New addition to Sire Advice has potential to save dairy industry €2.2 million
Advancements in DNA screening of animals have led to new discoveries and given farmers better tools for breeding decisions. Just like humans, cows can carry harmful genetic mutations. These are called lethal recessive mutations, which only cause problems if an animal inherits two copies of the faulty gene. If two carriers are bred together, there is a 25% chance their offspring will inherit both copies, leading to death—usually at the embryo stage.
Genotyping will identify these carrier animals, allowing farmers to avoid these risky matings. In Holstein-Friesian cows, two common lethal mutations are HH1 (Holstein Haplotype 1) and HH3 (Holstein Haplotype 3).
About 2% of Irish Holstein-Friesians carry the HH1 mutation, and around 5% carry HH3. This means that thousands of matings each year involve two carriers, leading to many cases where no viable calf is born.
The HH1 mutation is particularly problematic because it can cause pregnancy loss up to 200 days into gestation. In seasonal calving herds, this often means a cow is found to be not pregnant at the end of the breeding season, reducing efficiency.
To address this, the ICBF sire advice system, which already prevents inbreeding, has been updated to avoid mating carriers of lethal mutations. This improvement is expected to save the dairy industry about €2.2 million annually. The system can also be easily updated as new lethal mutations are discovered.
Calculating the Benefit
With a 5% prevalence of HH3, about 2.5% of dairy matings involve two carrier animals. If 1 million dairy cows receive an average of 1.5 artificial insemination (AI) services each, this results in approximately 3,750 HH3 carrier-to-carrier matings. Adding around 600 similar matings for HH1, the total comes to about 4,350.
If the cost of losing a heifer (after factoring in the cull cow value) is €1,000, then the financial loss from these 4,350 carrier-to-carrier matings (where half of the pregnancies won’t succeed anyway), adds up to around €2.2 million.
Other updates to Sire Advice include:
Automatic Upload: Farmers’ Dairy and Beef Gene Ireland bull selections are now automatically uploaded.
Saved Selections: Bulls chosen in a previous run are saved, making it easier to adjust bull teams quickly.
Milk Solids Slider: A new combined milk solids slider simplifies the selection of dairy sires.
Beef Index Slider: A beef sub-index slider helps farmers make more informed choices when selecting beef AI sires.
Inclusion of TB PTA%: The bulls TB resistance % is now displayed in a traffic light system.
Breeding for TB Resistance
Farmers can breed cattle that are less likely to become TB reactors by selecting cows and bulls for breeding that have the highest overall EBI as well as the lowest breeding value for TB resistance.
Genetic resistance to TB typically ranges from 1% to 15%, with an average of 8.5%. This means that, on average, 8.5% of a bull’s offspring could become TB reactors if exposed to the bovine TB bacterium.
In 2024, there were 41,000 TB reactors, with around 490,000 cattle exposed to TB (based on the average TB breeding value of 8.5%). If this breeding value were to improve to 4.5%—a 4% unit increase in genetic resistance—the number of reactors would drop to 22,000, nearly half of 2024’s total.
By choosing bulls with stronger TB resistance, farmers can significantly lower the number of TB cases in their herds, reducing costs, stress, and workload.
Improved Visibility of TB
To make selection easier, ICBF has introduced a traffic light system for TB resistance:
- Green: Top 33% (high TB resistance)
- Orange: Middle 33% (average TB resistance)
- Red: Bottom 33% (low TB resistance)
These colour codes are now visible in:
- The ICBF Active Bull List
- Animal Search
- EBI Profile
- ICBF Sire Advice
The image below displays the Health Sub-Index traits for three high EBI bulls with good, average and poor resistance for TB.
Key Takeaway
- Enhancing genetic resistance to TB can significantly reduce the number of reactors, minimize herd disruptions, and lower costs.
- To improve TB resistance, aim to use bulls with a breeding value below 8.5%. For faster progress, select bulls with a breeding value below 6.5%.