production. The increase in total emissions at the farm level can be avoided by combining the increase in productivity (and emissions per animal) with a reduction in herd size. Effects will mainly depend on the extend of increase in productivity and feed intake, changes in feed efficiency, and changes in the footprint of the feed ration.
| Literature references | Selective breeding for improved performance (multiple traits) |
|---|---|
| Shi et al., 2024 | Balancing farm profit and greenhouse gas emissions along the dairy production chain through breeding indices |
| De Haas et al., 2021 | Selective breeding as a mitigation tool for methane emissions from dairy cattle |
| Amer et al., 2018 | A methodology framework for weighting genetic traits that impact greenhouse gas emission intensities in selection indexes |
| Richardson et al., 2022 | Reducing greenhouse gas emissions through genetic selection in the Australian dairy industry |
| González-Recio et al., 2020 | Mitigation of greenhouse gases in dairy cattle via genetic selection: 2. Incorporating methane emissions into the breeding goal |
| Arndt et al., 2015 | Feed conversion efficiency in dairy cows: Repeatability, variation in digestion and metabolism of energy and nitrogen, and ruminal methanogens |
| Selective breeding for higher milk yield and solids | |
|---|---|
| March et al., 2021 | Effect of Nutritional Variation and LCA Methodology on the Carbon Footprint of Milk Production From Holstein Friesian Dairy Cows |
| Van Middelaar et al., 2014 | Methods to determine the relative value of genetic traits in dairy cows to reduce greenhouse gas emissions along the chain |
| Manzanilla-Pech et al., 2022 | Selecting for Feed Efficient Cows Will Help to Reduce Methane Gas Emissions |
| Including methane in the breeding goal | |
|---|---|
| Richardson et al., 2022 | Reducing greenhouse gas emissions through genetic selection in the Australian dairy industry |
| González-Recio et al., 2020 | Mitigation of greenhouse gases in dairy cattle via genetic selection: 2. Incorporating methane emissions into the breeding goal |
| Manzanilla-Pech et al., 2022 | Selecting for Feed Efficient Cows Will Help to Reduce Methane Gas Emissions |
| De Haas et al., 2021 | Selective breeding as a mitigation tool for methane emissions from dairy cattle |
| Starsmore et al., 2023 | Residual methane emissions in grazing lactating dairy cows |
| Change from low to high yielding breed | |
|---|---|
| Zehetmeijer et al., 2014 | A dominance analysis of greenhouse gas emissions, beef output and land use of German dairy farms |
| Capper and Cady, 2012 | A comparison of the environmental impact of Jersey compared with Holstein milk for cheese production |
| Uddin et al., 2021 | Carbon footprint of milk from Holstein and Jersey cows fed low or high forage diet with alfalfa silage or corn silage as the main forage source |
| Vellinga and De Vries, 2018 | Effectiveness of climate change mitigation options considering the amount of meat produced in dairy systems |
| De Souza Congio et al., 2021 | Enteric methane mitigation strategies for ruminant livestock systems in the Latin America and Caribbean region: A meta-analysis |
| Dall-Orsoletta et al., 2019 | A quantitative description of the effect of breed, first calving age and feeding strategy on dairy systems enteric methane emissions |