The ICBF and Teagasc have introduced a new sub-index into the EBI called the carbon sub-index. Up to now, EBI was focused on maximising traits that deliver more profit on Irish dairy farms, with milk production and fertility the largest sub-indices.

Each made up 33% of the EBI, followed by calving sub-index at 10%, milk and beef at 8% each and management and health at 4% each.

This multi-trait approach to selecting the best animals has served the dairy sector well, with substantial gains in both milk solids and fertility achieved on farms over the last two decades.

These genetic gains, resulting in improved efficiency are seen as an important step to reducing the greenhouse gas emissions from dairy farming.

Because of this, improving EBI is one of the key pillars in the Teagasc marginal abatement cost curve (MACC).

However, this approach presumes that because more milk is produced and because cows last longer that there will be less dairy cows and less replacements in the country producing the same overall level of milk.

As we have seen in recent years, dairy cow numbers have been increasing, so while indirectly the carbon footprint per kilo of milk may be decreasing, the overall level of emissions from the sector has been increasing because there are more cows in the country.

While it remains to be seen whether or not dairy cow numbers continue to increase or not, there is a clear need to ensure that genetically, the carbon footprint of the dairy herd is reducing. We already know that not all animals emit the same level of methane.

ICBF and Teagasc say that in the next two years there will be enough information to include methane emissions as a trait in the EBI. This will allow farmers to breed cows with low methane emissions on a per-cow basis, which will then be captured in the national carbon inventory.

Introducing the carbon sub-index is the first step in that process. The carbon sub-index reflects the additional indirect carbon costs of producing more milk or having poorer fertility or having big cows that eat more feed.

Carbon, or carbon dioxide equivalents (CO2e) can be traded, and the value used in the new sub-index is €80/t.


The make-up of the new EBI is outlined in Table 1. As expected, introducing a new sub-index reduces the relative weighting of other sub-indices.

In most cases, a part of the other sub-indices has been taken to make up the new carbon sub-index. For example, fertility and maintenance traits make up a high proportion of the carbon sub-index. Improving these traits reduces the carbon footprint.

Milk production is also part of the carbon sub-index but in this case it’s got a negative value because producing more kilos of milk, fat and protein increase carbon.

ICBF say that the introduction of the carbon sub-index reduces the relative gain in profit by around 5%, because of the fact that 10% of the index has been shifted to carbon.

“The EBI has already started us on the right pathway in terms of breeding a more fertile cow. The carbon sub-index is effectively putting a carbon cost on the existing traits in the EBI plus a new trait that we’re going to bring in, which is earlier finishing age.

"The carbon cost is €80/t but there is also the cost of producing more milk, which is the extra cost of feed and fertiliser which consolidates into the carbon sub-index,” says ICBF’s Andrew Cromie.

“This allows us to capture the additional costs or opportunities around carbon to reward those existing high EBI animals that are also going to be good on the carbon sub-index.

"In overall terms the carbon sub-index is going to favour more fertile and slightly lighter type of animal. We always knew this was going to be the outcome in the context of carbon,” he says.

Cow size or maintenance is effectively being used as a proxy measurement for carbon footprint until the direct methane trait is incorporated into the EBI.

The overall carbon sub-index makes up 10% of the EBI, of which liveweight is one part. Plus, the relative emphasis on maintenance as a standalone trait has reduced from 8% to 4%.


Andrew doesn’t see the changes as having a big impact on cow size; “I would say that within the next decade the impact of these changes will be that the typical cow might go from an average liveweight of 580kg down to 570kg.

"On the other hand, with the changes that are also being made to beef in the EBI, herds that are currently weighing 480kg will probably go to 520kg,” he says.

The change to beef is that a new trait, age at slaughter, is being introduced to both the beef and carbon sub-index.

This will reward animals that get to finishing weight in a shorter time than other animals because the longer a beef animal takes to finish the more methane it produces.

There is also increased emphasis on carcase conformation and carcase fat, but no real change is expected on carcase weight, with a slight decline likely to continue.

ICBF says that the economic value for carcase weight would need to be €7/kg in order for it to have a substantial impact. impact. Carcase value has increased in this round of changes from €2.90/kg to €4.50/kg.

However, new in-spec requirements have been incorporated, meaning that sires that produce carcases that are either too heavy or too light will be heavily hit.

This penalty isn’t linear, with a 12c/kg penalty on carcases lighter than 250kg and a 45c/kg penalty on carcases lighter than 220kg.

According to the ICBF the changes will lead to some re-ranking among bulls, but in the main the changes are small, with the majority of bulls moving by just a couple of points, and 95% of all active bulls moving by between -€44 and €44. There are 33 bulls that move by more than €50 each way but none of these are within the top 100 active bull list.

Within the top 100 active bulls the average movement in EBI after these changes is an increase of €12 across all 100 bulls with a maximum change of -€9 and €37.


The important role of cow size or liveweight in terms of carbon efficiency is a key acknowledgement in this round of EBI changes.

For the coming season, AI companies will have to put forward bulls that are not only high in all the existing traits, but are high in the carbon sub-index too. Given the importance of carbon footprint now and into the future, farmers will have to decide for themselves how much weighting they will place on it when choosing bulls.

Marrying the twin objectives of reducing the carbon footprint of the dairy herd and increasing the beef merit of its offspring is not an easy task.

I don’t think anybody is saying that these changes achieve that, but they are a step in the right direction leaving aside not improving carcase weight.

With increased pressure coming on calf transport to the continent and the imminent banning of calf slaughter there will be tens if not hundreds of thousands more calves from the dairy herd in Ireland over the coming years.

Like it or not, dairy farmers will have to find a home for these calves that suits their own business model and/or creates a viable business model for someone else.