Along with the launch of the new carbon sub-index, there has also been a number of updates to the beef sub-index within the economic breeding index (EBI).
This is the first time since 2014 that changes have been made to the beef sub-index.
The updated beef sub-index will account for 10% of the total EBI, rather than the previous 8%.
Updates to the beef sub-index are important for a number of reasons especially considering that 57% of national kill origin is from the dairy herd and this figure is going to increase in the coming years.
Changes to sub-index
There have been three main changes to the beef sub-index within the EBI, with the inclusion of an age of slaughter trait, in-spec carcass traits and economic value updates.
Like the new carbon sub-index, it is the first time that age of slaughter has been included in a cattle breeding objective.
The use of sexed semen on dairy cows will result in the majority of surplus calves from the dairy herd entering the beef herd having been sired by beef bulls.
But without more emphasis on beef traits, it will be difficult to improve the overall quality from the dairy herd – as the cow contributes up to half the beef merit of the calf.
Beef sub-index
A study conducted by Teagasc compared the old sub-index to the updated sub-index on 46,000 Friesian steers slaughtered from large beef herds in 2021 and 2022.
The study found that the old sub-index was doing a ‘fairly good job’ according to Alan Twomey from Teagasc.
The difference between the top 20% and bottom 20% is outlined in the table below.
Bottom 20% Top 20% Difference Carcass weight 307 322 15 Weight spec (280-380kg) 72% 75% 3% Conformation spec (≥0=) 26% 37% 11% Fat spec (≥2+ and ≤4=) 85% 85% 0% Age at slaughter (days) 771 768 -4
Looking at the new sub-index, the results are outlined in the table below.
The biggest change between the two is in the age of slaughter with 20 days saved between the top 20% and bottom 20% of dairy sires.
Bottom 20% Top 20% Difference Carcass weight 308 320 12 Weight spec (280-380kg) 73% 76% 3% Conformation spec (≥0=) 25% 40% 15% Fat spec (≥2+ and ≤4=) 84% 87% 3% Age at slaughter (days) 781 761 -20
There will be increased variation between dairy sires on beef sub-index, as there will be a €50 difference between the top and bottom 20% of bulls – compared to €29 in old index.
According to Twomey this will make it easier to select dairy bulls that are high value for beef without compromising on dairy traits.
But it will penalise bulls with poor genetic merit for beef traits, according to Twomey.
The new index will align with dairy beef index (DBI) and the commercial beef value (CBV).