Reducing the carbon 'hoofprint' of the dairy herd

Teagasc geneticist Donagh Berry outlined how the EBI can be used to reduce the carbon “hoofprint” of the national dairy herd. He said that methane is a greenhouse gas which is produced naturally when vegetation is burned, digested or rotted without the presence of oxygen.

He outlined the Teagasc MACC curve, which shows the greenhouse gas abatement strategy for Irish agriculture. Basically, this graph looks at different actions, how much they cost and what the reduction in greenhouse gas from undertaking each action will be.

It should always be borne in mind when comparing breeding to non-breeding technologies or solutions that breeding is cumulative and permanent

“After fertiliser type, EBI has the largest abatement potential; this is despite the fact that the curve is for all agriculture and not just dairy.

“Furthermore, unlike fertiliser type, the economic return from exploiting EBI far outweighs the cost.

“It should always be borne in mind when comparing breeding to non-breeding technologies or solutions that breeding is cumulative and permanent.

“Therefore, unlike many abatement strategies which can revert to baseline if not continuously implemented, usually at a cost, the benefit of EBI accumulates over time,” Donagh said.

He also said that any abatement strategy will only be useful if they can be captured within the national inventory.

He said that EBI by itself won’t reduce greenhouse gasses. Instead, it is the impact of EBI on reducing emissions that will be captured in the national inventory.

Effectively, we want cows to live longer

The big thing here is methane emissions, and while most research around reducing methane emissions in cattle is looking at altering rumen function through the use of feed additives, he argued that the easiest and lowest-cost method is to focus on gross efficiencies, such as those delivered by EBI.

“Effectively, we want cows to live longer. In human terms, increasing average lactation numbers is like asking people to live to 108. So functional type traits become more important if cows are going to be living for longer.”

He presented data showing that EBI is increasing linearly by €10 per year since 2005, with most of this gain coming in fertility and milk sub-indices.

“Modelling the change in herd characteristics based on the national EBI of Irish cows calving in 2001 to 2003 versus those calving in 2014 to 2016, the kg carbon dioxide equivalent per kg fat and protein corrected milk was 14% lower.”

This, he said, shows that focusing on efficiency will help to reduce greenhouse gas emissions while at the same time improving profitability at farm level. Donagh outlined how modelling work comparing the EBI with a carbon breeding index (looking at the impact on greenhouse gas emissions for each trait in the EBI) shows strong correlations.

What this means is that, on average, higher-EBI animals are expected to produce less carbon per lactation

“A strong correlation exists of 0.87 between the CBI and the EBI.

“What this means is that, on average, higher-EBI animals are expected to produce less carbon per lactation, which is very good result.”

He said that in the Holstein breed, the analysis found that every €10 improvement in EBI is associated with a reduction of 61.7kg CO2 equivalents per lactation.

However, the analysis also found that selecting for higher milk solids per cow, without focusing on health or fertility sub-index, will actually result in higher carbon emissions.

This is because efficiency will be reduced with higher replacement rates and a lower reliance on grazed grass due to spread-out calving patterns.

He said that any change to the makeup of the EBI will have to be carefully considered. He said the traits must firstly be important (which carbon clearly is), it must have genetic diversity (so breeding will improve the trait) and it must be measureable.

Donagh said that plans are under way to integrate the Carbon Breeding Index into the EBI

Although Teagasc is currently working on research projects to more easily measure methane emissions from animals while grazing, the amount of data being collected to date is small. He said that ongoing work on using milk samples to predict methane emissions is showing promising results.

Donagh said that plans are under way to integrate the Carbon Breeding Index into the EBI.

This is likely to be introduced as an additional sub-index into the EBI, reducing the weighting on the milk sub-index.

Speaking from the floor, Andrew Cromie said that this carbon index will be introduced later this year.

Doreen Corridan, vet with Munster Bovine, posed the question as to whether farmers should actually milk all their cows.

She presented data from milk-recording herds which shows that the top 10% of cows left a margin of €1,473/cow, while the bottom 10% left a margin of €774/cow, presuming costs of €1,114/cow.

She said based on the cows own worth (COW) index, the difference between the top and bottom 10% was €699/cow or €69,900 in a 100-cow herd.

She also a presented an example of a real farm situation where, based on the COW index, the average cows in the high-COW herd were the most profitable cows in the low-COW herd.

Likewise, the average cows in the high-COW herd were the most profitable cows in the low-COW herd.

She said herds that have a low EBI and a low COW index should not be breeding their own replacements.

Instead, they should put their cows in-calf to beef straws and purchase high-EBI replacements from farms with a high EBI and high COW herd.

“They need to purchase high-EBI heifers, balanced for fertility and production, calving in February and from herds with a high health status, particularly Johne’s Disease. There will be an element of short-term pain in this strategy, but it will yield long-term dividends,” Doreen said.

Dairy farmer Donal O’Reilly is milking 200 cows near Watergrasshill in Cork. He grew 17t/ha on the milking block in 2019, with 1.7t/ha grown in the spring.

The milking block is stocked at 3.65 cows/ha and the overall farm is stocked at 2.5 cows/ha.

Milk production in 2019 was high at 510kg MS/cow from 1t of meal fed. Donal said he plans to reduce the amount of meal fed during the summer and be more strategic with meal at the shoulders of the year.

– 180 cows to calve in February.

– 35 cows to calve in March.

– Five cows to calve in April.

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