The development and refinement of the Economic Breeding Index (EBI) over the last 25 years has provided Irish farmers with a powerful, data-driven tool to select animals that are not only more productive but also more sustainable. As part of the recent Teagasc National Dairy Conference, Professor Donagh Berry reflected on the progress achieved since its launch in 2001.
Below is just one section of the paper published in the Teagasc National Dairy Conference proceedings by Donagh Berry, Teagasc and Margaret Kelleher, ICBF, focusing on ‘does the EBI work in practice?’.
The EBI is, by far, the most extensively validated dairy cow breeding index globally. Three principal approaches have been employed in Ireland to validate the EBI. These include controlled studies complemented by cross-sectional analyses based on either animal-level data, or herd-level data.
Importantly, convergent evidence across the different validation strategies provides strong confidence to the sector on using the EBI or the individual genetic evaluations.
Controlled studies comparing different strains of Holstein-Friesians have been conducted at Moorepark for decades. More recently, these studies have focused on sub-populations that were divergent for the EBI at the time of evaluation. The primary advantage of such controlled studies is that they enable detailed investigation of complex or deep measurements that would otherwise be challenging to measure at scale on commercial farms.
Beyond their scientific value, these controlled studies also serve as high-visibility demonstration sites, enabling farmers to observe the animals and their performance data first-hand. The regular dissemination of results, often through social media and open day events, helps foster a sense of ownership and engagement among farmers, thereby enhancing trust and adoption of the EBI.
Results from controlled studies comparing dairy cows representative of the national average EBI, with those in the top 5% nationally, demonstrated that the genetically elite cows produced more milk solids, had a greater dry matter intake capacity relative to body weight, maintained better body condition throughout lactation, exhibited superior reproductive performance, and had increased longevity.
Collectively, these advantages translated into higher net profit per farm and per hectare for the high-EBI group. The superiority of the elite EBI cows was consistent across three feeding systems that differed in concentrate supplementation level and stocking rate. Furthermore, sensitivity analyses of milk price and concentrate costs did not result in any re-ranking of genotypes in terms of profitability.
A cross-sectional analysis of 536,923 individual records from Irish dairy cows was recently undertaken to relate on-farm performance to corresponding genetic evaluations for each trait; the study also examined associations between the EBI, its sub-indexes, and animal performance.
The conclusions from the large study were that selection on EBI is expected to, on average, improve productivity through increased yield and concentration of milk fat and protein, despite a modest reduction in milk volume.
Furthermore, EBI selection was associated with improved reproductive performance, greater survival, better health, lighter bodyweight, and fewer calving complications, with minimal impact on the beef merit of progeny.
A complementary herd-level cross-sectional analysis of 1,131 Irish dairy herds with both herd physical and economic performance and herd mean EBI data over a three-year period was originally undertaken over 13 years ago. Results from that study concluded that, as expected, higher mean herd genetic merit for individual traits was associated with superior herd-level performance for those traits. Herd EBI was negatively associated with milk yield but positively associated with milk composition, resulting in higher milk price. Mean herd net margin per cow increased by €1.94 for each one-unit increase in mean herd EBI.
Given that EBI is expressed on a predicted transmitting ability scale, the expected increase was €2 per unit, indicating excellent agreement between observed and expected responses.
Collectively, findings from these validation studies confirm that genetic merit estimates for performance traits reliably translate into corresponding phenotypic differences that generally align with expectations. Moreover, selection based on EBI consistently increases profit per lactation, and this response was robust across diverse production systems.